| With high speed urbanization process, the increase of impervious surface area affected the city's original hydrologic cycle and changed the urban area rainfall runoff conditions, which led to the frequent occurrence of city waterlogging disasters. On the other hand, it brings tight water supplies and decline in the quality of the urban water environment under the influence of population and industry agglomeration. In order to resolve the problem of urban waterlogging and water shortage, urban rainwater utilization provides a validity path. The low impact development technology, can effectively cut down the total runoff volume and peak flow rate, and delay the time that peak flow occurred from the source that runoff generated by the means of rainfall intercepting for infiltration, storage and so on through the combination of a series of different measures. However, there are not valid ways to assess benefits of combined rainwater utilization technologies, which resulted choosing technologies random. Therefore, it's significant to research the assess of urban rainfall water utilization.First, basic conditions of mountainous urban rainwater utilization were analyzed, which took Chongqing City as an example. The results of annual rainfall characteristics showed that there were no obvious changes in annual precipitation. Inner annual runoff characteristics demonstrated that the high flow period and low water season was nearly equal and the rainfall was mainly concentrated in July. Moreover, the precipitation contributing by medium or heavy rains(which means 10~50mm/d precipitation) made up about half of the total. Based on these analyses, exceptional precipitation conditions, such abundant and stable are foundation for Chongqing to explore techniques of rainwater accumulation and utilization. In addition, rainfall infiltration and storage technologies should be adopted because of complex composition, short time and distance of mountainous urban rainwater runoff.Then the author analyzed common rainfall infiltration and storage technologies from these aspects such as formation, function, economic benefits and problems of rainwater infiltration. Typical measures were introduced, including the permeable pavement, green roof, sinking style ecological pond, retention system, reservoirs, pitcher and grassed swale. What's more, infiltration technologies were assessed. All those provided reference for select of rainwater utilization.Based on the above analysis, this paper built the comprehensive evaluation model of mountainous urban rainwater utilization. As well as being applied.(1) Integrated evaluation method and derivative method were analyzed, including multivariate analysis theory(principal component analysis, factor analysis, clustering methodology and discriminant analysis), data envelopment analytical method of operations research theory, fuzzy comprehensive evaluation of fuzzy mathematics, grey correlation analysis of grey system theory and artificial neural network and genetic algorithm of artificial science. All the methods include three steps in order quantitative values, weighted values and average values. Therefor this paper selected fuzzy comprehensive evaluation and grey correlation analysis to build the model.(2) The author evaluated three plans of rainwater utilization of Lijia Longhu in order to test the effectiveness of the comprehensive evaluation model. And the results showed that the second project was the best which meant the best fit for mountainous city was eco-utilization of rainwater. Meanwhile, indexes can be adapted through results analysis.(3) The comprehensive evaluation model of rainwater utilization based on fuzzy comprehensive evaluation include appraisal module, rainwater utilization technology module and comprehensive evaluation module. These modules could realize comprehensive evaluation of rainwater utilization technology and effectively guide the selection of projects of mountainous urban rainwater utilizationg. |
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