A Study On The Eutrophication Of The Three Gorges Reservoir

Eutrophication is one of the ecologic problems in lakes, reservoirs and rivers. It is occurred sometimes in the reach of back water of some tributaries after Three Gorges Reservoir storing up to 135m in June 2003. It indicated that some of tributaries are in danger of eutrophication. The water environment issues in Three Gorges Reservoir and its predictive technology for eutrophication are thoroughly discussed in this thesis. With lot of monitoring data, the water quality of present condition in Three Gorges Reservoirs is assessed. The progress in the field of eutrophication research on lakes and reservoirs is reviewed. From ecological point of view, we expatiated on the mechanism of eutrophication and put forward a set of index and a standard for the eutrophication of reservoirs. A complete and deep research on the income sources and loads of N and P are has done. The cause and the influence condition of eutrophication in Three Gorges Reservoir is studied at the laboratory and on the field. Based on the results, a deeper study on one-dimensional and two-dimensional dynamical model of eutrophication is taken to predict the eutrophication in Three Gorges Reservoir. Main creative work of this thesis is as following:Through the deeply study on the income sources and loads of nutrient N and P, it is found that the load of N and P in reservoirs mainly come from upstream and non-point source. Therefore, the key point to control the eutrophication is to reduce the input loads from upstream and the non-point source.Aim to the characteristics of the Three Gorges Reservoir, the factor of water flow velocity is introduced into the eutrophication assessment and its grading system according to lots of field observations and analysis. The new method is well applied to the eutrophication assessment of Three Gorges Reservoir.The growth and death rate of algae are observed on the spots alone the YangtzeRiver and Jialing River in the reach of Chongqing city. The influent parameters to the algae growth rate, such as strength of sunshine, current velocity and suspended substance are studied by experiment modeling. The relationship between the parameters and chlorophyll-a are analyzed. It is enriched the content of the eutrophication study of Three Gorges Reservoir.With a ID and 2D dynamical model and the algae growth statistic model established on the basis of the monitoring data, the eutrophication state in the trunk stream of Three Gorges Reservoir and in the downstream area of the wastewater outlet is compellingly calculated. By the analogy in association with the meteorological condition, hydrologic character and the chlorophyll-a level, the possibility of eutrophication in the trunk stream and main tributaries of three gorges is predicted and assessed for the year of 2010.