Study On The Eutrophication Trend In The Tributary Of Three Gorges Reservoir Region

Research on forecasting eutrophication is always hot issue and nodus, and most of them were focused on the eutrophication in lake, while few were focused on the eutrophication in river. Lake eutrophication depends mainly on dissoluble phosphorous concentration, and river have close affinity with not only P concentration, but also velocity of flow and climate situation, however, over a long period of time, research on it haven't taken into account the influence that velocity of flow and climate situation work on, and there is no current research including all three factor.At first, this paper have investigated hydrology, water quality, pollution source and watershed situation of over thirty tributaries including Jialing River and Wujiang River in detail, and have monitored eutrophic status quo of mid- and large-scale reservoirs related closely with tributaries in Three-gorge Reservoir area, and then have analyzed the eutrophic characteristic of river and reservoir, and the regression correlativity between chla and TP , SD in tributaries and reservoirs, especially for Wujiang River and Changshou Lake, so it is indicated that chla have evident correlation with TP and SD in 35 mid- and large-scale reservoirs, and chla have little correlation with TP and SD in tributaries. There is no universal rule in river eutrophication, unlike in Lake.In order to probe into the pattern of river eutrophication, the author simulated the change of water quality in the Reach of Wujiang River between Wulong and Fuling by employing QUAL2E water quality model, setting its borderline condition and pitching and modifying thermometrically the model parameter, and emphasized the simulation: the two water quality situation that "black tide" appears and doesn't appear before Three-gorge Reservoir shape, and the two situation after Three-gorge Reservoir shape and when it run at high water line, that is, in the vicinity of 175m. The simulation is validated and compared with real data, proved to be exact. Finally, author ratiocinated the biochemical dynamics during eutrophic course, and theorized biochemically-dynamic model equation for eutrophication, to clarify eutrophic cause and effect of main lead- to factors, and, based on the model equation, author bring forward a series of critical concentration of P in the condition that other factors works in the different ways.