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Climate change and its impact on water availability of large international rivers over the mainland Southeast Asia

Liu, Zhaofei, Wang, Rui, Yao, Zhijun
Hydrological processes 2018 v.32 no.26 pp. 3966-3977
basins, climate, climate change, dams (hydrology), drought, dry season, evapotranspiration, irrigation water, melting, periodicity, rivers, runoff, snowmelt, water budget, watersheds, Mekong River, South East Asia
Changes in climate and the resulting hydrologic variability are of great concern in international river basins. Based on observed station data, climate change and its impact on water availability in large international rivers across mainland Southeast Asia (MSA) were investigated by a combined method of trend detection and hydrologic budget balance analysis. This method can be applied easily to other studies to evaluate impacts of climate change on run‐off and water resources at the basin scale. Precipitation showed a decreasing trend in the MSA during 1960–2016, especially in the dry season. Decreasing precipitation and increasing evapotranspiration were the main reasons for severe droughts during recent years. Climate change was the main reason for run‐off changes over the MSA. The presence of dams in the upstream region was not enough to change the annual variability of natural run‐off in the Mekong River. Run‐off and precipitation changes showed significant variances in different basins and regions, and in different periods. The overall trend of precipitation and run‐off showed a periodicity of about 35 years. Nonprecipitation effects were also significant in some regions, including increasing irrigation water demand in the Red River and increasing glacial melt in the Brahmaputra River basin. Melt increased at least 75.2 × 10⁸ m³/10a during 1960–2003, representing 1.2% of mean annual run‐off in the Brahmaputra River. The positive effect of glacial meltwater was almost equal to the negative effect of evapotranspiration on run‐off change in the Lancang River. Increasing evapotranspiration played a dominant effect on run‐off changes in the Yarlung Zangbo River basin during 1960–2010.