天津市地下水功能评价与区划研究

On the function assessment and zoning division of the groundwater in Tianjin municipality

天津市地下水长期处于超采状态,造成地面沉降、水质污染、水位下降等负面效应,因此开展天津市地下水功能评价和区划研究具有重要意义。根据天津市水文地质特征,筛选出地下水功能的主导因子,构建评价指标体系,采用综合评价方法对资源功能、地质环境功能和脆弱性功能进行评价。在评价指标权重方面,采用层次分析法与变差系数法相结合的主客观方法,克服了单一方法在实际应用中可信度存在一定偏差的缺陷,提高了评价的精度和可信度。评价结果与天津市水文地质条件及环境状况相符合。

This article is to present our study results on the zoning d-i vision and function assessment of the groundwater situation in Tianjin municipality. As is known, Tianjin is one of the metropolitans facing the most serious problem of land subsidence in China, plus its greatest scarcity ofwater resources. The serious scarcity ofwater resources comes from numerous reasons, such as excessively extracted groundwater resources to meet the needs of industrial and agricultural deve-l opment. All of the above demands forwater led to continuous declining groundwater level and aggravated the subsidence of the land surface. Therefore, it is of extreme urgency and significance tomake efforts in zoning and assessing the groundwater function of the city. To promote the success of our research, we have first of all sorted outthe dominant factors of groundwater function and established corresponding guiding principles in accordance with the hydrogeological characteristics of Tianjin such as geological structure, the geo-strata lithology, topography and geomorphology in addition to the related local hydrological and meteorological information. The key problem is to establish and confirm the evaluation weights in the comprehensive eva-l uation systems. It is forthis purpose thatwe have divided our evaluation weight into two aspects, the subjective weight and the objective weight. The subjective weight includes Delphi method, link scoring method and analytic hierarchy process（AHP）, etc, and the objective weight includes the coefficient of variation method, entropy method and standard deviation method, etc. Balancing the advantages and disadvantages of the subjective weight aswell as the objective weight, we have chosen the synthetic evaluation weight by AHP and coeff-i cient of the variation methods, which help to overcome the problem of dependability caused by single method. It is just on such a basis, we have made our assessment of the water resource function, its geolog-i cal environment function and vulnerability function in an integrate way. The results of our evaluation can be divided into five grades in accordance with the relative classification method. According to the evaluation results, we have worked out the resource function, the geological environment function and the vulnerability function with the area planning maps plotted. And, finally, the evaluation results are well accepted and prove to be suitable for the local hydrogeological characteristics and environment conditions in Tianjin. Thus, the assessmentmethod can be taken as a theoretical basis for the rational exploitation and sustainable development of the urban groundwater.