Assessment Of Pollution Load From Rainfall Runoff In The Shiwuli River Basin

In recent years,urban malodorous black river in China has become the focus of attention in water pollution control.With the acceleration of urbanization and the intensification of rainstorm,surface runoff has become an important cause of deterioration of urban water quality and river ecosystem.In order to improve the surface water quality effectively,it is necessary to focus on the control of runoff pollution.In this study,the spatial and temporal distribution of rainfall runoff pollution in the Shiwuli River Basin in 2016 was evaluated.We conducted remote sensing interpretation of land use types,carried out Runoff Curve modelling by and monitoring localization correction and runoff sampling experiments.The evaluation process is realized automatically by computer language.The purpose of this study is to grasp the information of runoff pollution sources and pollution loads comprehensively,systematically and truly,and to provide basic data for carrying on further pollution control projects in the basin.Through the simulation and calculation of pollution load in the Shiwuli River Basin,we have implemented daily analysis on time scale and high resolution grids analysis spatially.Finally,we constructed the high-resolution spatial information database of pollution sources for rainfall runoff in the basin.Based on the calculation results,the following conclusions are obtained:(1)In 2016,the loads of COD,NH3-N,TP and TN generated by runoff in the Shiwuli River Basin were 11707.6,148.4,43.5 and 538.8 tons,accounting for 23.4%,3.7%,8.2%and 9.0%of the total pollution sources respectively.Unlike point sources entering rivers after being reduced by sewage treatment plants,the direct discharge of runoff pollution needs great attention,especially the COD index.(2)In temporal distribution,all kinds of pollutants were mainly produced in summer,with the highest load in July and October.COD,NH3-N,TP and TN accounted for 23.3%,28.5%,26.6%and 29.1%of the annual load respectively in July,and 25.2%,9.6%,18.1%and 23.1%in October.The main reason for the concentrated distribution is the seasonal distribution of rainfall.Therefore,the control of runoff pollution needs to be carried out in conjunction with the prediction of rainfall.(3)In spatial distribution,the middle and lower reaches of the basin have higher COD and TP loads per unit area,due to the concentration of unconstructed land,grassland and shrubs;the NH3-N loads per unit area in the areas are higher with the dense distribution of commercial districts,residential and administrative regions;And the lower reaches of the basin are still carrying out the work of returning farmland to forests because of the urbanization process,so the TN load per unit area is higher than that in the upper and middle reaches.From the regional level,COD pollution control should mainly focuses on Baohe District and Binhu New District,TP pollution control focuses on Baohe District,NH3-N and TN pollution should be treated in all Districts.(4)From the contribution of land use types,grassland and shrub contributed the highest COD pollution,accounting 33.9%to the total;Residential and administrative regions contributed 63.5%to the total amount of NH3-N and 37.0%to the total amount of TP,Forest and orchard land contributed 35.9%to the total amount of TN.Based on the results above,suggestions are put forward:① strengthen the planning,utilization and supervision of land types,speed up the process of urbanization transition,and enhance the drainage basin’s capacity to degradate runoff pollutants;② strengthen the daily cleaning and renovation of crowded commercial districts and old residential districts by environmental sanitation departments;③standardizing the business activities of small shops and daily activities of residents to reduce food waste and pet manure disposal;④ Carry out the investigation of rain and sewage pipeline network in the river basin to ensure the diversion of rain and sewage and the dredging of existing pipelines.⑤ Strengthen the management and control of runoff pollution,formulate emergency plans for runoff pollution,and promote the construction of "sponge cities".⑥Strengthen the management of basic data information in the watershed,establish a data sharing information platform to realize the full coverage and real-time updating of watershed data,and establish a decision-making platform for digital and intelligent watershed;...