Abstract
Abstract. The hydrological effects of the Grain for Green project (GFGP) on the Loess Plateau have been extensively 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 in 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 using the Soil and Water Assessment Tool (SWAT). The results indicated that cropland exhibited a decreasing trend, declining from 40.2 % of the basin area in 1990 to 17.6 % in 2010, and that the woodland and grassland areas correspondingly increased. With the land use changes from 1990 to 2010, the water yield showed a decreasing trend which was mainly due to decrease in surface runoff. In contrast, evapotranspiration (ET) showed an increasing trend over the same period, resulting in a persistent decrease in soil water. The conversion of sloping cropland to grassland or woodland exerted negative effects on water yield and soil water. Compared with the land use condition in 2010, the negative effects were most evident where cropland with a slope ≥ 15° was converted to woodland, with decreases in surface runoff and soil water of 17.1 and 6.4 %, respectively. These results suggest that the expansive reforestation on sloping land in the loess hilly–gully region decreased water yield and increased ET, resulting in reduced soil water. The results of this study can be used to support sustainable land use planning and water resource management on the Loess Plateau in China.
Highlights
Land surface change is one of the most important drivers of ecohydrological changes (Li et al, 2009; Blöschl et al, 2007)
A soil survey map with 20 m resolution was obtained from the Institute of Soil and Water Conservation (ISWC), Chinese Academy of Sciences (CAS), and we developed a user soil database required for the model that linked to the digital soil map using ArcGIS
We found that cropland, grassland, and woodland were the dominant land use types in the Yanhe Basin, and land use conversion among these types occurred since 1990 due to the implementation of the Grain for Green” project (GFGP)
Summary
Land surface change is one of the most important drivers of ecohydrological changes (Li et al, 2009; Blöschl et al, 2007). The impacts of land use and land cover (LULC) changes on water resources and hydrological processes in a river basin are mainly reflected in the overland surface runoff, streamflow, evapotranspiration (ET), and soil water (Bari and Smettem, 2004; Chawla and Mujumdar, 2015; Liu et al, 2008b; Zucco et al, 2014). The river basins on the Loess Plateau are important because of the dense population, intensive cultivation, and the high demand for water in the area. This region is characterized by insufficient water resources and severe soil erosion, and it has historically experienced vegetation degradation and desertification (Zhao et al, 2013; Guo et al, 2002). The hydrological processes on the sloping land and in the river systems have changed, but the extent of these changes and their relationships to LULC change remain unclear
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