Molecular weight-dependent spectral and metal binding properties of sediment dissolved organic matter from different origins.

Multidecadal water quality deterioration in the largest freshwater lake in China (Poyang Lake): Implications on eutrophication management

Precipitation, as a primary hydrological variable in the water cycle plays an important role in hydrological modeling. The reliability of hydrological modeling is highly related to the quality of precipitation data. Accurate long-term gauged precipitation in the Mekong River Basin, however, is limited. Therefore, the main objective of this study is to assess the performances of various gridded precipitation datasets in rainfall-runoff and flood-inundation modeling of the whole basin. Firstly, the performance of the Rainfall-Runoff-Inundation (RRI) model in this basin was evaluated using the gauged rainfall. The calibration (2000-2003) and validation (2004-2007) results indicated that the RRI model had acceptable performance in the Mekong River Basin. In addition, five gridded precipitation datasets including APHRODITE, GPCC, PERSIANN-CDR, GSMaP (RNL), and TRMM (3B42V7) from 2000 to 2007 were applied as the input to the calibrated model. The results of the simulated river discharge indicated that TRMM, GPCC, and APHRODITE performed better than other datasets. The statistical index of the annual maximum inundated area indicated similar conclusions. Thus, APHRODITE, TRMM, and GPCC precipitation datasets were considered suitable for rainfall-runoff and flood inundation modeling in the Mekong River Basin. This study provides useful guidance for the application of gridded precipitation in hydrological modeling in the Mekong River basin.

/pdf/comparison-of-gridded-precipitation-datasets-for-rainfall-1d3rn1kqr2.pdf

Comparison of gridded precipitation datasets for rainfall-runoff and inundation modeling in the Mekong River Basin.

Exploring the spatiotemporal water quality variations and their influencing factors in a large floodplain lake in China

Changes of inundation area and water turbidity of Tonle Sap Lake: responses to climate changes or upstream dam construction?

Sediment dynamics in a large shallow lake characterized by seasonal flood pulse in Southeast Asia.

The Mekong River Basin (MRB) in Southeast Asia is among the world’s ten largest rivers, both in terms of its discharge and sediment load. The spatial and temporal resolution to accurately determine the sediment load/yield from tributaries and sub-basin that enters the Mekong mainstream still lacks from the large-scale model. In this study, the SWAT model was applied to the MRB to assess long-term basin hydrology and to quantify the sediment load and spatial sediment yield in the MRB. The model was calibrated and validated (1985–2016) at a monthly time step. The overall proportions of streamflow in the Mekong River were 34% from surface runoff, 21% from lateral flow, 45% from groundwater contribution. The average annual sediments yield presented 1295 t/km2/year in the upper part of the basin, 218 t/km2/year in the middle, 78 t/km2/year in the intensive agricultural area and 138 t/km2/year in the highland area in the lower part. The annual average sediment yield for the Mekong River was 310 t/km2/year from upper 80% of the total MRB before entering the delta. The derived sediment yield and a spatial soil erosion map can explicitly illustrate the identification and prioritization of the critical soil erosion-prone areas of the MR sub-basins.

Assessment of Hydrology and Sediment Yield in the Mekong River Basin Using SWAT Model

Characterization of total suspended solid dynamics in a large shallow lake using long‐term daily satellite images

Projecting changes in the frequency and intensity of future precipitation and flooding is critical for the development of social infrastructure under climate change. The Mekong River is among the world's large‐scale rivers severely affected by climate change. This study aims to define the duration of precipitation contributing to peak floods based on its correlation with peak discharge and inundation volume in the Lower Mekong Basin (LMB). We assessed the changes in precipitation and flood frequency using a large ensemble Database for Policy Decision‐Making for Future Climate Change (d4PDF). River discharge in the Mekong River Basin (MRB) and flood inundation in the LMB were simulated by a coupled rainfall‐runoff and inundation (RRI) model. Results indicated that 90‐day precipitation counting backward from the day of peak flooding had the highest correlation with peak discharge (R² = .81) and inundation volume (R² = .81). The ensemble mean of present simulation of d4PDF (1951–2010) showed good agreement with observed extreme flood events in the LMB. The probability density of 90‐day precipitation shifted from the present to future climate experiments with a large variation of mean (from 777 to 900 mm) and SD (from 57 to 96 mm). Different patterns of sea surface temperature significantly influence the variation of precipitation and flood inundation in the LMB in the future (2051–2110). Extreme flood events (50‐year, 100‐year, and 1,000‐year return periods) showed increases in discharge, inundation area, and inundation volume by 25%–40%, 19%–36%, and 23%–37%, respectively.

Projection of extreme flood inundation in the Mekong River basin under 4K increasing scenario using large ensemble climate data

Abstract. The Cambodian floodplains experience a yearly flood pulse that is
essential to sustain fisheries and the agricultural calendar. Sixty years of data, from 1960–2019, are used to track the changes to the flood pulse there.
We find that minimum water levels over 2010–2019 increased by up to 1.55 m at Kratie and maximum water levels decreased by up to 0.79 m at Prek
Kdam when compared to 1960–1991 levels, causing a reduction of the annual
flood extent. Concurrently, the duration of the flooding season has
decreased by about 26 d (Kampong Cham) and 40 d (Chaktomuk), with the
season starting later and ending much earlier. Along the Tonle Sap River,
the average annual reverse flow from the Mekong to the Tonle Sap Lake has
decreased by 56.5 %, from 48.7 km3 in 1962–1972 to 31.7 km3 in
2010–2018. As a result, wet-season water levels at Tonle Sap Lake
dropped by 1.05 m in 2010–2019 compared to 1996–2009, corresponding to a 20.6 %
shrinkage of the lake area. We found that upstream contributors such as
current hydropower dams cannot fully account for the observed decline in
flood pulse. Instead, local anthropogenic causes such as irrigation and
channel incision are important drivers. We estimate that water withdrawal in
the Cambodian floodplains is occurring at a rate of (2.1 ± 0.3) km3 yr−1. Sediment decline and ongoing sand-mining operations
have also caused channel erosion. As the flood pulse is essential for the
ecological habitats, fisheries and livelihoods of the region, its reduction
will have major implications throughout the basin, from the Tonle Sap system
to the Vietnamese Mekong Delta downstream.


/pdf/drastic-decline-of-flood-pulse-in-the-cambodian-floodplains-1qb8lxz7.pdf

Ty Sok

Papers

Sediment dynamics in a large shallow lake characterized by seasonal flood pulse in Southeast Asia.

Assessment of Hydrology and Sediment Yield in the Mekong River Basin Using SWAT Model

Characterization of total suspended solid dynamics in a large shallow lake using long‐term daily satellite images

Projection of extreme flood inundation in the Mekong River basin under 4K increasing scenario using large ensemble climate data

Drastic decline of flood pulse in the Cambodian floodplains (Mekong River and Tonle Sap system)