Changes and drivers of long-term land evapotranspiration in the Yangtze River Basin: A water balance perspective

Evapotranspiration (ET) serves as a crucial indicator for understanding both global and regional water cycles and the impacts of climate change. Traditionally, water balance-based ET derived using satellite gravimetry, runoff and precipitation is considered as a benchmark for ET assessment. However, this method faces limitations in providing long-term, high temporal resolution ET estimates because of the relatively short observation period of the Gravity Recovery and Climate Experiment (GRACE) satellites. To address this challenge, we reconstruct longterm terrestrial water storage change (TWSC) using statistical reconstruction and hydrological models. Then we estimate the long-term ET and its driving factors in the Yangtze River Basin (YRB) using the water balance equation and ridge regression. Dividing the study period into three subperiods between the end of the 20th century and around 2015, ET in the upper and middle YRB exhibits a decreasing-rising-decreasing trend. ET and precipitation in the upper and middle YRB show an increasing trend throughout the entire study period, indicating an intensification of the water cycle in the YRB. ET changes over the past four decades are mainly driven by changes in surface vegetation cover and precipitation. This study provides valuable scientific references for the reproduction and prediction of the basin water cycle and the refinement of ET models under historical and different future climate scenarios.