Water Conservation Function And Pollution Prediction Of Ecosystem In Water Source Area Of Nanning City

At present,the problems of drinking water source supplying Nanning city include single originated,relatively heavy polluted,incomplete emergency water supply network constructions,weak safety protection system and weak guarantee measures.In this paper,by adopting methods include information collection,site visiting,field investigation,expert discussions,questionnaire survey,sampling analysis and others,the related natural environment safety,socio-economic development indicators,related planning content and water supply,drainage Status,sewage treatment,water source protection zone division and other information for drinking water source in Nanning city was fully recorded,and obtain the following conclusions:(a)Through the investigation of the construction and management status of water supplying,water quality and protection areas in water source area,reserve and planning water source area,the discharge and compliance status of pollutants in water source area for Nanning city was evaluated.The major indicators of discharged pollutants(COD and NH3-N)in municipal,industrial and agricultural sewage were monitored on 17 inland rivers in Nanning city.Under scenario 1:the sewage treatment rates,industrial and agricultural pollutants emission maintain the same level as reference year(2012),the water quality was forecasted based on pollutant emission combined with the conservation function of water source area,that the COD and NH3-N concentrations of water source of Yongjiang river in 2016 and 2020 would meet the corresponding requirements of water environment function area;Un scenario 2:the treatment rate of municipal sewage would reach 90%in 2016 and 95%in 2020,and the pollution of industries and agriculture would achieve the goal of energy saving and emission reduction,the water quality was forecasted based on pollutant emission combined with the conservation function of water source area,that the COD and NH3-N concentrations of water source of Yongjiang river in 2016 and 2020 would meet the corresponding requirements of water environment function area.But in scenario 1,the COD and NH3-N level would rise stepwise by year in 17 inland rivers until 2020,and pose environmental safety risks for the water source area.(b)Based on the principle and method of ecological function zoning,two typical waters ecosystems-River Basin and Lake Reservoir in Nanning were studied based on the basic theory of ecology,multivariate quantitative analysis and satellite remote sensing interpretation.The water conservation function capacities of one river type and nine lake type ecosystems were estimated,and the capacities of water conservation was assessed in the surrounding environment of rivers and reservoirs.The results showed that:(1)The water conservation capacity of Nanning river ecosystem(c)(Zuojiang-Youjiang-Yongjiang River basin)was generally low,and the extent of water-saving index of 500m buffer zone was 17-35.9,the proportion of natural ecological factor to artificial ecological factors was 1:0.6-1.6;For 5 km buffer zone,the extent of water saving index slightly improved and enhanced to 26.6-39.8,the proportion of natural ecological factors to artificial ecological factor was in a ratio of 1:1-1.2.(2)The lake reservoir ecosystem possessed relative better water conservation function than river basin systems in Nanning,the order of water conservation function of nine reservoirs is:Fengting reservoir>Zhicunhe reservoir>Tuunliu reservoir>Xiyun Reservoirs>Tianhuling Reservoir>Tianli Reservoir>Dongshan Reservoir>Dawangtan Reservoir>Longtan Reservoir,the water conservations of Dongshan Reservoir,Dawangtan Reservoir,Longtan Reservoir were classified as "poor".