Response of streamflow to environmental changes: A Budyko-type analysis based on 144 river basins over China.

Understanding response of streamflow to environmental changes is crucial for large-scale water resources management and ecosystem restoration. There is no consensus on how environmental change influence streamflow in different regions across climate gradient, as previous studies mainly focused on a single river basin or climate region. This study analyzed the variations of aridity index and its contributions to streamflow change based on Budyko's framework approach using bias-corrected precipitation measurement, parameters-optimized potential evapotranspiration and observed streamflow in 144 basins across China. The parameter n in the Budyko type equation exhibits significant spatial heterogeneity, with larger values in the water-limited region than in the energy-limited region, which suggests more pronounced impact of basin characteristic or vegetation change on hydrological cycle. The absolute value of sensitivity coefficient in the water-limited region (-2.56) was larger than both equitant (-2.13) and energy limited region (-1.57), indicating that the streamflow was more sensitive to aridity index change in the water-limited region than in the equitant and energy-limited regions. The dominant factor affecting streamflow under energy-limited and equitant conditions is aridity index (i.e. climate change), with median relative contribution rates of 79.9% and 55.5%, respectively. In contrast, non-climatic factors dominate the variation of streamflow in the water-limited region, the effect of climate change on streamflow has been offset by other factors. This study suggests that the water management practices, such as water diversion across river basins and ecological restorations, should fully consider the differences in hydrological responses to climatic conditions.