| The study of runoff variation in the basin is not only the key issues of water resources development and management, planning and sustainable development of watershed, but also is scientific guidance for the prevention of soil erosion and the restoration of the basin ecological environment, on the basis of objective understanding of the water-cycle characteristics. In this paper, Daxihe is the research object. SWAT model based on GIS is constructed, the main content and results are as follows:(1)Based on DEM, land use, soil, weather data and other information, the DEM, land use maps and soil type map of Daxihe basin, other spatial database meteorological attribute database and soil property databases are established using the software and procedures, such as ArcGIS10.1, Excel, SPAW and Swatweather.The catchment area, basin slope, the flow direction, river networks and other basic hydrological information are extracted from the DEM of Daxihe basin. The basin is divided into 29 sub-basin; According land use, soil area threshold and slope rating, the basin is divided into 178 hydrological response unit(HRU), implementing distributed description of watershed.(2)Based on meteorological data files and input file automatically created by SWAT model, the SWAT model of Daxihe basin is built. According to the measured runoff from 1980 to 1986 in hydrological station Zhangjiagou, the parameters are optimized using sufi-2 algorithm of SWAT-CUP tools for the simulated results. The results obtained 14 sensitivity parameters effecting on runoff: soil saturated hydraulic conductivity, the silt effective hydraulic conductivity of main river, base flow recession coefficient, biological mixing effect, runoff coefficient of shallow groundwater, soil available water-holding capacity, soil evaporation compensation coefficient, groundwater lag time, delay runoff coefficient, the main river Manning n values, the the thickness of soil surface to the bottom for each soil, water demand maximum canopy, deep aquifer permeability coefficient, runoff curve number, while values of the parameters were obtained. According to the calibration results of model, the measured monthly runoff data of 1987 to 1990 was used to validate the simulation.The monthly runoff calibrated and validated results show that the correlation co-efficient are 0.79, 0.79 respectively during the period of calibration and verification. Nash-Suttcliffe(Ens) are 0.82, 0.82. The simulation results are stable and good and meet the requirements. So the SWAT model can be applied in Daxihe basin.(3) Based on 30 m resolution DEM data, using the same soil, land use data and meteorological data, the effect of different resolution DEM data on elevation, slope, sub-basin dividing, position and the hydrological simulation results. The results showed that: when the DEM resolution from 30 meters reducing to 500 meters, maximum and mean elevation of basin, and standard deviation show a slow downward trend, the minimum elevation is unchanged. The basin slope is influenced by resolution, and extracted maxmum slope is reduced 81.2% with the lower resolution DEM. When the resolution is greater than 100 meters, channel position is coincident, and river shape, drainage density is same basically, while the curvature of river divided by other resolution DEM is relatively flat and river location has some offset. The minimum threshold catchment area becomes smaller as the resolution reducing, total basin area is smaller, number of sub-basin is from 29 dropped to 21, and the average area becomes larger. When the DEM grid cells increased to 500 meters from 100 meters, simulated runoff values has a slight downward trend, but they are not very different overall. In terms of the runoff, simulated sediment has larger sensitivity to DEM resolution, sediment decreased by about 45%. The 17 kinds of land use is divided into seven categories, five and three. Based on the same as other data, simulated was run. Results show that: the simulated runoff results are not very sensitive of classificating methods, but the impacts of them on simulated sediment are large.(4) To explore the influence of different land use patterns on the process of runoff, the research set the 3 different scenarios. The simulated runoff is greater than forestation runoff scenarios’ s in 1985 the actual land use, the runoff is minimized when all arable land back to grassland. Using assumed climate scenarios, precipitation is unchanged, increased 20%, 10%, decreased by 10%, 20% based on existing meteorological data; the temperature is unchanged, rise 2℃, 1℃, reduce 1℃, 2℃ on the basis of the existing meteorological data of high, a total of 25 kinds of scenario. The results show that: the impact of climate change river basin runoff is very significant; compared with temperature changes, runoff is influenced by rainfall; under different climate scenarios, there is a simulated runoff significant difference. |
PDF Full Text Request