Eutrophication Investigation On The Backwater Reach Of The Branch River Of The Three Gorges Reservoir

Eutrophication is one of the major water pollution challenges that facing the world. After the completion of Three Gorges Reservoir Dam, due to the rise in water level and reduction in the water flow velocity, the capacity of pollution dispersion and purification decreased markedly. If the total amount of pollutants discharge is out the control, the water quality will worse considerably, which in turn will result in sound condition for eutrophication. After the construction of Reservoir Dam, many branch estuaries will transform into dead water area, even during flooding period, it will provide beneficial hydrological condition for eutrophication with a protracted and narrow back water area. Besides, with the rise in temperature and reduction in foggy day in winter, increase in sunlight will beneficial to organisms' photosynthesis and promote algebra's growth and reproduction, as a result, the eutrophication outbreak is likely to take place. This article is based on background value monitoring in major branch rivers before Reservoir water storage, the author apply trophic level index approach to evaluate the background trophic level in Reservoir Area. Furthermore, through field observation on eutrophication on back-water reach of typical Daling River, we try to study current trophic status of backwater reach of the major branch rivers, and provided countermeasures for prevent and control water eutrophication in branch rivers in Reservoir Areas. The research findings are the following:(1) Carry out field investigation on 19 major branch rivers in Chongqing section before the water storage of Three Gorges Reservior, and apply trophic level index approach to evaluate the background trophic level in Reservoir Area.(2) Conduct comprehensive analysis on key factors such as the water current, sunlight, nutrient discharge conditions on major branch rivers before 135 meters water storage and focus on evaluation on water trophic status on backwater area of a branch river, that is to say, through analysis and field monitoring , we try to identify and evaluate current trophic status, to explore transform trend on nutrient and eutrophication before and after 135m water storage, preliminarily predict transform trend on eutrophication in major branch rivers after 155m and 175m water storage.(3) The above-mentioned research aim to explore eutrophication transform trend on backwater reach in major branch rivers after Three Gorges Dam construction and provide corresponding countermeasures, which is of significant value.