Hydrological Regime Alteration in Zuli River Basin Based on IHA-RVA Method

[Objective] This study aims to investigate the hydrological regime alteration in rivers in the soil erosion region of the Loess Plateau under the combined influence of climate change and human activities.[Methods]Using daily runoff data, this study conducted a comprehensive evaluation of the degree of hydrological regime alteration in the basin using the Indicators of Hydrologic Alteration-Range of Variability Approach (IHA-RVA). [Results] Climate warming and soil-water conservation measures jointly led to a significant decrease in the annual average runoff in the Zuli River Basin, with an abrupt change occurring around 1995.Following the abrupt change of runoff, both monthly average flow and related extreme flow indicators exhibited a trend of uniform intra-annual distribution. The degree of change in extreme hydrological indicators was greater than that in monthly average flow indicators,with the change in low-flow duration reaching up to 95% and the change in monthly average flow in November being only 1%.The occurrence time of annual minimum flows advanced significantly,whereas the occurrence time of maximum flows was delayed. After the hydrological abrupt change,both the frequency and duration of high and low flows at the Jingyuan Station decreased significantly.The Zuli River Basin experienced more frequent flow changes,while the amplitude of these changes gradually diminished. After the abrupt change of runoff in the Zuli River Basin, the overall hydrological alteration degree was 48%, which was classified as moderate alteration. [Conclusions] Human activities, primarily driven by soil-water conservation measures, strongly influence the hydrological regime alteration in the Zuli River Basin. Following the abrupt change of runoff, a notable decrease in basin runoff is observed, accompanied by a trend towards more uniform intra-annual distribution. This study provides methodological frameworks and theoretical foundations for ecological conservation and water resource management in arid, soil erosion regions.