Runoff And Sediment Simulation Of Xinjiang River Basin Based On SWAT Model

Xinjiang is one of the five major rivers in the Poyang Lake basin in which the meteorology, hydrology, land use changes has had a great impact on its water resources in water quantity and quality.However, there is few study focusing on the hydrological response to land use change in this area. So it is particularly important to research on the spatio-temporal characteristics of hydrometeorological elements in the Xinjiang basin and have a simulation of its runoff and sediment to help use learn about the distribution of the element of climate, water resources and soil erosion, etc, at the same time, provide scientific reference to rational allocation of water resources and soil and water conservation in this basin, getting ready for the flood and the drought.In this paper,we first analyze the characteristics of extreme climate, the drought and flood based on hydrometeorological data using several mathematical statistics methods to learn the spatio-temporal characteristics of hydrometeorological elements.Then,we use the SWAT model to have a water and sediment simulation with the technology of GIS and RS in the combination of geographical and hydrometeorological data.Meanwhile,we also focus on analyzing the influence of land use changes to water and sediment in Xinjiang basin.The main results were showed as below.(1) Analyzing the characteristics of extreme climate changes in quantity based on the RClimDex model and12extreme climatic index.It shows that trend of the index representing low temperature events goes down while trend of the index representing high temperature events goes upward.The extreme precipitation indices takes on a trend of rise in different extent.We use SPEI index to calculate the changing characteristics of the drought and flood in this basin at a multi-time scale and find that6drought events and7flood events above the middle level have happened in recent46years using SPEI12by the year scale. We also use the method of EEMD in combination of R/S, variance analysis and significant test finding the average period is2.88and6.57years respectively and the frequency of drought and flood events in the future is positively related to that in the past. The drought in autumn and the flood in summer is the most severe among all four seasons. At the annual scale,long-term heavy drought mainly took place in the Eastern and Northcentral of the Xinjiang basin while the heavy flood mainly distributed in the Eastern basin. We find the water and sediment take the main cycle of11years in Xinjiang basin through the tool of the continuous complex Morlet wavelet transform analysis(2) Simulating runoff and sediment in Xinjiang basin based on the SWAT model,using the LH-OAT method to analyze the sensitivity parameters,evaluating the simulation result parameters through calibration and uncertainty analysis with the SUFI-2algorithm,we can find that the top three sensitive parameters influencing the runoff are CN2, SURLAG and ALPHA_BF,According to the five criteria: P-factor,R-factor, ENS, R2and Re,it is feasible and reliable to apply the SWAT model in the simulation of runoff and sediment in Xinjiang basin.Rate of regular in the validation period, runoff simulation effect is better than the sediment.Through selecting SUFI-2algorithm2.5%-97.5%confidence interval interval as95%(95PPU) and calculating the values of P-factor and R-factor, we can conclude that uncertainty of regular water and sediment simulation are smaller than that of the validation, where uncertainty of runoff is smaller than that of sediment.(3) Analyzing water and sediment response in different land use scenarios combining ArcGIS with the best results of SWAT model, we can find that the two land-use scenarios are dominated by farmland, woodland, grassland.Generally, the total monthly, annual water and sediment under land use scenario in2000is slightly larger than1990. Districts with an annual output of more water are mainly distributed in the Northwest, Northcentral and Southwest of the basin, while the little in the southeastern, which is more consistent with the spatial distribution of yearly average precipitation. In conclusion,annual water and sediment output under the land use scenarios in2000is more than1990.