The Application Of Cloud Model In Assessment Of Water Eutrophication And The Extension Of Hydrological Series

The evaluation of water eutrophication is important in the field of ecological environmental protection. According to the characteristics of the inevitable fuzziness and randomness in the evaluation of water eutrophication, this paper introduces the cloud model method to evaluate the eutrophication of China’s12typical lakes and reservoirs. The comprehensive cloud of each factor on each level has been generated based on the assessment index and assessment factors. According to the measured data for lakes and reservoirs, the degree of certainty for each evaluation material can be obtained. The eutrophication level of lakes and reservoirs is then determined by the maximum degree of certainty. Comparing the evaluation results from this developed cloud model method with the actual water quality conditions and the results from some widely used methods, such as nutritional status index method, simple scoring formula method and fuzzy comprehensive assessment method, it can be concluded that the cloud model method is reliable, simple and straightforward, thus its feasibility and effectiveness is verified.The cloud model is a mathematical representation of fuzziness and randomness. It has strong robustness for the uncertain question. Wavelet analysis has time-frequency localization features, known as’Mathematics microscope’, which can decompose and reconstruct the hydrological series by wavelet transform. In this paper, a cloud model method and wavelet-cloud model method were used in hydrological series extension. The cloud model method used the cloud rules generator to connect the reference station series with the design station series for extension. The wavelet-cloud model method employed wavelet analysis method to decompose the measured non-stationary series. And then use the cloud model method to create an extension model for each decomposition layer series, weighted each layer’s extension results to get the final extension value. Based on the rainfall and runoff data from the Yellow River, Heihe River and Huaihe River, extend the series by using the cloud model method and wavelet analysis-cloud model method, the examples show that:the two methods are both feasible, and the wavelet analysis-cloud model method has a high extension precision, which excelled the traditional extension method and the cloud model method.