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Impact of Wind on the Spatio-Temporal Variation in Concentration of Suspended Solids in Tonle Sap Lake, Cambodia

Impact of Wind on the Spatio-Temporal Variation in Concentration of Suspended Solids in Tonle Sap... Article Impact of Wind on the Spatio-Temporal Variation in Concentration of Suspended Solids in Tonle Sap Lake, Cambodia 1 1 , 2 , 1 3 , 4 5 1 Michitaka Sato , Rajendra Khanal *, Sovannara Uk , Sokly Siev , Ty Sok and Chihiro Yoshimura Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, 2-12-1-M1-4, Ookayama, Meguro-ku, Tokyo 152-8552, Japan; tokodai88@gmail.com (M.S.); uk.s.ab@m.titech.ac.jp (S.U.); yoshimura.c.aa@m.titech.ac.jp (C.Y.) Policy Research Institute, A Think-Tank of the Government of Nepal, 3rd Floor of Federal Secretariat Construction and Management Building, Sano Gaucharan-5, Kathmandu 44600, Nepal General Department of Science, Technology & Innovation, Ministry of Industry, Science, Technology & Innovation, Preah Norodom Boulevard, Sangkat Phsar Thmey III, Khan Daun Penh, Phnom Penh 120203, Cambodia; siev.sokly@misti.gov.kh Research and Innovation Center, Institute of Technology of Cambodia, Phnom Penh 12000, Cambodia Faculty of Hydrology and Water Resources Engineering, Institute of Technology of Cambodia, Russian Federation Blvd., P.O. Box 86, Phnom Penh 12156, Cambodia; sokty@itc.edu.kh * Correspondence: rajendra.khanal@gmail.com Abstract: Even though wind, water depth, and shear stress are important factors governing sediment resuspension in lakes, their actual relations to total suspended solids (TSS) distribution in natural environments have not been well elucidated. This study aims to elucidate the impact of the wind on the spatio-temporal variation of TSS in Tonle Sap Lake, Cambodia, during low-water (March and June, <1 m) and high-water (September and December, 8–10 m) seasons. To this end, wind and TSS data Citation: Sato, M.; Khanal, R.; Uk, S.; for December 2016 and March, June, and September 2017 were collected and analyzed. For spatial Siev, S.; Sok, T.; Yoshimura, C. Impact interpolation of wind speed, the inverse distance weighted method was found to be better (R = 0.49) of Wind on the Spatio-Temporal 2 2 than the vectorized average (R = 0.30) and inverse of the ratio of distance (R = 0.31). Spatial Variation in Concentration of interpolation showed that the wind speed and direction on the lake were <5 m/s and southward Suspended Solids in Tonle Sap Lake, during the low-water season and <7 m/s and westward during the high-water season. The TSS Cambodia. Earth 2021, 2, 424–439. concentration in the low-water season was higher (>50 mg/L) than that in the high-water season. https://doi.org/10.3390/earth2030025 The TSS concentration during the low-water season was empirically described by wind speed (W), 3 3 (W/D) (t_wave) Academic Editors: water depth (D), and shear stress (t_wave) with a function of W , W /D, and exp or exp , Christopher Gomez, Junun Sartohadi depending on the location in the lake. The critical shear stress due to wind-induced waves at most of and Frans Persendt the places in the lake was higher than the total shear stress indicated. Sedimentation was predominant in December and June, and erosion (siltation) was dominant in March. Most of the siltation in March Received: 27 March 2021 was dominant in the southern part of the lake. Accepted: 30 June 2021 Published: 6 July 2021 Keywords: wind speed and direction; spatio-temporal; total suspended solids; interpolation; shear stress; Tonle Sap Lake Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Sediment re-suspension occurs because of the advection and diffusion of sediments into water columns by wind events when bottom shear stresses are enough to entrain materials from the lake bed [1,2]. Sediment resuspension takes from hours to days to reach Copyright: © 2021 by the authors. equilibrium condition, when total suspended solids (TSS) are uniformly distributed in Licensee MDPI, Basel, Switzerland. lakes [3–9]. The basic physical processes and dominant factors in cohesive sediment trans- This article is an open access article port in shallow lakes are flocculation, deposition, siltation, and environmental parameters distributed under the terms and (e.g., wind speed, water depth, and vegetation type) [1,10,11]. conditions of the Creative Commons A number of studies that have analyzed the impact of habitat structure, land use Attribution (CC BY) license (https:// land cover, hydrodynamic properties, and sediment and organic matter characteristics on creativecommons.org/licenses/by/ sediment resuspension are available [12–14]. The relationship of wind-induced sediment 4.0/). Earth 2021, 2, 424–439. https://doi.org/10.3390/earth2030025 https://www.mdpi.com/journal/earth Earth 2021, 2 425 resuspension between wind and shear stress based on TSS simulation from force derived by shear stress in the water bottom had been developed using a highly dimensional hydrodynamic model [11,15–18]. However, the spatial distribution of wind-induced re- suspension and simplified empirical equations based on meteorological and environmental factors to elucidate the interaction of the wind with TSS simulations have not been assessed in detail. A pragmatic approach that can describe the relationship of wind waves and total suspended sediment concentrations is to use relatively simple empirical formulas that can utilize wavelength as a function of wind velocity and fetch, and re-suspension occurs if the total shear stress is greater than the critical shear stress, which is considered the case if the wavelength exceeds twice the water depth. The basic processes involved in cohesive sediment transport, such as flocculation, deposition, and erosion, have been studied by many scientists [10].. Carper and Bachmann (1984) [19] and Scheffer (2004) [5] showed that an empirical approach works well to describe re-suspension in a shallow lake. In addition, models based on the nonlinear shallow water equation for coastal engineering have been widely used to quantify wind and several physical wave characteristics, including wave height, length, peak period, maximum orbital velocity, and shear stress [20,21]. Håkanson and Bryhn (2008) [22] reviewed the mechanisms of wave development, which can be calculated on the basis of the bottom current velocity (computed from water depth, wave height, wave length, and wave period). Resuspension occurs when deep-water waves enter water shallower than one-half of the wavelength. The extent of re-suspension is also a function of the energy imparted to the system by wind waves and lake bathymetry. At low wind speed, no resuspension occurs as the critical fetch is larger than the maximum fetch in a lake. Above a critical wind speed, the re-suspended fraction of a lake rises with increasing wind. Due to the sharp decrease in re-suspension with water depth, a change in water level can affect wind-induced re-suspension. Siev et al. (2018) [23] investigated sediment dynamics in Tonle Sap Lake (TSL) and observed simulated TSS concentration to fit well with the observed TSS concentration during flooding. However, during other periods, such as during dry and wet seasons when water depth and wind speed varies a lot, TSS concentration was underestimated, probably because of the lack of understanding of the influence of wind on the spatio- temporal variation of TSS. The transfer of energy from wind that leads to a variation of TSS concentration is dependent on the spatio-temporal variation of metrological parameters, especially wind speed, and the physical properties of the sediment, such as particle size, shear stress, and time to reach equilibrium [24]. The simultaneous action of wind-induced currents and surface waves leads to an increase in the bottom shear stress, which may exceed the critical shear stress and cause re-suspension [1,25]. The occurrence of shear stress in the water column is divided into two parts, namely, currents and waves. Surface waves have a more pronounced contribution to re-suspended sediments than the currents [11,26–29]. Current-induced shear stress is dominant in open channels and rivers, whereas in lakes and ponds, wave-induced shear stress contributes to sediment resuspension [26,30–32]. In general, wave-induced shear stress contributes as much as 70% of the total re-suspension in shallow lakes [33]. The general objective of this study is to elucidate the impact of the wind on the spatio- temporal variation in concentration of suspended solids in TSL. The specific objectives include (i) finding a proper method for spatial interpolation of the wind and (ii) elucidating the relationship of sediment re-suspension to wind, sediment characteristics, and other environment variables for TSS estimation. 2. Materials and Methods 2.1. Study Area TSL, one of the largest freshwater lakes with unique reversal hydrodynamics flowing between Mekong River (MR) and Tonle Sap River (TSR), is of utmost importance for economic, livelihood, culture, and recreation not only in Cambodia but also in lower Mekong Basin. There are two distinct seasons in Cambodia, namely, wet and dry. As a Earth 2021, 2, FOR PEER REVIEW 3 2. Materials and Methods 2.1. Study Area TSL, one of the largest freshwater lakes with unique reversal hydrodynamics flowing Earth 2021, 2 between Mekong River (MR) and Tonle Sap River (TSR), is of utmost importance for eco 426 - nomic, livelihood, culture, and recreation not only in Cambodia but also in lower Mekong Basin. There are two distinct seasons in Cambodia, namely, wet and dry. As a result, TSL has distinct features during the dry and wet seasons. The area, length, width, and depth result, TSL has distinct features during the dry and wet seasons. The area, length, width, of TSL vary from 2.5k to 15k km , 120 to 250 km, 3 to 100 km, and <1 to as much as 10 m and depth of TSL vary from 2.5k to 15k km , 120 to 250 km, 3 to 100 km, and <1 to as much during dry and wet seasons, respectively. The average outflow from TSL to TSR during as 10 m during dry and wet seasons, respectively. The average outflow from TSL to TSR the dry season and inflow from MR to TSL during the wet season vary from 380 to 8200 during the dry season and inflow from MR to TSL during the wet season vary from 380 to 3 3 m /s and from 100 to 7000 m /s, respectively. During the wet season, there is a huge influx 3 3 8200 m /s and from 100 to 7000 m /s, respectively. During the wet season, there is a huge of sediment discharge from MR to TSL, and in one of the studies, as much as 80% of sed- influx of sediment discharge from MR to TSL, and in one of the studies, as much as 80% of iment influx from the Mekong Basin has been found to be retained by TSL [23,34–35]. The sediment influx from the Mekong Basin has been found to be retained by TSL [23,34,35]. TSS concentrations during dry and wet seasons vary from 4 to 650 mg/L and from 3 to 125 The TSS concentrations during dry and wet seasons vary from 4 to 650 mg/L and from 3 to mg/L, respectively (reference: TSL fact sheet in [36]). TSL is always under the influence of 125 mg/L, respectively (reference: TSL fact sheet in [36]). TSL is always under the influence the wind. The average and maximum wind speeds during dry and wet seasons vary from of the wind. The average and maximum wind speeds during dry and wet seasons vary 3–4 to 6.2–8.8 m/s and from 2–3 to 12.3 m/s, respectively. from 3–4 to 6.2–8.8 m/s and from 2–3 to 12.3 m/s, respectively. Sedimentation across TSL during the dry season varies from 0.1 to 0.16 mm/year [37]. Sedimentation across TSL during the dry season varies from 0.1 to 0.16 mm/year [37]. The sedimentation rate during dry and wet seasons varies in the range 306.7 ± 369.6 to The sedimentation rate during dry and wet seasons varies in the range 306.7  369.6 to 194.4 ± 43.3 g⁄m ⁄day [23]. During the dry season, when the lake is very shallow (<1 m), 194.4  43.3 g/m /day [23]. During the dry season, when the lake is very shallow (<1 m), there is active re-suspension of the sediment in the lake [34]. The sediment of TSL and the there is active re-suspension of the sediment in the lake [34]. The sediment of TSL and floodplain mainly composed of silt (4–63 μm) and clay (<4 μm), which is favorable for re- the floodplain mainly composed of silt (4–63 m) and clay (<4 m), which is favorable for suspension [23]. The map of the study area, sampling sites for wind speed, and TSS col- re-suspension [23]. The map of the study area, sampling sites for wind speed, and TSS lection cross section (CS) point are shown in Figure 1. collection cross section (CS) point are shown in Figure 1. b) a) CS = cross section of the lake TSS sampling cross section Wind observation site Wind interpolated site TSS sampling site Fig 1. Study area, and sampling site across Tonle Sap Lake, Cambodia Figure 1. (a) Study area and (b) cross sections (CS) of Tonle Sap Lake, Cambodia, for the sampling of total suspended Figure 1. (a) Study area and (b) cross sections (CS) of Tonle Sap Lake, Cambodia, for the sampling of total suspended solids. solids. 2.2. Data Preparation 2.2. Data Preparation Wind data were obtained from the Natural Climatic Data Center from 1949 to 2019 at Wind data were obtained from the Natural Climatic Data Center from 1949 to 2019 12 stations in Cambodia. However, because many wind datapoints were missing and none at 12 stations in Cambodia. However, because many wind datapoints were missing and covered wind across TSL, it was necessary to sort the wind data and to use interpolation none covered wind across TSL, it was necessary to sort the wind data and to use interpo- to find wind characteristics at a particular location in TSL. Before interpolation, it is a lation to find wind characteristics at a particular location in TSL. Before interpolation, it is prerequisite to characterize the data. Wind data were interpolated by three methods: a prerequisite to characterize the data. Wind data were interpolated by three methods: (i) (i) inverse distance weighted (IDW) in ArcGIS; (ii) vectorized average; and (iii) inverse inverse distance weighted (IDW) in ArcGIS; (ii) vectorized average; and (iii) inverse of of ratio of distance. The interpolated data were selected by best-fit Pearson correlation coefficient (r) and root mean square error (RMSE) among those three methods (Table 1). A detail methodology for interpolation is given in Supplementary File S1. Earth 2021, 2 427 Table 1. Pearson correlation coefficient (r) and RMSE of interpolation for wind data. IDW Pursat Battam Bang Average Year 2008 2009 2010 2010 Evaluation Value r RMSE r RMSE r RMSE r RMSE r RMSE (1) Speed IDW 0.75 0.68 0.57 0.70 0.31 1.19 0.32 0.70 0.49 0.81 Vectorized average 0.78 1.11 0.36 1.26 0.20 1.96 0.14 0.84 0.30 1.29 Inverse of ratio 0.55 0.91 0.17 0.98 0.56 1.65 0.05 0.96 0.31 1.13 (2) Direction IDW 0.35 122 0.11 162 0.60 255 0.19 163 0.01 176 Vectorized average 0.31 56 0.34 176 0.58 192 0.12 83 0.01 127 Inverse of ratio 0.24 142 0.27 145 0.12 284 0.43 177 0.05 187 (3) Direction + Speed (Inner product) IDW 0.02 0.28 0.14 0.07 0.02 0.02 Vectorized average 0.06 0.05 0.00 0.24 0.03 0.06 Inverse of ratio 0.45 0.07 0.66 0.40 0.03 0.45 (4) Direction + Speed (Polar coordinates) r x y x y x y x y x y IDW 0.32 0.63 0.25 0.01 0.55 0.24 0.54 0.62 0.14 0.25 Vectorized average 0.64 0.61 0.55 0.40 0.04 0.30 0.23 0.22 0.36 0.23 Inverse of ratio 0.89 0.33 0.42 0.90 0.49 0.24 0.48 0.37 0.36 0.11 RMSE x y x y x y x y x y IDW 1.21 3.38 2.37 3.30 0.57 3.48 1.39 4.02 1.39 3.55 Vectorized average 1.19 1.30 2.92 1.92 0.55 1.05 1.53 1.56 1.55 1.46 Inverse of ratio 1.32 3.11 1.37 2.85 1.32 3.13 0.26 3.80 1.07 3.22 As the speed calculation direction of the wind is also important, vectorized speed should be taken for the average calculation. Wind data were characterized across each CS (CS 1 to 7; Figure 1). Characterization of wind data was conducted using a wind rose diagram, which shows the speed and direction of the wind at a location for a specified time interval. The graphical wind data were then sorted by wind speed and direction such that the distance covered by wind per unit time could be calculated. The wind rose diagrams from December 2016 and March, June, September, and December 2017 at three locations, namely, Khlong Yai, Siem Reap, and Phnom Penh, are shown in Supplementary File S1. Data sorted from the wind rose were then taken for the interpolation of the wind at various locations. For wind speed, the value of r from the IDW method in Pursat for 2008 and 2009 was greater than or equal to 0.57, and for 2010, r from the inverse of ratio method was 0.56 (Table 1). Depending on the year and site, the r and RMSE values were different. No specific interpolation methods could be said to be the ideal method, but IDW could be said to be comparatively better than the vectorized average and inverse of ratio method as the average r from IDW (0.49) was comparatively greater than that from vectorized average (0.30) and inverse of ratio (0.31). However, wind direction should also be considered while interpolating wind speed. Interpolation of wind speed was conducted using two methods, namely, inner product and polar coordinates. In inner product, each value of wind speed and direction was expressed as one vector, and the product of observed and interpolated Earth 2021, 2 428 wind data was taken as the inner product, the cosine value of which gave the Pearson correlation coefficient. In the polar coordinate method, polar coordinates were obtained by converting from linear coordinates to polar coordinates and by taking the average. The weighted r and RMSE for wind speed and direction from the IDW method can be said to be comparatively better than those from the other two methods, consistent with an earlier finding [38]. Hence, interpolation of wind speed by IDW was applied for TSS simulation. 2.3. TSS and Other Environmental Variables The TSS data are the same as those reported earlier [23], and were collected during September 2016 to June 2017. Besides TSS, other environmental variables were also an- alyzed, namely, particle size distribution of suspended sediments, average diameter of sediment particles, settling velocity, air and water temperature, precipitation, and wa- ter depth. The average diameter of sediment particles was calculated by the mass ratio of sedi- ment and settling velocities as governed by Stokes’ law as shown in Equation (1): D (r r )g s 0 s50 b = , (1) 18h where b is the settling velocity (m/s), r , r are the densities of the sediment and fluid s 0 3 2 (g/cm ), g is gravity acceleration (m/s ), and h is fluid viscosity (g/cm/s). Settling velocity varied spatially but not temporally. 2.4. Empirical Relationships Empirical relationships between wind and TSS were derived using observed TSS, inter- polated wind speed, and other environmental parameters (i.e., water level and shear stress). The method of derivation is nonlinear regression analysis using the least squares method, and accuracy of the derivation is compared by correlation coefficient under three conditions: (i) the whole area of TSL, (ii) season variation, and (iii) a specific CS in a lake. Empirical analysis is based on the assumption that sediment suspension occurs under steady-state conditions. The details of the empirical calculation are given in Supplementary File S2. 