Divergent Hydrological Effects of Revegetation over the Chinese Loess Plateau Driven by East Asian Summer Monsoon Variability

Abstract Large-scale revegetation on the Chinese Loess Plateau has profoundly influenced the terrestrial water cycle through biophysical processes. However, previous studies have primarily focused on the hydrological effects of revegetation averaged over specific periods, ignoring the potential influence of interannual climate variability on the revegetation effects. This study investigates the role of East Asian summer monsoon (EASM) variability—a key driver of the plateau’s interannual climate—in shaping the hydrological outcomes of revegetation. Using the Weather Research and Forecasting (WRF) Model coupled with a water vapor tracer, we reveal divergent hydrological effects of revegetation due to EASM variability. In strong EASM years, revegetation increases precipitation (0.51 mm day −1 ), completely offsetting increased evapotranspiration (0.31 mm day −1 ) and yielding a net gain (0.20 mm day −1 ) in water yield (defined as precipitation minus evapotranspiration). Conversely, weak EASM years show precipitation reduction (−0.04 mm day −1 ) alongside evapotranspiration increase (0.26 mm day −1 ), resulting in water yield decline (−0.30 mm day −1 ). In normal EASM years, the hydrological effects of revegetation exhibit intermediate behavior between those observed in strong and weak EASM years. The divergent precipitation responses to revegetation primarily stem from substantial variations in precipitation derived from water vapor inflow beyond the plateau. These differences are mediated through distinct responses in both local boundary layer processes and large-scale atmospheric circulation patterns under different EASM intensity regimes. These findings underscore the importance of integrating climate variability into the hydrological assessment of revegetation, offering valuable insights for the sustainable development of ongoing revegetation projects over the Loess Plateau.