Study On The Impact Of Land Use On Non-point Source Pollution In Paihe River Basin Based On HSPF Model

There are two main types of water environmental pollution,which are point source pollution and non-point source pollution.With the continuous and scientific control of point source pollution,the proportion of non-point source pollution in water environmental pollution has increased year by year.Characterized by randomness,complexity and extensiveness,the non-point source pollution in the basin has always been the focus and difficulty of water environment pollution control in China.And owing to the constraints of low water environment capacity,unreasonable land use structure,and weak supervision in small and medium-sized river basins,water eutrophication and other serious environmental pollution problems are more likely to occur in these areas.Therefore,it is necessary to carry out comprehensive and scientific treatment to control the non-point source pollution in the drainage basin.The quantitative research on non-point source pollution can not only reasonably and objectively describe the distribution of pollution sources,influencing factors and migration and transformation laws,but also provide scientific basins for the comprehensive treatment of the ecological environment of the river basin,which is conductive to fundamentally solve the negative impact of non-point source pollution.This paper takes Paihe river basin as the research object.Based on the full collection of meteorological,hydrological and water quality,land use and other related pollution source data,this paper use the HSPF model(Hydrological Simulation Program-Fortran)with the combination of RS and GIS technology to have reasonable parameter calibration,so as to quantitatively describe the non-point source pollution load in the basin,and then further analyze the temporal and spatial distribution characteristics of non-point source pollution in the basin;and by setting different control conditions to simulate and compare the changes of non-point source pollution load in different scenarios,the treatment measures of non-point source pollution based on land use are discussed at the end of the paper.The main research results are as follows:(1)By summarizing the current situation of non-point source pollution and relevant theories,and comparing different models,the main existing problems in the current study of non-point source pollution are analyzed;and combined with the actual situation of the basin,HSPF is selected as the target model and its suitability is further analyzed;(2)Obtaining the data of land use status of the Paihe river basin in different years by the interpretation of the remote sensing image of Landsat80LI image in 2015-2018,so as to analyze their temporal and spatial variation characteristics and trends;(3)Constructing the HSPF model of the Paihe river basin by basing on the WDM database,and use the measured flow data in 2018 to analyze the sensitivity parameters and parameterization of the basin hydrology.The results show that the relative errors of total runoff in calibration period are 7.34%,Nash coefficients of monthly and daily runoff are 0.86 and 0.60,the coefficient of determination are 0.94 and 0.79 respectively,the relative errors of total runoff in verification period are 4.70%,the Nash coefficients of monthly and daily runoff are 0.96 and 0.63 respectively,and the coefficient of determination are 0.98 and 0.78,respectively,which generally meet the simulation accuracy requirements;(4)On the basis of hydrological simulation,the HSPF model is used to simulate sediment and water quality,with 2015-2016 as the calibration period and 2017-2018 as the verification period for sensitivity parameter analysis and parameter determination.Finally,the concentration simulation results of ammonia nitrogen total phosphorus is obtained.The results show that the relative errors of ammonia-nitrogen simulation in 2015-201 8 are-18.06%,-16.27%,-37.48%,and 7.35%respectively;and the relative errors of total phosphorus simulation are 24.74%,4.54%,-10.13%,and-40.13%respectively.The overall simulation effect is ideal,and the simulation trend is consistent with the measured situation;(5)Using the HSPF model to output the non-point source pollution load of total nitrogen and total phosphorus,and analyze the temporal and spatial distribution characteristics of non-point source pollution load in the Paihe river basin and the pollution contribution rate of different land use types;(6)Simulating the changes of non-point source pollution load in Paihe river basin under the different land use type adjustment and best management practices by setting four types of scenarios,and finally summarize and explore the best management mode and pollution control measures for non-point source pollution under land use.