Water Quality Response To Landscape Change In Baihe Watershed

Baihe Watershed located at upstream area of Miyun reservoir. It is the main water source of Beijing city. Its water quailty is important for the capital's living and producing activity. Because the government actualize the enviroment protection and furrow turn to grasses and forest policy, the landscape structure have changed a lot during the past ten years.By means of GIS, a distribute hydrologic model named SWAT (Soil and Water Assessment Tools) is used in this paper. By the study of runoff, sediment or water quality of the experiment watershed, we hopely to find out relationship between rainfall or landscape structure change with water ecological response.Based on the landscape pattern of Baihe watershed in 2000 and atmosphere and runoff from 1990 to 2007 and the sediment and water quality from year 2001 to 2006, sensitive parameter have been analysised and calibrated and verified. The result shows that ENS≥0.7, R~2≥0.7 of monthly runoff, sediment, water quality, which make the model suitable for the research area.Analysis and compare landscape patterns of Baihe basin between 1988 and 2000,and try to find out the regulation of the inner elements change. With the help of SWAT, study the response of the runoff, sediment and water quality to the different landscape patterns under in the same weather condition. It shows that forest play a more important part.Finally take the present landscape pattern as a standard, simulate the water reponse to the different land covers and weather conditions. In the scenario prediction of land covers, the convention of cropland to forest or grassland has a ecological effect of not only reducing water and sediment content, but also reducing the total nitogen and total phosphorus. It seems that covention of cropland to forest has a better effect than the convention of cropland to grassland in reducing water and sediment content. In the scenario prediction of climate change, the runoff,sediment and total nitogen and total phosphorus has a possitive correlation with the rainfall and negative correlation with the temperature.