Study On Effect Of Sand To Eutrophication In Chongqing Region Of The Three Gorges Reservoir

The Three Gorges Project (TGP) on the Yangtze River is the world-famous largest hydroelectric project. It will possess comprehensive utilization benefits for flood control, power generation and navigation improvement. But the construction of TGP will produce widespread and profound impact on ecology and environment of the Three Gorges Reservior (TGR). Whereas the content of sand in TGR is high and many inspecting data has indicated that sand could adsorb contamination and nutritious salts in water body, the effect of sand to the environment of water body in TGR is not allowed to be neglected. The form of the TGR would change the flowing rule of current and the flowing rule of sand in the Yangtze River and its tributaries, which would change the existing form and the space-time distributing rule of contamination in TGR. Accordingly, the viewpoint that sand exert effect on the environment of water body has been considered in this study. In this study, the space-time distributing of sand in Chongqing region of TGR, the characteristic of sand and the effect of sand to the environment of water body all are considered to discuss the potential of eutrophication in Chongqing region of TGR. At first, the space-time distributing of sand in Chongqing region of TGR has being studied based on granularmetric analysis data of sand. Afterwards, the dependence relation of sand and nitrogen/phosphorus has been analyzed, and the change of water quality as a result of the sedimentation of sand has been studied by the simulating experiments. The study indicated that the sand has both positive effect on the potential of eutrophication for which can adsorb phosphorus and negative effect for which depositing can increase diaphaneity of waterbody, which be propitious to photosynthesis of algae. Finally, the space-time distributing of sand in Chongqing region of TGR and three factors (the condition of nutritious salts, the condition of hydrology, the condition of climate) which are needed by eutrophication, all are integrated to analyze the potential of eutrophication in Chongqing region of TGR. The conclusions as following: Firstly, eutrophication wouldn't take place in Chongqing region of TGR during the period when the reservoir discharges water; Secondly, eutrophication would likely to take place in tributaries of TGR and the water area in the bay of TGR where the current flows slowly during the period when the reservoir sluices water especially from Mar. to Apr.. The deep researches about whether eutrophication would take place in the Yangtze River are still needed.