The Application Of SWAT Model In Upstream Runoff Simulation Of Yellow River Shizuishan Station

Yellow River Basin has vast territory and is facing severe water problems, in-deep knowledge and understanding of its hydrologic cycle is of great significance to rational allocation of water resources and solve the water problem. Hydrologic model, the indispensable tools in the exploitation and management of large water resources, could help us to recognize the past and recent hydrological regime and predict that of future, therefore, the establishment of distributed hydrological model in this basin are necessary means and important technical supports to solve water problems. SWAT is the hydrologic model which was developed by the US Department of Agriculture and has solid physical foundation, allows launching long-period runoff simulation of large and medium-sized basins for many years in the unit of day and a large number of studies have shown that the simulation effect is better.Against this background, we collected the data of DEM, soil, land use, hydrology, meteorology etc in this basin, then established the SWAT model of the upstream of Yellow River Shizuishan station and simulated watershed runoff process within months. It is discrete as 193 sub-basins and 1081 hydrological response units based on features of underlying surface. The period of 1981-1985 and 1986-1989 were selected as the model calibration period and verification period, utilizing the existing reconstruction results of the natural runoff for monitoring section of Lanzhou and Shizuishan station to register and validate the model in turn. The results show:(1) In calibration and validation period, the model simulation Re of Lanzhou are-0.87% and-3.54%; R2 are 0.73 and 0.71; Ens are 0.72 and 0.6. For the total exports Shizuishan station, Re are 0.78% and-2.57%; R2 are 0.74 and 0.67; Ens are 0.73 and 0.53. They all have reached the requirements of model applicability, demonstrating that the established SWAT model in this study is available to simulate runoff process of upstream of Shizuishan station. However, validation period evaluation indexes are generally lower than calibration period, which may be related to small water basin between 1986 and 1989.(2) The impact for changes in the input value of some most sensitive parameters of the model on the simulation results were discussed. We found in the two selected sub-basin runoff simulation, parameters like SOL_AWC, ESCO,RCHRG_DP, whose overall trend was the same corresponding, not the same degree however; parameters like CN2、GW_REVAP were not sensitive at the same time. Due to the large differences in the spatial and temporal scales of the basin climate、land surface conditions, hydrological model parameters could not be taken in the uniform assignment mode, otherwise it is bound to produce large errors.In conclusion, SWAT model has a good accuracy for long-period runoff simulation of large-sized basins in arid and semiarid region, which could be a technical reference to understand and acknowledge the hydrologic cycle process of Yellow River basin, to solve the river basin’s water problems as well. Meanwhile, SWAT model could provide some theoretical basis for the scientific management and reasonable utilization of water resources in Yellow River Basin.