Study On Water Environment Carrying Capacity Of Dahuofang River Basin

The theory of water environment carring capacity in a river basin is the foundation and theoretical basis for the green and sustainable development in China.Nowdays,the water environment problems are becoming more and more complicated and the comprehensive management of water environment in river basin needs to be steadily improved.The control calculation of total pollutants quantity in river basins and environmental management based on water environmental carrying capacity theory has the important theoretical significance and application value.This paper took the Dahuofang river basin as the research object and mainly contents listed as study the following:(1)Based on the requirements for targeted water quality specified in ?Regulations on Protection of Drinking Water Sources in Dahuofang of Liaoning Province?,the water quality of three inflow rivers and the Dahuofang Reservoir in the basin were evaluated and analyzed,making clear the main pollution sources and pollution factors in the Dahuofang River Basin.(2)Based on the GIS platform,the basic spatial information database of the Dahuofang river basin was established,then the water environment of the Dahuofang river basin was quantitatively simulated using the Soil & Water Assessment Tool(SWAT).(3)According to the water quality analysis,the total phosphorus is selected as the total quantity control factor,and combined with the hydrological simulation results of the sub-basins SWAT model in the river basin,the water environment capacity of the river basin in different water periods was calculated using the formula.(4)The actual pollutants loads from Hunhe river in the Dahuofang river basin at the different water periods was computed,the carrying status of the Hunhe river was evaluated,and the reladed amount and reduction measures were finally determined.The main results are listed as follows:(1)Based on the analysis on the water quality in the Dahuofang reservoir and the three inflow rivers,the total phosphorus in Hun river is highest compared other,other rivers in the tributary of the Dahuofang river basin,with a multi-year average of 3.39mg/L,followed by Suzi river with that of 3.04mg/L,and Shehe river has the lowest of 2.72mg/L.Based on the analysis of nitrogen and phosphorus ratios in the water area of the reservoir area,the total phosphorus in the reservoir was the restriction factor preventing eutrophication of the reservoir.therefore,total phosphorus was selected as the water environmental control index in the study.(2)The point and non-point source pollution loads of the Dahuofang River Basin were firstly estimated and the main pollution source of the basin is non-point source pollution,including: poultry excrement,chemical fertilizers and pesticides in agricultural planting,A water environment model using SWAT was established in the Dahuofang river basin.The model parameters were calibrated using SWAT-CUP module and the measured hydrologic and water quality data from 2008 to 2016,The evaluation of the modelling accuracy showed that the model calculation satisfied the requirements for runoff and water quality accuracy in the Dahuofang river basin.(3)The water environmental capacities of the Dahuofang river basin in the wet,normal and dry season were calculated respectively,showing a reduction in sequence in the three seasons.Based on the actual sewage discharge in the Dahuofang river basin,although the basin has a larger assimilative capacity in the wet season then other seasons,it showed a serious overload problem.To solve the problem of the serious non-point source in the basin,measures on reducing of the accumulated pollutants in the dry season and decreasing in fertilization in the wet season should be taken,and pollution treatment should be enhanced during dry season.