| After the 135-m water storage, drastic changes have been made to hydrological situation of every branch river in the Reservoirs Area. Although most of rivers remain long and narrow fluvial situation, water flow velocity of backwater reach decreased evidently.The waterbody almostly becomes a man-made lake.In the paper, the characteristic features of distribution for space-time and changing rules of the water trophic status of backwater reach on the Daning River after the 135-m storage are discussed primarily. The research mainly included eutrophication monitoring, which carry out by means of on-the-spot observation and lab analysis according to three different monitoring schemes, namely, long river beach monitoring, open water area monitoring and upright-monitoring. On the basis of experimental study, evaluation have been made by applying Tropic Level Index (TLI) in testing results. We found that after the 135-m water storage of the Three Gorges Reservior, it is very likely and unavoidable for eutrophication outbreak in the backwater reach of sub-branch rivers in Reservoir Area. The research findings are the following:i After the 135-m water storage, "agale bloom" of the backwater reach water of Daning River break out in certain change rules during the year. The two more dangerous periods to bring "water bloom"are early-summer and early-autumn.They are the period from April to May and the period from September to October.During the periods, there are high water temperature, strong light, low water speed, long time,and high nitrogen- phosphorus nutritions. Just these factors leads to high trophic situation even eutrophication outbreak.ii In comparasion and analysis of these results of four long-reach monitoring, we found some rules. Along with water level seasonal changing, the middle part of backwater reach on the Daning River changes between Shuanglong and Yinwo-tan. The most dangerous reach to bring... |
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