Spatiotemporal response of the water cycle to land use conversions in a typical hilly-gully basin on the Loess Plateau, China
Abstract. The hydrological effects of the ‘Grain for Green’ project (GFGP) on the Loess Plateau have been largely debated due to the complexity of the water system and its multiple driving factors. The aim of this study was to investigate the response of the hydrological cycle to the GFGP measures based on a case study of the Yanhe basin, a typical hilly-gully area on the Loess Plateau of China. First, we analyzed the land use and land cover (LULC) changes from 1990 to 2010. Then, we evaluated the effects of LULC changes and sloping land conversion on the main hydrological components in the basin considering the land surface characteristics and climate impacts. The Soil and Water Assessment Tool (SWAT) was used for this analysis. The results indicated that farmland exhibited a decreasing trend declining from 40.2 % of the basin area in 1990 to 17.6 % in 2010, and the woodland and grassland areas correspondingly increased due to the implementation of the GFGP in the basin. Due to land use changes from 1990 to 2010, surface runoff and the water yield exhibited decreasing trends, whereas evapotranspiration (ET) increased, resulting in a persistent decrease in soil water. Additionally, converting cropland areas with slopes ≥ 15° or > 25° to grassland and woodland had negative effects on surface runoff, the water yield and soil water and a positive effect on ET. The magnitudes of the hydrological effects generated by sloping cropland to woodland conversion were greater than those for sloping cropland to grassland conversion. These results suggest that the expansive revegetation of sloping land could reduce runoff generation, particularly in woodland areas, but these effects could reduce the soil water volume in the region. Overall, this study can be used to improve sustainable land use planning and water resource management on the Loess Plateau in China.