Impact of Wind on the Spatio-Temporal Variation in Concentration of Suspended Solids in Tonle Sap Lake, Cambodia (original) (raw)
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Assessment of suspended sediment load variability in the Tonle Sap and Lower Mekong Rivers, Cambodia
CATENA, 2021
The Mekong River in Southeast Asia, one of the world's great rivers, has been facing disruption of its sediment balance and resultant impacts on nutrient fluxes, aquatic ecology, floodplains and the delta. Using monitoring data from 1993-2018, we estimated the temporal variability of sediment loads in Tonle Sap and Lower Mekong Rivers in Cambodia, assessing the sediment linkage between the Tonle Sap Lake and the Mekong mainstem, which are connected by a seasonally reversing flow through the Tonle Sap River. We estimated the annual sediment in the Mekong mainstem of 72±38 Mt/year at Kratie (upstream) and 78±22 Mt/year at Chroy Changvar from 1993-2018 (just upstream of the Tonle Sap confluence). Our sediment load estimation of the Mekong River is consistent with other recent estimates of sediment load on the Lower Mekong. However, the result is lower than reported in some older studies (prior to the 2000s), which is consistent with sediment trapping by dams on Upper Mekong mainstem and major tributaries. Our analysis indicates that Tonle Sap Lake provided 0.65±0.6 Mt/year of sediment annually to the Lower Mekong River from 1995 to 2000. However, since 2001, Tonle Sap Lake has become a sink for sediment, accumulating an average of 1.35±0.7 Mt annually. Net storage of sediment in Tonle Sap Lake reduces the annual sediment transport to the delta, further compounding the effects of reduced sediment delivery to the delta resulting from upstream dam development and instream sand mining.
Water Practice and Technology
The Ca River basin has an area of 27,200 km2 distributed across the territories of two countries: Vietnam (65.2%) and Lao (34.8%). Spatial and temporal variations in suspended sediment (SS) and dissolved nutrients (PO43-, NO3-, SiO2) were determined in two hydrological stations located along the Ca River 4–6 times per month in the rainy season and 1–4 times per month in the dry season, between the months of August 2017 and July 2018. A loading–discharge (L–Q) curve was used to analyze the correlation among water physicochemical parameters with seasonal river discharge. The results indicate that SS was higher in upstream flows compared to downstream flows, which is primarily due to erosion. Seasonal SS and dissolved phosphate have an inverse correlation trend to that of dissolved silica. Results revealed that the concentration of phosphate and SS was higher in the rainy season than in the dry season. This finding proves that rain washes particulate matter from the surface runoff into...
Sustainability
The extreme variation in the amount of annual precipitation and rainfall during single events is typical of the East Asian monsoon climate and may greatly influence the characteristics of the suspended sediment load. The turbidity in Lake Imha which is the eighth largest multipurpose dam in Korea has been the cause of major water quality problems for use as drinking water. The turbidity rose to 882 NTU, and it remained over 30 NTU continuously for 170 days during 2002, as the result of significant amounts of soil erosion from the watershed during the Asian monsoon typhoon. In this study, characteristics of suspended sediment loadings under the Asian summer monsoon climate was investigated by comparing the variation of yearly suspended sediment loads and the ratio of maximum suspended sediment loads in a single event to yearly suspended sediment load from Lake Imha watershed using the Hydrologic Simulation Program-FORTRAN (HSPF). The model calibration is performed according to the 2009-2010 events, and simulation results characterized suspended sediment loadings under the Asian summer monsoon climate for 2001-2010. Water sampling and flow rate measurements were performed every 4-6 h, and calibration was performed using hourly simulated sediment loads. The calibration results demonstrated good agreement with the observed data. The characteristics of suspended sediment loadings under the Asian summer monsoon climate are a high variance of the yearly suspended sediment load and a significant of amount of suspended sediment load during a single event influenced by the typhoon intensity. The maximum yearly suspended sediment load was 10 times higher than the minimum yearly value. About half of the yearly suspended sediment load was loaded with a single event under the Asian summer monsoon climate and the ratio of suspended sediment loads by a single event to total yearly loads ranged from 29% to 90%. Structural best management practices (BMPs) to trap suspended sediment in stormwater such as stormwater ponds or wetlands rely on much more storage volume or area and non-structural BMPs to minimize soil erosion by source control such as mulching or revegetation in disturbed areas, which are important BMPs, especially in the Asian summer monsoon region.
