Sustainable Evaluation of Urban Water Resources and Environment Complex System in North Coastal Cities

The sustainability evaluation of urban water resources and environment complex system(UWECS) is a fuzzy problem, so the fuzzy variable model is applied to evaluate the sustainability of UWRCS. Compared with other fuzzy methods, the model can scientifically identify the relative membership degree and function between sample index and standard interval of each level index, and it can reasonably determine the evaluation level of each sample by varying model and its parameters. One of the most important factors in the evaluation process is the calculation method of the comprehensive weight. So assuming the subjective weights have been assigned, the reliability analysis method is used to choose the objective approach from the view point of combination reliability. The comprehensive weight vector is constructed based on the reliability analysis of different weight combination methods. Finally, as a case study, Dalian UWECS from 1996 to 2005 is evaluated. And following evaluation results are obtained: (1) The status can be divided into two stages: Firstly, the system keeps in normal status from 1996 to 1997. Secondly, the system keeps in sustainable status from 1998 to 2005, and the evolution trend is fluctuating in 1999 because of the unsteady exploitation of groundwater. With further analysis, the excessive exploitation of groundwater is also the key unsustainable factor in most of the coastal north cities in China in recent 10 years.