Study On Cause And Control Countermeasure For Water Pollution Of Reservoir In Mountain City

This paper selects Shuanglong lake and Wuyi reservoir in Chongqing Municipal as researching subjects. Firstly, based on the investigation of hydrology and pollution, it analyzes origin and distribution of pollutants in Shuanglong lake and Wuyi reservoir. Then, according to 12 monitoring indicators provided by the Chongqing Municipal Environmental Monitoring Center as evaluation factors and standard-level 5 as a target, it combines single factor index appraisal method, comprehensive water quality indicator index appraisal method and comprehensive nutrition status index appraisal method to evaluate the water quality of Shuanglong lake and Wuyi reservoir and to obtain major pollutants and excessive multiples. Finally, it determines target reductions of major pollutants of Shuanglong lake and Wuyi reservoir by estimating water environmental capacity.The results are as follows:(1) The main pollutants of the Wuyi Reservoir are total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODcr) and ammonia (NH3-N). The load contribution ratio of inside source pollution are 61.5%,77.1%,66.0% and 42.94%, of living-point source pollution are 17.6%,13.9%,14.86% and 32.52% and of surface runoff and agricultural non-point source pollution were 20.9%,9.0%,19.14% and 24.54%. Wuyi reservoir’s water quality present a overall trend to level-5 and deteriorate seriously.The overall evaluation of Wuyi reservoir’s water quality is mesotrophication from 2011 to 2012 and hyper eutrophication in 2013. More attention should be paid. According to the calculation of reservoir’s management objectives, it derived that the content of NH3-N still remains portion of the environmental capacity to accommodate future certain pollutant input and the target reductions of TN, TP and CODCr reaching standard-level 5 were 2.52(t/a),0.324(t/a) and 5.59(t/a).(2) The main pollutants of Shuanglong lake are TN, TP and CODCr.The load contribution ratio of the inside source pollution were 6.93%,10.7% and 37.2%, of living-point source pollution were 71.46%,85.7% and 46.6% and of surface runoff and agricultural non-point source pollution were 21.61%,3.6% and 16.2%. The water quality has changed from oligotrophication in 2011 tomesotrophication in 2013.The comprehensive water quality indicator index was as high as 6.421 in 2012, belongs to level-5 but not black-odor. Content of TP has exceeded 1.25 times especially. It has a higher risk to outbreak "bloom". According to the calculation of reservoir’s management objectives, it derived that the content of TN and CODCr remains portion of the environmental capacity to accommodate future certain pollutant input and the target reductions of TN reaching standard-level 5 were 0.002 (t/a).Finally, it proposes some reasonable and economic waste prevention measures based on the state quo of Shuanglong lake and Wuyi reservoir from the inside source pollution prevention and the outside source pollution prevention. Specific measures include:building network around the lake and reservoir; separating rain and sewage thoroughly; removing garbage; exploiting percolation ditch of rainwater interception, grass ditch and ecological interception band for initial rainwater purifying; replacing ecological greenbelt to vegetable plot; building ecological buffer zone and ecological hydrophilic corridor; clearing eutrophic plant such as water algae and water cabbage; regular dredging and adding clean water; constructing shallow water ecosystems in Repulse Bay area; increasing artificial reoxygenation and flowing water systems; implementing biological driving technology, and so on. This paper’s research provides technical support for water pollution prevention of reservoir in mountain city.