2.5. Mechanism Elucidation of Wind-Induced Sediment Re-Suspension In order to estimate the balance of the total shear stress (wind-induced waves and currents) and critical shear stress on sediment re-suspension and to analyze the fluctuation of TSS throughout the lake, wind-induced sediment re-suspension was evaluated using two methods: (i) shear stress analysis and (ii) assessment of re-suspension rate. The details of the mathematical calculation of these two methods are given in Supplementary File S3. Shear stress can be calculated by the following equation: 0.5 2p r v t = H , (2) wave 2pD 2sinh where t is the shear stress by wind-induced waves (Pa), r is water density, v is the wave 0 kinematic viscosity of water (cm /s), H is wave height (cm), T is wave period (s), D is water depth (cm), and L is wave length (cm). Wave period and length can be calculated using the different equations of Bretschneider methods [39]. Waves are considered long waves and deep-water waves during dry and wet seasons, respectively. The magnitudes of bottom shear stresses due to current (t ) and wind-induced curr shear stress at the surface of the lake (t ) are estimated using a quadratic drag law, as given in Equation (3): jt j = 0.1t = 0.1C r W , (3) curr 0 D a Earth 2021, 2 429 where r denotes the density of air and C denotes the drag coefficient a D C = 0.001(0.75 + 0.067W). (4) Shear stress due to currents in large shallow lakes such as TSL is significantly smaller than the shear stress due to waves [40]. Hence, it is necessary to balance the critical shear stresses (t ) cr t = t rRgD , (5) cr c s50 where R = r r/r (the submerged specific gravity), r is the sediment density, D s s s50 denotes the sediment grain size, and g is the acceleration due to gravity. The critical (nondi- mensional) Shield’s parameter t can be obtained by curve fittings to the experimental dataset for incipient motion developed by [41]: h i 0.6 (7.7R ) 0.6 ep t = 0.5 0.22Re + 0.06 10 , (6) c p where Re = gRD D /h , with h denoting the kinematic viscosity of water. p s50 s50 0 0 Re-suspension rate was calculated by following Equation (7): dS 1 (7) = (bS + E), dt D where S is the depth-averaged suspended sediment concentration mgm , D is the depth of the water column (m), b is the settling velocity ms , and E is the erosion rate 3 1 mgm s . Additionally, E = aW , (8) where a and p are empirical constants and W is the wind speed . Putting the value of E in Equation (8) and differentiating yield the value of S as given in Equation (9) under steady-state conditions and Equation (10) under unsteady- state conditions. p p dS 1 aW aW p (bt/D) = (bS + aW ),S = + S(0) e , (9) dt D b b dS U H b = f exp = f exp K  W , 0 0 dt PE D (10) S = f exp K  W t + S(0). In addition, to understand re-suspension dynamics, it is required to identify the time required to reach equilibrium TSS. This equilibrium time was compared for three months aW December, March, and June. In addition, convergence of TSS = was considered the maximum TSS and background TSS (= S(0)) was considered the minimum TSS in the whole TSL and in each point (CS1–CS7). The monthly average settling velocity (b) and water depth (D) were used for the calculation of suspended sediment concentration (S). 3. Results and Discussion 3.1. Characterization of Wind Data The comparison of the wind speed and direction observed at Khlong Yai, Siem Reap, and Phnom Penh from December 2016 to December 2017 is shown in Figure 2 and Table 1. In March, the wind direction is mainly southward and changes toward the southeast or southwest depending on the locations (see the wind rose diagram in Supplementary File S1 and Table 2). The difference in wind speed is probably due to difference in altitude. Khlong Yai is at a lower altitude of 6 m compared to Siem Reap at 8 m and Phnom Penh at 12 m. The wind speed in December and March was, in general, less than 5 m/s, but in June and September, the wind speed was as much 7 m/s (Table 2). Earth 2021, 2 430 3.2. Interpolation of Wind Data The interpolated wind speeds at various CS across TSL and observed TSS are shown in Figure 3. The TSS concentration, in general, during the wet season in December and September was less than 50 mg/L, but during the dry season in March and June, it was greater than 50 mg/L and peaked up to 400 mg/L in March and was greater than 600 mg/L in June (Figure 3). The difference in TSS concentration can be explained by the difference in sediment characteristics, namely, sediment diameter, sediment ratio, and settling velocity, as shown in Table 3. Sand, silt, and clay did not differ much across various CS. However, settling velocity differed because of the difference in the average diameter of sediment particles. For example, the settling velocities at CS3-5 and CS7-3 were higher (>10 m/day) and the average particle diameter was higher (>10 m) than at other points. The larger the sediment size, the faster the settling velocity and the lower the TSS concentration. Earth 2021, 2, FOR PEER REVIEW The average sediment diameter at CS4 was smaller than that in other CSs. Hence, the 7 settling velocity at CS4, in general, was smaller and the TSS concentration was higher than that in other CSs (Table 3). It can be concluded that one of the factors that influence TSS concentration is the particle size or the settling velocity. In addition, because TSS did not 1 and Table 2). The difference in wind speed is probably due to difference in altitude. exhibit direct correlation with the wind speed (Figure 3), it was felt necessary to identify Khlong Yai is at a lower altitude of 6 m compared to Siem Reap at 8 m and Phnom Penh the empirical relation of TSS with the wind by adding additional factors such as shear at 12 m. The wind speed in December and March was, in general, less than 5 m/s, but in stress and water depth. June and September, the wind speed was as much 7 m/s (Table 2). a) Khlong Yai b) Siem Reap c) Phnom Penh Figure 2. Wind speed in Cambodia at (a) Khlong Yai, (b) Siem Reap, and (c) Phnom Penh. Fig 2. Wind speed in Cambodia at, a) Khilong Vai, b) Seiem Reap, and c) Phnom Penh Figure 2. Wind speed in Cambodia at (a) Khlong Yai, (b) Siem Reap, and (c) Phnom Penh. Table 2. Comparison of the wind and TSS at (1) Khlong Yai, (2) Siem Reap, and (3) Phnom Penh. Total Suspended Solid Month Wind (TSS) Wind Direction Wind Speed 1) Khlong Yai 1) Khlong Yai 2) Siem Reap 2) Siem Reap 3) Phnom Penh 3) Phnom Penh 1: Higher in 2017 than in 2016, and • TSS varies by year Direction changes to N at once similar in range as in Mar • Compared to 5–12.5 1: Trends change slightly between 2: Max: 12.3 m/s, turbulence calms mg/L in 2016, TSS are higher December 2016 and 2017, but mainly is west- down compared to Sep than 50 mg/L ward 3: Average increases compared to • CS4-1 only is over 200 2,3: Direction changes to N at once Sep mg/L 1: Relatively lower wind speed • Completely different Trends do not change regardless of (Ave: 3–4 m/s, max: 3.6–5.7 m/s) wind speed on each location year March 2: Occasional stronger wind (7.2–8.2 • Higher TSS (>200 mg/L) 1: Main direction: West or East wind, m/s) in: CS2-2, CS3-2, CS3-7, CS4- No NE or SW direction 3: Max: 6.2–8.8 m/s 1~4–3, CS6-2~6–5 Wind speed (m/s) Wind speed (m/s) Wind speed (m/s) Earth 2021, 2 431 Table 2. Comparison of the wind and TSS at (1) Khlong Yai, (2) Siem Reap, and (3) Phnom Penh. Month Wind Total Suspended Solid (TSS) Wind Direction Wind Speed (1) Khlong Yai (1) Khlong Yai (2) Siem Reap (2) Siem Reap (3) Phnom Penh (3) Phnom Penh 1: Higher in 2017 than in 2016, Direction changes to N at once  TSS varies by year and similar in range as in Mar 1: Trends change slightly between  Compared to 5–12.5 mg/L in 2: Max: 12.3 m/s, turbulence December 2016 and 2017, but mainly is 2016, TSS are higher than calms down compared to Sep westward 50 mg/L 3: Average increases compared 2,3: Direction changes to N at once  CS4-1 only is over 200 mg/L to Sep Completely different wind Trends do not change regardless of speed on each location year 1: Relatively lower wind speed  Higher TSS (>200 mg/L) in: 1: Main direction: West or East wind, (Ave: 3–4 m/s, max: 3.6–5.7 m/s) CS2-2, CS3-2, CS3-7, CS4-1~4–3, March No NE or SW direction 2: Occasional stronger wind CS6-2~6–5 2: Frequent southern wind, relatively (7.2–8.2 m/s)  Ave: 169.5, max: 405, min: 4.5 unstable 3: Max: 6.2–8.8 m/s (mg/L) 3: Only SE in 2016 and 2017  Strong wind 6= High TSS Shallow depth 6= High TSS 1: Average does not change in Mar, max changes (3.6 m/s in Mar Highest TSS Trends do not change regardless ! 15.4 m/s in Jun) of year Max: 652 mg/L 2: Increases by 5 m/s from 7.2–8.2 June 1: NS from EW in Mar CS2 and CS3 have higher TSS ! 8.8–13.3 m/s 2: SW stable Some places showed lower TSS 3: Speed does not change, with 3: SW to SE in Mar than that in Mar occasional max, 6.2–8.8 ! 12.9–23.2 m/s Trends do not change regardless of 1: No turbulence and a stable year wind of 2–3 m/s 1: Frequent westward, 2016 and 2017 2: 15–20 m/s in 2016, no show same trends.  Max: ~50 mg/L turbulence and a stable wind September 2: Overall westward,  Strong wind 6= High TSS around 7 m/s NW ratio increases in 2017  Relatively stable and lower TSS 3: Speed is the same or slightly 3: S and N from SW higher than that in Jun at around 4: Westward wind trend 10 m/s Earth 2021, 2, FOR PEER REVIEW 10 remainsDirection varies by year Interpolated wind Speed TSS December 2016 March 2017 June 2017 September 2017 Figure 3. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia. Figure 3. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia. Fig 4. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia 3.3. Empirical Relation A number of empirical relations were tried for the correlation of TSS with wind speed, water depth, and shear stress (Supplementary File 3), and they can be summarized as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in Table 4. Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Regression Relation R RMSE Whole lake 3 2 𝑆𝑆𝑇 = −20.9 𝑊 ⁄𝐷 + 102.8 𝑊 ⁄𝐷 − 96.1 𝑊 ⁄𝐷 + 75 0.06 111 (dry + wet season) 𝑆𝑆𝑇 = −0.456𝜏 + 8 Wet season 0.03 2.0 𝑣𝑒𝑎𝑤 3 2 𝑆𝑆𝑇 = 0.80𝑊 − 3.9𝑊 + 4.5𝑊 + 8 0.02 2.0 Dry season 𝑆𝑆𝑇 = 459.3𝑊 − 2244.5𝑊 + 2861 0.06 141 Dry season −5 Cross section 1 𝑆𝑆𝑇 = 5.6 × 10 × (5 𝑊 ⁄𝐷 ) + 5 0.96 53 Cross section 2 𝑆𝑆𝑇 = −3766.9𝑊 + 19242𝑊 − 23467 0.71 259 3 2 𝑆𝑆𝑇 = −143.6 𝑊 ⁄𝐷 + 146 𝑊 ⁄𝐷 + 132.7 𝑊 ⁄𝐷 + 540 0.69 256 3 2 Cross section 3 𝑆𝑆𝑇 = −310.3𝑊 + 1331.3𝑊 − 702.7𝑊 − 1399 0.42 198 3 2 𝑆𝑆𝑇 = −1232.4 𝑊 ⁄𝐷 + 6050 𝑊 ⁄𝐷 − 7417 𝑊 ⁄𝐷 + 368 0.41 182 3 2 Cross section 4 𝑆𝑆𝑇 = 723.0𝑊 − 2757𝑊 + 1128.8𝑊 + 3156 0.59 159 3 2 ⁄ ⁄ ⁄ 𝑆𝑆𝑇 = 2731.3 𝑊 𝐷 − 12498.2 𝑊 𝐷 + 14129.7 𝑊 𝐷 0.59 156 + 72 3 2 Cross section 5 𝑆𝑆𝑇 = 128.3 𝑊 ⁄𝐷 − 617.4 𝑊 ⁄𝐷 + 750.8 𝑊 ⁄𝐷 + 22 0.56 79 𝑆𝑆𝑇 = −50.9𝜏 + 320 0.58 73 𝑣𝑒𝑎𝑤 3 2 Cross section 6 𝑆𝑆𝑇 = 437.4𝑊 − 1610.5𝑊 + 636.1𝑊 + 1690 0.82 175 −5 𝑆𝑆𝑇 = 1.8 × 10 × (6.1𝑊 ) − 6 0.81 153 3 2 Cross section 7 ⁄ ⁄ ⁄ 0.88 82 𝑆𝑆𝑇 = 84.2 𝑊 𝐷 − 165.6 𝑊 𝐷 − 144.2 𝑊 𝐷 + 53 𝑆𝑆𝑇 = 1675.8 × (−0.40𝜏 ) − 134 0.77 51 𝑣𝑒𝑎𝑤 W = wind speed (m/s), D = water depth (m), 𝜏 = shear stess (Pa), and TSS = total suspended solids (mg/L). 𝑎𝑤𝑣𝑒 It is evident from Table 4 that a single equation does not fit well to the simulated TSS 2 2 2 across the whole TSL (R = 0.06) or even during dry (R = 0.06) and wet seasons (R = 0.03). As the TSL lake is huge and its area and depth vary from <1 m and 5 km to 5 m and 16 𝑒𝑥𝑝 𝑒𝑥𝑝 𝑒𝑥𝑝 Ea Eart rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 9 9 Ea Ea Ea Eart rt rt rth h h h 2 2 2 20 0 0 02 2 2 21 1 1 1, , , , 2 2 2 2,,,, F F F FO O O OR R R R P P P PE E E EER ER ER ER R R R REV EV EV EVI I I IEW EW EW EW 9 9 9 9 Ea Ea Ea Eart rt rt rth h h h 2 2 2 20 0 0 02 2 2 21 1 1 1, , , , 2 2 2 2,,,, F F F FO O O OR R R R P P P PE E E EER ER ER ER R R R REV EV EV EVI I IIEW EW EW EW 9 9 9 9 Ea Eart rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 9 9 Earth 2021, 2, FOR PEER REVIEW 9 Earth 2021, 2, FOR PEER REVIEW 9 Ea rth 2021, 2, FOR PEER REVIEW 9 Ea rth 2021, 2, FOR PEER REVIEW 9 Ea Ea rt rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 9 9 Ea Ea rt rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 9 9 Earth 2021, 2, FOR PEER REVIEW 9 Ea rth 2021, 2, FOR PEER REVIEW 9 Earth 2021, 2, FOR PEER REVIEW 9 Earth 2021, 2 432 Ta Table ble 3 3.. S Sed edime imen nt t c ch ha ar ra ac ct ter eris ist tics ics a ac cr ro oss ss v va ar rio ious us c cr ro oss ss se sec ct tio ion ns s (CS (CS) ) in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Ta Ta Ta Ta Table ble ble ble ble 3 3 3 3 3..... S S S S Sed ed ed ed edime ime ime ime imen n n n nt t t t t c c c c ch h h h ha a a a ar r r r ra a a a ac c c c ct t t t ter er er er eris is is is ist t t t tics ics ics ics ics a a a a ac c c c cr r r r ro o o o oss ss ss ss ss v v v v va a a a ar r r r rio io io io ious us us us us c c c c cr r r r ro o o o oss ss ss ss ss se se se se sec c c c ct t t t tio io io io ion n n n ns s s s s (CS (CS (CS (CS (CS) ) ) ) ) in in in in in To To To To Ton n n n nle le le le le S S S S Sa a a a ap L p L p L p L p La a a a ak k k k ke, e, e, e, e, Ca Ca Ca Ca Cam m m m mb b b b bo o o o odi di di di dia a a a a..... Ta Ta Table ble ble 3 3 3... S S Sed ed edime ime imen n nt tt c c ch h ha a ar r ra a ac c ct tter er eris is ist ttics ics ics a a ac c cr r ro o oss ss ss v v va a ar r rio io ious us us c c cr r ro o oss ss ss se se sec c ct ttio io ion n ns s s (CS (CS (CS) ) ) in in in To To Ton n nle le le S S Sa a ap L p L p La a ak k ke, e, e, Ca Ca Cam m mb b bo o odi di dia a a... Ta Table ble 3 3.. S Sed edime imen nt t c ch ha ar ra ac ct ter eris ist tics ics a ac cr ro oss ss v va ar rio ious us c cr ro oss ss se sec ct tio ion ns s (CS (CS) ) in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Ta Table ble 3 3.. S Sed edime imen nt t c ch ha ar ra ac ct ter eris ist tics ics a ac cr ro oss ss v va ar rio ious us c cr ro oss ss se sec ct tio ion ns s (CS (CS) ) in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Ta Ta Table ble ble 3 3 3... S S Sed ed edime ime imen n nt t t c c ch h ha a ar r ra a ac c ct t ter er eris is ist t tics ics ics a a ac c cr r ro o oss ss ss v v va a ar r rio io ious us us c c cr r ro o oss ss ss se se sec c ct t tio io ion n ns s s (CS (CS (CS) ) ) in in in To To Ton n nle le le S S Sa a ap L p L p La a ak k ke, e, e, Ca Ca Cam m mb b bo o odi di dia a a... Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t Ma Ma Ma Mass ss ss ss R R R Ra a a at t t ti i i io o o o of of of of S S S Se e e ed d d di i i im m m me e e en n n nt t t t Ma Ma Ma Mass ss ss ss R R R Ra a a at t t ti i i io o o o of of of of S S S Se e e ed d d di i i im m m me e e en n n nt t t t Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t Mass Ratio of Sediment Mass Ratio of Sediment Mass Ratio of Sediment Mass Ratio of Sediment Ma Ma Mass ss ss R R Ra a at t ti i io o o of of of S S Se e ed d di i im m me e en n nt t t A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m//d day ay) ) Mass Ratio of Sediment A A A Ar r r re e e ea a a a P P P Poin oin oin oint t t t A A A Ave ve ve ver r r ra a a age ge ge ge Di Di Di Dia a a ame me me met t t te e e er r r r ( ( ( (𝛍𝐦𝛍𝐦𝛍𝐦𝛍𝐦 ) ) ) ) S S S Se e e et t t tt t t tl l l li i i in n n ng g g g V V V Ve e e el l l loci oci oci ocit t t ty y y y ( ( ( (m m m m/ // /d d d day ay ay ay) ) ) ) Mass Ratio of Sediment A A A Ar r r re e e ea a a a P P P Poin oin oin oint t t t A A A Ave ve ve ver r r ra a a age ge ge ge Di Di Di Dia a a ame me me met t t te e e er r r r ( ( ( (𝛍𝐦𝛍𝐦𝛍𝐦 𝛍𝐦 ) ) ) ) S S S Se e e et t t tt t t tl l l li i i in n n ng g g g V V V Ve e e el l l loci oci oci ocit t t ty y y y ( ( ( (m m m m/ / //d d d day ay ay ay) ) ) ) A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) Mass Ratio of Sediment Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) Mass Ratio of Sediment A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) A Ar re ea a P Poin oint t T A A able ve ver r3. a age ge Sediment Di Dia ame mecharacteristics t te er r ( (𝛍𝐦𝛍𝐦 ) ) acrS S oss e et tt tvarious l li in ng g V Ve e cr l loci oci osst tsections y y ( (m m/ /d day ay (CS) ) ) in Tonle Sap ( (%, %, Lake, S Sa an nd d Cambodia. , , Silt Silt, , Cl Cla ay y) ) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) ( ( ( (%, %, %, %, S S S Sa a a an n n nd d d d, , , , Silt Silt Silt Silt, , , , Cl Cl Cl Cla a a ay y y y) ) ) ) ( ((%, %, %, S S Sa a an n nd d d, , , Silt Silt Silt, , , Cl Cl Cla a ay y y) )) ( (%, %, S Sa an nd d, , Silt Silt, , Cl Cla ay y) ) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) (%, Sand, Silt, Clay) (%, Sand, Silt, Clay) ( (%, %, S Sa an nd d, , Silt Silt, , Cl Cla ay y) ) (%, Sand, Silt, Clay) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) ( ( ( (%, %, %, %, S S S Sa a a an n n nd d d d, , , , Silt Silt Silt Silt, , , , Cl Cl Cl Cla a a ay y y y) ) ) ) (%, Sand, Silt, Clay) (%, Sand, Silt, Clay) (%, Sand, Silt, Clay) Area Point Average Diameter (m) Settling Velocity (m/day) Mass Ratio of Sediment (%, Sand, Silt, Clay) CS CS1 1- -1 1 6 6..5 50 0 4 4..1 16 6 CS CS CS CS1 1 1 1- - - -1 1 1 1 6 6 6 6....5 5 5 50 0 0 0 4 4 4 4....1 1 1 16 6 6 6 CS CS CS1 1 1- --1 1 1 6 6 6...5 5 50 0 0 4 4 4...1 1 16 6 6 CS CS1 1- -1 1 6 6..5 50 0 4 4..1 16 6 CS1-1 6.50 4.16 CS1-1 6.50 4.16 CS CS1 1- -1 1 6 6..5 50 0 4 4..1 16 6 CS1-1 6.50 4.16 CS CS CS CS1 1 1 1- - - -1 1 1 1 6 6 6 6....5 5 5 50 0 0 0 4 4 4 4....1 1 1 16 6 6 6 CS1-1 6.50 4.16 CS1-1 6.50 4.16 CS1-1 CS1-1 6.50 6.50 4.16 4.16 CS CS1 1- -2 2 6 6..4 48 8 4 4..1 14 4 CS CS CS1 1 1 CS CS CS CS1 1 1 1- - - -2 2 2 2 6 6 6 6....4 4 4 48 8 8 8 4 4 4 4....1 1 1 14 4 4 4 CS CS CS CS CS1 1 1 1 1 CS CS CS CS1 1 1 1- - - -2 2 2 2 6 6 6 6....4 4 4 48 8 8 8 4 4 4 4....1 1 1 14 4 4 4 CS CS CS1 1 1 CS CS1 1- -2 2 6 6..4 48 8 4 4..1 14 4 CS1 CS1-2 6.48 4.14 CS1 CS1-2 6.48 4.14 CS CS1 1 CS1-2 6.48 4.14 CS1-2 6.48 4.14 CS1 CS CS CS1 1 1- - -2 2 2 6 6 6...4 4 48 8 8 4 4 4...1 1 14 4 4 CS CS CS1 1 1 CS1-2 6.48 4.14 CS CS1 1 CS1-2 6.48 4.14 CS1-2 6.48 4.14 CS1 CS1-2 6.48 4.14 CS1 CS1-2 6.48 4.14 CS1 CS CS1 1- -3 3 5 5..0 08 8 2 2..5 55 5 CS CS CS CS1 1 1 1- - - -3 3 3 3 5 5 5 5....0 0 0 08 8 8 8 2 2 2 2....5 5 5 55 5 5 5 CS CS CS CS1 1 1 1- - - -3 3 3 3 5 5 5 5....0 0 0 08 8 8 8 2 2 2 2....5 5 5 55 5 5 5 CS CS1 1- -3 3 5 5..0 08 8 2 2..5 55 5 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS CS1 1- -3 3 5 5..0 08 8 2 2..5 55 5 CS CS1 1- -3 3 CS1-3 5 5..0 08 8 5.08 2.55 2 2..5 55 5 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS CS CS2 2 2- - -1 1 1 6 6 6...7 7 78 8 8 4 4 4...5 5 53 3 3 CS CS CS CS CS2 2 2 2 2- - - - -1 1 1 1 1 6 6 6 6 6.....7 7 7 7 78 8 8 8 8 4 4 4 4 4.....5 5 5 5 53 3 3 3 3 CS CS CS2 2 2- - -1 1 1 6 6 6...7 7 78 8 8 4 4 4...5 5 53 3 3 CS2-1 6.78 4.53 CS2-1 6.78 4.53 CS CS2 2- -1 1 6 6..7 78 8 4 4..5 53 3 CS2-1 6.78 4.53 CS CS CS2 2 2- - -1 1 1 6 6 6...7 7 78 8 8 4 4 4...5 5 53 3 3 CS2-1 6.78 4.53 CS2-1 CS2-1 6.78 6.78 4.53 4.53 CS2-1 6.78 4.53 CS2-1 6.78 4.53 CS CS2 2- -2 2 4 4..8 86 6 2 2..3 33 3 CS CS CS CS2 2 2 2- - - -2 2 2 2 4 4 4 4....8 8 8 86 6 6 6 2 2 2 2....3 3 3 33 3 3 3 CS CS CS CS2 2 2 2- - - -2 2 2 2 4 4 4 4....8 8 8 86 6 6 6 2 2 2 2....3 3 3 33 3 3 3 CS CS2 2- -2 2 4 4..8 86 6 2 2..3 33 3 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS CS CS2 2 2- - -2 2 2 4 4 4...8 8 86 6 6 2 2 2...3 3 33 3 3 CS2-2 CS2-2 4.86 4.86 2.33 2.33 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS CS2 2- -3 3 5 5..5 50 0 2 2..9 98 8 CS CS2 2 CS CS CS CS2 2 2 2- - - -3 3 3 3 5 5 5 5....5 5 5 50 0 0 0 2 2 2 2....9 9 9 98 8 8 8 CS CS CS CS2 2 2 2 CS CS CS CS2 2 2 2- - - -3 3 3 3 5 5 5 5....5 5 5 50 0 0 0 2 2 2 2....9 9 9 98 8 8 8 CS CS CS CS2 2 2 2 CS CS2 2- -3 3 5 5..5 50 0 2 2..9 98 8 CS CS2 2 CS2-3 5.50 2.98 CS2 CS CS2 2- -3 3 5 5..5 50 0 2 2..9 98 8 CS CS2 2 CS2CS2-3 5.50 2.98 CS2 CS CS2 2- -3 3 5 5..5 50 0 2 2..9 98 8 CS CS2 2 CS CS2 2- -3 3 CS2-3 5 5..5 50 0 5.50 2.98 2 2..9 98 8 CS CS2 2 CS2-3 5.50 2.98 CS2 CS2-3 5.50 2.98 CS2 CS2-3 5.50 2.98 CS2 CS CS2 2- -4 4 5 5..6 61 1 3 3..1 11 1 CS CS CS CS2 2 2 2- - - -4 4 4 4 5 5 5 5....6 6 6 61 1 1 1 3 3 3 3....1 1 1 11 1 1 1 CS CS CS2 2 2- --4 4 4 5 5 5...6 6 61 1 1 3 3 3...1 1 11 1 1 CS CS2 2- -4 4 5 5..6 61 1 3 3..1 11 1 CS2-4 5.61 3.11 CS2-4 5.61 3.11 CS CS2 2- -4 4 5 5..6 61 1 3 3..1 11 1 CS2-4 5.61 3.11 CS CS CS CS2 2 2 2- - - -4 4 4 4 CS2-4 5 5 5 5....6 6 6 61 1 1 1 5.61 3.11 3 3 3 3....1 1 1 11 1 1 1 CS2-4 5.61 3.11 CS2-4 5.61 3.11 CS2-4 5.61 3.11 CS CS CS2 2 2- - -5 5 5 7 7 7...8 8 84 4 4 6 6 6...0 0 05 5 5 CS CS CS CS CS2 2 2 2 2- - - - -5 5 5 5 5 7 7 7 7 7.....8 8 8 8 84 4 4 4 4 6 6 6 6 6.....0 0 0 0 05 5 5 5 5 CS CS CS2 2 2- - -5 5 5 7 7 7...8 8 84 4 4 6 6 6...0 0 05 5 5 CS2-5 7.84 6.05 CS2-5 7.84 6.05 CS CS2 2- -5 5 CS2-5 7 7..8 84 4 7.84 6.05 6 6..0 05 5 CS2-5 7.84 6.05 CS CS CS2 2 2- - -5 5 5 7 7 7...8 8 84 4 4 6 6 6...0 0 05 5 5 CS2-5 7.84 6.05 CS2-5 7.84 6.05 CS2-5 7.84 6.05 CS2-5 7.84 6.05 CS CS3 3- -1 1 6 6..8 87 7 4 4..6 65 5 CS CS CS CS3 3 3 3- - - -1 1 1 1 6 6 6 6....8 8 8 87 7 7 7 4 4 4 4....6 6 6 65 5 5 5 CS CS CS CS3 3 3 3- - - -1 1 1 1 6 6 6 6....8 8 8 87 7 7 7 4 4 4 4....6 6 6 65 5 5 5 CS CS3 3- -1 1 6 6..8 87 7 4 4..6 65 5 CS3-1 6.87 4.65 CS CS3 3- -1 1 6 6..8 87 7 4 4..6 65 5 CS3-1 6.87 4.65 CS CS3 3- -1 1 CS3-1 6 6..8 87 7 6.87 4.65 4 4..6 65 5 CS CS3 3- -1 1 6 6..8 87 7 4 4..6 65 5 CS3-1 6.87 4.65 CS3-1 6.87 4.65 CS3-1 6.87 4.65 CS CS3 3- -2 2 5 5..4 48 8 2 2..9 96 6 CS CS CS CS3 3 3 3- - - -2 2 2 2 5 5 5 5....4 4 4 48 8 8 8 2 2 2 2....9 9 9 96 6 6 6 CS CS CS3 3 3- --2 2 2 5 5 5...4 4 48 8 8 2 2 2...9 9 96 6 6 CS CS3 3- -2 2 5 5..4 48 8 2 2..9 96 6 CS3-2 5.48 2.96 CS3-2 5.48 2.96 CS CS3 3- -2 2 CS3-2 5 5..4 48 8 5.48 2.96 2 2..9 96 6 CS3-2 5.48 2.96 CS CS CS CS3 3 3 3- - - -2 2 2 2 5 5 5 5....4 4 4 48 8 8 8 2 2 2 2....9 9 9 96 6 6 6 CS3-2 5.48 2.96 CS3-2 5.48 2.96 CS3-2 5.48 2.96 CS CS CS3 3 3- - -3 3 3 5 5 5...6 6 65 5 5 3 3 3...1 1 15 5 5 CS CS CS CS CS3 3 3 3 3- - - - -3 3 3 3 3 5 5 5 5 5.....6 6 6 6 65 5 5 5 5 3 3 3 3 3.....1 1 1 1 15 5 5 5 5 CS CS