Hydrologic alteration by hydropower dams and climate change in the Sesan Basin

The Sesan River, a major tributary of the Lower Mekong River, is renowned for its diverse biomes and is an important resource for its nearby inhabitants. Hydropower dams have proliferated in the basin, yet their hydrologic impacts remain poorly understood, particularly when combined with the influence of climate change. This study evaluates hydrologic alterations resulting from the operation of hydropower dams and projected climate change in the basin. Climate change projections are estimated under two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5), and daily streamflow is simulated using the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS). The degree of hydrologic alteration is assessed using the Indicators of Hydrologic Alteration (IHA) under dam operation, climate change, and dams and climate change combined. Dam operations induce moderate alteration, while climate change alone causes low alteration. The combined scenario causes higher alteration than the individual scenarios, but the alteration falls within the moderate category.