Impacts of land use change scenarios on storm-runoff generation in Xitiaoxi basin, China

Land use change has significant impacts on hydrologic processes at the watershed level. This paper combines an empirical land use change model and an event-scale, rainfall-runoff model to quantify the impacts of potential land use change on the storm-runoff generation in the Xitiaoxi basin upstream of Taihu Lake watershed. The HEC-HMS rainfall-runoff model is calibrated and validated for 7 storm events in the study area, and the results show good consistency between the simulated and measured hydrographs at the outlet of the basin with Nash-Sutcliff efficiency ranging from 75% to 95%. Then two future land use scenarios for the year 2050 are forecasted using the CLUE-s model based on the land use of 2002: (1) scenario A with an increase in urban area from 9.2% to 17% of the entire watershed and (2) scenario B with an increase from 9.2% to 14%. Finally, the calibrated HEC-HMS model is applied for these future land use scenarios under designed storms with different recurrence intervals to assess the potential land use impacts on the storm-runoff generation. The results indicate that the future land use scenarios are projected to increase the total runoff as well as the peak discharge, and that the magnitude of increment relates to the expansion rate of built-up area. In the case of rainstorms with recurrence intervals of 10, 50 and 100 years, the simulated peak discharges increase by 3.8%, 2.6% and 2.3% under scenario A, and by 2.8%, 1.9% and 1.7% under scenario B, respectively; while the total runoff is projected to increase by 4.7%, 3.4% and 3.0% under scenario A, and by 3.3%, 2.5% and 2.1% under scenario B. It can be concluded that the sensitivity of hydrologic response to land use change tends to increase as the recurrence interval of rainfall events decreases. Additionally, remarkable spatial variations of the land use changes and its impacts can be observed at the subbasin level, and the most sensitive subbasin is closeby the city. The results of this paper can provide useful support for land use planning and management, and the methods applied here have proved a useful tool for land use impact studies. (C) 2009 Elsevier Ltd and INQUA. All rights reserved.