CS3 3 3- - -3 3 3 5 5 5...6 6 65 5 5 3 3 3...1 1 15 5 5 CS3-3 5.65 3.15 CS3-3 CS3-3 5.65 5.65 3.15 3.15 CS CS3 3- -3 3 5 5..6 65 5 3 3..1 15 5 CS3-3 5.65 3.15 CS CS CS3 3 3- - -3 3 3 5 5 5...6 6 65 5 5 3 3 3...1 1 15 5 5 CS CS3 3- -3 3 5 5..6 65 5 3 3..1 15 5 CS3-3 5.65 3.15 CS3-3 5.65 3.15 CS CS CS3 3 3 CS3CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS CS CS CS CS3 3 3 3 3 CS CS CS CS3 3 3 3- - - -4 4 4 4 3 3 3 3....4 4 4 42 2 2 2 1 1 1 1....1 1 1 16 6 6 6 CS CS CS3 3 3 CS CS CS CS3 3 3 3- - - -4 4 4 4 3 3 3 3....4 4 4 42 2 2 2 1 1 1 1....1 1 1 16 6 6 6 CS3 CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS3 CS3-4 CS3-4 3.42 3.42 1.16 1.16 CS CS3 3 CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS3 CS3-4 3.42 1.16 CS CS CS3 3 3 CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS3 CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS3 CS3-4 3.42 1.16 CS3 CS3-4 3.42 1.16 CS3 CS3-4 3.42 1.16 CS CS3 3- -5 5 1 10 0..9 9 1 11 1..7 7 CS CS CS CS3 3 3 3- - - -5 5 5 5 1 1 1 10 0 0 0....9 9 9 9 1 1 1 11 1 1 1....7 7 7 7 CS CS CS CS3 3 3 3- - - -5 5 5 5 1 1 1 10 0 0 0....9 9 9 9 1 1 1 11 1 1 1....7 7 7 7 CS CS3 3- -5 5 CS3-5 1 10 0..9 9 10.9 11.7 1 11 1..7 7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS CS CS3 3 3- - -5 5 5 1 1 10 0 0...9 9 9 1 1 11 1 1...7 7 7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS CS3 3- -6 6 9 9..3 36 6 8 8..6 65 5 CS CS CS CS3 3 3 3- - - -6 6 6 6 9 9 9 9....3 3 3 36 6 6 6 8 8 8 8....6 6 6 65 5 5 5 CS CS CS3 3 3- --6 6 6 9 9 9...3 3 36 6 6 8 8 8...6 6 65 5 5 CS CS3 3- -6 6 CS3-6 9 9..3 36 6 9.36 8.65 8 8..6 65 5 CS3-6 9.36 8.65 CS3-6 9.36 8.65 CS CS3 3- -6 6 9 9..3 36 6 8 8..6 65 5 CS3-6 9.36 8.65 CS CS CS CS3 3 3 3- - - -6 6 6 6 9 9 9 9....3 3 3 36 6 6 6 8 8 8 8....6 6 6 65 5 5 5 CS3-6 9.36 8.65 CS3-6 9.36 8.65 CS3-6 9.36 8.65 CS CS3 3- -7 7 CS3-7 4 4..4 46 6 4.46 1.96 1 1..9 96 6 CS CS CS CS3 3 3 3- - - -7 7 7 7 4 4 4 4....4 4 4 46 6 6 6 1 1 1 1....9 9 9 96 6 6 6 CS CS CS CS3 3 3 3- - - -7 7 7 7 4 4 4 4....4 4 4 46 6 6 6 1 1 1 1....9 9 9 96 6 6 6 CS CS3 3- -7 7 4 4..4 46 6 1 1..9 96 6 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS CS CS3 3 3- - -7 7 7 4 4 4...4 4 46 6 6 1 1 1...9 9 96 6 6 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS CS CS CS4 4 4 4- - - -1 1 1 1 2 2 2 2....4 4 4 49 9 9 9 0 0 0 0....6 6 6 61 1 1 1 CS CS CS CS4 4 4 4- - - -1 1 1 1 CS4-1 2 2 2 2....4 4 4 49 9 9 9 2.49 0.61 0 0 0 0....6 6 6 61 1 1 1 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS4-1 2.49 0.61 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS4-1 2.49 0.61 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS4-1 2.49 0.61 CS4-1 2.49 0.61 CS4-1 2.49 0.61 CS CS CS4 4 4- - -2 2 2 6 6 6...2 2 28 8 8 3 3 3...8 8 89 9 9 CS CS CS CS CS4 4 4 4 4- - - - -2 2 2 2 2 CS4-2 6 6 6 6 6.....2 2 2 2 28 8 8 8 8 6.28 3.89 3 3 3 3 3.....8 8 8 8 89 9 9 9 9 CS CS CS4 4 4- - -2 2 2 6 6 6...2 2 28 8 8 3 3 3...8 8 89 9 9 CS4-2 6.28 3.89 CS4-2 6.28 3.89 CS CS4 4- -2 2 6 6..2 28 8 3 3..8 89 9 CS4-2 6.28 3.89 CS CS CS4 4 4- - -2 2 2 6 6 6...2 2 28 8 8 3 3 3...8 8 89 9 9 CS4-2 6.28 3.89 CS4-2 6.28 3.89 CS4-2 6.28 3.89 CS4-2 6.28 3.89 CS CS4 4- -3 3 2 2..2 28 8 0 0..5 51 1 CS CS CS CS CS4 4 4 4 4- - - - -3 3 3 3 3 2 2 2 2 2.....2 2 2 2 28 8 8 8 8 0 0 0 0 0.....5 5 5 5 51 1 1 1 1 CS CS CS CS4 4 4 4- - - -3 3 3 3 CS4-3 2 2 2 2....2 2 2 28 8 8 8 2.28 0.51 0 0 0 0....5 5 5 51 1 1 1 CS4-3 2.28 0.51 CS4-3 2.28 0.51 CS CS4 4- -3 3 2 2..2 28 8 0 0..5 51 1 CS4-3 2.28 0.51 CS CS CS4 4 4- - -3 3 3 2 2 2...2 2 28 8 8 0 0 0...5 5 51 1 1 CS4-3 2.28 0.51 CS4-3 2.28 0.51 CS4-3 2.28 0.51 CS4-3 2.28 0.51 CS CS4 4- -4 4 2 2..6 62 2 0 0..6 68 8 CS CS CS CS4 4 4 4- - - -4 4 4 4 CS4-4 2 2 2 2....6 6 6 62 2 2 2 2.62 0.68 0 0 0 0....6 6 6 68 8 8 8 CS CS CS CS4 4 4 4- - - -4 4 4 4 2 2 2 2....6 6 6 62 2 2 2 0 0 0 0....6 6 6 68 8 8 8 CS CS4 4- -4 4 2 2..6 62 2 0 0..6 68 8 CS4-4 2.62 0.68 CS4-4 2.62 0.68 CS4-4 2.62 0.68 CS4-4 2.62 0.68 CS CS4 4- -4 4 2 2..6 62 2 0 0..6 68 8 CS CS4 4- -4 4 2 2..6 62 2 0 0..6 68 8 CS4-4 2.62 0.68 CS CS CS4 4 4 CS4 CS CS CS CS CS4 4 4 4 4 CS4-4 2.62 0.68 CS CS CS4 4 4 CS4 CS4 CS CS4 4 CS4-4 2.62 0.68 CS4 CS CS CS4 4 4 CS4 CS4 CS4 CS CS4 4- -5 5 3 3..0 00 0 0 0..8 89 9 CS CS CS CS4 4 4 4- - - -5 5 5 5 CS4-5 3 3 3 3....0 0 0 00 0 0 0 3.00 0.89 0 0 0 0....8 8 8 89 9 9 9 CS4 CS CS CS4 4 4- --5 5 5 3 3 3...0 0 00 0 0 0 0 0...8 8 89 9 9 CS CS4 4- -5 5 3 3..0 00 0 0 0..8 89 9 CS4-5 3.00 0.89 CS4-5 3.00 0.89 CS CS4 4- -5 5 3 3..0 00 0 0 0..8 89 9 CS4-5 3.00 0.89 CS CS CS CS4 4 4 4- - - -5 5 5 5 3 3 3 3....0 0 0 00 0 0 0 0 0 0 0....8 8 8 89 9 9 9 CS4-5 3.00 0.89 CS4-5 3.00 0.89 CS4-5 3.00 0.89 CS CS CS4 4 4- - -6 6 6 6 6 6...4 4 48 8 8 4 4 4...1 1 14 4 4 CS CS CS CS CS4 4 4 4 4- - - - -6 6 6 6 6 CS4-6 6 6 6 6 6.....4 4 4 4 48 8 8 8 8 6.48 4.14 4 4 4 4 4.....1 1 1 1 14 4 4 4 4 CS CS CS4 4 4- - -6 6 6 6 6 6...4 4 48 8 8 4 4 4...1 1 14 4 4 CS4-6 6.48 4.14 CS4-6 6.48 4.14 CS CS4 4- -6 6 6 6..4 48 8 4 4..1 14 4 CS4-6 6.48 4.14 CS CS CS4 4 4- - -6 6 6 6 6 6...4 4 48 8 8 4 4 4...1 1 14 4 4 CS4-6 6.48 4.14 CS4-6 6.48 4.14 CS4-6 6.48 4.14 CS4-6 6.48 4.14 CS CS4 4- -7 7 5 5..8 83 3 3 3..3 35 5 CS CS CS CS4 4 4 4- - - -7 7 7 7 5 5 5 5....8 8 8 83 3 3 3 3 3 3 3....3 3 3 35 5 5 5 CS CS CS CS4 4 4 4- - - -7 7 7 7 CS4-7 5 5 5 5....8 8 8 83 3 3 3 5.83 3.35 3 3 3 3....3 3 3 35 5 5 5 CS CS4 4- -7 7 5 5..8 83 3 3 3..3 35 5 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS CS CS4 4 4- - -7 7 7 5 5 5...8 8 83 3 3 3 3 3...3 3 35 5 5 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS CS4 4- -8 8 2 2..7 71 1 0 0..7 72 2 CS CS CS CS4 4 4 4- - - -8 8 8 8 2 2 2 2....7 7 7 71 1 1 1 0 0 0 0....7 7 7 72 2 2 2 CS CS CS4 4 4- --8 8 8 CS4-8 2 2 2...7 7 71 1 1 2.71 0.72 0 0 0...7 7 72 2 2 CS CS4 4- -8 8 2 2..7 71 1 0 0..7 72 2 CS4-8 2.71 0.72 CS4-8 2.71 0.72 CS CS4 4- -8 8 2 2..7 71 1 0 0..7 72 2 CS4-8 2.71 0.72 CS CS CS CS4 4 4 4- - - -8 8 8 8 2 2 2 2....7 7 7 71 1 1 1 0 0 0 0....7 7 7 72 2 2 2 CS4-8 2.71 0.72 CS4-8 2.71 0.72 CS4-8 2.71 0.72 CS CS CS5 5 5- - -1 1 1 5 5 5...8 8 85 5 5 3 3 3...3 3 37 7 7 CS CS CS CS CS5 5 5 5 5- - - - -1 1 1 1 1 5 5 5 5 5.....8 8 8 8 85 5 5 5 5 3 3 3 3 3.....3 3 3 3 37 7 7 7 7 CS CS CS5 5 5- - -1 1 1 5 5 5...8 8 85 5 5 3 3 3...3 3 37 7 7 CS5-1 5.85 3.37 CS5-1 5.85 3.37 CS CS5 5- -1 1 5 5..8 85 5 3 3..3 37 7 CS5-1 5.85 3.37 CS CS CS5 5 5- - -1 1 1 5 5 5...8 8 85 5 5 3 3 3...3 3 37 7 7 CS CS5 5- -1 1 5 5..8 85 5 3 3..3 37 7 CS5 CS5-1 5.85 3.37 CS CS CS CS CS5 5 5 5 5 CS CS CS5 5 5 CS CS5 5 CS5 CS5-1 5.85 3.37 CS5 CS CS5 5 CS5 CS CS CS CS5 5 5 5 CS5 CS5 CS CS5 5- -2 2 4 4..8 80 0 2 2..2 27 7 CS CS CS CS5 5 5 5- - - -2 2 2 2 4 4 4 4....8 8 8 80 0 0 0 2 2 2 2....2 2 2 27 7 7 7 CS CS CS5 5 5- --2 2 2 4 4 4...8 8 80 0 0 2 2 2...2 2 27 7 7 CS CS5 5- -2 2 4 4..8 80 0 2 2..2 27 7 CS5 CS5-2 4.80 2.27 CS5-2 4.80 2.27 CS CS5 5- -2 2 4 4..8 80 0 2 2..2 27 7 CS5-2 4.80 2.27 CS CS CS CS5 5 5 5- - - -2 2 2 2 4 4 4 4....8 8 8 80 0 0 0 2 2 2 2....2 2 2 27 7 7 7 CS5-2 4.80 2.27 CS5-2 4.80 2.27 CS5-2 4.80 2.27 Earth 2021, 2, FOR PEER REVIEW 9 Earth 2021, 2, FOR PEER REVIEW 9 Ta Table ble 3 3.. S Sed edime imen nt t c ch ha ar ra ac ct ter eris ist tics ics a ac cr ro oss ss v va ar rio ious us c cr ro oss ss se sec ct tio ion ns s (CS (CS) ) in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Mass Ratio of Sediment Mass Ratio of Sediment A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) ( (%, %, S Sa an nd d, , Silt Silt, , Cl Cla ay y) ) CS CS1 1- -1 1 6 6..5 50 0 4 4..1 16 6 CS1-2 6.48 4.14 CS CS1 1 CS1-2 6.48 4.14 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS CS2 2- -1 1 6 6..7 78 8 4 4..5 53 3 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS2-3 5.50 2.98 CS2 CS2-3 5.50 2.98 CS2 CS CS2 2- -4 4 5 5..6 61 1 3 3..1 11 1 CS CS2 2- -5 5 7 7..8 84 4 6 6..0 05 5 CS3-1 6.87 4.65 CS3-1 6.87 4.65 CS CS3 3- -2 2 5 5..4 48 8 2 2..9 96 6 CS CS3 3- -3 3 5 5..6 65 5 3 3..1 15 5 CS CS3 3 CS3-4 3.42 1.16 CS3-4 3.42 1.16 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS CS3 3- -6 6 9 9..3 36 6 8 8..6 65 5 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS4-1 2.49 0.61 CS4-1 2.49 0.61 CS CS4 4- -2 2 6 6..2 28 8 3 3..8 89 9 CS CS4 4- -3 3 2 2..2 28 8 0 0..5 51 1 CS4-4 2.62 0.68 CS4-4 2.62 0.68 CS CS4 4 CS CS4 4- -5 5 3 3..0 00 0 0 0..8 89 9 Earth 2021, 2 433 CS CS4 4- -6 6 6 6..4 48 8 4 4..1 14 4 CS4-7 5.83 3.35 CS4-7 5.83 3.35 Table 3. Cont. Ea Eart rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 10 10 Earth 2021, 2, FOR PEER REVIEW 10 Ea Ea Ea Ea Eart rt rt rt rth h h h h 2 2 2 2 20 0 0 0 02 2 2 2 21 1 1 1 1, , , , , 2 2 2 2 2,,,,, F F F F FO O O O OR R R R R P P P P PE E E E EER ER ER ER ER R R R R REV EV EV EV EVI I I I IEW EW EW EW EW 10 10 10 10 10 Ea Ea rt rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 10 10 Earth 2021, 2, FOR PEER REVIEW 10 Ea rth 2021, 2, FOR PEER REVIEW 10 CS CS4 4- -8 8 2 2..7 71 1 0 0..7 72 2 Area Point Average Diameter (m) Settling Velocity (m/day) Mass Ratio of Sediment (%, Sand, Silt, Clay) CS CS5 5- -1 1 CS5-1 5 5..8 85 5 5.85 3.37 3 3..3 37 7 Mass Ratio of Sediment Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t Ma Ma Mass ss ss R R Ra a at t ti i io o o of of of S S Se e ed d di i im m me e en n nt t t Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t CS CS5 5 Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t Mass Ratio of Sediment A A Ar r re e ea a a P P Poin oin oint t t A A Ave ve ver r ra a age ge ge Di Di Dia a ame me met t te e er r r ( ( (𝛍𝐦𝛍𝐦𝛍𝐦 ) ) ) S S Se e et t tt t tl l li i in n ng g g V V Ve e el l loci oci ocit t ty y y ( ( (m m m/ / /d d day ay ay) ) ) Mass Ratio of Sediment A A Ar r re e ea a a P P Poin oin oint t t A A Ave ve ver r ra a age ge ge Di Di Dia a ame me met t te e er r r ( ( (𝛍𝐦𝛍𝐦 𝛍𝐦 ) ) ) S S Se e et t tt t tl l li i in n ng g g V V Ve e el l loci oci ocit t ty y y ( ( (m m m/ //d d day ay ay) ) ) A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) Area CS CS Poin 5 5- -2 2 t CS5-2Average Di 4 4..a 8 8me 0 0 4.80 ter (𝛍𝐦 ) Settling 2.27 Ve 2 2l..oci 2 27 7 ty (m/day) ( ( (%, %, %, S S Sa a an n nd d d, , , Silt Silt Silt, , , Cl Cl Cla a ay y y) ) ) (%, Sand, Silt, Clay) ( ( ( (%, %, %, %, S S S Sa a a an n n nd d d d, , , , Silt Silt Silt Silt, , , , Cl Cl Cl Cla a a ay y y y) ) ) ) ( (%, %, S Sa an nd d, , Silt Silt, , Cl Cla ay y) ) (%, Sand, Silt, Clay) (%, Sand, Silt, Clay) CS5-3 8.01 6.33 CS5CS CS5 5- -3 3 8 8..0 01 1 6 6..3 33 3 CS5-3 8.01 6.33 CS CS CS5 5 5- - -3 3 3 8 8 8...0 0 01 1 1 6 6 6...3 3 33 3 3 CS CS5 5- -3 3 8 8..0 01 1 6 6..3 33 3 CS CS5 5- -3 3 8 8..0 01 1 6 6..3 33 3 CS5-3 8.01 6.33 CS5-3 8.01 6.33 CS CS CS5 5 5- - -4 4 4 1 1 1...6 6 68 8 8 0 0 0...2 2 28 8 8 CS5-4 1.68 0.28 CS5-4 1.68 0.28 CS CS CS CS5 5 5 5- - - -4 4 4 4 1 1 1 1....6 6 6 68 8 8 8 0 0 0 0....2 2 2 28 8 8 8 CS CS5 5- -4 4 1 1..6 68 8 0 0..2 28 8 CS5-4 1.68 0.28 CS5-4 1.68 0.28 CS5-5 2.02 0.40 CS CS5 5- -5 5 CS5-5 2 2..0 02 2 2.02 0.40 0 0..4 40 0 CS CS CS5 5 5- - -5 5 5 2 2 2...0 0 02 2 2 0 0 0...4 4 40 0 0 CS CS5 5- -5 5 2 2..0 02 2 0 0..4 40 0 CS CS5 5- -5 5 2 2..0 02 2 0 0..4 40 0 CS5-5 2.02 0.40 CS5-5 2.02 0.40 CS CS6 6- -1 1 7 7..3 38 8 5 5..3 37 7 CS6-1 7.38 5.37 CS CS CS6 6 6- - -1 1 1 7 7 7...3 3 38 8 8 5 5 5...3 3 37 7 7 CS CS6 6- -1 1 CS6-1 7 7..3 38 8 7.38 5.37 5 5..3 37 7 CS CS6 6- -1 1 7 7..3 38 8 5 5..3 37 7 CS6-1 7.38 5.37 CS6-1 7.38 5.37 CS6-2 4.19 1.73 CS CS6 6- -2 2 4 4..1 19 9 1 1..7 73 3 CS CS CS6 6 6- - -2 2 2 4 4 4...1 1 19 9 9 1 1 1...7 7 73 3 3 CS CS6 6- -2 2 CS6-2 4 4..1 19 9 4.19 1.73 1 1..7 73 3 CS CS6 6- -2 2 4 4..1 19 9 1 1..7 73 3 CS6-2 4.19 1.73 CS6-2 4.19 1.73 CS6 CS CS6 6 CS CS6 6- -3 3 2 2..1 15 5 0 0..4 46 6 CS CS CS6 6 6 CS6CS6-3 2.15 0.46 CS CS6 6 CS6-3 2.15 0.46 CS CS CS CS6 6 6 6- - - -3 3 3 3 CS6-3 2 2 2 2....1 1 1 15 5 5 5 2.15 0.46 0 0 0 0....4 4 4 46 6 6 6 CS CS6 6 CS CS6 6- -3 3 2 2..1 15 5 0 0..4 46 6 CS6 CS6 CS6-3 2.15 0.46 CS6-3 2.15 0.46 CS CS CS6 6 6- - -4 4 4 3 3 3...9 9 94 4 4 1 1 1...5 5 53 3 3 CS6-4 3.94 1.53 CS CS CS CS6 6 6 6- - - -4 4 4 4 CS6-4 3 3 3 3....9 9 9 94 4 4 4 3.94 1.53 1 1 1 1....5 5 5 53 3 3 3 CS CS6 6- -4 4 3 3..9 94 4 1 1..5 53 3 CS6-4 3.94 1.53 CS6-4 3.94 1.53 CS6-5 3.10 0.95 CS CS6 6- -5 5 3 3..1 10 0 0 0..9 95 5 CS CS CS6 6 6- - -5 5 5 3 3 3...1 1 10 0 0 0 0 0...9 9 95 5 5 CS CS6 6- -5 5 CS6-5 3 3..1 10 0 3.10 0.95 0 0..9 95 5 CS CS6 6- -5 5 3 3..1 10 0 0 0..9 95 5 CS6-5 3.10 0.95 CS6-5 3.10 0.95 CS CS7 7- -1 1 7 7..8 83 3 6 6..0 05 5 CS7-1 7.83 6.05 CS CS CS7 7 7- - -1 1 1 7 7 7...8 8 83 3 3 6 6 6...0 0 05 5 5 CS CS7 7- -1 1 7 7..8 83 3 6 6..0 05 5 CS CS7 7- -1 1 7 7..8 83 3 6 6..0 05 5 CS7-1 7.83 6.05 CS7-1 7.83 6.05 CS7-1 7.83 6.05 CS CS7 7- -2 2 3 3..4 49 9 1 1..2 20 0 CS7-2 3.49 1.20 CS CS CS7 7 7- - -2 2 2 3 3 3...4 4 49 9 9 1 1 1...2 2 20 0 0 CS CS7 7- -2 2 3 3..4 49 9 1 1..2 20 0 CS CS7 7- -2 2 3 3..4 49 9 1 1..2 20 0 CS7-2 3.49 1.20 CS7-2 3.49 1.20 CS7-2 3.49 1.20 CS CS CS7 7 7 CS7 CS CS CS CS7 7 7 7 CS CS7 7 CS7 CS7 CS7 CS CS7 7- -3 3 1 10 0..3 3 1 10 0..4 4 CS7-3 10.3 10.4 CS CS CS7 7 7- - -3 3 3 1 1 10 0 0...3 3 3 1 1 10 0 0...4 4 4 CS CS7 7- -3 3 1 10 0..3 3 1 10 0..4 4 CS CS7 7- -3 3 1 10 0..3 3 1 10 0..4 4 CS7-3 10.3 10.4 CS7-3 10.3 10.4 CS7-3 10.3 10.4 CS7-4 3.31 1.08 CS CS7 7- -4 4 3 3..3 31 1 1 1..0 08 8 CS CS CS7 7 7- - -4 4 4 3 3 3...3 3 31 1 1 1 1 1...0 0 08 8 8 CS CS7 7- -4 4 3 3..3 31 1 1 1..0 08 8 CS CS7 7- -4 4 3 3..3 31 1 1 1..0 08 8 CS7-4 3.31 1.08 CS7-4 CS7-4 3.31 3.31 1.08 1.08 T TSS SS IIIn n nttte e erp rp rpo o ollla a attte e ed d d w w wiiin n nd d d Sp Sp Spe e ee e ed d d TSS Interpolated wind Speed T T TSS SS SS IIIIn n n ntttte e e erp rp rp rpo o o olllla a a atttte e e ed d d d w w w wiiiin n n nd d d d Sp Sp Sp Spe e e ee e e ed d d d T TSS SS T TSS SS IIn ntte erp rpo olla atte ed d w wiin nd d Sp Spe ee ed d Interpolated wind Speed TSS Interpolated wind Speed TSS December 2016 D De ece cemb mbe er r 2 20 01 16 6 3.3. Empirical Relation M M Ma a arch rch rch 2 2 20 0 01 1 17 7 7 D D De e ece ce cemb mb mbe e er r r 2 2 20 0 01 1 16 6 6 D De ece cemb mbe er r 2 20 01 16 6 March 2017 M M M Ma a a arch rch rch rch 2 2 2 20 0 0 01 1 1 17 7 7 7 D De ece cemb mbe er r 2 20 01 16 6 M Ma arch rch 2 20 01 17 7 December 2016 December 2016 March 2017 March 2017 A number of empirical relations were tried for the correlation of TSS with wind speed, water depth, and shear stress (Supplementary File S3), and they can be summarized as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in Table 4. It is evident from Table 4 that a single equation does not fit well to the simulated TSS 2 2 2 across the whole TSL (R = 0.06) or even during dry (R = 0.06) and wet seasons (R = 0.03). 2 2 As the TSL lake is huge and its area and depth vary from <1 m and 5 km to 5 m and 16 km Ju Ju Jun n ne e e 2 2 20 0 01 1 17 7 7 Ju Ju Jun n ne e e 2 2 20 0 01 1 17 7 7 Ju Jun ne e 2 20 01 17 7 Se Sep ptte emb mbe er r 2 20 01 17 7 during the dry and wet seasons, respectively, itSe is p necessary tember 20to 17segregate the lake based on Ju Jun ne e 2 20 01 17 7 Se Se Sep p pttte e emb mb mbe e er r r 2 2 20 0 01 1 17 7 7 June 2017 Se Sep ptte emb mbe er r 2 20 01 17 7 June 2017 Se Sep ptte emb mbe er r 2 20 01 17 7 September 2017 September 2017 cross sections and to propose an empirical relation for each CS, and during each season. The correlation coefficient increased from CS1 to CS7 while moving from the northern to the southern part of the lake, and TSS was better correlated by squared or cubed transformation of wind speed over water depth and power exponent of wind speed (Table 4), which was in agreement with the hypothesis that the higher the wind speed is, the higher is the TSS. In general, the most significant empirical equations for various CS 2 3 3 were the following: CS1 = exp(W /D); CS2 = W or W /D; CS3, CS4, and CS5 = W or 3 3 3 W /D; CS6 = W or exp(W); and CS7 = W /D (Figure 4). Fig Figure ure 3 3.. I In nt ter erpo pola lat ted ed w win ind d sp speed eed a an nd d t to ot ta al l suspen suspende ded d so soli lid ds s (TS (TSS S) ) c co on nc cen ent tr ra at tiio on n a ac cr ro oss ss To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. FigureF 3ig . I n 4t . er Inpo terp lato ed la tw ed in w d in sp deed spe ae nd d a tn ot d a l to suspen tal susp dee d nso deli dd so s (TS lids S) (T co SS) ncen co trn ace tion nt ra actrio on ss a To cro nle ss ST ao p L nlea k Sa e, p Ca Lm ake bo,di Ca a.mb odia FigureF F 3iig g . I 4 4 n.. t er IIn npo tte erp rp lat o o ed lla at tw e ed d in w w d iin n sp d d eed sp spe e a e e n d d d a atn n od d ta tt l o o suspen tta all su susp sp de e ed n nd d so e eli d dd so so s (TS lliid ds s S) (T (T cSS) SS) oncen co co trn n ace ce tion n ntt ra ra acttr iio o on n ss a a To cro cro nss ss le S T T a o o p L n nlle ea Sa Sa ke,p p Ca L La a m ke ke bo ,, di C Ca a a.mb mb o od diia a Fig Fig Fig Figure ure ure ure 3 3 3 3.... I I I In n n nt t t ter er er erpo po po pola la la lat t t ted ed ed ed w w w win in in ind d d d sp sp sp speed eed eed eed a a a an n n nd d d d t t t to o o ot t t ta a a al l l l suspen suspen suspen suspende de de ded d d d so so so soli li li lid d d ds s s s (TS (TS (TS (TSS S S S) ) ) ) c c c co o o on n n nc c c cen en en ent t t tr r r ra a a at t t ti i iio o o on n n n a a a ac c c cr r r ro o o oss ss ss ss To To To Ton n n nle le le le S S S Sa a a ap L p L p L p La a a ak k k ke, e, e, e, Ca Ca Ca Cam m m mb b b bo o o odi di di dia a a a.... F F Fiiig g g 4 4 4... IIIn n nttte e erp rp rpo o ollla a attte e ed d d w w wiiin n nd d d sp sp spe e ee e ed d d a a an n nd d d ttto o ottta a alll su su susp sp spe e en n nd d de e ed d d so so sollliiid d ds s s (T (T (TSS) SS) SS) co co con n nce ce cen n ntttra ra ratttiiio o on n n a a acro cro cross ss ss T T To o on n nllle e e Sa Sa Sap p p L L La a ake ke ke,,, C C Ca a amb mb mbo o od d diiia a a F Fiig g 4 4.. IIn ntte erp rpo olla atte ed d w wiin nd d sp spe ee ed d a an nd d tto otta all su susp spe en nd de ed d so solliid ds s (T (TSS) SS) co con nce cen nttra rattiio on n a acro cross ss T To on nlle e Sa Sap p L La ake ke,, C Ca amb mbo od diia a Fig Figure ure 3 3.. I In nt ter erpo pola lat ted ed w win ind d sp speed eed a an nd d t to ot ta al l suspen suspende ded d so soli lid ds s (TS (TSS S) ) c co on nc cen ent tr ra at ti io on n a ac cr ro oss ss To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. F Fiig g 4 4.. IIn ntte erp rpo olla atte ed d w wiin nd d sp spe ee ed d a an nd d tto otta all su susp spe en nd de ed d so solliid ds s (T (TSS) SS) co con nce cen nttra rattiio on n a acro cross ss T To on nlle e Sa Sap p L La ake ke,, C Ca amb mbo od diia a Figure 3. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia. FigureF 3 ig . I4 n.t er Inpo terp lao ted lat e wd in w d in sp d eed spe a en dd atn od ta tl o suspen tal susp de ed nd so eli dd so s (TS lids S) (T cSS) oncen co trn ace tion nt ra actr io on ss a To cro nss le S T a op L nlea Sa ke,p Ca La m ke bo , di Ca a.mb odia Fig 4. