Satellite observations and modeling to understand the Lower Mekong River Basin streamflow variability

Abstract

In this work, we have used the Soil & Water Assessment Tool (SWAT) to examine streamflow variability of the Lower Mekong River Basin (LMRB) associated with changes in the Upper Mekong River Basin (UMRB) inflows. Two hypothetical experiments were formulated and evaluated for the LMRB, where we conducted runoff simulations with multiple inflow changes that include upstream runoff yield increase and decrease scenarios. Streamflow variability of the LMRB was quantified by two streamflow metrics that explain flow variability and predictability, and high flow disturbance. The model experiments were performed for the Lower Mekong River Basin with identical climate, soil, and other watershed characteristics data. Remote sensing precipitation (Tropical Rainfall Measurement Mission, TRMM, and Global Precipitation Measurement mission, GPM), meteorological data as well as spatial data that include a digital elevation model, newly developed soil information (Harmonized World Soil Database, HWSD), and land use and land cover were processed as input to the LMRB model simulations. Observed daily streamflow data along the Lower Mekong River from Chiang Sean, Thailand to Kratie, Cambodia were used for calibration and validation. Our work results suggest that the Lower Mekong River streamflow is highly variable and has a low predictability (Colwell index of about 32%). We found that releasing more water from upstream Mekong during rainfall months by 30% would result in a reduction in the Lower Mekong streamflow predictability by about 21%. This reduction in predictability is mainly attributed to a decrease in the Contingency index. Our work shows that the ability to predict floods/droughts at the Lower Mekong River would be reduced if there is any anticipated change (i.e., increase/decrease) from UMRB releases. Our results also show that releasing more flows from the upstream Mekong would also affect flood duration and the frequency of flood occurrences downstream. The results of this work thus help to quantify the sensitivity of streamflow variability at the Lower Mekong River Basin to upstream anthropogenic changes.

A Review of SWAT Studies in Southeast Asia: Applications, Challenges and Future Directions

“…Some of the earliest applications of SWAT in the SEA were for hydrologic analyses of the Mekong River basin [14,39,40]. Analyses of parts or all of the Mekong system with SWAT have continued to the present [41][42][43][44][45] along with increasing numbers of studies that have been performed for specific watersheds located in various SEA countries [46][47][48][49][50][51][52][53]. These SWAT studies have been performed for a wide range of water resource issues, watershed size, and climatic conditions, but there have been no analyses to date of the overall implications of these studies for the SEA region.…”

Developing Land Use Land Cover Maps for the Lower Mekong Basin to Aid Hydrologic Modeling and Basin Planning

“…The LULC maps from the project are being used to help SWAT modelers improve predictions of water flow dynamics that in turn is being used for aiding water management and basin planning in the LMB. Updated LULC maps along with soils, terrain, and precipitation maps from the project are being used to generate needed SWAT modeling products [41][42][43]. The LULC maps from the project also provided more specific maps of rice paddies (single-versus double-cropped or rainfed versus irrigated) that are potentially helpful for aiding other basin planning efforts in the LMB, including flood damage monitoring and assessment applications [44,45].…”

Ground and satellite based observation datasets for the Lower Mekong River Basin

“…This paper reports various hydrological time series and remote sensing data that was used to model and understand the streamflow variability in the Lower Mekong River Basin (LMRB) [1] . Mohammed et al, [1] used the Soil & Water Assessment Tool (SWAT) hydrologic model ( https://swat.tamu.edu/ ) to simulate hydrological fluxes in the LMRB and explore the streamflow regime changes as a result of expected upstream flow changes (i.e., the Chinese part of the Mekong River). Fig.…”

“… In ‘Satellite observations and modeling to understand the Lower Mekong River Basin streamflow variability’ [1] hydrological fluxes, meteorological variables, land cover land use maps, and soil characteristics and parameters data were compiled and processed for the Lower Mekong River Basin. In this work, daily streamflow time series data at nine gauges located at five different countries in the Mekong region (Thailand, Laos People׳s Democratic Republic (PDR), Myanmar, Cambodia, and Viet Nam) is presented.…”