Study On The Ecological Response Of Hydrology On Land-Use/Forest Vegetation Change In Typical Watershed In Loess Plateau

The soil erosion is a important ecological problem in the western region of our country。relevant researches enunciated that until 1999 the soil erosion area in western region (not including Tibet) is 104,369,000 hectares, 62.5% part of the national soil erosion total area. The forest vegetation which has huge hydrology function such as restrainting headwaters, regulating flows,improving water quality,protecting soil and water environment, so the forest vegetation ecological construction is the critical path to resolving the problem of water resources and water environment.This thesis chooses Luoyugou watershed in Gansu province Tianshui city as the example research area, imitating and studying the runoff,sediment and water quality in the research area with the application of distributed hydrological model SWAT(the Soil and Water Assessment Tool), and stressing on the influence of precipitation and forest vegetation change to ecological hydrology responds.This thesis carried out the imitated research of hydrology in some small watershed in western region with a distributed hydrological model. With the support of GIS technology, the spatial database (integrating DEM, soil, and landusemap et al.) and non-spatial database (integrating climate, and land management data et al.) were established.With the support of SWAT model, the 10 sub-watersheds have been automatically delineated by the DEM and waterstreams. And the model has been calibrated and validated with the real data collected from the study area in the years from 1986 to 2000. In calibration period, the relative error is within 14%, relative coefficient and Nash-Suttcliffe coefficient are 96.1% and 0.89, in validation period relative error is within 8.8%, relative coefficient and Nash-Suttcliffe coefficient are 91.5% and 0.82 respectively. The results show that SWAT model could be successfully used to model this area.According to the analysis result of SWAT model, applying the GIS spatial analysis function, the thesis analyze the special distribution of runoff,sediment and nutrient loss in 1986,1995 and 2000 and the contribution of hydrological respondes by different kinds of landuse. The result showes that the precipitation and landuse both deeply influence the runoff,sediment and nutrient loss.The more rainfall in a month, the more runoff,sediment and nutrient loss; contrarily is the opposite. The change of landuse mainly expresses in the decrease of the plantation area and the increment of the forest area, the relative hydrology change is the decrease of runoff,sediment and nutrient loss. Thereinto, the largest amount of runoff,sediment and nutrient loss in 1986 are produced on plantation area, the largest amount of runoff,sediment and nutrient loss in 1995 and 2000 are produced on terrace.Through the establishment of scenery model, different analysises are carried on the influence of hydrology responds with different precipitation, different forest vegetation cover and different water...