Evaluation Of Water Resources Carrying Capacity In Minqin Oasis Based On Improved Fuzzy Comprehensive Method

Water resource play an important role in regional ecological environment and economic development.In some arid areas,economy growth exceeds the maximum carrying capacity of water resource,resulting the destruction of the supply and requirement cycle and the reduction of available water resource.Accordingly,Making comprehensive evaluation for water resource carrying capacity become a primary task in dealing with sustainable development problem in these regions.In order to evaluate the water resource carrying capacity of arid regions scientifically and accurately,the concept of water resource in arid area was proposed from prospective of the“natural-water resource-socioeconomic-ecological”composite system,and the improved fuzzy comprehensive evaluation model was used to evaluate and analyze the water resource carrying capacity of Minqin County in the typical arid area in 2006-2015,which would provide theoretical basis for water resource allocation and ecological restoration policy in similar areas.Some conclusions were attained as follows:(1)The paper proposed the concept of water resource carrying capacity in arid area,that is the coordination degree between the“water resources”and“natural conditions”,“social economy”,“ecological environment”subsystems and the comprehensive support capacity of water resource for composite systems to promote the virtuous cycle of ecological environment and the continuous improvement of social and economic level,based on the principle of sustainable development in the specific historical period and combined with the actual natural conditions in arid area.(2)Taking into account the existing references and national standard values in developed regions,the paper expounded the selection principles of the evaluation indexes and separated the evaluation system of water resource carrying capacity into four subsystems,including natural condition,water resource,socioeconomic and ecology.Then a 3-layer evaluation system was established,with 1 target,4 guidelines and 29 indicators.(3)This paper introduced an approach to calculate the index weight combined analytic hierarchy process and entropy weight method.The results showed that the water resource subsystem(0.4272)and ecological subsystem(0.3075)had higher influence on the water resource carrying capacity in Minqin oasis,while the natural subsystem(0.0853)and the Socia-economic subsystem(0.18)was relatively low.(4)Taking the three indexes including"arbor coverage","shrub coverage"and"herbage coverage"belong to ecological environment subsystem as examples,and studying the method to set grading threshold of Minqin Oasis Index.The formula for calculating the indirect method of vegetation water demand quota was improved by optimizing the phreatic evaporation intensity(E)and vegetation impact coefficient(K),and the results showed that the water demand quota of arbor was 2.0265 million m~3/hm~2,shrub was 1.6596 million m~3/hm~2 and herbage was 1.3832 million m~3/hm~2.On this basis,the coverage of Arbor,Shrub and herbage were calculated under"degradation mode","Maintenance Mode","Development mode"and"optimal Mode"respectively by quantifying the indexes and their synergies in the three subsystems of social economy,ecology and water resources utilization efficiency,and the hierarchical threshold of these three indexes was set by these values.(5)The water resources carrying capacity of Minqin County in Gansu Province were evaluated by fuzzy comprehensive evaluation method.The evaluation results showed that the average value of the water resources carrying capacity index of Minqin County was 2.5858 in 2006-2015,and the water resources carrying capacity was at the status from“relatively poor”to“general”and was in a growing trend.Among them,the“natural”,“water resources”,“ecological”subsystems at the“poor”level,and the“sco-economic”subsystems at the“general”level.The coordination degree between the“water resources”subsystem and the“soc-economic”subsystem were relatively poor,reflecting the socio-economic water utilization exceeded sustainable ability.The coordination degree between“water resource”and other subsystems had gradually increased.The evaluation results were in line with the actual situation of Minqin County,which could provide reference for the evaluation of water resources carrying capacity in similar arid areas.