3.2 Hydrological modeling using GBHM
The GBHM is a distributed hydrological model that was proposed in 1998 by Yang et al. (1998). In this model, the basin can be divided into several mountain slope units, and the regional runoff generation and concentration processes are expressed based on the ”slope-river course” using physical equations (Lyu et al., 2019; Ma et al., 2010). The model can be described according to the following components: input, spatial database, calculation of hydrological processes, and output (Yang et al., 2002). Model input data include basic geographic information data (e.g., DEM, river network), daily meteorological data (e.g., precipitation, temperature), annual land use data, and annual NDVI data. To adequately characterize the hydrological response of the Qinhe River Basin to the construction of reservoirs, the principal parameters of the model were adjusted for the present study. The impacts of underlying changes at the surface and major soil and water conservation measures on temporal and spatial changes in runoff for the basin were also examined. A schematic illustration of the improved model is displayed in Figure 3.