Spatiotemporal dynamics of future hydrology in the Pearl River Basin: Controls of climate change and land surface

Study region: The Pearl River Basin in China. Study focus: The hydrological cycle is anticipated to undergo systematic alterations due to climate change, impacting future water resources and ecosystem functions. Driven by an optimized subset of General Circulation Models through a comprehensive framework of multi-level calibrations, we employed a well-validated Soil and Water Assessment Tool to predict streamflow and investigate the underlying dynamics in the basin. New hydrological insights for the region: The combined effects of the variability in regional monsoon climate and land surface processes jointly control the spatiotemporally varied streamflow. There is a highly nonlinear temporal trend, with slight near-term reduction and a significant long-term increase. It is also spatially heterogeneous, with more significant increases in the eastern basin than in the western, attributed to an asymmetrically strengthened/weakened East/South Asian Summer Monsoons. Land use affects the response of streamflow to climate change. Lateral flow is most variable in forested hills due to their high water interception rates, while aquifer flow varies most in agricultural areas with their coarse soils and high water storage capacity; both show an increasing trend during the wet season because of elevated precipitation and a decreasing trend due to increased evapotranspiration during the dry season. Surface flow consistently increases the most in urban regions due to low evaporation and intensified precipitation.