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia 3.3. Empirical Relation 3 3..3 3.. E Em mp pir irica ical l R Re elat lation ion 3 3 3...3 3 3... E E Em m mp p pir ir irica ica ical l l R R Re e elat lat lation ion ion 3 3..3 3.. E Em mp pir irica ical l R Re elat lation ion 3 3..3 3.. E Em mp pir irica ical l R Re elat lation ion 3.3. Empirical Relation 3.3. Empirical Relation A A n num umb ber er o of f empi empiri rica call re rela lati tio on ns s were were tri tried ed f fo or r th the e c co orr rrel ela atio tion n o of f T TS SS S w wiith th wi win nd d A number of empirical relations were tried for the correlation of TSS with wind A A A n n num um umb b ber er er o o of f f empi empi empiri ri rica ca cal ll re re rela la lati ti tio o on n ns s s were were were tri tri tried ed ed f f fo o or r r th th the e e c c co o orr rr rrel el ela a atio tio tion n n o o of f f T T TS S SS S S w w wi iith th th wi wi win n nd d d A A n num umb ber er o of f empi empiri rica cal l re rela lati tio on ns s were were tri tried ed f fo or r th the e c co orr rrel ela atio tion n o of f T TS SS S w wi ith th wi win nd d A A n num umb ber er o of f empi empiri rica cal l re rela lati tio on ns s were were tri tried ed f fo or r th the e c co orr rrel ela atio tion n o of f T TS SS S w wi ith th wi win nd d A number of empirical relations were tried for the correlation of TSS with wind A number of empirical relations were tried for the correlation of TSS with wind spee speed d,, wa water ter d dep epth th,, a an nd d sh shea ear r st stre ress ss ( (S Suppl upplement ementa ary ry F Fiile le 3 3) ),, a an nd d th they ey ca can n b be e su sum mm ma ari riz zed ed speed, water depth, and shear stress (Supplementary File 3), and they can be summarized spee spee speed d d,,, wa wa water ter ter d d dep ep epth th th,,, a a an n nd d d sh sh shea ea ear r r st st stre re ress ss ss ( ( (S S Suppl uppl upplement ement ementa a ary ry ry F F Fi iile le le 3 3 3) ) ),,, a a an n nd d d th th they ey ey ca ca can n n b b be e e su su sum m mm m ma a ari ri riz z zed ed ed spee speed d,, wa water ter d dep epth th,, a an nd d sh shea ear r st stre ress ss ( (S Suppl upplement ementa ary ry F Fi ile le 3 3) ),, a an nd d th they ey ca can n b be e su sum mm ma ari riz zed ed spee speed d,, wa water ter d dep epth th,, a an nd d sh shea ear r st stre ress ss ( (S Suppl upplement ementa ary ry F Fi ile le 3 3) ),, a an nd d th they ey ca can n b be e su sum mm ma ari riz zed ed speed, water depth, and shear stress (Supplementary File 3), and they can be summarized speed, water depth, and shear stress (Supplementary File 3), and they can be summarized a as s a a b best est- -f fiit t cur curv ve e f fo or r th the e wh who olle e lla ake, ke, d dry ry a an nd d wet wet se sea aso son ns, s, a an nd d va vari rio ous us CS CS a as s s sh ho own wn iin n as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in a a a as s s s a a a a b b b best est est est- - - -f f f fi i iit t t t cur cur cur curv v v ve e e e f f f fo o o or r r r th th th the e e e wh wh wh who o o ol l lle e e e l l lla a a ake, ke, ke, ke, d d d dry ry ry ry a a a an n n nd d d d wet wet wet wet se se se sea a a aso so so son n n ns, s, s, s, a a a an n n nd d d d va va va vari ri ri rio o o ous us us us CS CS CS CS a a a as s s s s s s sh h h ho o o own wn wn wn i i iin n n n a as s a a b best est- -f fi it t cur curv ve e f fo or r th the e wh who ol le e l la ake, ke, d dry ry a an nd d wet wet se sea aso son ns, s, a an nd d va vari rio ous us CS CS a as s s sh ho own wn i in n as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in Ta Ta Tab b bl l le e e 4 4 4... Ta Ta Tab b bl lle e e 4 4 4... Ta Tab bl le e 4 4.. Ta Tab bl le e 4 4.. Table 4. Table 4. Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Ta Table ble 4 4.. Empir Empirica ical l r rel ela at tio ion n fo for r TS TSS S in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Ta Ta Table ble ble 4 4 4... Empir Empir Empirica ica ical ll r r rel el ela a at t tio io ion n n fo fo for r r TS TS TSS S S in in in To To Ton n nle le le S S Sa a ap L p L p La a ak k ke, e, e, Ca Ca Cam m mb b bo o odi di dia a a... Ta Table ble 4 4.. Empir Empirica ical l r rel ela at tio ion n fo for r TS TSS S in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Ta Table ble 4 4.. Empir Empirica ical l r rel ela at tio ion n fo for r TS TSS S in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Earth 2021, 2 434 Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Regression Relation R RMSE Whole lake 3 2 TSS = 20.9W /D + 102.8W /D 96.1W /D + 75 0.06 111 (dry + wet season) Wet season TSS = 0.456t + 8 0.03 2.0 wave 3 2 TSS = 0.80W 3.9W + 4.5W + 8 0.02 2.0 Dry season TSS = 459.3W 2244.5W + 2861 0.06 141 Dry season Cross section 1 TSS = 5.6 10  exp(5W /D) + 5 0.96 53 Cross section 2 TSS = 3766.9W + 19242W 23467 0.71 259 3 2 TSS = 143.6W /D + 146W /D + 132.7W /D + 540 0.69 256 3 2 Cross section 3 TSS = 310.3W + 1331.3W 702.7W 1399 0.42 198 3 2 TSS = 1232.4W /D + 6050W /D 7417W /D + 368 0.41 182 Earth 2021, 2, FOR PEER REVIEW 11 3 2 Cross section 4 0.59 159 TSS = 723.0W 2757W + 1128.8W + 3156 3 2 0.59 156 TSS = 2731.3W /D 12498.2W /D + 14129.7W /D + 72 2 3 2 km during the dry and wet seasons, respectively, it is necessary to segregate the lake Cross section 5 TSS = 128.3W /D 617.4W /D + 750.8W /D + 22 0.56 79 based on cross sections and to propose an empirical relation for each CS, and during each TSS = 50.9t + 320 0.58 73 wave season. 3 2 Cross section 6 0.82 175 TSS = 437.4The W co1610.5 rrelatioW n co +e636.1 fficient W + incr 1690 eased from CS1 to CS7 while moving from the north- ern to th e 5southern part of the lake, and TSS was better correlated by squared or cubed TSS = 1.8 10  exp(6.1W) 6 0.81 153 transformation of wind speed over water depth and power exponent of wind speed (Table 3 2 Cross section 7 TSS = 84.2W /D 165.6W /D 144.2W /D + 53 0.88 82 4), which was in agreement with the hypothesis that the higher the wind speed is, the higher is the TSS. In general, the most significant empirical equations for various CS were TSS = 1675.8 exp(0.40t ) 134 0.77 51 wave 2 3 3 3 the following: CS1 = (𝑊 ⁄𝐷 ); CS2 = W or W /D; CS3, CS4, and CS5 = W or W /D; CS6 W = wind speed (m/s), D = water depth (m), t = shear stess (Pa), and TSS = total suspended solids (mg/L). wave ( ) ⁄ = W or 𝑊 ; and CS7 = 𝑊 𝐷 (Figure 4). CS2 CS1 CS2 R : > 0.686 CS5 TSS: R : > 0.563 R : 0.962 CS3 CS7 CS3 and CS4 CS4 R : > 0.774 CS3 – R : >0.412 CS5 CS4 – R : 0.589 CS6 CS6 CS7 R : > 0.813 Figure 4. Empirical relation of TSS with the wind speed and lake depth across various cross sections (CS) in Tonle Sap Figure 4. Empirical relation of TSS with the wind speed and lake depth across various cross sections (CS) in Tonle Sap Lake, Lake, Cambodia (W = wind speed, D = water depth, and 𝜏 = shear stress; for details, please refer to Table 4). 𝑎𝑤𝑣𝑒 Cambodia (W = wind speed, D = water depth, and t = shear stress; for details, please refer to Table 4). wave The TSS concentration across TSL could be better correlated with wind speed, depth, and shear stress with equations as given in Table 4. As the TSS in the dry season was higher than that in the wet season, the TSS is expected to be affected by wind speed, depth, and shear stress. Even though shear stress is a main factor governing sediment re-suspen- sion, wind speed and depth, but not shear stress, were the primary factors governing TSS concentration (Table 4). For better simulation of TSS concentration, other sediment (set- tling velocity, wind flux, and wind wave energy) and environmental factors (wave length and wave height) need to be considered in hydrodynamic models. 3.4. Mechanism of Sediment Re-Suspension The current study was conducted to assess the role of the wind field on sediment re- suspension and the probability of sediment suspension using the wind fetch model. On the other hand, the spatial distribution of wind-induced sediment re-suspension has not been thoroughly described and it is necessary to research for sediment re-suspension pre- dictions in large shallow lakes. The impact of water level fluctuation on the sediment dy- namics in TSL has been described in a recently published paper [42]. Wave action and subsequent fetches are more likely to cause re-suspension by bottom scouring and are 𝑒𝑥𝑝 𝑒𝑥𝑝 Earth 2021, 2 435 The TSS concentration across TSL could be better correlated with wind speed, depth, and shear stress with equations as given in Table 4. As the TSS in the dry season was higher than that in the wet season, the TSS is expected to be affected by wind speed, depth, and shear stress. Even though shear stress is a main factor governing sediment re-suspension, wind speed and depth, but not shear stress, were the primary factors governing TSS concentration (Table 4). For better simulation of TSS concentration, other sediment (settling velocity, wind flux, and wind wave energy) and environmental factors (wave length and wave height) need to be considered in hydrodynamic models. 3.4. Mechanism of Sediment Re-Suspension The current study was conducted to assess the role of the wind field on sediment re- suspension and the probability of sediment suspension using the wind fetch model. On the other hand, the spatial distribution of wind-induced sediment re-suspension has not been thoroughly described and it is necessary to research for sediment re-suspension predictions in large shallow lakes. The impact of water level fluctuation on the sediment dynamics in TSL has been described in a recently published paper [42]. Wave action and subsequent fetches are more likely to cause re-suspension by bottom scouring and are determined by wind speed and fetch [43]. The total shear stress (Pa) as a sum of wind-induced waves and wind-induced currents, and critical shear stress for CS from 1 to 7, for different time periods, December, March, and June, are shown in Supplementary File S3. Critical shear stress at most of the places was higher than the total shear stress (Supplementary File S3), indicating three important points: (i) there was sedimentation (no erosion) of the sediment at most of the CS during the transition period of reversal flow from TSL to MR via TSR in December (end of the rainy season) and from MR to TSL in June (beginning of the rainy season); (ii) most of the sediment that was discharged at various CS in TSL is retained (i.e., no outflow) within the lake; and (iii) whatever erosion of the sediment occurred in TSL, it was predominant in the southern part of the lake at CS5, 6, and 7. Wind-induced wave shear stress was larger than the wind-induced current shear stress, though the latter was negligible. It can be presumed that shear stress could not be said to be the cause of sediment re-suspension as the total shear stress was mostly lesser than the critical shear stress. The shear stress due to wind-induced waves did not vary at different CS of the lake. In general, the shear stress due to waves is smaller at the center of the lake than at the shore. Shear stress increased toward the shoreline of the lake, perhaps due to transfer of wind energy at the shoreline, as when wind moves from land to middle of the lake, wind energy is much smaller at the middle of the lake where there is much water. This phenomenon could explain why the turbidity at the bank is higher than that at the center of the lake. The higher turbidity at the bank is caused by the shallow water and wave breaking. In this case, it is believed that wind energy is one of the crucial factors governing sediment resuspension, as the energy from the wind near the shoreline is naturally stored and is utilized for sediment re-suspension. The selected sites, where the total shear stress was greater than the critical shear stress, were then taken for the comparison of shear stress with TSS (Table 5). As shown in Table 5 and Figure 5, TSS decreases with the increase in water depth (R = 0.57). Considering that most of the time when the total shear stress was greater than the critical shear stress was in March, which is the middle of the dry season, it can be generalized that the shallower the water depth is, the higher is the total shear stress. The total shear stress increased toward the southern part of TSL. Sediment re-suspension occurred in all seasons in CS7-4, which is located at the southernmost point. Around the south side of TSL, the MR, one of the largest tributaries of TSL, is located nearby, and the inflow of water and sediment from this river has a higher value than that of other tributaries. It can be inferred that sediment re-suspension is likely to occur in places with higher amounts of sediment. Earth 2021, 2 436 Table 5. Comparison of TSS, water depth, total shear stress, and critical shear stress across selected sites. TSS Water Depth Total Shear Critical Shear Date Point (mg/L) (m) Stress (Pa) Stress (Pa) 21 December 2016 CS7-4 6 8.0 2.93 1.63 30 March 2017 CS5-2 158 0.3 5.85 2.36 Earth 2021, 2, FOR PEER REVIEW 13 15 March 2017 CS5-4 55 0.5 3.30 3.94 16 March 2017 CS5-4 137 1.6 2.53 0.83 26 March 2017 CS5-5 140 0.6 2.26 0.83 15 March CS6-5 72 0.8 1.76 1.52 15 March 2017 CS6-2 189 1.3 3.06 2.06 15 15 Ma Mar rchch 2017 CS6-5 72 0.8 1.76 1.52 CS7-1 279 0.5 5.81 3.85 15 March 2017 CS7-1 279 0.5 5.81 3.85 15 March 15 March 2017 CS7-4 289 1.0 3.25 1.63 CS7-4 289 1.0 3.25 1.63 2 July 2017 CS7-4 25 5.5 2.66 1.63 2 July 2017 CS7-4 25 5.5 2.66 1.63 -0.661 y = 21.742x R² = 0.5691 0 50 100 150 200 250 300 TSS (mg/L) Figure 5. Relationship of TSS with water depth (data source Table 5). Figure 5. Relationship of TSS with water depth (data source Table 5). In addition, there was spatio-temporal variation in the relationship between TSS and In addition, there was spatio-temporal variation in the relationship between TSS and each environmental parameter (Supplementary File S4). In general, there was a negative each environmental parameter (Supplementary File 4). In general, there was a negative correlation among TSS, settling velocity, and critical shear stress. In other words, the lower correlation among TSS, settling velocity, and critical shear stress. In other words, the lower the settling velocity was, the lower the critical shear stress and the higher the TSS. Loss the settling velocity was, the lower the critical shear stress and the higher the TSS. Loss on on ignition (LOI at 550 C) was higher during the dry season compared to that during the ignition (LOI at 550 °C) was higher during the dry season compared to that during the wet season, which meant that the amount of organic matter changed according to season wet season, which meant that the amount of organic matter changed according to season and that it varied greatly depending on the location. As TSL is huge, it is recommended to and that it varied greatly depending on the location. As TSL is huge, it is recommended perform clustering of the lake according to the site for detailed characterization of the TSS to perform clustering of the lake according to the site for detailed characterization of the and to understand the impact of the wind on sediment re-suspension. TSS and to understand the impact of the wind on sediment re-suspension. 3.5. Time to Reach Equilibrium TSS 3.5. Time to Reach Equilibrium TSS The time to reach equilibrium TSS in March, June, and December is shown in Table 6. The time to reach equilibrium TSS in March, June, and December is shown in Table There was a significant difference in time to reach equilibrium TSS: 9, 20, and 32 days in 6. There was a significant difference in time to reach equilibrium TSS: 9, 20, and 32 days March, June, and December, respectively, corresponding to average depths of 1.2, 2.7, and in March, June, and December, respectively, corresponding to average depths of 1.2, 2.7, 4.7 m (Table 6). The higher the depth is, the higher is the time to reach equilibrium TSS. In and 4.7 m (Table 6). The higher the depth is, the higher is the time to reach equilibrium addition, time for equilibrium differed, and there were no significant differences in settling TSS. In addition, time for equilibrium differed, and there were no significant differences in settling velocity and wind speed in each month. It can be interpreted that there is an impact of the wind and other sediment and environmental factors in governing sediment re-suspension. Table 6. Calculation of time to reach equilibrium TSS in Tonle Sap Lake, Cambodia. March (2017) June (2017) December (2016) 𝛼𝑊 Max ( ) 433 684 15.5 Observed TSS ( ) Min (𝑆 0 ) 4.5 12 4.3 (mg/L) Ave 176.8 157.4 4.8 Water depth (m) Earth 2021, 2 437 velocity and wind speed in each month. It can be interpreted that there is an impact of the wind and other sediment and environmental factors in governing sediment re-suspension. Table 6. Calculation of time to reach equilibrium TSS in Tonle Sap Lake, Cambodia. March (2017) June (2017) December (2016) aW 433 684 15.5 Max Observed TSS Min (S(0)) 4.5 12 4.3 (mg/L) Ave 176.8 157.4 4.8 Average wind speed (m/s) (W) 2.3 2.5 2.4 Average water depth (m) (D) 1.2 2.8 4.7 Average settling velocity (m/day) (b) 3.2 3.3 3.3 Time for equilibrium TSS (day) 9 20 32 The parameters in Table 6 are based on Equation (11): p p aW aW (bt/D) S = + S(0) e , (11) b b aW where = is considered the maximum TSS and background TSS (= S(0)) is con- sidered the minimum TSS in the whole TSL and in each point (CS1–CS7). The monthly average settling velocity (b) and water depth (D) were used for the calculation of suspended sediment concentration (S). 4. Conclusions In March, the wind direction is mainly southward and changes toward the southeast or southwest depending on the locations. In general, the wind speed in December and March was less than 5 m/s, but in June and September, the wind speed was as much 7 m/s. On the basis of the weighted Pearson correlation coefficient (r) and RMSE, wind interpolation using the IDW method was found to be comparatively better than the vectorized average and inverse of the ratio of distance. The TSS concentration, in general, during the wet season in December and September was less than 50 mg/L, but during the dry season in March and June, it was greater than 50 mg/L and peaked up to 400 mg/L in March and greater than 600 mg/L in June. The sediment characteristics with respect to sand, silt, and clay did not differ much across various CS in TSL. Settling velocity (m/day) across 37 sites across TSL varied from 0.28 to 11.70, with an average of 3.25  2.75. TSS did not exhibit direct correlation with the settling velocity and sediment character- istics (LOI and particle diameter). The empirical equation to correlate TSS with wind speed (W), water depth (D), and shear stress (t_wave), especially during dry season (W/D) 2 3 3 for different CS across TSL is, CS1= exp ; CS2= W or W /D; CS3, and CS4 = W 3 3 3 (W) 3 (t_wave) or W /D; CS5 = W /D or t_wave; CS6 = W or exp ; and CS7 = W /D or exp (for detailed equation, please refer to Table 4). The shear stress due to waves was smaller at the center of the lake and increased toward the shoreline, which is one of the reasons why TSL exhibits higher TSS at the shoreline than at the center of the lake. The total shear stress was greater than the critical shear stress, especially during the dry season in March, when TSS is higher and water depth is lower, compared to the wet season, when TSS is low and water depth is higher. The higher wind-induced critical shear stress than the total shear stress at most of the CS in TSL indicated sedimentation occurs predominantly during the transition phase Earth 2021, 2 438 of the reversal flow between TSL and MR during December and June, and erosion (siltation) is dominant during March. Additionally, most of the siltation in March was dominant in the southern part of the lake, at CS5, 6, and 7. The times to reach equilibrium TSS in March, June, and December were 9, 20, and 32 days, respectively. In general, the higher the depth is, the longer the time to reach equilibrium TSS. Supplementary Materials: The following are available online at https://www.mdpi.com/article/10 .3390/earth2030025/s1, Supplementary File S1: wind interpolation; Supplementary File S2: Empirical relation; Supplementary File S3: mechanism; Supplementary File S4: Relationship of TSS with wind speed, water depth, settling velocity, and loss on ignition across Tonle Sap Lake, Cambodia. Author Contributions: Conceptualization, M.S., R.K., S.U., S.S., C.Y.; methodology, M.S., R.K., T.S., C.Y.; software, M.S., S.S.; validation, M.S., S.S., R.K., C.Y.; formal analysis, M.S.; investigation, M.S.; resources, R.K., C.Y., data curation, M.S., S.U., S.S., writing—original draft preparation, R.K.; writing— review and editing, R.K., C.Y.; visualization, M.S., R.K.; supervision, S.S., S.U., R.K., C.Y.; project administration, R.K., C.Y.; funding acquisition, C.Y. All authors have read and agreed to the published version of the manuscript. Funding: This is one of the outcomes from Science and Technology Research Partnership for Sus- tainable Development (SATREPS—JST/JICA: grant-number JPMJSA1503) Project in Cambodia— Establishment of Environmental Conservation Platform of Tonle Sap Lake. Data Availability Statement: All relevant data are reported in this paper. Acknowledgments: Science and Technology Research Partnership for Sustainable Development (SATREPS—JST/JICA: grant-number JPMJSA1503) Project in Cambodia—Establishment of Environ- mental Conservation Platform of Tonle Sap Lake. Acknowledgments also go to the project members involved in sampling, especially Oeurng Chantha (Institute of Technology of Cambodia) and his team, and Thea Sive (Satreps—JICA). Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. References 1. Hawley, N.; Lesht, B. Sediment resuspension in Lake St. Clair. Limnol. Oceanogr. 1992, 37, 1720–1737. [CrossRef] 2. Vlag, D.P. A model for predicting waves and suspended silt concentration in a shallow lake. Hydrobiologia 1992, 235, 119–131. [CrossRef] 3. Barica, J. 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Shear stress and sediment resuspension in relation to submersed macrophyte biomass. Hydrobiologia 2004, 515, 181–191. [CrossRef] 41. Parker, G.; Toro-Escobar, C.M.; Ramey, M.; Beck, S. Effect of floodwater extraction on mountain stream morphology. J. Hydraul. Eng. 2003, 129, 885–895. [CrossRef] 42. Khanal, R.; Uk, S.; Kodikara, D.; Siev, S.; Yoshimura, C. Impact of water level fluctuation on sediment and phosphorous dynamics in Tonle Sap Lake, Cambodia. Water Air Soil Pollut. 2021, 232, 1–15. [CrossRef] 43. Gloor, M.; Wüest, A.; Münnich, M. Benthic boundary mixing and resuspension induced by internal seiches. Hydrobiologia 1994, 284, 59–68. [CrossRef] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Earth Multidisciplinary Digital Publishing Institute

