Characteristics and attribution analysis of runoff changes based on Budyko hypothesis and SWAT model in the Heihe River Basin, China

At present, climate change and human activities (CCHU) affect runoff to varying degrees, and the extent of this impact varies across regions and evaluation methods. Taking the Heihe River Basin in Shaanxi Province, China, as an example, we evaluated environmental conditions and runoff patterns and assessed the contributions to runoff changes using the Budyko hypothesis and the Soil and Water Assessment Tool (SWAT) design. The results showed that: (1) From 1955 to 2022, the average annual precipitation and potential evapotranspiration in the basin were 787.5 mm and 859.0 mm, exhibiting a non-significant increasing rate of 0.29 mm/a and 0.35 mm/a, respectively; the average temperature was 7.3 °C, with a significant increasing rate of 0.02 °C/a. (2) The average runoff depth in the basin was 390.13 mm, with a decrease rate of -2.59 mm/a. An abrupt change in runoff was observed in 1997, primarily because of the construction of the Jinpen Reservoir. (3) From the base period (1955–1996) to the change period (1997–2022), the runoff depth in the basin decreased by 81.15 mm. (4) Analysis using the Budyko hypothesis and the SWAT model revealed that human activity accounted for over 90% of the runoff change.