Estimating Reservoir Residence Time Across the Mekong River Basin: Incorporating Future SWOT Mission Observations with Current Remote Sensing Data

The Mekong River Basin is undergoing rapid hydropower development. Sixteen dams are planned on the main stem of the Mekong and many more on its extensive tributaries. Understanding the effects that current and future dams have on the river system and water cycle as a whole is vital for the millions of people living in the basin. reservoir residence time, the amount of time water spends stored in a reservoir, is a key parameter in investigating these impacts. Current satellite missions provide key information for estimating reservoir time across the basin. These missions will soon be joined by the forthcoming Surface Water and Ocean Topography (SWOT) mission, which is poised to provide an unprecedented amount of surface water observations.  SWOT, when augmented by current satellite missions, will provide the necessary information to estimate the residence time of reservoirs across the entire basin in a more comprehensive way than ever before. In this study, we first combine observations from current satellite missions (altimetry, spectral imaging, precipitation) to estimate the residence times of existing reservoirs. We then use this information to project how future reservoirs will increase the residence time of the river system. Next, we explore how SWOT observations can be used to improve residence time estimation by examining the accuracy of reservoir surface area and elevation observations as well as the accuracy of river discharge observations.