Study On The Impact Of River Water Quality And Pollutant Carrying Capacity Of The Changhua River Water Diversion Project In The Water Supply Area

The water diversion project is an important measure to alleviate the contradiction between supply and demand of water resources in water scarce areas.At the same time,it also puts forward higher requirements for the prevention and control of water pollution in the affected areas.Conducting water quality impact analysis and pollution prevention and control of the retreating rivers in the affected areas has important practical significance for ensuring water environment safety.This article takes the Changjiang receiving area of the Changhua River Water Diversion Project in Hainan Province as the research object,and uses fuzzy comprehensive evaluation and cluster analysis methods to conduct an evaluation of the current water environment quality and analysis of the trend of water quality changes;Based on the division of pollution control units in the lower reaches of the Changhua River basin,COD,ammonia nitrogen,and TP were selected as pollutant indicators to predict the inflow load of each pollutant under different pollution control measures;A one-dimensional water quality model was constructed for the lower reaches of the Changhua River,and the impact of the water transfer project on the water quality of its river channel was predicted and analyzed;Finally,the water pollution carrying capacity of the studied river section was calculated,and the pollutant reduction and remaining pollution carrying capacity of the water area under different pollution control schemes were analyzed,providing a basis for the water environment management of the retreating rivers in the receiving area.The main research results obtained are as follows:(1)The water quality of the 7 monitoring sections in the current year’s water receiving area can meet the water quality target requirements;Using spatial clustering analysis for each pollution indicator,the spatial distribution characteristics of each key indicator were studied,and it was determined that the trend of changes in each water quality indicator was basically stable,and the spatial distribution was basically consistent,meeting the requirements of water quality objectives in each water functional area.(2)27 pollution control units are divided for the lower reaches of Changjiang River,and the inflow load of COD,ammonia nitrogen,TP and other pollutants of each unit in the current year is calculated;Predicted the generation of pollutants in the lower reaches of the Changhua River basin in the planning year,and developed 6 scenarios for pollutants entering the river based on local pollution prevention and control planning plans,and calculated the load of pollutants entering the river under each scenario.(3)Three typical non flood and flood seasons were selected as the predicted water periods to predict the water quality changes in the lower reaches of the Changhua River after the planned annual water transfer.The feasibility of meeting the water quality standards of the retreating rivers in the receiving area was analyzed.(4)A calculation model for the pollutant carrying capacity of the lower reaches of the Changhua River was constructed,and the allowable pollutant carrying capacity of pollutants such as COD,ammonia nitrogen,and TP,as well as the remaining pollutant carrying capacity under the standard scenario,were calculated.The reduction of pollution load for each control unit was determined,and the Shilu River Basin was identified as a key prevention and control unit,with TP as a key pollution prevention and control indicator.Seven water pollution prevention and control measures were developed.