Study On Models For Assessing And Predicting Water Quality Of The Poyang Lake

The Poyang Lake is the largest fresh water lake with abundant water and biology resources in China. It has multiple functions including flood control, shipping,irrigation, aquaculture and tourism. Mutual coordination development of social economy and environment protection is important for exploitation strategy of the lake area.Water pollution control is the main target of environment protection of the Poyang Lake.To complete those tasks,it is essential and necessary to assess and predict the water quality of the Poyang Lake.Water environment quality assessment contains large quantities of complex phenomenon and interaction, moreover,there are much fuzzy phenomenon and conception. Based on the principle of fuzzy mathematics, the fuzzy synthetic evaluating model for assessing water quality was established in this paper.The model was applied to assess water quality in two years from 2003 to 2004,and the calculating process of evaluating was introduced. The results showed that the main contaminations of the river were TP and TN,TP was the first control contamination.Fuzzy synthetic evaluating model couldn't only give us the synthetic assessing result of the Water quality but also identified the main contaminations and those supplied scientific evidence for managing and planning the Poyang Lake.The complexity of water environment and lack of data is the characteristics of grey system.Focused on these uncertainty questions,grey model x¹(t+1)=[x⁰(1)-(a/b)]e^-at+(a/b) was established in this paper according to grey system theory.This model was applied to predict such as pH, DO,COD_Mn,NH₃-N water quality parameter of the Poyang Lake.The precision of this model and the results Of predicting were very well according the analysis of error.In the water environment such as the Poyang Lake where the data of water quality is scarce and the change of water quality parameter is gently, grey model can be applied compatibly.