[A-HW18] 水循環・水環境

[AHW18-03] A comprehensive analysis of the water balance for the Tonle Sap Lake system

*Davin Tes¹、Raksmey Ang^1,2、Tsuyoshi Kinouchi¹ (1.Tokyo Institute of Technology、2.Cambodia Development Resource Institute)

キーワード：Major feature, Mekong River, Tonle Sap Lake system, Water balance

The Tonle Sap Lake and floodplain system play an important role in supporting the ecosystem in the Mekong River Basin. However, the lake system has experienced intensive environmental changes during the last few decades due to the alteration of the lake and the Mekong River. Accordingly, an up-to-date analysis of the water balance components is crucial for providing insight information on the changes in the lake system’s major features. Therefore, in this study, we propose a comprehensive assessment of the water balance model considering the temporal dynamic change of the floodplain over 20 years from 2001 to 2020. On average, the lake receives 45% of its annual volume from the Mekong River, of which 44% comes from its tributaries and 11% from local precipitation. On the other hand, 81.5% of the lake's water volume is discharged into the Mekong River, while the remaining 18.5% is evaporated from the lake water surface and floodplain. The results demonstrate that the average annual reverse flow from the Mekong River decreased by 23.9% between 2001 and 2010, from 44.63 km³ to 33.98 km³ between 2011 and 2020, whereas the tributary inflow rose slightly, from 37.5 to 39.3 km³. As a result, the lake's outflow to the Mekong River decreased from 68.36 km³ in 2001-2010 to 60.9 km³ in 2011-2020. In addition, based on the water balance analysis, the findings reveal that the influence of Mekong inflow on the annual water volume of Tonle Sap Lake is expected to decrease as response to the hydropower development in the Mekong mainstream. These findings provide guidance for strengthening the effectiveness of management strategies and environmental conservation initiatives in the Basin.