Studies On Water Quality And Prediction Model Of Huizhou West Lakes

At present, water environment pollution has been become a worldwide problem. As a typical urban shallow lake, Huizhou West Lake has been eutrophication. In the present study, the water quality was analyzed and its changing trend before and after ecological restoration by modeling. The results from theorial forecasting and pratical application both demonstrated that macrophyte had an obvious effect on the lake restoration.Based on the mass balance principle of input and output of lake, and the water quality investigation data from August to October in 2004, the present study constructed the algae-type and macrophyte-type water quality forecasting models of Huizhou West Lake. With the assistance of MATLAB, the parameters in models were calibrated by least-square method, and then the model equations were validated, whose error analysis was carried out by the 12-month data of water quality during 2003-2004. Compared with the national industry criteria, the conclusions could be drawn as follows: the eligible rate of the validation results was above 90%, and the relative errors of forecasting were controlled within ±20%, demonstrating that the construced models in the present study had excellent precision and feasibility. At last, the changes of water quality of Huizhou West Lake in future decade were predicted. The forecasting results from the macrophyte-type model demonstrated that external nutrient loading and the amount of nutrient assimilated by macrophyte would be equal when the covering rate of macrophyte reached 40% or above, and then the concentration of nutrients would decend and reach to a constant, so the water quality could keep in a clear state, which revealed that macrophytes have strong effects on lake restoration.In practice, the data of water quality of ecological restoration area demonstated that, total phosphorus (TP) concentrations of ecological restoration area were within the range of 0.02-0.03mg/L, and those of Pinghu were all above 0.05 mg/L; in addition, the factors of water quality in ecological restoration area, such as chlorophyll a (Chl-a), secchi depth (SD) and suspend solid (SS), were also significantly improved; all above reveal that macrophyte has an effective restoration function for Huizhou West Lake.In all, this present study can provide scientific references for Huizhou West Lake to effectively avoid further deterioration of water quality, and reasonably exploit the water resource and maintain the balance of lake ecosystems.