Impact of Wind on the Spatio-Temporal Variation in Concentration of Suspended Solids in Tonle Sap Lake, Cambodia

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Article Impact of Wind on the Spatio-Temporal Variation in Concentration of Suspended Solids in Tonle Sap Lake, Cambodia 1 1 , 2 , 1 3 , 4 5 1 Michitaka Sato , Rajendra Khanal *, Sovannara Uk , Sokly Siev , Ty Sok and Chihiro Yoshimura Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, 2-12-1-M1-4, Ookayama, Meguro-ku, Tokyo 152-8552, Japan; tokodai88@gmail.com (M.S.); uk.s.ab@m.titech.ac.jp (S.U.); yoshimura.c.aa@m.titech.ac.jp (C.Y.) Policy Research Institute, A Think-Tank of the Government of Nepal, 3rd Floor of Federal Secretariat Construction and Management Building, Sano Gaucharan-5, Kathmandu 44600, Nepal General Department of Science, Technology & Innovation, Ministry of Industry, Science, Technology & Innovation, Preah Norodom Boulevard, Sangkat Phsar Thmey III, Khan Daun Penh, Phnom Penh 120203, Cambodia; siev.sokly@misti.gov.kh Research and Innovation Center, Institute of Technology of Cambodia, Phnom Penh 12000, Cambodia Faculty of Hydrology and Water Resources Engineering, Institute of Technology of Cambodia, Russian Federation Blvd., P.O. Box 86, Phnom Penh 12156, Cambodia; sokty@itc.edu.kh * Correspondence: rajendra.khanal@gmail.com Abstract: Even though wind, water depth, and shear stress are important factors governing sediment resuspension in lakes, their actual relations to total suspended solids (TSS) distribution in natural environments have not been well elucidated. This study aims to elucidate the impact of the wind on the spatio-temporal variation of TSS in Tonle Sap Lake, Cambodia, during low-water (March and June, <1 m) and high-water (September and December, 8–10 m) seasons. To this end, wind and TSS data Citation: Sato, M.; Khanal, R.; Uk, S.; for December 2016 and March, June, and September 2017 were collected and analyzed. For spatial Siev, S.; Sok, T.; Yoshimura, C. Impact interpolation of wind speed, the inverse distance weighted method was found to be better (R = 0.49) of Wind on the Spatio-Temporal 2 2 than the vectorized average (R = 0.30) and inverse of the ratio of distance (R = 0.31). Spatial Variation in Concentration of interpolation showed that the wind speed and direction on the lake were <5 m/s and southward Suspended Solids in Tonle Sap Lake, during the low-water season and <7 m/s and westward during the high-water season. The TSS Cambodia. Earth 2021, 2, 424–439. concentration in the low-water season was higher (>50 mg/L) than that in the high-water season. https://doi.org/10.3390/earth2030025 The TSS concentration during the low-water season was empirically described by wind speed (W), 3 3 (W/D) (t_wave) Academic Editors: water depth (D), and shear stress (t_wave) with a function of W , W /D, and exp or exp , Christopher Gomez, Junun Sartohadi depending on the location in the lake. The critical shear stress due to wind-induced waves at most of and Frans Persendt the places in the lake was higher than the total shear stress indicated. Sedimentation was predominant in December and June, and erosion (siltation) was dominant in March. Most of the siltation in March Received: 27 March 2021 was dominant in the southern part of the lake. Accepted: 30 June 2021 Published: 6 July 2021 Keywords: wind speed and direction; spatio-temporal; total suspended solids; interpolation; shear stress; Tonle Sap Lake Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Sediment re-suspension occurs because of the advection and diffusion of sediments into water columns by wind events when bottom shear stresses are enough to entrain materials from the lake bed [1,2]. Sediment resuspension takes from hours to days to reach Copyright: © 2021 by the authors. equilibrium condition, when total suspended solids (TSS) are uniformly distributed in Licensee MDPI, Basel, Switzerland. lakes [3–9]. The basic physical processes and dominant factors in cohesive sediment trans- This article is an open access article port in shallow lakes are flocculation, deposition, siltation, and environmental parameters distributed under the terms and (e.g., wind speed, water depth, and vegetation type) [1,10,11]. conditions of the Creative Commons A number of studies that have analyzed the impact of habitat structure, land use Attribution (CC BY) license (https:// land cover, hydrodynamic properties, and sediment and organic matter characteristics on creativecommons.org/licenses/by/ sediment resuspension are available [12–14]. The relationship of wind-induced sediment 4.0/). Earth 2021, 2, 424–439. https://doi.org/10.3390/earth2030025 https://www.mdpi.com/journal/earth Earth 2021, 2 425 resuspension between wind and shear stress based on TSS simulation from force derived by shear stress in the water bottom had been developed using a highly dimensional hydrodynamic model [11,15–18]. However, the spatial distribution of wind-induced re- suspension and simplified empirical equations based on meteorological and environmental factors to elucidate the interaction of the wind with TSS simulations have not been assessed in detail. A pragmatic approach that can describe the relationship of wind waves and total suspended sediment concentrations is to use relatively simple empirical formulas that can utilize wavelength as a function of wind velocity and fetch, and re-suspension occurs if the total shear stress is greater than the critical shear stress, which is considered the case if the wavelength exceeds twice the water depth. The basic processes involved in cohesive sediment transport, such as flocculation, deposition, and erosion, have been studied by many scientists [10].. Carper and Bachmann (1984) [19] and Scheffer (2004) [5] showed that an empirical approach works well to describe re-suspension in a shallow lake. In addition, models based on the nonlinear shallow water equation for coastal engineering have been widely used to quantify wind and several physical wave characteristics, including wave height, length, peak period, maximum orbital velocity, and shear stress [20,21]. Håkanson and Bryhn (2008) [22] reviewed the mechanisms of wave development, which can be calculated on the basis of the bottom current velocity (computed from water depth, wave height, wave length, and wave period). Resuspension occurs when deep-water waves enter water shallower than one-half of the wavelength. The extent of re-suspension is also a function of the energy imparted to the system by wind waves and lake bathymetry. At low wind speed, no resuspension occurs as the critical fetch is larger than the maximum fetch in a lake. Above a critical wind speed, the re-suspended fraction of a lake rises with increasing wind. Due to the sharp decrease in re-suspension with water depth, a change in water level can affect wind-induced re-suspension. Siev et al. (2018) [23] investigated sediment dynamics in Tonle Sap Lake (TSL) and observed simulated TSS concentration to fit well with the observed TSS concentration during flooding. However, during other periods, such as during dry and wet seasons when water depth and wind speed varies a lot, TSS concentration was underestimated, probably because of the lack of understanding of the influence of wind on the spatio- temporal variation of TSS. The transfer of energy from wind that leads to a variation of TSS concentration is dependent on the spatio-temporal variation of metrological parameters, especially wind speed, and the physical properties of the sediment, such as particle size, shear stress, and time to reach equilibrium [24]. The simultaneous action of wind-induced currents and surface waves leads to an increase in the bottom shear stress, which may exceed the critical shear stress and cause re-suspension [1,25]. The occurrence of shear stress in the water column is divided into two parts, namely, currents and waves. Surface waves have a more pronounced contribution to re-suspended sediments than the currents [11,26–29]. Current-induced shear stress is dominant in open channels and rivers, whereas in lakes and ponds, wave-induced shear stress contributes to sediment resuspension [26,30–32]. In general, wave-induced shear stress contributes as much as 70% of the total re-suspension in shallow lakes [33]. The general objective of this study is to elucidate the impact of the wind on the spatio- temporal variation in concentration of suspended solids in TSL. The specific objectives include (i) finding a proper method for spatial interpolation of the wind and (ii) elucidating the relationship of sediment re-suspension to wind, sediment characteristics, and other environment variables for TSS estimation. 2. Materials and Methods 2.1. Study Area TSL, one of the largest freshwater lakes with unique reversal hydrodynamics flowing between Mekong River (MR) and Tonle Sap River (TSR), is of utmost importance for economic, livelihood, culture, and recreation not only in Cambodia but also in lower Mekong Basin. There are two distinct seasons in Cambodia, namely, wet and dry. As a Earth 2021, 2, FOR PEER REVIEW 3 2. Materials and Methods 2.1. Study Area TSL, one of the largest freshwater lakes with unique reversal hydrodynamics flowing Earth 2021, 2 between Mekong River (MR) and Tonle Sap River (TSR), is of utmost importance for eco 426 - nomic, livelihood, culture, and recreation not only in Cambodia but also in lower Mekong Basin. There are two distinct seasons in Cambodia, namely, wet and dry. As a result, TSL has distinct features during the dry and wet seasons. The area, length, width, and depth result, TSL has distinct features during the dry and wet seasons. The area, length, width, of TSL vary from 2.5k to 15k km , 120 to 250 km, 3 to 100 km, and <1 to as much as 10 m and depth of TSL vary from 2.5k to 15k km , 120 to 250 km, 3 to 100 km, and <1 to as much during dry and wet seasons, respectively. The average outflow from TSL to TSR during as 10 m during dry and wet seasons, respectively. The average outflow from TSL to TSR the dry season and inflow from MR to TSL during the wet season vary from 380 to 8200 during the dry season and inflow from MR to TSL during the wet season vary from 380 to 3 3 m /s and from 100 to 7000 m /s, respectively. During the wet season, there is a huge influx 3 3 8200 m /s and from 100 to 7000 m /s, respectively. During the wet season, there is a huge of sediment discharge from MR to TSL, and in one of the studies, as much as 80% of sed- influx of sediment discharge from MR to TSL, and in one of the studies, as much as 80% of iment influx from the Mekong Basin has been found to be retained by TSL [23,34–35]. The sediment influx from the Mekong Basin has been found to be retained by TSL [23,34,35]. TSS concentrations during dry and wet seasons vary from 4 to 650 mg/L and from 3 to 125 The TSS concentrations during dry and wet seasons vary from 4 to 650 mg/L and from 3 to mg/L, respectively (reference: TSL fact sheet in [36]). TSL is always under the influence of 125 mg/L, respectively (reference: TSL fact sheet in [36]). TSL is always under the influence the wind. The average and maximum wind speeds during dry and wet seasons vary from of the wind. The average and maximum wind speeds during dry and wet seasons vary 3–4 to 6.2–8.8 m/s and from 2–3 to 12.3 m/s, respectively. from 3–4 to 6.2–8.8 m/s and from 2–3 to 12.3 m/s, respectively. Sedimentation across TSL during the dry season varies from 0.1 to 0.16 mm/year [37]. Sedimentation across TSL during the dry season varies from 0.1 to 0.16 mm/year [37]. The sedimentation rate during dry and wet seasons varies in the range 306.7 ± 369.6 to The sedimentation rate during dry and wet seasons varies in the range 306.7  369.6 to 194.4 ± 43.3 g⁄m ⁄day [23]. During the dry season, when the lake is very shallow (<1 m), 194.4  43.3 g/m /day [23]. During the dry season, when the lake is very shallow (<1 m), there is active re-suspension of the sediment in the lake [34]. The sediment of TSL and the there is active re-suspension of the sediment in the lake [34]. The sediment of TSL and floodplain mainly composed of silt (4–63 μm) and clay (<4 μm), which is favorable for re- the floodplain mainly composed of silt (4–63 m) and clay (<4 m), which is favorable for suspension [23]. The map of the study area, sampling sites for wind speed, and TSS col- re-suspension [23]. The map of the study area, sampling sites for wind speed, and TSS lection cross section (CS) point are shown in Figure 1. collection cross section (CS) point are shown in Figure 1. b) a) CS = cross section of the lake TSS sampling cross section Wind observation site Wind interpolated site TSS sampling site Fig 1. Study area, and sampling site across Tonle Sap Lake, Cambodia Figure 1. (a) Study area and (b) cross sections (CS) of Tonle Sap Lake, Cambodia, for the sampling of total suspended Figure 1. (a) Study area and (b) cross sections (CS) of Tonle Sap Lake, Cambodia, for the sampling of total suspended solids. solids. 2.2. Data Preparation 2.2. Data Preparation Wind data were obtained from the Natural Climatic Data Center from 1949 to 2019 at Wind data were obtained from the Natural Climatic Data Center from 1949 to 2019 12 stations in Cambodia. However, because many wind datapoints were missing and none at 12 stations in Cambodia. However, because many wind datapoints were missing and covered wind across TSL, it was necessary to sort the wind data and to use interpolation none covered wind across TSL, it was necessary to sort the wind data and to use interpo- to find wind characteristics at a particular location in TSL. Before interpolation, it is a lation to find wind characteristics at a particular location in TSL. Before interpolation, it is prerequisite to characterize the data. Wind data were interpolated by three methods: a prerequisite to characterize the data. Wind data were interpolated by three methods: (i) (i) inverse distance weighted (IDW) in ArcGIS; (ii) vectorized average; and (iii) inverse inverse distance weighted (IDW) in ArcGIS; (ii) vectorized average; and (iii) inverse of of ratio of distance. The interpolated data were selected by best-fit Pearson correlation coefficient (r) and root mean square error (RMSE) among those three methods (Table 1). A detail methodology for interpolation is given in Supplementary File S1. Earth 2021, 2 427 Table 1. Pearson correlation coefficient (r) and RMSE of interpolation for wind data. IDW Pursat Battam Bang Average Year 2008 2009 2010 2010 Evaluation Value r RMSE r RMSE r RMSE r RMSE r RMSE (1) Speed IDW 0.75 0.68 0.57 0.70 0.31 1.19 0.32 0.70 0.49 0.81 Vectorized average 0.78 1.11 0.36 1.26 0.20 1.96 0.14 0.84 0.30 1.29 Inverse of ratio 0.55 0.91 0.17 0.98 0.56 1.65 0.05 0.96 0.31 1.13 (2) Direction IDW 0.35 122 0.11 162 0.60 255 0.19 163 0.01 176 Vectorized average 0.31 56 0.34 176 0.58 192 0.12 83 0.01 127 Inverse of ratio 0.24 142 0.27 145 0.12 284 0.43 177 0.05 187 (3) Direction + Speed (Inner product) IDW 0.02 0.28 0.14 0.07 0.02 0.02 Vectorized average 0.06 0.05 0.00 0.24 0.03 0.06 Inverse of ratio 0.45 0.07 0.66 0.40 0.03 0.45 (4) Direction + Speed (Polar coordinates) r x y x y x y x y x y IDW 0.32 0.63 0.25 0.01 0.55 0.24 0.54 0.62 0.14 0.25 Vectorized average 0.64 0.61 0.55 0.40 0.04 0.30 0.23 0.22 0.36 0.23 Inverse of ratio 0.89 0.33 0.42 0.90 0.49 0.24 0.48 0.37 0.36 0.11 RMSE x y x y x y x y x y IDW 1.21 3.38 2.37 3.30 0.57 3.48 1.39 4.02 1.39 3.55 Vectorized average 1.19 1.30 2.92 1.92 0.55 1.05 1.53 1.56 1.55 1.46 Inverse of ratio 1.32 3.11 1.37 2.85 1.32 3.13 0.26 3.80 1.07 3.22 As the speed calculation direction of the wind is also important, vectorized speed should be taken for the average calculation. Wind data were characterized across each CS (CS 1 to 7; Figure 1). Characterization of wind data was conducted using a wind rose diagram, which shows the speed and direction of the wind at a location for a specified time interval. The graphical wind data were then sorted by wind speed and direction such that the distance covered by wind per unit time could be calculated. The wind rose diagrams from December 2016 and March, June, September, and December 2017 at three locations, namely, Khlong Yai, Siem Reap, and Phnom Penh, are shown in Supplementary File S1. Data sorted from the wind rose were then taken for the interpolation of the wind at various locations. For wind speed, the value of r from the IDW method in Pursat for 2008 and 2009 was greater than or equal to 0.57, and for 2010, r from the inverse of ratio method was 0.56 (Table 1). Depending on the year and site, the r and RMSE values were different. No specific interpolation methods could be said to be the ideal method, but IDW could be said to be comparatively better than the vectorized average and inverse of ratio method as the average r from IDW (0.49) was comparatively greater than that from vectorized average (0.30) and inverse of ratio (0.31). However, wind direction should also be considered while interpolating wind speed. Interpolation of wind speed was conducted using two methods, namely, inner product and polar coordinates. In inner product, each value of wind speed and direction was expressed as one vector, and the product of observed and interpolated Earth 2021, 2 428 wind data was taken as the inner product, the cosine value of which gave the Pearson correlation coefficient. In the polar coordinate method, polar coordinates were obtained by converting from linear coordinates to polar coordinates and by taking the average. The weighted r and RMSE for wind speed and direction from the IDW method can be said to be comparatively better than those from the other two methods, consistent with an earlier finding [38]. Hence, interpolation of wind speed by IDW was applied for TSS simulation. 2.3. TSS and Other Environmental Variables The TSS data are the same as those reported earlier [23], and were collected during September 2016 to June 2017. Besides TSS, other environmental variables were also an- alyzed, namely, particle size distribution of suspended sediments, average diameter of sediment particles, settling velocity, air and water temperature, precipitation, and wa- ter depth. The average diameter of sediment particles was calculated by the mass ratio of sedi- ment and settling velocities as governed by Stokes’ law as shown in Equation (1): D (r r )g s 0 s50 b = , (1) 18h where b is the settling velocity (m/s), r , r are the densities of the sediment and fluid s 0 3 2 (g/cm ), g is gravity acceleration (m/s ), and h is fluid viscosity (g/cm/s). Settling velocity varied spatially but not temporally. 2.4. Empirical Relationships Empirical relationships between wind and TSS were derived using observed TSS, inter- polated wind speed, and other environmental parameters (i.e., water level and shear stress). The method of derivation is nonlinear regression analysis using the least squares method, and accuracy of the derivation is compared by correlation coefficient under three conditions: (i) the whole area of TSL, (ii) season variation, and (iii) a specific CS in a lake. Empirical analysis is based on the assumption that sediment suspension occurs under steady-state conditions. The details of the empirical calculation are given in Supplementary File S2. 