Future projections of flooding characteristics in the Lancang-Mekong River Basin under climate change

Abstract

Climate change intensifies hydrological cycle, bringing critical challenges to the global and regional socio-economic development. Here we used four global climate models to project future precipitation that drives hydrological modeling of future 30-year daily runoff in a large international river basin, the Lancang-Mekong River Basin (LMRB). We applied four probability distribution functions to fit the flood peak and maximum 3-day flood volume series at four major hydrologic stations. The copula function was used to establish the joint distribution between extreme precipitation and flood peak to estimate the impact of precipitation change on floods. Results show that annual maximum 30-day precipitation (AM30D) and flood peak at Pakse station are highly correlated. Future basin-averaged AM30D is projected to increase under most climate scenarios, although AM30D varies widely in spatial distribution. The extreme values of AM30D (e.g., AM1D and AM3D) in the future (2021–2050) are larger than those in historical period (1981–2004). The temporal distribution of future AM30D is more uneven, showing the “bimodal” distribution. For the Yun Jinghong station, large uncertainty is estimated in change of direction of annual maximum flood peak and maximum 3-day flood volume. As for the other three stations, they are all projected to have larger flood risks in spite of different magnitudes. The larger the return period, the larger the increase, the greater the impact of climate change. The change of basin-averaged AM30D precipitation in the future will lead to the increase of flood peak at Pakse station via the bivariate frequency analysis. From the perspective of water conservancy project safety, considering the “adverse principle”, flood control design according to the design results derived from the joint distribution of two variables between AM30D and flood peak can reduce the risk of flood disaster. This study can provide scientific reference and basis for flood control and disaster reduction and water resources cooperation policy development in LMRB.