Spatial hydrological responses to land use and land cover changes in a typical catchment of the Yangtze River Delta region

This study assessed the individual and combined effects of land-use and land-cover changes (LUCCs) on spatial hydrological responses by using an integrated approach involving the Soil and Water Assessment Tool (SWAT) and geographically weighted regression (GWR) models in the Xitiaoxi River Basin (XRB). The LUCCs and their spatial patterns from 1985 to 2008 were evaluated in the XRB. The hydrological processes during the period from 1980-2015 were then generated by the SWAT model under the 1985 and 2008 land-use scenarios. GWR models were constructed to quantify the spatial impacts of LUCCs at the sub-basin scale. The results showed that the predominant trend of land-use conversion was between forest-grass land and agricultural land, and the diminishing portion of forest-grass land (25.93 km2) and agricultural land (46.77 km2) contributed to the expansion of urban land during the period 1985-2008. Moreover, the urban area increased from 5.6% to 17.05%, and the change ratio progressed towards the centre of the XRB. These changes in land use caused the average annual water yield and surface runoff to increase by 1.09% and 11.87%, respectively, and the average annual evapotranspiration (ET), percolation and baseflow to decrease by 0.73%, 16.53% and 17.26%, respectively. In addition, the results of the GWR models indicated that the responses of each hydrological component exhibited spatial differences. The comprehensive land-use intensification index (La), selected to reflect the combined effects of LUCCs, was positively correlated with water yield and surface runoff but negatively correlated with ET, percolation and baseflow. La had a greater effect on water yield, surface runoff, percolation and baseflow in rural areas than in the urbanized region. The combined effects of LUCCs in certain local areas increased water yield and surface runoff by up to 13.7% and 114.2%, respectively. The local coefficient indicated that rural regions might be exposed to greater effects of LUCCs. The results of this study could be useful to understand the effects of LUCCs on the spatial patterns of each hydrological component and to help improve flood control and water resource management.