Effects Of The Changsha Hydropower Project On Eutrophication Of Xiangjiang River In Changsha

The study show that water quality have significant effects by the construction of the Changsha Hydropower Project,at the same time compared with water quality than the same period before water storage.through the water quality monitoring by the state environmental quality standards for surface water as the evaluation basis, evaluating the impact on water quality by the experimental data. The study relates water nutrient state changes in the state and the mathematical model, computer technology together, and then analysis of water body nutrition influential factors and pollutants,the watershed environmental management providing decision-making basis at the same time.Selected the six water profiles of Xiangjiang river(Changsha) and monitored ten indicators of water quality.Monitoring methods are conducted by national standard method.By the analysis,after the impoundment,water quality of Xiangjiang river(Changsha) mainly maintain above the national water quality standard III,the dissolved oxygen content in waters changed little,Still was mainly affected by temperature.after the Hydrological environment into reservoir,Phosphorus becomes key pollutants,Although content declined but over standard rate still reached 61.29%,TN and COD's content in water also increased than before and sustained beyond the corresponding water quality standards,especially the sum of TN content in each profile to exceed bid up to 92.70%.Overall,TP and NH3 are greatly influenced by impoundment,both influenced by sediment settling in the water area.In order to further understand the main factors of Xiangjiang water nutrition state changes,By using the neural network tool box of Matlab software the grey-BP neural network model is established.On the basis of the theory of principal component analysis and related experience,screen out Temperature,NH3-N,DO,TP,TN five water quality indicators.Established Grey-BP neural network model.And doing optimization.Simulated predict to chlorophyll a concentration and algal abundance.The results show that,Through gray-BP neural network model which based on principal component analysis optimized.The network solution can better simulate the chlorophyll a concentration and change of Algal abundance in Xiangjiang river(Changsha), whole network error is 0.0558,network training data's goodness of fit index is 0.93708,overall fitting effect is 0.90373,the overall fitting effect is good. Establishment of 13 BP network models based on the principal component analysis,by analyzing the results of the Xiangjiang River waters nutritional status and arranged it's order:Temp>DO>NH3-N>TP>TN.At last,this study based on water quality analysis of Hydropower Project before and after the impoundment.puts forward a new thought for Xiangjiang river(Changsha) water environmental protection and input control measures of water nutrients.