Sediment accumulation owing to backwater effect in the lower reach of the Stung Sen River, Cambodia
Geomorphology, 2017
We examined channel bars at two sites in the lower reach of the Stung Sen River, which flows into Lake Tonle Sap, Cambodia, to identify sediment transport and accumulation processes during monsoon-related flood events and to investigate how sediment transport capacity changes as a result of enhanced backwater effect of the lake. Channel bars in the lower reach of the Stung Sen River that emerge in the dry season were classified into type A (lateral bars), type B (point bars), type C (concave-bank benches) and type D (diagonal and island bars, or fluvial dunes) based on Nagumo et al.'s previous study. Type B, type C, and type D channel bars were at our study sites of SEN-01 and SEN-02, about 83 and 77 km from the river mouth respectively. Computation of water surface profiles showed that sediment transport capacity of the Stung Sen River decreased abruptly after the peak flow stage because of the backwater effect from Lake Tonle Sap during the decreasing flow stage. Our observations suggest that alternating layers of sand and silt to clay layers accumulate to form type C channel bars, corresponding to changes in sediment transport capacity controlled by backwater effects from Lake Tonle Sap and by changes in flow depths and associated slackwater systems. The accumulation of alternating silt and sand layers of type B channel bars results from lateral sediment transportation that is accelerated with an increase of secondary flow, whereas development of type D channel bars is related to bedload mobility.
Journal of Hydrology: Regional Studies, 2017
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Geologos, 2021
Concentrations of suspended sediment transported by rivers are influenced by interactions between multiple drivers that act on a range of spatial and temporal scales. Such levels vary over the year, as well as across multi-year periods. Most conventional approaches to determining suspended load are based upon analyses of total suspended sediment concentration (SSC), i.e., the sum of mineral and organic matter. This approach makes it difficult, if not impossible, to determine the impact of multiple environmental factors on changes in suspension concentration precisely. The present paper focuses on the mineral and organic components of suspended sediment with the aim of determining how our knowledge of the share of each individual component can improve interpretations of SSC fluctuations during a hydro-logical year. The analysis conducted (personal and other researchers’ results) has shown that mineral and organic suspensions demonstrate mutually incompatible opposite trends under inf...
Buloma: Buletin Oseanografi Marina, 2023
Changes in total suspended solids (TSS) concentrations provide information to determine the quality of the carrying capacity of waters as marine resources. This research aims to analyze the concentration and distribution of TSS in marine waters due to anthropogenic impacts on land. The concentration and distribution changes of TSS were analyzed using a geospatial model approach. The in-situ data were collected in August 2021 and June 2022 at 11 stations in the east monsoon and analyzed in the laboratory using the gravimetric method. The results show that TSS concentration changes at the study area significantly increased concentration from 40,3-85,4 mg/L in 2021 to 64,7-140,5 mg/L in 2022, increased by 37,6-39,2%, distributed to the east in open water due to the influence of the surface current, which is driven by the wind and tidal current. The anthropogenic factors, such as land use and micro-industrial activities, were dominantly correlated with the increase in TSS concentration in the waters, which is driven by input from land due to the influence of precipitation. This research provides comprehensive monitoring, evaluating, and managing scheme data and information to researchers, local governments, and environmentalists for mitigation planning to reduce the subtraction of water quality due to anthropogenic impacts.
Suspended sediment properties in the Lower Mekong River, from fluvial to estuarine environments
Estuarine, Coastal and Shelf Science, 2019
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