2.5. Mechanism Elucidation of Wind-Induced Sediment Re-Suspension In order to estimate the balance of the total shear stress (wind-induced waves and currents) and critical shear stress on sediment re-suspension and to analyze the fluctuation of TSS throughout the lake, wind-induced sediment re-suspension was evaluated using two methods: (i) shear stress analysis and (ii) assessment of re-suspension rate. The details of the mathematical calculation of these two methods are given in Supplementary File S3. Shear stress can be calculated by the following equation: 0.5 2p r v t = H , (2) wave 2pD 2sinh where t is the shear stress by wind-induced waves (Pa), r is water density, v is the wave 0 kinematic viscosity of water (cm /s), H is wave height (cm), T is wave period (s), D is water depth (cm), and L is wave length (cm). Wave period and length can be calculated using the different equations of Bretschneider methods [39]. Waves are considered long waves and deep-water waves during dry and wet seasons, respectively. The magnitudes of bottom shear stresses due to current (t ) and wind-induced curr shear stress at the surface of the lake (t ) are estimated using a quadratic drag law, as given in Equation (3): jt j = 0.1t = 0.1C r W , (3) curr 0 D a Earth 2021, 2 429 where r denotes the density of air and C denotes the drag coefficient a D C = 0.001(0.75 + 0.067W). (4) Shear stress due to currents in large shallow lakes such as TSL is significantly smaller than the shear stress due to waves [40]. Hence, it is necessary to balance the critical shear stresses (t ) cr t = t rRgD , (5) cr c s50 where R = r r/r (the submerged specific gravity), r is the sediment density, D s s s50 denotes the sediment grain size, and g is the acceleration due to gravity. The critical (nondi- mensional) Shield’s parameter t can be obtained by curve fittings to the experimental dataset for incipient motion developed by [41]: h i 0.6 (7.7R ) 0.6 ep t = 0.5 0.22Re + 0.06 10 , (6) c p where Re = gRD D /h , with h denoting the kinematic viscosity of water. p s50 s50 0 0 Re-suspension rate was calculated by following Equation (7): dS 1 (7) = (bS + E), dt D where S is the depth-averaged suspended sediment concentration mgm , D is the depth of the water column (m), b is the settling velocity ms , and E is the erosion rate 3 1 mgm s . Additionally, E = aW , (8) where a and p are empirical constants and W is the wind speed . Putting the value of E in Equation (8) and differentiating yield the value of S as given in Equation (9) under steady-state conditions and Equation (10) under unsteady- state conditions. p p dS 1 aW aW p (bt/D) = (bS + aW ),S = + S(0) e , (9) dt D b b dS U H b = f exp = f exp K  W , 0 0 dt PE D (10) S = f exp K  W t + S(0). In addition, to understand re-suspension dynamics, it is required to identify the time required to reach equilibrium TSS. This equilibrium time was compared for three months aW December, March, and June. In addition, convergence of TSS = was considered the maximum TSS and background TSS (= S(0)) was considered the minimum TSS in the whole TSL and in each point (CS1–CS7). The monthly average settling velocity (b) and water depth (D) were used for the calculation of suspended sediment concentration (S). 3. Results and Discussion 3.1. Characterization of Wind Data The comparison of the wind speed and direction observed at Khlong Yai, Siem Reap, and Phnom Penh from December 2016 to December 2017 is shown in Figure 2 and Table 1. In March, the wind direction is mainly southward and changes toward the southeast or southwest depending on the locations (see the wind rose diagram in Supplementary File S1 and Table 2). The difference in wind speed is probably due to difference in altitude. Khlong Yai is at a lower altitude of 6 m compared to Siem Reap at 8 m and Phnom Penh at 12 m. The wind speed in December and March was, in general, less than 5 m/s, but in June and September, the wind speed was as much 7 m/s (Table 2). Earth 2021, 2 430 3.2. Interpolation of Wind Data The interpolated wind speeds at various CS across TSL and observed TSS are shown in Figure 3. The TSS concentration, in general, during the wet season in December and September was less than 50 mg/L, but during the dry season in March and June, it was greater than 50 mg/L and peaked up to 400 mg/L in March and was greater than 600 mg/L in June (Figure 3). The difference in TSS concentration can be explained by the difference in sediment characteristics, namely, sediment diameter, sediment ratio, and settling velocity, as shown in Table 3. Sand, silt, and clay did not differ much across various CS. However, settling velocity differed because of the difference in the average diameter of sediment particles. For example, the settling velocities at CS3-5 and CS7-3 were higher (>10 m/day) and the average particle diameter was higher (>10 m) than at other points. The larger the sediment size, the faster the settling velocity and the lower the TSS concentration. Earth 2021, 2, FOR PEER REVIEW The average sediment diameter at CS4 was smaller than that in other CSs. Hence, the 7 settling velocity at CS4, in general, was smaller and the TSS concentration was higher than that in other CSs (Table 3). It can be concluded that one of the factors that influence TSS concentration is the particle size or the settling velocity. In addition, because TSS did not 1 and Table 2). The difference in wind speed is probably due to difference in altitude. exhibit direct correlation with the wind speed (Figure 3), it was felt necessary to identify Khlong Yai is at a lower altitude of 6 m compared to Siem Reap at 8 m and Phnom Penh the empirical relation of TSS with the wind by adding additional factors such as shear at 12 m. The wind speed in December and March was, in general, less than 5 m/s, but in stress and water depth. June and September, the wind speed was as much 7 m/s (Table 2). a) Khlong Yai b) Siem Reap c) Phnom Penh Figure 2. Wind speed in Cambodia at (a) Khlong Yai, (b) Siem Reap, and (c) Phnom Penh. Fig 2. Wind speed in Cambodia at, a) Khilong Vai, b) Seiem Reap, and c) Phnom Penh Figure 2. Wind speed in Cambodia at (a) Khlong Yai, (b) Siem Reap, and (c) Phnom Penh. Table 2. Comparison of the wind and TSS at (1) Khlong Yai, (2) Siem Reap, and (3) Phnom Penh. Total Suspended Solid Month Wind (TSS) Wind Direction Wind Speed 1) Khlong Yai 1) Khlong Yai 2) Siem Reap 2) Siem Reap 3) Phnom Penh 3) Phnom Penh 1: Higher in 2017 than in 2016, and • TSS varies by year Direction changes to N at once similar in range as in Mar • Compared to 5–12.5 1: Trends change slightly between 2: Max: 12.3 m/s, turbulence calms mg/L in 2016, TSS are higher December 2016 and 2017, but mainly is west- down compared to Sep than 50 mg/L ward 3: Average increases compared to • CS4-1 only is over 200 2,3: Direction changes to N at once Sep mg/L 1: Relatively lower wind speed • Completely different Trends do not change regardless of (Ave: 3–4 m/s, max: 3.6–5.7 m/s) wind speed on each location year March 2: Occasional stronger wind (7.2–8.2 • Higher TSS (>200 mg/L) 1: Main direction: West or East wind, m/s) in: CS2-2, CS3-2, CS3-7, CS4- No NE or SW direction 3: Max: 6.2–8.8 m/s 1~4–3, CS6-2~6–5 Wind speed (m/s) Wind speed (m/s) Wind speed (m/s) Earth 2021, 2 431 Table 2. Comparison of the wind and TSS at (1) Khlong Yai, (2) Siem Reap, and (3) Phnom Penh. Month Wind Total Suspended Solid (TSS) Wind Direction Wind Speed (1) Khlong Yai (1) Khlong Yai (2) Siem Reap (2) Siem Reap (3) Phnom Penh (3) Phnom Penh 1: Higher in 2017 than in 2016, Direction changes to N at once  TSS varies by year and similar in range as in Mar 1: Trends change slightly between  Compared to 5–12.5 mg/L in 2: Max: 12.3 m/s, turbulence December 2016 and 2017, but mainly is 2016, TSS are higher than calms down compared to Sep westward 50 mg/L 3: Average increases compared 2,3: Direction changes to N at once  CS4-1 only is over 200 mg/L to Sep Completely different wind Trends do not change regardless of speed on each location year 1: Relatively lower wind speed  Higher TSS (>200 mg/L) in: 1: Main direction: West or East wind, (Ave: 3–4 m/s, max: 3.6–5.7 m/s) CS2-2, CS3-2, CS3-7, CS4-1~4–3, March No NE or SW direction 2: Occasional stronger wind CS6-2~6–5 2: Frequent southern wind, relatively (7.2–8.2 m/s)  Ave: 169.5, max: 405, min: 4.5 unstable 3: Max: 6.2–8.8 m/s (mg/L) 3: Only SE in 2016 and 2017  Strong wind 6= High TSS Shallow depth 6= High TSS 1: Average does not change in Mar, max changes (3.6 m/s in Mar Highest TSS Trends do not change regardless ! 15.4 m/s in Jun) of year Max: 652 mg/L 2: Increases by 5 m/s from 7.2–8.2 June 1: NS from EW in Mar CS2 and CS3 have higher TSS ! 8.8–13.3 m/s 2: SW stable Some places showed lower TSS 3: Speed does not change, with 3: SW to SE in Mar than that in Mar occasional max, 6.2–8.8 ! 12.9–23.2 m/s Trends do not change regardless of 1: No turbulence and a stable year wind of 2–3 m/s 1: Frequent westward, 2016 and 2017 2: 15–20 m/s in 2016, no show same trends.  Max: ~50 mg/L turbulence and a stable wind September 2: Overall westward,  Strong wind 6= High TSS around 7 m/s NW ratio increases in 2017  Relatively stable and lower TSS 3: Speed is the same or slightly 3: S and N from SW higher than that in Jun at around 4: Westward wind trend 10 m/s Earth 2021, 2, FOR PEER REVIEW 10 remainsDirection varies by year Interpolated wind Speed TSS December 2016 March 2017 June 2017 September 2017 Figure 3. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia. Figure 3. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia. Fig 4. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia 3.3. Empirical Relation A number of empirical relations were tried for the correlation of TSS with wind speed, water depth, and shear stress (Supplementary File 3), and they can be summarized as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in Table 4. Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Regression Relation R RMSE Whole lake 3 2 𝑆𝑆𝑇 = −20.9 𝑊 ⁄𝐷 + 102.8 𝑊 ⁄𝐷 − 96.1 𝑊 ⁄𝐷 + 75 0.06 111 (dry + wet season) 𝑆𝑆𝑇 = −0.456𝜏 + 8 Wet season 0.03 2.0 𝑣𝑒𝑎𝑤 3 2 𝑆𝑆𝑇 = 0.80𝑊 − 3.9𝑊 + 4.5𝑊 + 8 0.02 2.0 Dry season 𝑆𝑆𝑇 = 459.3𝑊 − 2244.5𝑊 + 2861 0.06 141 Dry season −5 Cross section 1 𝑆𝑆𝑇 = 5.6 × 10 × (5 𝑊 ⁄𝐷 ) + 5 0.96 53 Cross section 2 𝑆𝑆𝑇 = −3766.9𝑊 + 19242𝑊 − 23467 0.71 259 3 2 𝑆𝑆𝑇 = −143.6 𝑊 ⁄𝐷 + 146 𝑊 ⁄𝐷 + 132.7 𝑊 ⁄𝐷 + 540 0.69 256 3 2 Cross section 3 𝑆𝑆𝑇 = −310.3𝑊 + 1331.3𝑊 − 702.7𝑊 − 1399 0.42 198 3 2 𝑆𝑆𝑇 = −1232.4 𝑊 ⁄𝐷 + 6050 𝑊 ⁄𝐷 − 7417 𝑊 ⁄𝐷 + 368 0.41 182 3 2 Cross section 4 𝑆𝑆𝑇 = 723.0𝑊 − 2757𝑊 + 1128.8𝑊 + 3156 0.59 159 3 2 ⁄ ⁄ ⁄ 𝑆𝑆𝑇 = 2731.3 𝑊 𝐷 − 12498.2 𝑊 𝐷 + 14129.7 𝑊 𝐷 0.59 156 + 72 3 2 Cross section 5 𝑆𝑆𝑇 = 128.3 𝑊 ⁄𝐷 − 617.4 𝑊 ⁄𝐷 + 750.8 𝑊 ⁄𝐷 + 22 0.56 79 𝑆𝑆𝑇 = −50.9𝜏 + 320 0.58 73 𝑣𝑒𝑎𝑤 3 2 Cross section 6 𝑆𝑆𝑇 = 437.4𝑊 − 1610.5𝑊 + 636.1𝑊 + 1690 0.82 175 −5 𝑆𝑆𝑇 = 1.8 × 10 × (6.1𝑊 ) − 6 0.81 153 3 2 Cross section 7 ⁄ ⁄ ⁄ 0.88 82 𝑆𝑆𝑇 = 84.2 𝑊 𝐷 − 165.6 𝑊 𝐷 − 144.2 𝑊 𝐷 + 53 𝑆𝑆𝑇 = 1675.8 × (−0.40𝜏 ) − 134 0.77 51 𝑣𝑒𝑎𝑤 W = wind speed (m/s), D = water depth (m), 𝜏 = shear stess (Pa), and TSS = total suspended solids (mg/L). 𝑎𝑤𝑣𝑒 It is evident from Table 4 that a single equation does not fit well to the simulated TSS 2 2 2 across the whole TSL (R = 0.06) or even during dry (R = 0.06) and wet seasons (R = 0.03). As the TSL lake is huge and its area and depth vary from <1 m and 5 km to 5 m and 16 𝑒𝑥𝑝 𝑒𝑥𝑝 𝑒𝑥𝑝 Ea Eart rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 9 9 Ea Ea Ea Eart rt rt rth h h h 2 2 2 20 0 0 02 2 2 21 1 1 1, , , , 2 2 2 2,,,, F F F FO O O OR R R R P P P PE E E EER ER ER ER R R R REV EV EV EVI I I IEW EW EW EW 9 9 9 9 Ea Ea Ea Eart rt rt rth h h h 2 2 2 20 0 0 02 2 2 21 1 1 1, , , , 2 2 2 2,,,, F F F FO O O OR R R R P P P PE E E EER ER ER ER R R R REV EV EV EVI I IIEW EW EW EW 9 9 9 9 Ea Eart rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 9 9 Earth 2021, 2, FOR PEER REVIEW 9 Earth 2021, 2, FOR PEER REVIEW 9 Ea rth 2021, 2, FOR PEER REVIEW 9 Ea rth 2021, 2, FOR PEER REVIEW 9 Ea Ea rt rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 9 9 Ea Ea rt rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 9 9 Earth 2021, 2, FOR PEER REVIEW 9 Ea rth 2021, 2, FOR PEER REVIEW 9 Earth 2021, 2, FOR PEER REVIEW 9 Earth 2021, 2 432 Ta Table ble 3 3.. S Sed edime imen nt t c ch ha ar ra ac ct ter eris ist tics ics a ac cr ro oss ss v va ar rio ious us c cr ro oss ss se sec ct tio ion ns s (CS (CS) ) in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Ta Ta Ta Ta Table ble ble ble ble 3 3 3 3 3..... S S S S Sed ed ed ed edime ime ime ime imen n n n nt t t t t c c c c ch h h h ha a a a ar r r r ra a a a ac c c c ct t t t ter er er er eris is is is ist t t t tics ics ics ics ics a a a a ac c c c cr r r r ro o o o oss ss ss ss ss v v v v va a a a ar r r r rio io io io ious us us us us c c c c cr r r r ro o o o oss ss ss ss ss se se se se sec c c c ct t t t tio io io io ion n n n ns s s s s (CS (CS (CS (CS (CS) ) ) ) ) in in in in in To To To To Ton n n n nle le le le le S S S S Sa a a a ap L p L p L p L p La a a a ak k k k ke, e, e, e, e, Ca Ca Ca Ca Cam m m m mb b b b bo o o o odi di di di dia a a a a..... Ta Ta Table ble ble 3 3 3... S S Sed ed edime ime imen n nt tt c c ch h ha a ar r ra a ac c ct tter er eris is ist ttics ics ics a a ac c cr r ro o oss ss ss v v va a ar r rio io ious us us c c cr r ro o oss ss ss se se sec c ct ttio io ion n ns s s (CS (CS (CS) ) ) in in in To To Ton n nle le le S S Sa a ap L p L p La a ak k ke, e, e, Ca Ca Cam m mb b bo o odi di dia a a... Ta Table ble 3 3.. S Sed edime imen nt t c ch ha ar ra ac ct ter eris ist tics ics a ac cr ro oss ss v va ar rio ious us c cr ro oss ss se sec ct tio ion ns s (CS (CS) ) in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Ta Table ble 3 3.. S Sed edime imen nt t c ch ha ar ra ac ct ter eris ist tics ics a ac cr ro oss ss v va ar rio ious us c cr ro oss ss se sec ct tio ion ns s (CS (CS) ) in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Ta Ta Table ble ble 3 3 3... S S Sed ed edime ime imen n nt t t c c ch h ha a ar r ra a ac c ct t ter er eris is ist t tics ics ics a a ac c cr r ro o oss ss ss v v va a ar r rio io ious us us c c cr r ro o oss ss ss se se sec c ct t tio io ion n ns s s (CS (CS (CS) ) ) in in in To To Ton n nle le le S S Sa a ap L p L p La a ak k ke, e, e, Ca Ca Cam m mb b bo o odi di dia a a... Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Table 3. Sediment characteristics across various cross sections (CS) in Tonle Sap Lake, Cambodia. Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t Ma Ma Ma Mass ss ss ss R R R Ra a a at t t ti i i io o o o of of of of S S S Se e e ed d d di i i im m m me e e en n n nt t t t Ma Ma Ma Mass ss ss ss R R R Ra a a at t t ti i i io o o o of of of of S S S Se e e ed d d di i i im m m me e e en n n nt t t t Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t Mass Ratio of Sediment Mass Ratio of Sediment Mass Ratio of Sediment Mass Ratio of Sediment Ma Ma Mass ss ss R R Ra a at t ti i io o o of of of S S Se e ed d di i im m me e en n nt t t A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m//d day ay) ) Mass Ratio of Sediment A A A Ar r r re e e ea a a a P P P Poin oin oin oint t t t A A A Ave ve ve ver r r ra a a age ge ge ge Di Di Di Dia a a ame me me met t t te e e er r r r ( ( ( (𝛍𝐦𝛍𝐦𝛍𝐦𝛍𝐦 ) ) ) ) S S S Se e e et t t tt t t tl l l li i i in n n ng g g g V V V Ve e e el l l loci oci oci ocit t t ty y y y ( ( ( (m m m m/ // /d d d day ay ay ay) ) ) ) Mass Ratio of Sediment A A A Ar r r re e e ea a a a P P P Poin oin oin oint t t t A A A Ave ve ve ver r r ra a a age ge ge ge Di Di Di Dia a a ame me me met t t te e e er r r r ( ( ( (𝛍𝐦𝛍𝐦𝛍𝐦 𝛍𝐦 ) ) ) ) S S S Se e e et t t tt t t tl l l li i i in n n ng g g g V V V Ve e e el l l loci oci oci ocit t t ty y y y ( ( ( (m m m m/ / //d d d day ay ay ay) ) ) ) A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) Mass Ratio of Sediment Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) Mass Ratio of Sediment A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) A Ar re ea a P Poin oint t T A A able ve ver r3. a age ge Sediment Di Dia ame mecharacteristics t te er r ( (𝛍𝐦𝛍𝐦 ) ) acrS S oss e et tt tvarious l li in ng g V Ve e cr l loci oci osst tsections y y ( (m m/ /d day ay (CS) ) ) in Tonle Sap ( (%, %, Lake, S Sa an nd d Cambodia. , , Silt Silt, , Cl Cla ay y) ) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) ( ( ( (%, %, %, %, S S S Sa a a an n n nd d d d, , , , Silt Silt Silt Silt, , , , Cl Cl Cl Cla a a ay y y y) ) ) ) ( ((%, %, %, S S Sa a an n nd d d, , , Silt Silt Silt, , , Cl Cl Cla a ay y y) )) ( (%, %, S Sa an nd d, , Silt Silt, , Cl Cla ay y) ) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) (%, Sand, Silt, Clay) (%, Sand, Silt, Clay) ( (%, %, S Sa an nd d, , Silt Silt, , Cl Cla ay y) ) (%, Sand, Silt, Clay) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) ( ( ( (%, %, %, %, S S S Sa a a an n n nd d d d, , , , Silt Silt Silt Silt, , , , Cl Cl Cl Cla a a ay y y y) ) ) ) (%, Sand, Silt, Clay) (%, Sand, Silt, Clay) (%, Sand, Silt, Clay) Area Point Average Diameter (m) Settling Velocity (m/day) Mass Ratio of Sediment (%, Sand, Silt, Clay) CS CS1 1- -1 1 6 6..5 50 0 4 4..1 16 6 CS CS CS CS1 1 1 1- - - -1 1 1 1 6 6 6 6....5 5 5 50 0 0 0 4 4 4 4....1 1 1 16 6 6 6 CS CS CS1 1 1- --1 1 1 6 6 6...5 5 50 0 0 4 4 4...1 1 16 6 6 CS CS1 1- -1 1 6 6..5 50 0 4 4..1 16 6 CS1-1 6.50 4.16 CS1-1 6.50 4.16 CS CS1 1- -1 1 6 6..5 50 0 4 4..1 16 6 CS1-1 6.50 4.16 CS CS CS CS1 1 1 1- - - -1 1 1 1 6 6 6 6....5 5 5 50 0 0 0 4 4 4 4....1 1 1 16 6 6 6 CS1-1 6.50 4.16 CS1-1 6.50 4.16 CS1-1 CS1-1 6.50 6.50 4.16 4.16 CS CS1 1- -2 2 6 6..4 48 8 4 4..1 14 4 CS CS CS1 1 1 CS CS CS CS1 1 1 1- - - -2 2 2 2 6 6 6 6....4 4 4 48 8 8 8 4 4 4 4....1 1 1 14 4 4 4 CS CS CS CS CS1 1 1 1 1 CS CS CS CS1 1 1 1- - - -2 2 2 2 6 6 6 6....4 4 4 48 8 8 8 4 4 4 4....1 1 1 14 4 4 4 CS CS CS1 1 1 CS CS1 1- -2 2 6 6..4 48 8 4 4..1 14 4 CS1 CS1-2 6.48 4.14 CS1 CS1-2 6.48 4.14 CS CS1 1 CS1-2 6.48 4.14 CS1-2 6.48 4.14 CS1 CS CS CS1 1 1- - -2 2 2 6 6 6...4 4 48 8 8 4 4 4...1 1 14 4 4 CS CS CS1 1 1 CS1-2 6.48 4.14 CS CS1 1 CS1-2 6.48 4.14 CS1-2 6.48 4.14 CS1 CS1-2 6.48 4.14 CS1 CS1-2 6.48 4.14 CS1 CS CS1 1- -3 3 5 5..0 08 8 2 2..5 55 5 CS CS CS CS1 1 1 1- - - -3 3 3 3 5 5 5 5....0 0 0 08 8 8 8 2 2 2 2....5 5 5 55 5 5 5 CS CS CS CS1 1 1 1- - - -3 3 3 3 5 5 5 5....0 0 0 08 8 8 8 2 2 2 2....5 5 5 55 5 5 5 CS CS1 1- -3 3 5 5..0 08 8 2 2..5 55 5 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS CS1 1- -3 3 5 5..0 08 8 2 2..5 55 5 CS CS1 1- -3 3 CS1-3 5 5..0 08 8 5.08 2.55 2 2..5 55 5 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS CS CS2 2 2- - -1 1 1 6 6 6...7 7 78 8 8 4 4 4...5 5 53 3 3 CS CS CS CS CS2 2 2 2 2- - - - -1 1 1 1 1 6 6 6 6 6.....7 7 7 7 78 8 8 8 8 4 4 4 4 4.....5 5 5 5 53 3 3 3 3 CS CS CS2 2 2- - -1 1 1 6 6 6...7 7 78 8 8 4 4 4...5 5 53 3 3 CS2-1 6.78 4.53 CS2-1 6.78 4.53 CS CS2 2- -1 1 6 6..7 78 8 4 4..5 53 3 CS2-1 6.78 4.53 CS CS CS2 2 2- - -1 1 1 6 6 6...7 7 78 8 8 4 4 4...5 5 53 3 3 CS2-1 6.78 4.53 CS2-1 CS2-1 6.78 6.78 4.53 4.53 CS2-1 6.78 4.53 CS2-1 6.78 4.53 CS CS2 2- -2 2 4 4..8 86 6 2 2..3 33 3 CS CS CS CS2 2 2 2- - - -2 2 2 2 4 4 4 4....8 8 8 86 6 6 6 2 2 2 2....3 3 3 33 3 3 3 CS CS CS CS2 2 2 2- - - -2 2 2 2 4 4 4 4....8 8 8 86 6 6 6 2 2 2 2....3 3 3 33 3 3 3 CS CS2 2- -2 2 4 4..8 86 6 2 2..3 33 3 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS CS CS2 2 2- - -2 2 2 4 4 4...8 8 86 6 6 2 2 2...3 3 33 3 3 CS2-2 CS2-2 4.86 4.86 2.33 2.33 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS CS2 2- -3 3 5 5..5 50 0 2 2..9 98 8 CS CS2 2 CS CS CS CS2 2 2 2- - - -3 3 3 3 5 5 5 5....5 5 5 50 0 0 0 2 2 2 2....9 9 9 98 8 8 8 CS CS CS CS2 2 2 2 CS CS CS CS2 2 2 2- - - -3 3 3 3 5 5 5 5....5 5 5 50 0 0 0 2 2 2 2....9 9 9 98 8 8 8 CS CS CS CS2 2 2 2 CS CS2 2- -3 3 5 5..5 50 0 2 2..9 98 8 CS CS2 2 CS2-3 5.50 2.98 CS2 CS CS2 2- -3 3 5 5..5 50 0 2 2..9 98 8 CS CS2 2 CS2CS2-3 5.50 2.98 CS2 CS CS2 2- -3 3 5 5..5 50 0 2 2..9 98 8 CS CS2 2 CS CS2 2- -3 3 CS2-3 5 5..5 50 0 5.50 2.98 2 2..9 98 8 CS CS2 2 CS2-3 5.50 2.98 CS2 CS2-3 5.50 2.98 CS2 CS2-3 5.50 2.98 CS2 CS CS2 2- -4 4 5 5..6 61 1 3 3..1 11 1 CS CS CS CS2 2 2 2- - - -4 4 4 4 5 5 5 5....6 6 6 61 1 1 1 3 3 3 3....1 1 1 11 1 1 1 CS CS CS2 2 2- --4 4 4 5 5 5...6 6 61 1 1 3 3 3...1 1 11 1 1 CS CS2 2- -4 4 5 5..6 61 1 3 3..1 11 1 CS2-4 5.61 3.11 CS2-4 5.61 3.11 CS CS2 2- -4 4 5 5..6 61 1 3 3..1 11 1 CS2-4 5.61 3.11 CS CS CS CS2 2 2 2- - - -4 4 4 4 CS2-4 5 5 5 5....6 6 6 61 1 1 1 5.61 3.11 3 3 3 3....1 1 1 11 1 1 1 CS2-4 5.61 3.11 CS2-4 5.61 3.11 CS2-4 5.61 3.11 CS CS CS2 2 2- - -5 5 5 7 7 7...8 8 84 4 4 6 6 6...0 0 05 5 5 CS CS CS CS CS2 2 2 2 2- - - - -5 5 5 5 5 7 7 7 7 7.....8 8 8 8 84 4 4 4 4 6 6 6 6 6.....0 0 0 0 05 5 5 5 5 CS CS CS2 2 2- - -5 5 5 7 7 7...8 8 84 4 4 6 6 6...0 0 05 5 5 CS2-5 7.84 6.05 CS2-5 7.84 6.05 CS CS2 2- -5 5 CS2-5 7 7..8 84 4 7.84 6.05 6 6..0 05 5 CS2-5 7.84 6.05 CS CS CS2 2 2- - -5 5 5 7 7 7...8 8 84 4 4 6 6 6...0 0 05 5 5 CS2-5 7.84 6.05 CS2-5 7.84 6.05 CS2-5 7.84 6.05 CS2-5 7.84 6.05 CS CS3 3- -1 1 6 6..8 87 7 4 4..6 65 5 CS CS CS CS3 3 3 3- - - -1 1 1 1 6 6 6 6....8 8 8 87 7 7 7 4 4 4 4....6 6 6 65 5 5 5 CS CS CS CS3 3 3 3- - - -1 1 1 1 6 6 6 6....8 8 8 87 7 7 7 4 4 4 4....6 6 6 65 5 5 5 CS CS3 3- -1 1 6 6..8 87 7 4 4..6 65 5 CS3-1 6.87 4.65 CS CS3 3- -1 1 6 6..8 87 7 4 4..6 65 5 CS3-1 6.87 4.65 CS CS3 3- -1 1 CS3-1 6 6..8 87 7 6.87 4.65 4 4..6 65 5 CS CS3 3- -1 1 6 6..8 87 7 4 4..6 65 5 CS3-1 6.87 4.65 CS3-1 6.87 4.65 CS3-1 6.87 4.65 CS CS3 3- -2 2 5 5..4 48 8 2 2..9 96 6 CS CS CS CS3 3 3 3- - - -2 2 2 2 5 5 5 5....4 4 4 48 8 8 8 2 2 2 2....9 9 9 96 6 6 6 CS CS CS3 3 3- --2 2 2 5 5 5...4 4 48 8 8 2 2 2...9 9 96 6 6 CS CS3 