Study On Hydrological Response To Basin Underlying Surface Change Based On SWAT

Water resources and water environmental problems are research hotspots of global environmental issues. The watershed underlying surface, which is one of important factors that influence the hydrological cycle, has been changed due to improper human activities, and it results in the changing of hydrological process. Therefore, studying on hydrological response to basin underlying surface change is significant for protecting water resources and formulating ecology plans.With the development of computer, remote sensing and GIS technologies, distributed hydrological model has become the important means of hydrological process studies. The physically-based SWAT(Soil and Water Assessment Tool) model, which is developed by USDA, has played an important role in hydrological research.In this paper, the upper Zhang river watershed of Hai river basin is selected. The SWAT model is applied to the streamflow simulation of this area, and then the hydrological response to basin underlying surface change in different scenes is simulated and analyzed. The main conclusions of the studv are as follows:(1) The basic data of upper Zhang river watershed are collected and the database of model is constructed by processing maps, calculating parameters and changing file format.(2) The relationship between the different partition numbers of subbasin and the results of streamflow simulation is analyzed and evaluated. The results indicate that the partition level of subbasin causes influence in river network generation and streamflow simulation. In order to ensure the natural conditions of hydrological process, the upper Zhang river watershed is delineated37subbasins with area threshold value of300km2(3) The values of8sensitive parameters are determined, which make the calibration process more reasonable and effective. Through comparison of the results of two calibration methods, the paper finds that calibrating from upstream to downstream has better simulation result than calibrating in total outlet directly.(4) The relative coefficient and Nash-Suttcliffe coefficient of streamflow in calibration period from2001to2004are satisfactory, while in verification period from2006to2009are unsatisfactory. The main reason is that the observational data from2006to2009are difficult to reflect the hydrological process in natural conditions and the data of water resources utilization is lacked.(5) Different underlying surface scenes are set up using extreme and spatial configuration methods. Through the simulation of hydrological process in each scene, the paper manages to analyze qualitatively the effects of underlying surface change on many hydrological elements, including of surface runoff, water yield, evapotranspiration and percolation in land phase and streamflow, evaporation losses, transmission losses in routing phase. The results indicate that the change of urban land causes dramatic influence in each hydrological element. The increased urban and farmland lead to reduced percolation, and increased surface runoff, water yield and streamflow. Forest has the capacity for water retention. In order to reduce water...