2. Geographical setting and data sources
2.1 Study area
The Qinhe River Basin, situated in the central Loess Plateau (34.8°–37.1°N, 112°–113°E), encompasses an area of approximately 7339.98 km2 to the north of the Runcheng Gauge Station. The Qinhe River, a first-class tributary of the Yellow River, runs through this basin. The area is characterized by short and intense periods of rainfall, which often result in flood and landslide disasters. In the flood season (June-October), the basin receives approximately 411 mm of precipitation, accounting for ≥ 70% of the total annual precipitation. Furthermore, the transport of sediments during this period constitutes ≥ 80% of the annual total (Liu et al., 2022). The basin is mainly mountainous, with river gradients mostly exceeding 5%, resulting in abundant hydraulic resources. The lower reaches of the basin are crucial for agricultural activities. To ensure the safety of these activities, conserve water resources, and prevent water-related disasters and soil erosion during the flood season, several water conservancy projects have been implemented since the 1950s. However, the construction of reservoirs and the extraction of large volumes of water for agricultural and industrial purposes have considerably altered the hydrological processes in the basin. In this study, we selected five representative reservoirs associated with the main streams and tributaries of the Qinhe River, which were constructed after 1950, to evaluate their impacts on the hydrological characteristics of the basin. The distribution of weather stations and reservoirs in the basin is presented in Figure 1.