Study On Runoff Simulation Of The Lengshui River Basin In Nanzheng Of Shaanxi Province

The Lengshui River basin is located in the southern part of Shaanxi Province,the main ridge of Micangshan to the south of Nan Zheng County,a tributary of the Han River,watershed area of 641.41 km2.The northern part of the Lengshui River basin is the southern margin of the Hanzhong basin,and the southern part is the Bashan mountain village.The terrain is ascending from north to south,followed by the plain area,the hilly area and the mountainous area.The water system in the area is complex,the vegetation is lush,the surface soil is more loose,the precipitation is rich,the mountain river is narrow,the gradient is large.Due to the special mountainous terrain,water system and rainfall characteristics,the torrential disasters in the study area have occurred,which has caused serious damage to the infrastructure of the hilly area.The safety of life and property of the local people has been greatly damaged and threatened.In this paper,the typical catchment of the mountain flood disaster in Nanzheng County-Lengshui River Basin is selected as the research object.SWAT model is used to study the regional runoff and provide scientific and technological support for regional water resources development and utilization,flood prevention and mitigation.The main findings and conclusions are as follows:(1)Based on the extensive research results of meteorological,hydrological,land use data and hydrological model of the basin,this paper analyzes the development history and research status of the hydrological model,and focuses on the development history,development and application prospect of the SWAT model.The basic principle,basic structure and operation process of each module data are discussed.(2)Based on the GIS platform,the spatial data database of Lengshui River Basin was established,including DEM layer,land use layer and soil layer.At the same time,six rainfall stations in the study area were collected from 2001 to 2014,and the station datas from the Cold and Arid Regions Scientific Data Center.Based on the model data of the SWAT model,the SWAT model is used as the model data,which as model weather data.Based on the calculation data of soil database parameters,the basic attribute database of SWAT model is established.Based on the land use,the soil type,the slope type,and the watershed is divided into 31 sub-basins and 223 hydrological response units(HRUs).(3)Based on the SUFI-2 algorithm of SWAT-CUP model,the model was calibrated and verified according to the measured monthly runoff data of Sanhuaushi hydrological station from 2000 to 2014.Through the parameter automatic rate determination and sensitivity analysis,seven parameters were the most sensitive parameters.The efficiency coefficient Ens and the correlation coefficient R2 are used as the criterion of model adaptability.During the calibration period,the efficiency coefficient Ens is 0.85,the correlation coefficient R2 is 0.97.During the verification period,the efficiency coefficient Ens is 0.89 and the correlation coefficient R2 is 0.82.The model is applicable to the Lengshui River Basin.(4)Three kinds of land use status were set up,namely,the existing land use status,the deterioration of land use mode and the relatively good condition of soil and water conservation measures,and the influence of regional runoff was simulated.It is found that the change of land use pattern has little effect on the annual runoff in the basin,but it has obvious effect on the change of monthly runoff and the runoff of the rainy season(April ~ October)than the dry season(November to March)more significant.Forest land reduction will increase the uneven distribution of runoff during the year,making the dry season more dry,more rainy season runoff,increase drought and floods.(5)The effect of climatic factors on regional runoff is simulated.The results show that the annual runoff is positively correlated with the precipitation and the negative correlation with the temperature when the climatic factors change.When the temperature is constant,the annual precipitation increases by 1.56m3/s,and the annual rainfall is reduced by 1.85m3/s.When the precipitation is constant,the temperature increases by 1?.The annual runoff is reduced by 0.71m3/s,and the annual runoff increases by 0.7m3/s when the temperature drops by 1?.The response of the runoff to the climate combination is more obvious than that of the dry season.