Runoff And Sediment Yield Simulation In Xihe River Basin Based On SWAT Model

SWAT model is a distributed hydrological model with strong physical basis,continuous time scale and watershed scale.It has a good effect on the simulation of runoff and sediment yield.The Xihe River basin belongs to the third sub-area of the loess hilly and gully region.The ecological environment is fragile,the water and soil loss is serious in the Xihe River basin.Based on the SWAT model,the paper simulates the runoff and sediment yield in the Xihe River,it has important significance for ecological environment construction and soil and water conservation work.The characteristics and laws of the meteorological and hydrological factors in the Xihe River basin are analyzed.According to the basic data as DEM,land use,soil type,meteorological,hydrological in the study area,the SWAT model of runoff and sediment yield was constructed in the Xihe River,and the measured runoff and sediment data were used to correct it.The runoff and sediment yield were simulated under different land use and different soil types,based on the simulation results,the effects of land use change on runoff and sediment are discussed,and the sensitivity of soil type factors to soil erosion is analyzed.The paper drawing the conclusion as follows:(1)The paper selects four meteorological stations near the Xihe River.The rainfall of Huajialing station,Minxian station,Tianshui station showed a decreasing trend,but Kongtong station showed an increasing trend in 1982-2015.The temperature of the four stations is on the rise in 1982-2015.Runoff was increase but sediment transport was decrease in the Xihe River,in 2001-2014.The main reason is that the establishment of the river demonstration area has changed the land use,improved the soil structure and optimized the industrial structure.(2)The simulated and measured values of runoff and sediment on the annual and monthly scales are in good agreement in the Xihe River,and the annual simulation results are better than the monthly simulation results.It shows that the model has a good applicability in Xihe River.(3)The main types of land use in the Xihe River basin are cultivated land and grassland.The cultivated land about 84.59% has not changed,the total area reduced37.35km2;the woodland about 95.56% has not change,the total area increased about9.93km2;the grassland about 89.87% has not changed,the total area increased about22.93km2;the construction land about 91.36% did not change,the increase of the total area is 3.14km2 from 2000 to 2015.(4)The change trend of annual runoff and sediment is basically consistent under different land use scenarios.The results show that both the woodland and the grassland will reduce the runoff and sediment,the effect of reducing runoff and sediment in forestland is better than in grassland,the cultivated land will increase the runoff and sediment.Land use will directly affect the runoff and sediment production process in this watershed.Under different land use scenarios,factors such as physical structure,permeability,porosity and porosity lead to a great difference in water holding capacity.(5)Under the assumption of different soil types,the trend of annual runoff and sediment is basically the same.The results showed that the sensitivity of soil erosion was followed by high-activity leaching soils,calcic karst soils,calcareous alluvial soils,and high-calcium active leaching soils.The soil sensitivity was also the same.Soil erosion depends not only on soil permeability,soil organic matter,soil aggregates,soil moisture,soil particle size,and soil bulk density,but also on climatic factors,topographic conditions,vegetation conditions,and human activities.