Eutrophication Risk Evaluation Method And Case Analysis

Eutrophication refers to the phenomenons that there are a variety of aquatic animals and plants reproducing and growing abnormally due to the discharge of excessive nutrients, and often accompanied by algae blooms. In order to evaluate and predict eutrophication, there are a large number of cases have been studied with different kinds of eutrophication models. It can be divided into four categories of all the eutrophication models, including the simple regression models, the single nutrient loads models, the phytoplankton and nutrient models and the ecological dynamics models. All of these models have shotcomings with a fixed structure, lacking of flexibility and poor of versatility.Among all of the parameters of eutrophication, the most important parameters is the parameters of water quality, followed by the parameters of hydrological and of meteorologica. The most critical parameters of water quality are COD, C, P, N, Chla and the ratio of nutrients, the most critical parameters of hydrological are pH, DO, water temperature and sedimentation rate, the most critical parameters of meteorological are temperature, light intensity, the most critical parameters of biological are the growth rate of algal and the photosynthesis rate of algal.Among the eutrophication prediction models in common used, the CE-QUAL-W2and the EFDC have the advantages in simulating the eutrophication in flowing water. The WASP and the CE-QUAL-ICM can only stimulate the water quality. Both of them should be coupled with hydrodynamic models in order to simulate the process of eutrophication accurately. AQUATOX has aspecial advantages in ecosystem modeling, it can simulate eutrophication ecosystem processes very well, but could not suitable to simulate in volatile water. In addition, there are a large number of parameters should be calibrated when it is applied to the domestic water bodies.According to the currently used methods of eutrophication assessment, combining with the hydrological frequency analysis curve of the risk probability, choosing the eutrophication risk assessment methods, which is suitable for the evaluation of the eutrophication risk in the amount of data less.Using Fuzzy Evaluation method to evaluate the eutrophication of two state-controlled monitoring sections in Important tributary of the Three Gorges reservoir area in Xiangxi. The result shows that the water quality of Xiangxi River are in different degrees of eutrophication, especially in summer, which is in the high incidence of cutrophication.With the combining of the hydrological frequency curve and fuzzy mathematics method, the calculating results show that the environment of the end of backwater area in Xiang River is very closed to the backwater area, which is very conducive to the occurrence of eutrophication. Therefore, Xiangxi River is at a high risk of eutrophication. To ensure the safety of the water quality of Xiangxi River, we should strengthen the management of eutrophication.