Precipitation changes and its interaction with terrestrial water storage determine water yield variability in the world's water towers

Abstract

Previous studies have quantified the contributions of climate factors, vegetation, and terrestrial water storage change, and their interaction effects on hydrological process variation within the Budyko framework; however, further decomposition of the contributions of water storage change has not been systematically investigated. Therefore, focusing on the 76 water tower units of the world, the annual water yield variance was first examined, followed by the contributions of changes in climate, water storage change, and vegetation, as well as their interaction effects on water yield variance; finally, the contribution of water storage change on water yield variance was further decomposed into the effect of changes in groundwater, snow water, and soil water. The results showed that large variability exists in the annual water yield with standard deviations ranging from to 10–368 mm in water towers globally. The water yield variability was primarily controlled by the precipitation variance and its interacted effect with water storage change, with the mean contributions of 60 % and 22 %, respectively. Among the three components of water storage change, the variance in groundwater change had the largest effect on water yield variability (7 %). The improved method helps separate the contribution of water storage components to hydrological processes, and our results highlight that water storage changes should be considered for sustainable water resource management in water-tower regions.