Quantitative analysis for the response of streamflow variation to driving factors in seven major basins across China

1.2 billion people and 90% of the national GDP are concentrated in China's seven river basins (RB7). Streamflow variation of RB7 caused by climate change and human disturbance posing a severe challenge to the water resources security situation in China. Quantifying streamflow changes under these two stresses is crucial for deeply understanding hydrologic process and reasonably utilizing water resource. The present study analyzed the trends of data series with Sen's slope estimator and Mann-Kendall test, and quantified the influences of precipitation (P), potential evapotranspiration (ET0) and underlying surface parameter (omega) on streamflow variation by Budyko hypothesis-based elasticity coefficient method in 9 catchments controlled by mainstream hydrological stations from seven major river basins across China. Results showed that: Annual streamflow in LRB, YRB1, and HaiRB displayed significant downward trends of -0.16, -0.67 and -0.53 mm.y- 1 during 1961-2020. Except for HuaiRB, the annual streamflow series of other catchments experienced significant mutations during 1984-2000. The elasticity coefficient epsilon P ranged from 1.65 to 3.56, epsilon ET0 ranged from -2.56 to -0.65, and epsilon omega ranged from -3.79 to -0.52. A higher sensitivity of streamflow to P and omega, comparing to ET0. Streamflow in the north basins was more sensitive to driving factors than in the south basins across China. Variations in annual streamflow in LRB and YZRB were mainly ascribed to the changes in P, with the contribution rates ranging 65.1-162%, while the underlying surface change dominated the streamflow reduction in SHRB, HaiRB, HuaiRB, YRB, and PRB, with the contribution rates ranging 60.0-163%. ET0 had a weak effect on streamflow change in most basins. The change of underlying surface omega was largely due to vegetation cover changing, urbanization expanding, water consumption increasing and water conservancy constructing.