Research On Non-point Source Pollution Of A Watershed In Northeast China Based On SWAT Model

Non-point source pollution is one of the main sources of pollution in river basins.Fully analyzing the non-point source pollution situation facing the river basin will provide an important basis for pollution control in the river basin.This article will take a watershed in Northeast China as the research object,analyze and evaluate the water quality of the watershed,analyze the distribution of pollution sources in the region,establish the SWAT hydrological and water quality model of the watershed,and calibrate and verify the model to predict the non-point source pollution of the watershed.Trends to identify critical pollution periods and critical pollution areas in the watershed.Firstly,water samples were collected from the watershed during non-flood and flood seasons,and permanganate index and related indicators analysis,nitrogen status analysis,phosphorus distribution status analysis,heavy metal pollution distribution status analysis,and pesticide detection rate analysis were conducted.It was found that the watershed is mainly faced with nitrogen and phosphorus pollution problems,and the content and spatial distribution are different in different periods,so it is necessary to establish a watershed SWAT hydrological and water quality model to grasp the pollution distribution status in each period.With the support of the existing detection data and pollution source data,a river basin digital elevation database,land use database,soil database and meteorological database were constructed;then the pollution source data of the river basin were identified and analyzed,including agricultural non-point sources and farming.Finally,the SWAT hydrological and water quality model of the basin was established.Using 2008-2010 as the model warm-up year,2011-2015 as the model rate year,2016-2018 as the model verification year,and based on the data of five local hydrological stations,the model was revised and tested.Use R2 and NS two indicators to evaluate the applicability of model simulation.The final model result satisfies R2?0.6 and NS? 0.5,the simulation effect meets the simulation accuracy requirements.Finally,on the basis of the model,the watershed is divided into 75 units.The model predicts the trends of runoff and pollutants from 2020 to 2050,and identifies the key pollution periods and key pollution areas in the river basin in the future.:(1)Key pollution period:The key pollution periods of the watershed in 2020-2050 are August 2024,August 2036,April,June and July of 2043,April and July of 2044,April and July of 2045.(2)Key pollution areas:After the spatial visualization of pollution in each key pollution period,the key pollution areas corresponding to each key pollution period are different.The main causes of pollution on the time scale:one is the surface runoff caused by the melting of snow and ice in the watershed;the second is the planting and fertilization of the watershed;and the third is the surface runoff caused by periods of heavy rainfall.The main cause of pollution on the spatial scale is agricultural cultivation in the basin.