3- -2 2 5 5..4 48 8 2 2..9 96 6 CS3-2 5.48 2.96 CS3-2 5.48 2.96 CS CS3 3- -2 2 CS3-2 5 5..4 48 8 5.48 2.96 2 2..9 96 6 CS3-2 5.48 2.96 CS CS CS CS3 3 3 3- - - -2 2 2 2 5 5 5 5....4 4 4 48 8 8 8 2 2 2 2....9 9 9 96 6 6 6 CS3-2 5.48 2.96 CS3-2 5.48 2.96 CS3-2 5.48 2.96 CS CS CS3 3 3- - -3 3 3 5 5 5...6 6 65 5 5 3 3 3...1 1 15 5 5 CS CS CS CS CS3 3 3 3 3- - - - -3 3 3 3 3 5 5 5 5 5.....6 6 6 6 65 5 5 5 5 3 3 3 3 3.....1 1 1 1 15 5 5 5 5 CS CS CS3 3 3- - -3 3 3 5 5 5...6 6 65 5 5 3 3 3...1 1 15 5 5 CS3-3 5.65 3.15 CS3-3 CS3-3 5.65 5.65 3.15 3.15 CS CS3 3- -3 3 5 5..6 65 5 3 3..1 15 5 CS3-3 5.65 3.15 CS CS CS3 3 3- - -3 3 3 5 5 5...6 6 65 5 5 3 3 3...1 1 15 5 5 CS CS3 3- -3 3 5 5..6 65 5 3 3..1 15 5 CS3-3 5.65 3.15 CS3-3 5.65 3.15 CS CS CS3 3 3 CS3CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS CS CS CS CS3 3 3 3 3 CS CS CS CS3 3 3 3- - - -4 4 4 4 3 3 3 3....4 4 4 42 2 2 2 1 1 1 1....1 1 1 16 6 6 6 CS CS CS3 3 3 CS CS CS CS3 3 3 3- - - -4 4 4 4 3 3 3 3....4 4 4 42 2 2 2 1 1 1 1....1 1 1 16 6 6 6 CS3 CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS3 CS3-4 CS3-4 3.42 3.42 1.16 1.16 CS CS3 3 CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS3 CS3-4 3.42 1.16 CS CS CS3 3 3 CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS3 CS CS3 3- -4 4 3 3..4 42 2 1 1..1 16 6 CS3 CS3-4 3.42 1.16 CS3 CS3-4 3.42 1.16 CS3 CS3-4 3.42 1.16 CS CS3 3- -5 5 1 10 0..9 9 1 11 1..7 7 CS CS CS CS3 3 3 3- - - -5 5 5 5 1 1 1 10 0 0 0....9 9 9 9 1 1 1 11 1 1 1....7 7 7 7 CS CS CS CS3 3 3 3- - - -5 5 5 5 1 1 1 10 0 0 0....9 9 9 9 1 1 1 11 1 1 1....7 7 7 7 CS CS3 3- -5 5 CS3-5 1 10 0..9 9 10.9 11.7 1 11 1..7 7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS CS CS3 3 3- - -5 5 5 1 1 10 0 0...9 9 9 1 1 11 1 1...7 7 7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS CS3 3- -6 6 9 9..3 36 6 8 8..6 65 5 CS CS CS CS3 3 3 3- - - -6 6 6 6 9 9 9 9....3 3 3 36 6 6 6 8 8 8 8....6 6 6 65 5 5 5 CS CS CS3 3 3- --6 6 6 9 9 9...3 3 36 6 6 8 8 8...6 6 65 5 5 CS CS3 3- -6 6 CS3-6 9 9..3 36 6 9.36 8.65 8 8..6 65 5 CS3-6 9.36 8.65 CS3-6 9.36 8.65 CS CS3 3- -6 6 9 9..3 36 6 8 8..6 65 5 CS3-6 9.36 8.65 CS CS CS CS3 3 3 3- - - -6 6 6 6 9 9 9 9....3 3 3 36 6 6 6 8 8 8 8....6 6 6 65 5 5 5 CS3-6 9.36 8.65 CS3-6 9.36 8.65 CS3-6 9.36 8.65 CS CS3 3- -7 7 CS3-7 4 4..4 46 6 4.46 1.96 1 1..9 96 6 CS CS CS CS3 3 3 3- - - -7 7 7 7 4 4 4 4....4 4 4 46 6 6 6 1 1 1 1....9 9 9 96 6 6 6 CS CS CS CS3 3 3 3- - - -7 7 7 7 4 4 4 4....4 4 4 46 6 6 6 1 1 1 1....9 9 9 96 6 6 6 CS CS3 3- -7 7 4 4..4 46 6 1 1..9 96 6 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS CS CS3 3 3- - -7 7 7 4 4 4...4 4 46 6 6 1 1 1...9 9 96 6 6 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS CS CS CS4 4 4 4- - - -1 1 1 1 2 2 2 2....4 4 4 49 9 9 9 0 0 0 0....6 6 6 61 1 1 1 CS CS CS CS4 4 4 4- - - -1 1 1 1 CS4-1 2 2 2 2....4 4 4 49 9 9 9 2.49 0.61 0 0 0 0....6 6 6 61 1 1 1 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS4-1 2.49 0.61 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS4-1 2.49 0.61 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS CS4 4- -1 1 2 2..4 49 9 0 0..6 61 1 CS4-1 2.49 0.61 CS4-1 2.49 0.61 CS4-1 2.49 0.61 CS CS CS4 4 4- - -2 2 2 6 6 6...2 2 28 8 8 3 3 3...8 8 89 9 9 CS CS CS CS CS4 4 4 4 4- - - - -2 2 2 2 2 CS4-2 6 6 6 6 6.....2 2 2 2 28 8 8 8 8 6.28 3.89 3 3 3 3 3.....8 8 8 8 89 9 9 9 9 CS CS CS4 4 4- - -2 2 2 6 6 6...2 2 28 8 8 3 3 3...8 8 89 9 9 CS4-2 6.28 3.89 CS4-2 6.28 3.89 CS CS4 4- -2 2 6 6..2 28 8 3 3..8 89 9 CS4-2 6.28 3.89 CS CS CS4 4 4- - -2 2 2 6 6 6...2 2 28 8 8 3 3 3...8 8 89 9 9 CS4-2 6.28 3.89 CS4-2 6.28 3.89 CS4-2 6.28 3.89 CS4-2 6.28 3.89 CS CS4 4- -3 3 2 2..2 28 8 0 0..5 51 1 CS CS CS CS CS4 4 4 4 4- - - - -3 3 3 3 3 2 2 2 2 2.....2 2 2 2 28 8 8 8 8 0 0 0 0 0.....5 5 5 5 51 1 1 1 1 CS CS CS CS4 4 4 4- - - -3 3 3 3 CS4-3 2 2 2 2....2 2 2 28 8 8 8 2.28 0.51 0 0 0 0....5 5 5 51 1 1 1 CS4-3 2.28 0.51 CS4-3 2.28 0.51 CS CS4 4- -3 3 2 2..2 28 8 0 0..5 51 1 CS4-3 2.28 0.51 CS CS CS4 4 4- - -3 3 3 2 2 2...2 2 28 8 8 0 0 0...5 5 51 1 1 CS4-3 2.28 0.51 CS4-3 2.28 0.51 CS4-3 2.28 0.51 CS4-3 2.28 0.51 CS CS4 4- -4 4 2 2..6 62 2 0 0..6 68 8 CS CS CS CS4 4 4 4- - - -4 4 4 4 CS4-4 2 2 2 2....6 6 6 62 2 2 2 2.62 0.68 0 0 0 0....6 6 6 68 8 8 8 CS CS CS CS4 4 4 4- - - -4 4 4 4 2 2 2 2....6 6 6 62 2 2 2 0 0 0 0....6 6 6 68 8 8 8 CS CS4 4- -4 4 2 2..6 62 2 0 0..6 68 8 CS4-4 2.62 0.68 CS4-4 2.62 0.68 CS4-4 2.62 0.68 CS4-4 2.62 0.68 CS CS4 4- -4 4 2 2..6 62 2 0 0..6 68 8 CS CS4 4- -4 4 2 2..6 62 2 0 0..6 68 8 CS4-4 2.62 0.68 CS CS CS4 4 4 CS4 CS CS CS CS CS4 4 4 4 4 CS4-4 2.62 0.68 CS CS CS4 4 4 CS4 CS4 CS CS4 4 CS4-4 2.62 0.68 CS4 CS CS CS4 4 4 CS4 CS4 CS4 CS CS4 4- -5 5 3 3..0 00 0 0 0..8 89 9 CS CS CS CS4 4 4 4- - - -5 5 5 5 CS4-5 3 3 3 3....0 0 0 00 0 0 0 3.00 0.89 0 0 0 0....8 8 8 89 9 9 9 CS4 CS CS CS4 4 4- --5 5 5 3 3 3...0 0 00 0 0 0 0 0...8 8 89 9 9 CS CS4 4- -5 5 3 3..0 00 0 0 0..8 89 9 CS4-5 3.00 0.89 CS4-5 3.00 0.89 CS CS4 4- -5 5 3 3..0 00 0 0 0..8 89 9 CS4-5 3.00 0.89 CS CS CS CS4 4 4 4- - - -5 5 5 5 3 3 3 3....0 0 0 00 0 0 0 0 0 0 0....8 8 8 89 9 9 9 CS4-5 3.00 0.89 CS4-5 3.00 0.89 CS4-5 3.00 0.89 CS CS CS4 4 4- - -6 6 6 6 6 6...4 4 48 8 8 4 4 4...1 1 14 4 4 CS CS CS CS CS4 4 4 4 4- - - - -6 6 6 6 6 CS4-6 6 6 6 6 6.....4 4 4 4 48 8 8 8 8 6.48 4.14 4 4 4 4 4.....1 1 1 1 14 4 4 4 4 CS CS CS4 4 4- - -6 6 6 6 6 6...4 4 48 8 8 4 4 4...1 1 14 4 4 CS4-6 6.48 4.14 CS4-6 6.48 4.14 CS CS4 4- -6 6 6 6..4 48 8 4 4..1 14 4 CS4-6 6.48 4.14 CS CS CS4 4 4- - -6 6 6 6 6 6...4 4 48 8 8 4 4 4...1 1 14 4 4 CS4-6 6.48 4.14 CS4-6 6.48 4.14 CS4-6 6.48 4.14 CS4-6 6.48 4.14 CS CS4 4- -7 7 5 5..8 83 3 3 3..3 35 5 CS CS CS CS4 4 4 4- - - -7 7 7 7 5 5 5 5....8 8 8 83 3 3 3 3 3 3 3....3 3 3 35 5 5 5 CS CS CS CS4 4 4 4- - - -7 7 7 7 CS4-7 5 5 5 5....8 8 8 83 3 3 3 5.83 3.35 3 3 3 3....3 3 3 35 5 5 5 CS CS4 4- -7 7 5 5..8 83 3 3 3..3 35 5 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS CS CS4 4 4- - -7 7 7 5 5 5...8 8 83 3 3 3 3 3...3 3 35 5 5 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS4-7 5.83 3.35 CS CS4 4- -8 8 2 2..7 71 1 0 0..7 72 2 CS CS CS CS4 4 4 4- - - -8 8 8 8 2 2 2 2....7 7 7 71 1 1 1 0 0 0 0....7 7 7 72 2 2 2 CS CS CS4 4 4- --8 8 8 CS4-8 2 2 2...7 7 71 1 1 2.71 0.72 0 0 0...7 7 72 2 2 CS CS4 4- -8 8 2 2..7 71 1 0 0..7 72 2 CS4-8 2.71 0.72 CS4-8 2.71 0.72 CS CS4 4- -8 8 2 2..7 71 1 0 0..7 72 2 CS4-8 2.71 0.72 CS CS CS CS4 4 4 4- - - -8 8 8 8 2 2 2 2....7 7 7 71 1 1 1 0 0 0 0....7 7 7 72 2 2 2 CS4-8 2.71 0.72 CS4-8 2.71 0.72 CS4-8 2.71 0.72 CS CS CS5 5 5- - -1 1 1 5 5 5...8 8 85 5 5 3 3 3...3 3 37 7 7 CS CS CS CS CS5 5 5 5 5- - - - -1 1 1 1 1 5 5 5 5 5.....8 8 8 8 85 5 5 5 5 3 3 3 3 3.....3 3 3 3 37 7 7 7 7 CS CS CS5 5 5- - -1 1 1 5 5 5...8 8 85 5 5 3 3 3...3 3 37 7 7 CS5-1 5.85 3.37 CS5-1 5.85 3.37 CS CS5 5- -1 1 5 5..8 85 5 3 3..3 37 7 CS5-1 5.85 3.37 CS CS CS5 5 5- - -1 1 1 5 5 5...8 8 85 5 5 3 3 3...3 3 37 7 7 CS CS5 5- -1 1 5 5..8 85 5 3 3..3 37 7 CS5 CS5-1 5.85 3.37 CS CS CS CS CS5 5 5 5 5 CS CS CS5 5 5 CS CS5 5 CS5 CS5-1 5.85 3.37 CS5 CS CS5 5 CS5 CS CS CS CS5 5 5 5 CS5 CS5 CS CS5 5- -2 2 4 4..8 80 0 2 2..2 27 7 CS CS CS CS5 5 5 5- - - -2 2 2 2 4 4 4 4....8 8 8 80 0 0 0 2 2 2 2....2 2 2 27 7 7 7 CS CS CS5 5 5- --2 2 2 4 4 4...8 8 80 0 0 2 2 2...2 2 27 7 7 CS CS5 5- -2 2 4 4..8 80 0 2 2..2 27 7 CS5 CS5-2 4.80 2.27 CS5-2 4.80 2.27 CS CS5 5- -2 2 4 4..8 80 0 2 2..2 27 7 CS5-2 4.80 2.27 CS CS CS CS5 5 5 5- - - -2 2 2 2 4 4 4 4....8 8 8 80 0 0 0 2 2 2 2....2 2 2 27 7 7 7 CS5-2 4.80 2.27 CS5-2 4.80 2.27 CS5-2 4.80 2.27 Earth 2021, 2, FOR PEER REVIEW 9 Earth 2021, 2, FOR PEER REVIEW 9 Ta Table ble 3 3.. S Sed edime imen nt t c ch ha ar ra ac ct ter eris ist tics ics a ac cr ro oss ss v va ar rio ious us c cr ro oss ss se sec ct tio ion ns s (CS (CS) ) in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Mass Ratio of Sediment Mass Ratio of Sediment A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) ( (%, %, S Sa an nd d, , Silt Silt, , Cl Cla ay y) ) CS CS1 1- -1 1 6 6..5 50 0 4 4..1 16 6 CS1-2 6.48 4.14 CS CS1 1 CS1-2 6.48 4.14 CS1-3 5.08 2.55 CS1-3 5.08 2.55 CS CS2 2- -1 1 6 6..7 78 8 4 4..5 53 3 CS2-2 4.86 2.33 CS2-2 4.86 2.33 CS2-3 5.50 2.98 CS2 CS2-3 5.50 2.98 CS2 CS CS2 2- -4 4 5 5..6 61 1 3 3..1 11 1 CS CS2 2- -5 5 7 7..8 84 4 6 6..0 05 5 CS3-1 6.87 4.65 CS3-1 6.87 4.65 CS CS3 3- -2 2 5 5..4 48 8 2 2..9 96 6 CS CS3 3- -3 3 5 5..6 65 5 3 3..1 15 5 CS CS3 3 CS3-4 3.42 1.16 CS3-4 3.42 1.16 CS3-5 10.9 11.7 CS3-5 10.9 11.7 CS CS3 3- -6 6 9 9..3 36 6 8 8..6 65 5 CS3-7 4.46 1.96 CS3-7 4.46 1.96 CS4-1 2.49 0.61 CS4-1 2.49 0.61 CS CS4 4- -2 2 6 6..2 28 8 3 3..8 89 9 CS CS4 4- -3 3 2 2..2 28 8 0 0..5 51 1 CS4-4 2.62 0.68 CS4-4 2.62 0.68 CS CS4 4 CS CS4 4- -5 5 3 3..0 00 0 0 0..8 89 9 Earth 2021, 2 433 CS CS4 4- -6 6 6 6..4 48 8 4 4..1 14 4 CS4-7 5.83 3.35 CS4-7 5.83 3.35 Table 3. Cont. Ea Eart rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 10 10 Earth 2021, 2, FOR PEER REVIEW 10 Ea Ea Ea Ea Eart rt rt rt rth h h h h 2 2 2 2 20 0 0 0 02 2 2 2 21 1 1 1 1, , , , , 2 2 2 2 2,,,,, F F F F FO O O O OR R R R R P P P P PE E E E EER ER ER ER ER R R R R REV EV EV EV EVI I I I IEW EW EW EW EW 10 10 10 10 10 Ea Ea rt rth h 2 20 02 21 1, , 2 2,, F FO OR R P PE EER ER R REV EVI IEW EW 10 10 Earth 2021, 2, FOR PEER REVIEW 10 Ea rth 2021, 2, FOR PEER REVIEW 10 CS CS4 4- -8 8 2 2..7 71 1 0 0..7 72 2 Area Point Average Diameter (m) Settling Velocity (m/day) Mass Ratio of Sediment (%, Sand, Silt, Clay) CS CS5 5- -1 1 CS5-1 5 5..8 85 5 5.85 3.37 3 3..3 37 7 Mass Ratio of Sediment Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t Ma Ma Mass ss ss R R Ra a at t ti i io o o of of of S S Se e ed d di i im m me e en n nt t t Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t CS CS5 5 Ma Mass ss R Ra at ti io o of of S Se ed di im me en nt t Mass Ratio of Sediment A A Ar r re e ea a a P P Poin oin oint t t A A Ave ve ver r ra a age ge ge Di Di Dia a ame me met t te e er r r ( ( (𝛍𝐦𝛍𝐦𝛍𝐦 ) ) ) S S Se e et t tt t tl l li i in n ng g g V V Ve e el l loci oci ocit t ty y y ( ( (m m m/ / /d d day ay ay) ) ) Mass Ratio of Sediment A A Ar r re e ea a a P P Poin oin oint t t A A Ave ve ver r ra a age ge ge Di Di Dia a ame me met t te e er r r ( ( (𝛍𝐦𝛍𝐦 𝛍𝐦 ) ) ) S S Se e et t tt t tl l li i in n ng g g V V Ve e el l loci oci ocit t ty y y ( ( (m m m/ //d d day ay ay) ) ) A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) A Ar re ea a P Poin oint t A Ave ver ra age ge Di Dia ame met te er r ( (𝛍𝐦𝛍𝐦 ) ) S Se et tt tl li in ng g V Ve el loci ocit ty y ( (m m/ /d day ay) ) Area Point Average Diameter (𝛍𝐦 ) Settling Velocity (m/day) Area CS CS Poin 5 5- -2 2 t CS5-2Average Di 4 4..a 8 8me 0 0 4.80 ter (𝛍𝐦 ) Settling 2.27 Ve 2 2l..oci 2 27 7 ty (m/day) ( ( (%, %, %, S S Sa a an n nd d d, , , Silt Silt Silt, , , Cl Cl Cla a ay y y) ) ) (%, Sand, Silt, Clay) ( ( ( (%, %, %, %, S S S Sa a a an n n nd d d d, , , , Silt Silt Silt Silt, , , , Cl Cl Cl Cla a a ay y y y) ) ) ) ( (%, %, S Sa an nd d, , Silt Silt, , Cl Cla ay y) ) (%, Sand, Silt, Clay) (%, Sand, Silt, Clay) CS5-3 8.01 6.33 CS5CS CS5 5- -3 3 8 8..0 01 1 6 6..3 33 3 CS5-3 8.01 6.33 CS CS CS5 5 5- - -3 3 3 8 8 8...0 0 01 1 1 6 6 6...3 3 33 3 3 CS CS5 5- -3 3 8 8..0 01 1 6 6..3 33 3 CS CS5 5- -3 3 8 8..0 01 1 6 6..3 33 3 CS5-3 8.01 6.33 CS5-3 8.01 6.33 CS CS CS5 5 5- - -4 4 4 1 1 1...6 6 68 8 8 0 0 0...2 2 28 8 8 CS5-4 1.68 0.28 CS5-4 1.68 0.28 CS CS CS CS5 5 5 5- - - -4 4 4 4 1 1 1 1....6 6 6 68 8 8 8 0 0 0 0....2 2 2 28 8 8 8 CS CS5 5- -4 4 1 1..6 68 8 0 0..2 28 8 CS5-4 1.68 0.28 CS5-4 1.68 0.28 CS5-5 2.02 0.40 CS CS5 5- -5 5 CS5-5 2 2..0 02 2 2.02 0.40 0 0..4 40 0 CS CS CS5 5 5- - -5 5 5 2 2 2...0 0 02 2 2 0 0 0...4 4 40 0 0 CS CS5 5- -5 5 2 2..0 02 2 0 0..4 40 0 CS CS5 5- -5 5 2 2..0 02 2 0 0..4 40 0 CS5-5 2.02 0.40 CS5-5 2.02 0.40 CS CS6 6- -1 1 7 7..3 38 8 5 5..3 37 7 CS6-1 7.38 5.37 CS CS CS6 6 6- - -1 1 1 7 7 7...3 3 38 8 8 5 5 5...3 3 37 7 7 CS CS6 6- -1 1 CS6-1 7 7..3 38 8 7.38 5.37 5 5..3 37 7 CS CS6 6- -1 1 7 7..3 38 8 5 5..3 37 7 CS6-1 7.38 5.37 CS6-1 7.38 5.37 CS6-2 4.19 1.73 CS CS6 6- -2 2 4 4..1 19 9 1 1..7 73 3 CS CS CS6 6 6- - -2 2 2 4 4 4...1 1 19 9 9 1 1 1...7 7 73 3 3 CS CS6 6- -2 2 CS6-2 4 4..1 19 9 4.19 1.73 1 1..7 73 3 CS CS6 6- -2 2 4 4..1 19 9 1 1..7 73 3 CS6-2 4.19 1.73 CS6-2 4.19 1.73 CS6 CS CS6 6 CS CS6 6- -3 3 2 2..1 15 5 0 0..4 46 6 CS CS CS6 6 6 CS6CS6-3 2.15 0.46 CS CS6 6 CS6-3 2.15 0.46 CS CS CS CS6 6 6 6- - - -3 3 3 3 CS6-3 2 2 2 2....1 1 1 15 5 5 5 2.15 0.46 0 0 0 0....4 4 4 46 6 6 6 CS CS6 6 CS CS6 6- -3 3 2 2..1 15 5 0 0..4 46 6 CS6 CS6 CS6-3 2.15 0.46 CS6-3 2.15 0.46 CS CS CS6 6 6- - -4 4 4 3 3 3...9 9 94 4 4 1 1 1...5 5 53 3 3 CS6-4 3.94 1.53 CS CS CS CS6 6 6 6- - - -4 4 4 4 CS6-4 3 3 3 3....9 9 9 94 4 4 4 3.94 1.53 1 1 1 1....5 5 5 53 3 3 3 CS CS6 6- -4 4 3 3..9 94 4 1 1..5 53 3 CS6-4 3.94 1.53 CS6-4 3.94 1.53 CS6-5 3.10 0.95 CS CS6 6- -5 5 3 3..1 10 0 0 0..9 95 5 CS CS CS6 6 6- - -5 5 5 3 3 3...1 1 10 0 0 0 0 0...9 9 95 5 5 CS CS6 6- -5 5 CS6-5 3 3..1 10 0 3.10 0.95 0 0..9 95 5 CS CS6 6- -5 5 3 3..1 10 0 0 0..9 95 5 CS6-5 3.10 0.95 CS6-5 3.10 0.95 CS CS7 7- -1 1 7 7..8 83 3 6 6..0 05 5 CS7-1 7.83 6.05 CS CS CS7 7 7- - -1 1 1 7 7 7...8 8 83 3 3 6 6 6...0 0 05 5 5 CS CS7 7- -1 1 7 7..8 83 3 6 6..0 05 5 CS CS7 7- -1 1 7 7..8 83 3 6 6..0 05 5 CS7-1 7.83 6.05 CS7-1 7.83 6.05 CS7-1 7.83 6.05 CS CS7 7- -2 2 3 3..4 49 9 1 1..2 20 0 CS7-2 3.49 1.20 CS CS CS7 7 7- - -2 2 2 3 3 3...4 4 49 9 9 1 1 1...2 2 20 0 0 CS CS7 7- -2 2 3 3..4 49 9 1 1..2 20 0 CS CS7 7- -2 2 3 3..4 49 9 1 1..2 20 0 CS7-2 3.49 1.20 CS7-2 3.49 1.20 CS7-2 3.49 1.20 CS CS CS7 7 7 CS7 CS CS CS CS7 7 7 7 CS CS7 7 CS7 CS7 CS7 CS CS7 7- -3 3 1 10 0..3 3 1 10 0..4 4 CS7-3 10.3 10.4 CS CS CS7 7 7- - -3 3 3 1 1 10 0 0...3 3 3 1 1 10 0 0...4 4 4 CS CS7 7- -3 3 1 10 0..3 3 1 10 0..4 4 CS CS7 7- -3 3 1 10 0..3 3 1 10 0..4 4 CS7-3 10.3 10.4 CS7-3 10.3 10.4 CS7-3 10.3 10.4 CS7-4 3.31 1.08 CS CS7 7- -4 4 3 3..3 31 1 1 1..0 08 8 CS CS CS7 7 7- - -4 4 4 3 3 3...3 3 31 1 1 1 1 1...0 0 08 8 8 CS CS7 7- -4 4 3 3..3 31 1 1 1..0 08 8 CS CS7 7- -4 4 3 3..3 31 1 1 1..0 08 8 CS7-4 3.31 1.08 CS7-4 CS7-4 3.31 3.31 1.08 1.08 T TSS SS IIIn n nttte e erp rp rpo o ollla a attte e ed d d w w wiiin n nd d d Sp Sp Spe e ee e ed d d TSS Interpolated wind Speed T T TSS SS SS IIIIn n n ntttte e e erp rp rp rpo o o olllla a a atttte e e ed d d d w w w wiiiin n n nd d d d Sp Sp Sp Spe e e ee e e ed d d d T TSS SS T TSS SS IIn ntte erp rpo olla atte ed d w wiin nd d Sp Spe ee ed d Interpolated wind Speed TSS Interpolated wind Speed TSS December 2016 D De ece cemb mbe er r 2 20 01 16 6 3.3. Empirical Relation M M Ma a arch rch rch 2 2 20 0 01 1 17 7 7 D D De e ece ce cemb mb mbe e er r r 2 2 20 0 01 1 16 6 6 D De ece cemb mbe er r 2 20 01 16 6 March 2017 M M M Ma a a arch rch rch rch 2 2 2 20 0 0 01 1 1 17 7 7 7 D De ece cemb mbe er r 2 20 01 16 6 M Ma arch rch 2 20 01 17 7 December 2016 December 2016 March 2017 March 2017 A number of empirical relations were tried for the correlation of TSS with wind speed, water depth, and shear stress (Supplementary File S3), and they can be summarized as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in Table 4. It is evident from Table 4 that a single equation does not fit well to the simulated TSS 2 2 2 across the whole TSL (R = 0.06) or even during dry (R = 0.06) and wet seasons (R = 0.03). 2 2 As the TSL lake is huge and its area and depth vary from <1 m and 5 km to 5 m and 16 km Ju Ju Jun n ne e e 2 2 20 0 01 1 17 7 7 Ju Ju Jun n ne e e 2 2 20 0 01 1 17 7 7 Ju Jun ne e 2 20 01 17 7 Se Sep ptte emb mbe er r 2 20 01 17 7 during the dry and wet seasons, respectively, itSe is p necessary tember 20to 17segregate the lake based on Ju Jun ne e 2 20 01 17 7 Se Se Sep p pttte e emb mb mbe e er r r 2 2 20 0 01 1 17 7 7 June 2017 Se Sep ptte emb mbe er r 2 20 01 17 7 June 2017 Se Sep ptte emb mbe er r 2 20 01 17 7 September 2017 September 2017 cross sections and to propose an empirical relation for each CS, and during each season. The correlation coefficient increased from CS1 to CS7 while moving from the northern to the southern part of the lake, and TSS was better correlated by squared or cubed transformation of wind speed over water depth and power exponent of wind speed (Table 4), which was in agreement with the hypothesis that the higher the wind speed is, the higher is the TSS. In general, the most significant empirical equations for various CS 2 3 3 were the following: CS1 = exp(W /D); CS2 = W or W /D; CS3, CS4, and CS5 = W or 3 3 3 W /D; CS6 = W or exp(W); and CS7 = W /D (Figure 4). Fig Figure ure 3 3.. I In nt ter erpo pola lat ted ed w win ind d sp speed eed a an nd d t to ot ta al l suspen suspende ded d so soli lid ds s (TS (TSS S) ) c co on nc cen ent tr ra at tiio on n a ac cr ro oss ss To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. FigureF 3ig . I n 4t . er Inpo terp lato ed la tw ed in w d in sp deed spe ae nd d a tn ot d a l to suspen tal susp dee d nso deli dd so s (TS lids S) (T co SS) ncen co trn ace tion nt ra actrio on ss a To cro nle ss ST ao p L nlea k Sa e, p Ca Lm ake bo,di Ca a.mb odia FigureF F 3iig g . I 4 4 n.. t er IIn npo tte erp rp lat o o ed lla at tw e ed d in w w d iin n sp d d eed sp spe e a e e n d d d a atn n od d ta tt l o o suspen tta all su susp sp de e ed n nd d so e eli d dd so so s (TS lliid ds s S) (T (T cSS) SS) oncen co co trn n ace ce tion n ntt ra ra acttr iio o on n ss a a To cro cro nss ss le S T T a o o p L n nlle ea Sa Sa ke,p p Ca L La a m ke ke bo ,, di C Ca a a.mb mb o od diia a Fig Fig Fig Figure ure ure ure 3 3 3 3.... I I I In n n nt t t ter er er erpo po po pola la la lat t t ted ed ed ed w w w win in in ind d d d sp sp sp speed eed eed eed a a a an n n nd d d d t t t to o o ot t t ta a a al l l l suspen suspen suspen suspende de de ded d d d so so so soli li li lid d d ds s s s (TS (TS (TS (TSS S S S) ) ) ) c c c co o o on n n nc c c cen en en ent t t tr r r ra a a at t t ti i iio o o on n n n a a a ac c c cr r r ro o o oss ss ss ss To To To Ton n n nle le le le S S S Sa a a ap L p L p L p La a a ak k k ke, e, e, e, Ca Ca Ca Cam m m mb b b bo o o odi di di dia a a a.... F F Fiiig g g 4 4 4... IIIn n nttte e erp rp rpo o ollla a attte e ed d d w w wiiin n nd d d sp sp spe e ee e ed d d a a an n nd d d ttto o ottta a alll su su susp sp spe e en n nd d de e ed d d so so sollliiid d ds s s (T (T (TSS) SS) SS) co co con n nce ce cen n ntttra ra ratttiiio o on n n a a acro cro cross ss ss T T To o on n nllle e e Sa Sa Sap p p L L La a ake ke ke,,, C C Ca a amb mb mbo o od d diiia a a F Fiig g 4 4.. IIn ntte erp rpo olla atte ed d w wiin nd d sp spe ee ed d a an nd d tto otta all su susp spe en nd de ed d so solliid ds s (T (TSS) SS) co con nce cen nttra rattiio on n a acro cross ss T To on nlle e Sa Sap p L La ake ke,, C Ca amb mbo od diia a Fig Figure ure 3 3.. I In nt ter erpo pola lat ted ed w win ind d sp speed eed a an nd d t to ot ta al l suspen suspende ded d so soli lid ds s (TS (TSS S) ) c co on nc cen ent tr ra at ti io on n a ac cr ro oss ss To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. F Fiig g 4 4.. IIn ntte erp rpo olla atte ed d w wiin nd d sp spe ee ed d a an nd d tto otta all su susp spe en nd de ed d so solliid ds s (T (TSS) SS) co con nce cen nttra rattiio on n a acro cross ss T To on nlle e Sa Sap p L La ake ke,, C Ca amb mbo od diia a Figure 3. