| The Jinjing River belongs to one of the tributaries of the Laodao River.It is the water source for the joint water plant in the northern part of Changsha County,and is also located in the upper reaches of the Xingsha water source in Changsha County.The Jinjing River Basin is developed in agriculture,and the application of chemical fertilizers in the basin is the main cause of non-point source pollution.The non-point source pollution in the basin is a great threat to the water quality.Therefore,based on the SWAT model method,this paper simulates the non-point source pollution in the Jinjing River Basin,and provides technical support for the water quality management of the Xingsha Water Plant.It is of great significance to the water resources protection of drinking water sources in the basin.This paper collects data conducts land use analysis,builds space,attribute and agricultural management database to establish the SWAT model of the Jinjing River Basin,simulates the runoff and pollutants in the basin,and obtains the following main results:(1)The land use change of the Jinjing River Basin from 2006 to 2016 was analyzed.The land use type was mainly forest land,followed by cultivated land and construction land.The proportion of these three types of area continued to increase with time.Through dynamic degree calculation and analysis,it is found that the main change trend of the Jinjing River Basin is the increase of forest land and construction land area,and the reduction of water area and cultivated land area.The calculation of transfer matrix can be used to understand that the main conversion mode of land use in the basin is the conversion of construction land to forest land and grassland and the conversion between cultivated land and woodland.(2)The SWAT model of the Jinjing River Basin was constructed and the runoff simulation was carried out.Based on the hydrological monitoring data,soil data and meteorological data,the SWAT model was established to divide the Jinjing River Basin into 11 sub-basins with a total of 104 hydrological response units(HRUs).The flow-by-month runoff data from 2006 to 2013 was used to determine and verify the runoff simulation of the basin.The verification period R2 and the Nash efficiency coefficient Ens were both greater than 0.8.It shows that the SWAT model built in the Jinjing River Basin has good applicability for runoff simulation.(3)Based on the SWAT model,the non-point source pollution load of total nitrogen,total phosphorus and ammonia nitrogen in the Jinjing River Basin in 2017 was simulated.The simulation results show that the Ens of the total nitrogen simulation results is 0.69 and the R2 is 0.85;the Ens and R2 of the total phosphorus simulation reach 0.75 or more;the Ens and R2 of the amnonia nitrogen simulation are close to 0.9,and the results show that the surface pollution simulation results are consistent with the actual pollution load.The SWAT model can be used to simulate the non-point source pollution in the Jinjing River Basin.(4)The correlation and proportional relationship between surface source,point source pollution and total pollution load in 2017 were analyzed and discussed.The monthly average total nitrogen simulation estimated load in the Jinjing River Basin is 27586.99 kg,the monthly average total nitrogen measured pollution load is 39926.74 kg;the monthly average total phosphorus simulated estimated load is 5228.94 kg,and the monthly average total phosphorus measured pollution load is 6649.75 kg;monthly average ammonia nitrogen The simulated estimated load is 13559.36 kg,and the montl:dy average amnonia nitrogen measured pollution load is 11583.16 kg.From the perspective of spatial distribution,the spatial pollution of non-point source pollution in Jinjing River is uneven,and the output is concentrated in areas with dense cultivated land.It is recommended to adopt scientific and efficient agricultural management measures to reduce the total agricultural non-point source pollution load in the basin. |
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