Climate change impact on water balance and hydrological extremes in the Lower Mekong Basin: a case study of Prek Thnot River Basin, Cambodia

Abstract

Climate change alters hydrological cycles and streamflow regimes at the local, regional and global levels. In this study, we aimed to assess the change in water balance change and hydrological extremes in the Prek Thnot River Basin of the Lower Mekong in Cambodia through a hydrological model (SWAT) under the two climate change scenarios (RCP2.6 and RCP8.5) following three different GCMs. An ensemble of 3 GCMs included GFDL-CM3, GISS-E2-R-CC and IPSL-CM5A-MR models and was applied to a well-calibrated SWAT model through climate change factors. Annual precipitation under RCP2.6 likely decreases by 0.1–0.5% for the near future (2021–2040) and mid-future (2051–2070) and decreases by 0.2–1.3% under RCP8.5. The decrease in precipitation will lead to reductions in water yield by 1–4% (RCP2.6) and 2–5% (RCP8.5). However, peak flow is expected to increase, while the low flow was projected to decrease (1–2% for RCP2.6 and 8–9% for RCP8.5). The study further found that high flow events will increase in both magnitude and frequency. The finding highlights water resources management issues in the Prek Thnot River Basin, including the frequency of future flood events. HIGHLIGHTS We estimated the climate change impact on water balance and hydrological extremes.; Annual water balance in the Prek Thnot River Basin is projected to decrease in the future.; Future streamflow is expected to increase in the wet season while decreasing in the dry season.; Peak flows have an increasing trend while low flows have a decreasing trend in the future.;

Keywords

• climate change
• hydrological extremes
• lower mekong basin
• prek thnot river basin
• swat model
• water balance