High Resolution Modeling of River‐Floodplain‐Reservoir Inundation Dynamics in the Mekong River Basin

Abstract

Numerous studies have examined the changes in streamflow in the Mekong River Basin (MRB) using observations and hydrological modeling; however, there is a lack of integrated modeling studies that explicitly simulate the natural and human-induced changes in flood dynamics over the entire basin.Here we simulate the river-floodplain-reservoir inundation dynamics over the MRB for 1979-2016 period using a newly integrated, high-resolution (~5 km) river hydrodynamics-reservoir operation model. The framework is based on the river-floodplain hydrodynamic model CaMa-Flood in which a new reservoir operation scheme is incorporated by including 86 existing MRB dams. The simulated flood extent is downscaled to a higher resolution (~90 m) to investigate fine-scale inundation dynamics, and results are validated with ground-and satellite-based observations. It is found that the historical variations in surface water storage have been governed primarily by climate variability; the impacts of dams on river-floodplain hydrodynamics were marginal until 2009. However, results indicate that the dam impacts increased noticeably in 2010 when the basin-wide storage capacity doubled due to the construction of new mega dams. Further, results suggest that the future flood dynamics in the MRB would be considerably different than in the past even without climate change and additional dams. However, it is also found that the impacts of dams can largely vary depending on reservoir operation strategies. This study is expected to provide the basis for high-resolution river-floodplain-reservoir modeling for a holistic assessment of the impacts of dams and climate change on the floodpulse-dependent hydro-ecological systems in the MRB and other global regions.

Development of a SWAT Hydropower Operation Routine and Its Application to Assessing Hydrological Alterations in the Mekong

“…Analysis of the hydrological alterations parameters shows that flow regime alteration is likely due to the operation of reservoirs. However, the magnitude and intensity of the alterations vary widely based on reservoir characteristics, location and operation policies, which has also been pointed out in other studies [58][59][60][64][65][66]. Our results indicated that, in addition to reservoir features, the location of the reservoir is also a significant factor for variations of the rate of hydrologic alterations, as the basin is characterized by wide variation in topography and physiography with complex climatic conditions.…”

The uncertainty of flood frequency analyses in hydrodynamic model simulations

“…These products are generated with different source data, methods, spatial resolution and time slots (Leyk et al, 2019). Smith et al (2019) evaluated the population exposure to a 1-in-100 year flood in 18 developing countries. The total exposed population ranges from 101 to 134 million when using three different products, but with an up to 60 % difference in population in Uganda.…”

“…Meanwhile, representing the flood defenses remains a big challenge because the global data for flood defenses are strongly limited (Sampson et al, 2015). Attempts to improve CaMa-Flood by integrating the dam regulation (Shin et al, 2020) and levees (Tanaka and Yamazaki, 2019) have been tested at a regional scale.…”

“…Meanwhile it is difficult to visualize the inundation map at a high resolution (< 100 m) for the globe. Therefore, high-resolution (3 arcsec, ∼ 90 m at the Equator) regional analysis related to the flood water depth and inundation area with their uncertainties was only conducted regionally over deltas, which are vulnerable to floods (Shin et al, 2020). The corresponding results on the uncertainties in water depth (including at specific points) and inundation area will be presented.…”

Solar energy and regional coordination as a feasible alternative to the 'Battery of Asia' plan

“…Res, we acquired data on storage-depth relationship, maximum surface extent, dam design specifications, and rule curves. The storage-depth relationship is modeled with Liebe's method 51 , the most common approach in large-scale studies [52][53][54] . The maximum surface extent of each reservoir is estimated by extracting surface water profiles from Landsat TM and ETM+ imagery, while the dam design specifications are obtained from the Mekong River Commission and the Electricity Generating Authority of Thailand-and complemented, where necessary, with information retrieved from other databases.…”