| Eutrophication of water bodies has become a global and difficult problem in controlling water pollution and is one of the most important environmental problems. The majority of fresh water inland lakes have been or would be eutrophic in Europe and North America. At present, eutrophication of inland water bodies is very serious in China, which is the main environmental problem of limiting economic development. Protection and prevention from water pollution in three lakes, namely Taihu lake, Dichi lake and Chaohu lake, has been listed among the most important items in the ninth-five year plan of national environmental protection.Qiandaohu lake is located in the western part of Zhejiang Province in China. It is a large reservoir which had been formed after setting up an artificial dam. The area of the whole watershed is 10,442 km2. Sixty percent of the watershed area is located in Anhui Province, China. Qiandaohu lake has been used for many purposes like electricity generation, flood control, aquaculture, shipping, tourism, as a domestic water resource, etc. It is an important water source for Qiantang River. Thirty percent of water resource in Qiantang river comes from this lake. Thus the lake has important effect on sustainable development of ecological, social and economic environment in Zhejiang Province. Qiandaohu lake was very famous for its clean water quality. But in recent years the water body has become seriously eutrophic especially during summer months in some areas of the lake and came to the attention of National, Provincial and City Environment Protection Agency.The main objective of this study involved the following: Sampling and Monitoring water from the lake; water quality assessment and biological assessment; ascertain the limiting factors for Phytoplankton growth; fuzzy cluster analyse of water pollution of all sampling points; predicting Total Phosphorus concentration in the lake by using Static Models; setting up regression models and their application; setting up an eco-dynamic model and its simulation. The following were the results.(1) According to water quality assessment, in general, water quality was very clean in Qiandaohu lake, and the majority of all sampling points were oligotrophic. Only thewater at Jiekou had been eutrophic. The result of biological assessment was that the average density of phytoplankton at all the sampling spots was more than 1,000,000 per litre, indicating that the lake was eutrophic going by the population density. But this density of phytoplankton was higher than that in similar lakes at the same pollution level. We can therefore, conclude that the concentration of chemical elements was relatively low, but the average density of phytoplanktion was very high, which might be a characteristic feature of deep lakes.(2) The average ratio between Total Nitrogen and Total Phosphorus in Qiandaohu lake was 34:1. The lowest and largest ratio was 14:1 and 59:1, respectively. In general, if the ratio was more than 14:1, phosphorus was thought as the limiting factor of lake eutrophication and this, it can be concluded that, affected the growth of phytoplankton in Qiandaohu lake. In addition, the study also analyzed the effect of water temperature, radiation and pH on phytoplankton, but these factors may not have had limiting effect on phytoplankton growth.(3) Compartmentalization of water environmental quality is very important for Qiandoahu lake to be properly utilized and protected. According to water pollution levels, the lake was divided into three zones, and these are (a) relatively seriously polluted zone, (b) clean water resource protection zone and (c) less seriously polluted zone. The same result was confirmed by the fuzzy cluster analyse.(4) Predicting water pollution has been a hotspot in the study of water pollution. In this study therefore we predicted Total phosphorus concentration by using several international general static models. The concentration value that the sixth model predicted was relatively consiste... |
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