Simulation Of Runoff And Sediment Yield In The Upper Reaches Of Huangqian Reservoir Based On SWAT Model

Water is the source of life and plays an important role in natural ecology and human activities.At the same time,it is also an important strategic resource affecting the national economic and social development.In recent years,with the development of China's economy and the increasing improvement of people's living standards,there is an increasing demand for water resources,especially in the northern earth rock mountainous areas where water resources are relatively scarce.Water resources have become an important factor restricting regional economic development.The per capita water resources in Taishan District of Tai'an City is 204m~3,Accounting for 8%of the national per capita share,it is a relatively serious water shortage area.Huangqian reservoir is the main water supply source in Tai'an City.It is located in the north of Huangqian Town,Taishan Scenic Spot,Tai'an City.It is a medium-sized reservoir focusing on flood control and urban water supply,taking into account agricultural irrigation,power generation and other comprehensive utilization.In order to better manage and make full use of the water resources in the upstream basin of Huangqian reservoir,realize the sustainable utilization of regional water resources and ensure the stability of water supply in Tai'an City,it is of practical significance to simulate and describe the runoff and sediment in the basin by using hydrological model through mathematical methods,and understand its temporal and spatial variation law.Based on SWAT Model(Soil and Water Assessment Tool),this paper simulated the runoff and sediment yield in the upstream basin of Huangqian reservoir,analyzed the adaptability of the model in the upstream basin of Huangqian reservoir,and quantitatively analyzed the runoff and sediment changes under different land use scenarios.The research results can provide a scientific basis for the rational development and utilization of water resources and land use optimization decision-making of Huangqian Reservoir and upstream basin.The main research conclusions are as follows:(1)A total of 16 parameters were selected for sensitivity analysis in this study.The results show that the most sensitive parameters are runoff curve number(CN2)?soil saturated hydraulic conductivity(SOL?K)?soil evaporation compensation coefficient(ESCO)?average slope(SLSUBBSN)and base flow extinction coefficient(ALPHA?BF).(2)The SWAT model after parameter calibration has good adaptability in the upstream basin of Huangqian reservoir.In this study,single outlet calibration was adopted in the calibration stage of SWAT model to calibrate and verify the four water systems of Shiwen River,shiwuzhi River,Honghe River and Mata River separately,and the applicability of the simulation results was evaluated.The determination coefficient(R~2)of each water system in the model calibration period and validation period is greater than 0.7,and the Nash efficiency coefficient(NSE)is greater than 0.5,the relative error(Re)is less than 25%.(3)From the temporal and spatial distribution of runoff,the runoff in the upstream basin of Huangqian reservoir is mainly concentrated from June to August,and spatially it is mainly distributed in the main rivers in the middle and lower reaches of Shiwen River and Mata river.From the temporal and spatial distribution of sediment,the sediment yield of the basin is mainly concentrated from June to August,and the high sediment output area is mainly distributed in the middle and upper reaches of Shiwen River and Mata River and the middle and lower reaches of shiwuzhi river;According to the sediment yield characteristics of different land use types,the sediment yield per unit area in the upper reaches of Huangqian reservoir is Garden>cultivated land>forest land>rural residential area>urban land;From the sediment yield characteristics of different slope grades,the sediment yield per unit area increases with the increase of slope grade.(4)In this study,four different land use scenarios were set up to simulate the runoff and sediment yield in the upstream basin of Huangqian reservoir.The results show that compared with cultivated land and garden land,forest land has a strong reduction effect on surface runoff and sediment;Moreover,the inhibitory effect of forest land on runoff and sediment yield is more obvious in flood season;Cultivated land has a positive effect on runoff and sediment yield in the basin,and its positive effect is mainly reflected in the flood season.Scenario 1 keeps other land use types unchanged.When the cultivated land above 15°in the area is transformed into forest land,the runoff and sediment yield in the upper reaches of Huangqian reservoir are reduced by 0.33%and 7.19%respectively;In scenario 2,when all the gardens above 25°in the area are changed into forest land,the runoff and sediment yield in the basin are reduced by 16.89%and 29.48%respectively;In scenario 3,when the cultivated land and garden land in the area are transformed into forest land,the runoff and sediment yield in the basin are reduced by 17.55%and 40.19%respectively;In scenario 4,when the forest land and garden land in the area are converted into cultivated land,the runoff yield of the basin increases by 16.23%and the sediment yield increases by 80.09%.