Runoff Simulation In Upstream Of The Shiyang River Basin Using SWAT Model

The Shiyang river basin is the ecological evironmental fragile zone in the arid regions of Northwest China, and the ecological enviroment problem in this zone is extremely serious. In-depth study of the basin, especially hydrological processes of the upstream mountains which is the watersources conservation area, is of great significance to improving governance of the basin's ecological environment. This paper summarized present research situation of home and abroad about the distributed hydrological model and the SWAT model. A brief description of the development, theory and strcuture of the SWAT model was given. Then the Jinta river basin as research area was selected, the runoff of the Jinta river basin was simulated by the SWAT model with the support of GIS. The SWAT model's suitability in upstream of the Shiyang River was researched, and the spatial and temporal distribution characteristics of the quantity of water was analysed. Finally, the scenes in different evironments was simulated based on the SWAT model, and the influence of diffierent land use and climate conditions on the runoff was studied.The main conclusions of this study are the following:(1) Stimulating the monthly runoff in the Jinta river basin achieved good results which shows that the SWAT model can accurately simulate the funoff in the high-altitude mountain, and has certain applicability.(2) The snow and snowmelt mechanism in the model improved the quality of the simulation. But because of the lack of glacier process, the SWAT model cann't simulate the more comprehensive and actual hydrological processes.(3) The lack of meteorological data in high altitude area greatly influence the simulation results(4) The SWAT model parameters which have relatively great impact on runoff in Jinta river basin are ALPHA_BF.GWQMN,TIMP,CN2.ESCO,SOL_K.SLOPE and SOL_AWC.This indicates the base flow and snow melting process are the main factors of hydrologic processes in the basin.(5) The temporal and spatial distribution of basin precipitation, evaporation, snowmelt quantity and runoff is significantly different. Rainfall, evaporation concentrated in July and August,runoff peak in July and snowmelt process is concentrated from March to June.The rainfall and runoff of upper and middle reaches is relatively large, the high evaporation areas are mainly in the northwest; The differences of temperature caused by terrain elevation led to the amount of snow storage and snow melting gradually decreased from upstream to downstream.(6) The increase of woodland and farmland area lead to the increase of runoff, while the increase of grasslands and bare area lead to a certain degree reduction of runoff. Climate change influence runoff significantly, and annual runoff significantly reduce with the reduction of rainfall and the increase of temperature. The rise of temperatures cause a small increase of spring runoff, and the runoff in other months have different degrees of reduction.