Spatial patterns of hydrological responses to land use/cover change in a catchment on the Loess Plateau, China

Abstract

The Loess Plateau of China has been experiencing great land use and land cover changes under the “Grain for Green” program to control severe soil loss from human activities. Over the past 30 years, annual streamflow and sediment delivery have also reduced in most areas of Loess Plateau. In consequence, a physically based model of Soil and Water Assessment Tool (SWAT) has been employed to simulate the responses of surface hydrology to human activities in a typical catchment in the upper reaches of the Beiluo River on China’s Loess Plateau.As a result of using various sources of information, including remote sensing, it has been shown that farmland in the catchment decreased by 22.8% in 2000 and 35.0% in 2010 compared to the area in 1990. Meanwhile, forestland increased by 22.6% in 2000 and 119.8% in 2010. The area of shrubland increased by a factor of 3.3 in 2000 and 5.5 in 2010. The vegetation coverage greatly increased in the catchment during this period. Using the SWAT model, it was found that the average ET at the sub-basin scale increased by 7.4mm in 2000 and 44.0mm in 2010 as the vegetation coverage improved compared to that in 1990. Meanwhile, the soil water content decreased by 8.1mm and 14.9mm and the surface runoff decreased by 6.1mm and 16.2mm by these two years. The trends in the evapotranspiration, surface runoff and soil water content were closely associated with alterations in the land use and cover categories at the sub-basin scale. Generally, the higher the increasing rate of forest and grassland, the more that evapotranspiration transferred and the less surface runoff and soil water content that was generated. Spatially, the ET, surface runoff and soil water content showed the same changing gradient with land use and cover from the northern and northwestern to the southern and southeastern areas of the catchment during these periods. The scenarios simulation showed that the streamflow were more sensitive to variability in the precipitation than temperature.These results are expected to be helpful to the sustainable watershed management and provide useful information regarding land use planning and ecosystem construction strategies in the future on the Loess Plateau.