Water Quality Simulation And Water Environment Management In Jiaokou&Zhougongzhai Reservoir Watershed, Ningbo

Jiaokou and Zhougongzhai Reservoirs combined dispatching supplies500,000t/d water,which has become major drinking water source area for Ningbo. As social and economicdevelopment, watershed pollution has been increasing, so that the safety of local drinking water isdirectly threatened. Choosing Jiaokou and Zhougongzhai Reservoir Watershed as the study object,according to the national survey of pollution source, statistical yearbook of the townships, DEM,and remote sensing image, surrounding management of the watershed water environment,pollution status of the watershed were analyzed, including water environment quality assessmentand analysis of pollutant sources. Based on GIS platform, water quality of the watershed wassimulated with software of WASP7.3, and visual analysis of simulation results was made, theone-dimensional steady-state water environment capacity was calculated in accordance with thegeographical characteristics at the same time. On this basis, the measures of water environmentmanagement were proposed.The main results:(1) Agricultural non-point source and domestic pollution source areprincipal sources in the reservoir watershed. COD, TN, and TP pollution is mainly from theagricultural non-point source, which is caused by the excessive application of fertilizers and soilerosion. NH3-N pollution is mainly from domestic pollution source, which is mainly caused bydirect discharge of domestic sewage and human excrement. The distributions about emissionpollution intensity of pollution loads are quite similar, there is some emission pollution intensityaround the reservoir.(2) Rainwater area of the watershed, hydrological network, reach gradient,and flow accumulation are extracted by using GIS technology, the one-dimensional steady-statewater quality model of WASP7.3is established. the simulated results: COD pollution doesn’t posea serious threat to water quality in the reservoir area. NH3-N and TP pollution have a certain effecton the water quality, the emission of NH3-N and TP need to be partially reduced in the watershed,so that the water quality meets I standard. TN pollution has a larger effect on the water quality, thereaches, where TN concentration up to I~II standard, is only35%of the total river length, theemission of TN needs to be substantially reduced in the watershed.(3) To meet I standard, the watershed needs to cut COD82.16t/a, NH3-N32.97t/a, TN169.21t/a, TP5.22t/a. The averagereduction rate of pollutants is over65.48%, reduction rate of TN is93.8%, NH3-N is81.4%, TP is79.7%, and COD is7.0%. Therefore, the management measures are suggested, including measuresof pollutants reduction, information management of water environment, and so on.