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia. FigureF 3 ig . I4 n.t er Inpo terp lao ted lat e wd in w d in sp d eed spe a en dd atn od ta tl o suspen tal susp de ed nd so eli dd so s (TS lids S) (T cSS) oncen co trn ace tion nt ra actr io on ss a To cro nss le S T a op L nlea Sa ke,p Ca La m ke bo , di Ca a.mb odia Fig 4. Interpolated wind speed and total suspended solids (TSS) concentration across Tonle Sap Lake, Cambodia 3.3. Empirical Relation 3 3..3 3.. E Em mp pir irica ical l R Re elat lation ion 3 3 3...3 3 3... E E Em m mp p pir ir irica ica ical l l R R Re e elat lat lation ion ion 3 3..3 3.. E Em mp pir irica ical l R Re elat lation ion 3 3..3 3.. E Em mp pir irica ical l R Re elat lation ion 3.3. Empirical Relation 3.3. Empirical Relation A A n num umb ber er o of f empi empiri rica call re rela lati tio on ns s were were tri tried ed f fo or r th the e c co orr rrel ela atio tion n o of f T TS SS S w wiith th wi win nd d A number of empirical relations were tried for the correlation of TSS with wind A A A n n num um umb b ber er er o o of f f empi empi empiri ri rica ca cal ll re re rela la lati ti tio o on n ns s s were were were tri tri tried ed ed f f fo o or r r th th the e e c c co o orr rr rrel el ela a atio tio tion n n o o of f f T T TS S SS S S w w wi iith th th wi wi win n nd d d A A n num umb ber er o of f empi empiri rica cal l re rela lati tio on ns s were were tri tried ed f fo or r th the e c co orr rrel ela atio tion n o of f T TS SS S w wi ith th wi win nd d A A n num umb ber er o of f empi empiri rica cal l re rela lati tio on ns s were were tri tried ed f fo or r th the e c co orr rrel ela atio tion n o of f T TS SS S w wi ith th wi win nd d A number of empirical relations were tried for the correlation of TSS with wind A number of empirical relations were tried for the correlation of TSS with wind spee speed d,, wa water ter d dep epth th,, a an nd d sh shea ear r st stre ress ss ( (S Suppl upplement ementa ary ry F Fiile le 3 3) ),, a an nd d th they ey ca can n b be e su sum mm ma ari riz zed ed speed, water depth, and shear stress (Supplementary File 3), and they can be summarized spee spee speed d d,,, wa wa water ter ter d d dep ep epth th th,,, a a an n nd d d sh sh shea ea ear r r st st stre re ress ss ss ( ( (S S Suppl uppl upplement ement ementa a ary ry ry F F Fi iile le le 3 3 3) ) ),,, a a an n nd d d th th they ey ey ca ca can n n b b be e e su su sum m mm m ma a ari ri riz z zed ed ed spee speed d,, wa water ter d dep epth th,, a an nd d sh shea ear r st stre ress ss ( (S Suppl upplement ementa ary ry F Fi ile le 3 3) ),, a an nd d th they ey ca can n b be e su sum mm ma ari riz zed ed spee speed d,, wa water ter d dep epth th,, a an nd d sh shea ear r st stre ress ss ( (S Suppl upplement ementa ary ry F Fi ile le 3 3) ),, a an nd d th they ey ca can n b be e su sum mm ma ari riz zed ed speed, water depth, and shear stress (Supplementary File 3), and they can be summarized speed, water depth, and shear stress (Supplementary File 3), and they can be summarized a as s a a b best est- -f fiit t cur curv ve e f fo or r th the e wh who olle e lla ake, ke, d dry ry a an nd d wet wet se sea aso son ns, s, a an nd d va vari rio ous us CS CS a as s s sh ho own wn iin n as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in a a a as s s s a a a a b b b best est est est- - - -f f f fi i iit t t t cur cur cur curv v v ve e e e f f f fo o o or r r r th th th the e e e wh wh wh who o o ol l lle e e e l l lla a a ake, ke, ke, ke, d d d dry ry ry ry a a a an n n nd d d d wet wet wet wet se se se sea a a aso so so son n n ns, s, s, s, a a a an n n nd d d d va va va vari ri ri rio o o ous us us us CS CS CS CS a a a as s s s s s s sh h h ho o o own wn wn wn i i iin n n n a as s a a b best est- -f fi it t cur curv ve e f fo or r th the e wh who ol le e l la ake, ke, d dry ry a an nd d wet wet se sea aso son ns, s, a an nd d va vari rio ous us CS CS a as s s sh ho own wn i in n as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in as a best-fit curve for the whole lake, dry and wet seasons, and various CS as shown in Ta Ta Tab b bl l le e e 4 4 4... Ta Ta Tab b bl lle e e 4 4 4... Ta Tab bl le e 4 4.. Ta Tab bl le e 4 4.. Table 4. Table 4. Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Ta Table ble 4 4.. Empir Empirica ical l r rel ela at tio ion n fo for r TS TSS S in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Ta Ta Table ble ble 4 4 4... Empir Empir Empirica ica ical ll r r rel el ela a at t tio io ion n n fo fo for r r TS TS TSS S S in in in To To Ton n nle le le S S Sa a ap L p L p La a ak k ke, e, e, Ca Ca Cam m mb b bo o odi di dia a a... Ta Table ble 4 4.. Empir Empirica ical l r rel ela at tio ion n fo for r TS TSS S in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Ta Table ble 4 4.. Empir Empirica ical l r rel ela at tio ion n fo for r TS TSS S in in To Ton nle le S Sa ap L p La ak ke, e, Ca Cam mb bo odi dia a.. Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Earth 2021, 2 434 Table 4. Empirical relation for TSS in Tonle Sap Lake, Cambodia. Regression Relation R RMSE Whole lake 3 2 TSS = 20.9W /D + 102.8W /D 96.1W /D + 75 0.06 111 (dry + wet season) Wet season TSS = 0.456t + 8 0.03 2.0 wave 3 2 TSS = 0.80W 3.9W + 4.5W + 8 0.02 2.0 Dry season TSS = 459.3W 2244.5W + 2861 0.06 141 Dry season Cross section 1 TSS = 5.6 10  exp(5W /D) + 5 0.96 53 Cross section 2 TSS = 3766.9W + 19242W 23467 0.71 259 3 2 TSS = 143.6W /D + 146W /D + 132.7W /D + 540 0.69 256 3 2 Cross section 3 TSS = 310.3W + 1331.3W 702.7W 1399 0.42 198 3 2 TSS = 1232.4W /D + 6050W /D 7417W /D + 368 0.41 182 Earth 2021, 2, FOR PEER REVIEW 11 3 2 Cross section 4 0.59 159 TSS = 723.0W 2757W + 1128.8W + 3156 3 2 0.59 156 TSS = 2731.3W /D 12498.2W /D + 14129.7W /D + 72 2 3 2 km during the dry and wet seasons, respectively, it is necessary to segregate the lake Cross section 5 TSS = 128.3W /D 617.4W /D + 750.8W /D + 22 0.56 79 based on cross sections and to propose an empirical relation for each CS, and during each TSS = 50.9t + 320 0.58 73 wave season. 3 2 Cross section 6 0.82 175 TSS = 437.4The W co1610.5 rrelatioW n co +e636.1 fficient W + incr 1690 eased from CS1 to CS7 while moving from the north- ern to th e 5southern part of the lake, and TSS was better correlated by squared or cubed TSS = 1.8 10  exp(6.1W) 6 0.81 153 transformation of wind speed over water depth and power exponent of wind speed (Table 3 2 Cross section 7 TSS = 84.2W /D 165.6W /D 144.2W /D + 53 0.88 82 4), which was in agreement with the hypothesis that the higher the wind speed is, the higher is the TSS. In general, the most significant empirical equations for various CS were TSS = 1675.8 exp(0.40t ) 134 0.77 51 wave 2 3 3 3 the following: CS1 = (𝑊 ⁄𝐷 ); CS2 = W or W /D; CS3, CS4, and CS5 = W or W /D; CS6 W = wind speed (m/s), D = water depth (m), t = shear stess (Pa), and TSS = total suspended solids (mg/L). wave ( ) ⁄ = W or 𝑊 ; and CS7 = 𝑊 𝐷 (Figure 4). CS2 CS1 CS2 R : > 0.686 CS5 TSS: R : > 0.563 R : 0.962 CS3 CS7 CS3 and CS4 CS4 R : > 0.774 CS3 – R : >0.412 CS5 CS4 – R : 0.589 CS6 CS6 CS7 R : > 0.813 Figure 4. Empirical relation of TSS with the wind speed and lake depth across various cross sections (CS) in Tonle Sap Figure 4. Empirical relation of TSS with the wind speed and lake depth across various cross sections (CS) in Tonle Sap Lake, Lake, Cambodia (W = wind speed, D = water depth, and 𝜏 = shear stress; for details, please refer to Table 4). 𝑎𝑤𝑣𝑒 Cambodia (W = wind speed, D = water depth, and t = shear stress; for details, please refer to Table 4). wave The TSS concentration across TSL could be better correlated with wind speed, depth, and shear stress with equations as given in Table 4. As the TSS in the dry season was higher than that in the wet season, the TSS is expected to be affected by wind speed, depth, and shear stress. Even though shear stress is a main factor governing sediment re-suspen- sion, wind speed and depth, but not shear stress, were the primary factors governing TSS concentration (Table 4). For better simulation of TSS concentration, other sediment (set- tling velocity, wind flux, and wind wave energy) and environmental factors (wave length and wave height) need to be considered in hydrodynamic models. 3.4. Mechanism of Sediment Re-Suspension The current study was conducted to assess the role of the wind field on sediment re- suspension and the probability of sediment suspension using the wind fetch model. On the other hand, the spatial distribution of wind-induced sediment re-suspension has not been thoroughly described and it is necessary to research for sediment re-suspension pre- dictions in large shallow lakes. The impact of water level fluctuation on the sediment dy- namics in TSL has been described in a recently published paper [42]. Wave action and subsequent fetches are more likely to cause re-suspension by bottom scouring and are 𝑒𝑥𝑝 𝑒𝑥𝑝 Earth 2021, 2 435 The TSS concentration across TSL could be better correlated with wind speed, depth, and shear stress with equations as given in Table 4. As the TSS in the dry season was higher than that in the wet season, the TSS is expected to be affected by wind speed, depth, and shear stress. Even though shear stress is a main factor governing sediment re-suspension, wind speed and depth, but not shear stress, were the primary factors governing TSS concentration (Table 4). For better simulation of TSS concentration, other sediment (settling velocity, wind flux, and wind wave energy) and environmental factors (wave length and wave height) need to be considered in hydrodynamic models. 3.4. Mechanism of Sediment Re-Suspension The current study was conducted to assess the role of the wind field on sediment re- suspension and the probability of sediment suspension using the wind fetch model. On the other hand, the spatial distribution of wind-induced sediment re-suspension has not been thoroughly described and it is necessary to research for sediment re-suspension predictions in large shallow lakes. The impact of water level fluctuation on the sediment dynamics in TSL has been described in a recently published paper [42]. Wave action and subsequent fetches are more likely to cause re-suspension by bottom scouring and are determined by wind speed and fetch [43]. The total shear stress (Pa) as a sum of wind-induced waves and wind-induced currents, and critical shear stress for CS from 1 to 7, for different time periods, December, March, and June, are shown in Supplementary File S3. Critical shear stress at most of the places was higher than the total shear stress (Supplementary File S3), indicating three important points: (i) there was sedimentation (no erosion) of the sediment at most of the CS during the transition period of reversal flow from TSL to MR via TSR in December (end of the rainy season) and from MR to TSL in June (beginning of the rainy season); (ii) most of the sediment that was discharged at various CS in TSL is retained (i.e., no outflow) within the lake; and (iii) whatever erosion of the sediment occurred in TSL, it was predominant in the southern part of the lake at CS5, 6, and 7. Wind-induced wave shear stress was larger than the wind-induced current shear stress, though the latter was negligible. It can be presumed that shear stress could not be said to be the cause of sediment re-suspension as the total shear stress was mostly lesser than the critical shear stress. The shear stress due to wind-induced waves did not vary at different CS of the lake. In general, the shear stress due to waves is smaller at the center of the lake than at the shore. Shear stress increased toward the shoreline of the lake, perhaps due to transfer of wind energy at the shoreline, as when wind moves from land to middle of the lake, wind energy is much smaller at the middle of the lake where there is much water. This phenomenon could explain why the turbidity at the bank is higher than that at the center of the lake. The higher turbidity at the bank is caused by the shallow water and wave breaking. In this case, it is believed that wind energy is one of the crucial factors governing sediment resuspension, as the energy from the wind near the shoreline is naturally stored and is utilized for sediment re-suspension. The selected sites, where the total shear stress was greater than the critical shear stress, were then taken for the comparison of shear stress with TSS (Table 5). As shown in Table 5 and Figure 5, TSS decreases with the increase in water depth (R = 0.57). Considering that most of the time when the total shear stress was greater than the critical shear stress was in March, which is the middle of the dry season, it can be generalized that the shallower the water depth is, the higher is the total shear stress. The total shear stress increased toward the southern part of TSL. Sediment re-suspension occurred in all seasons in CS7-4, which is located at the southernmost point. Around the south side of TSL, the MR, one of the largest tributaries of TSL, is located nearby, and the inflow of water and sediment from this river has a higher value than that of other tributaries. It can be inferred that sediment re-suspension is likely to occur in places with higher amounts of sediment. Earth 2021, 2 436 Table 5. Comparison of TSS, water depth, total shear stress, and critical shear stress across selected sites. TSS Water Depth Total Shear Critical Shear Date Point (mg/L) (m) Stress (Pa) Stress (Pa) 21 December 2016 CS7-4 6 8.0 2.93 1.63 30 March 2017 CS5-2 158 0.3 5.85 2.36 Earth 2021, 2, FOR PEER REVIEW 13 15 March 2017 CS5-4 55 0.5 3.30 3.94 16 March 2017 CS5-4 137 1.6 2.53 0.83 26 March 2017 CS5-5 140 0.6 2.26 0.83 15 March CS6-5 72 0.8 1.76 1.52 15 March 2017 CS6-2 189 1.3 3.06 2.06 15 15 Ma Mar rchch 2017 CS6-5 72 0.8 1.76 1.52 CS7-1 279 0.5 5.81 3.85 15 March 2017 CS7-1 279 0.5 5.81 3.85 15 March 15 March 2017 CS7-4 289 1.0 3.25 1.63 CS7-4 289 1.0 3.25 1.63 2 July 2017 CS7-4 25 5.5 2.66 1.63 2 July 2017 CS7-4 25 5.5 2.66 1.63 -0.661 y = 21.742x R² = 0.5691 0 50 100 150 200 250 300 TSS (mg/L) Figure 5. Relationship of TSS with water depth (data source Table 5). Figure 5. Relationship of TSS with water depth (data source Table 5). In addition, there was spatio-temporal variation in the relationship between TSS and In addition, there was spatio-temporal variation in the relationship between TSS and each environmental parameter (Supplementary File S4). In general, there was a negative each environmental parameter (Supplementary File 4). In general, there was a negative correlation among TSS, settling velocity, and critical shear stress. In other words, the lower correlation among TSS, settling velocity, and critical shear stress. In other words, the lower the settling velocity was, the lower the critical shear stress and the higher the TSS. Loss the settling velocity was, the lower the critical shear stress and the higher the TSS. Loss on on ignition (LOI at 550 C) was higher during the dry season compared to that during the ignition (LOI at 550 °C) was higher during the dry season compared to that during the wet season, which meant that the amount of organic matter changed according to season wet season, which meant that the amount of organic matter changed according to season and that it varied greatly depending on the location. As TSL is huge, it is recommended to and that it varied greatly depending on the location. As TSL is huge, it is recommended perform clustering of the lake according to the site for detailed characterization of the TSS to perform clustering of the lake according to the site for detailed characterization of the and to understand the impact of the wind on sediment re-suspension. TSS and to understand the impact of the wind on sediment re-suspension. 3.5. Time to Reach Equilibrium TSS 3.5. Time to Reach Equilibrium TSS The time to reach equilibrium TSS in March, June, and December is shown in Table 6. The time to reach equilibrium TSS in March, June, and December is shown in Table There was a significant difference in time to reach equilibrium TSS: 9, 20, and 32 days in 6. There was a significant difference in time to reach equilibrium TSS: 9, 20, and 32 days March, June, and December, respectively, corresponding to average depths of 1.2, 2.7, and in March, June, and December, respectively, corresponding to average depths of 1.2, 2.7, 4.7 m (Table 6). The higher the depth is, the higher is the time to reach equilibrium TSS. In and 4.7 m (Table 6). The higher the depth is, the higher is the time to reach equilibrium addition, time for equilibrium differed, and there were no significant differences in settling TSS. In addition, time for equilibrium differed, and there were no significant differences in settling velocity and wind speed in each month. It can be interpreted that there is an impact of the wind and other sediment and environmental factors in governing sediment re-suspension. Table 6. Calculation of time to reach equilibrium TSS in Tonle Sap Lake, Cambodia. March (2017) June (2017) December (2016) 𝛼𝑊 Max ( ) 433 684 15.5 Observed TSS ( ) Min (𝑆 0 ) 4.5 12 4.3 (mg/L) Ave 176.8 157.4 4.8 Water depth (m) Earth 2021, 2 437 velocity and wind speed in each month. It can be interpreted that there is an impact of the wind and other sediment and environmental factors in governing sediment re-suspension. Table 6. Calculation of time to reach equilibrium TSS in Tonle Sap Lake, Cambodia. March (2017) June (2017) December (2016) aW 433 684 15.5 Max Observed TSS Min (S(0)) 4.5 12 4.3 (mg/L) Ave 176.8 157.4 4.8 Average wind speed (m/s) (W) 2.3 2.5 2.4 Average water depth (m) (D) 1.2 2.8 4.7 Average settling velocity (m/day) (b) 3.2 3.3 3.3 Time for equilibrium TSS (day) 9 20 32 The parameters in Table 6 are based on Equation (11): p p aW aW (bt/D) S = + S(0) e , (11) b b aW where = is considered the maximum TSS and background TSS (= S(0)) is con- sidered the minimum TSS in the whole TSL and in each point (CS1–CS7). The monthly average settling velocity (b) and water depth (D) were used for the calculation of suspended sediment concentration (S). 4. Conclusions In March, the wind direction is mainly southward and changes toward the southeast or southwest depending on the locations. In general, the wind speed in December and March was less than 5 m/s, but in June and September, the wind speed was as much 7 m/s. On the basis of the weighted Pearson correlation coefficient (r) and RMSE, wind interpolation using the IDW method was found to be comparatively better than the vectorized average and inverse of the ratio of distance. The TSS concentration, in general, during the wet season in December and September was less than 50 mg/L, but during the dry season in March and June, it was greater than 50 mg/L and peaked up to 400 mg/L in March and greater than 600 mg/L in June. The sediment characteristics with respect to sand, silt, and clay did not differ much across various CS in TSL. Settling velocity (m/day) across 37 sites across TSL varied from 0.28 to 11.70, with an average of 3.25  2.75. TSS did not exhibit direct correlation with the settling velocity and sediment character- istics (LOI and particle diameter). The empirical equation to correlate TSS with wind speed (W), water depth (D), and shear stress (t_wave), especially during dry season (W/D) 2 3 3 for different CS across TSL is, CS1= exp ; CS2= W or W /D; CS3, and CS4 = W 3 3 3 (W) 3 (t_wave) or W /D; CS5 = W /D or t_wave; CS6 = W or exp ; and CS7 = W /D or exp (for detailed equation, please refer to Table 4). The shear stress due to waves was smaller at the center of the lake and increased toward the shoreline, which is one of the reasons why TSL exhibits higher TSS at the shoreline than at the center of the lake. The total shear stress was greater than the critical shear stress, especially during the dry season in March, when TSS is higher and water depth is lower, compared to the wet season, when TSS is low and water depth is higher. The higher wind-induced critical shear stress than the total shear stress at most of the CS in TSL indicated sedimentation occurs predominantly during the transition phase Earth 2021, 2 438 of the reversal flow between TSL and MR during December and June, and erosion (siltation) is dominant during March. Additionally, most of the siltation in March was dominant in the southern part of the lake, at CS5, 6, and 7. The times to reach equilibrium TSS in March, June, and December were 9, 20, and 32 days, respectively. In general, the higher the depth is, the longer the time to reach equilibrium TSS. Supplementary Materials: The following are available online at https://www.mdpi.com/article/10 .3390/earth2030025/s1, Supplementary File S1: wind interpolation; Supplementary File S2: Empirical relation; Supplementary File S3: mechanism; Supplementary File S4: Relationship of TSS with wind speed, water depth, settling velocity, and loss on ignition across Tonle Sap Lake, Cambodia. Author Contributions: Conceptualization, M.S., R.K., S.U., S.S., C.Y.; methodology, M.S., R.K., T.S., C.Y.; software, M.S., S.S.; validation, M.S., S.S., R.K., C.Y.; formal analysis, M.S.; investigation, M.S.; resources, R.K., C.Y., data curation, M.S., S.U., S.S., writing—original draft preparation, R.K.; writing— review and editing, R.K., C.Y.; visualization, M.S., R.K.; supervision, S.S., S.U., R.K., C.Y.; project administration, R.K., C.Y.; funding acquisition, C.Y. All authors have read and agreed to the published version of the manuscript. Funding: This is one of the outcomes from Science and Technology Research Partnership for Sus- tainable Development (SATREPS—JST/JICA: grant-number JPMJSA1503) Project in Cambodia— Establishment of Environmental Conservation Platform of Tonle Sap Lake. Data Availability Statement: All relevant data are reported in this paper. 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Journal

EarthMultidisciplinary Digital Publishing Institute

Published: Jul 6, 2021

Keywords: wind speed and direction; spatio-temporal; total suspended solids; interpolation; shear stress; Tonle Sap Lake

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