Runoff evolution characteristics and its response to climate change in the middle and lower reaches of Shule River Basin, Northwest China

Study region: The middle and lower reaches of the Shule River Basin (SRB) in northwestern China Study focus: Under the combined influences of climate change and human activities, runoff evolution in northwestern China's inland river basins has become increasingly complex. This study focuses on the Shuangtabao Reservoir Station (STBR) and the Danghe Reservoir Station (DHR) in the middle and lower reaches of the SRB. Based on long-term hydrometeorological observations, runoff dynamics were comprehensively analyzed at intra-annual, inter-annual, and seasonal scales. The dominant drivers of runoff variability were quantitatively identified, and hydrological responses under different climate scenarios were further evaluated. New hydrological insight for the region: The results showed significant intra-annual runoff unevenness, with peaks mainly in spring and summer. Inter-annual runoff exhibited an upward trend with strong positive persistence. Abrupt changes occurred in 1998 (STBR) and 2005 (DHR), with average annual runoff increasing by 52.01 % and 38.69 %, respectively, primarily driven by changes in underlying surface conditions. The Random Forest (RF)-Adaptive Boosting (AdaBoost) model outperformed the standalone RF model, showing higher simulation accuracy and generalization ability in arid inland basins. DHR was more sensitive to climate change than STBR. Under a 2.5 °C temperature rise and a 20 % increase in precipitation, simulated runoff increased by 6.61 % at STBR and 8.68 % at DHR. This study provides scientific support for water resource management and climate-adaptive regulation in arid basins.