天津市平原区第Ⅰ含水岩组地下水脆弱性评价研究

地下水脆弱性分区评价是合理开发利用地下水资源、防止地下水污染的重要基础性工作。传统的DRASTIC方法对评价参数赋予固定的经验性权重,存在一定缺陷。采用熵权法与层次分析法相结合的方法,对权重确定方法加以改进,并以易受污染的天津市平原区第Ⅰ含水岩组地下水为研究对象开展实例研究。改进权重的DRASTIC方法突出了影响程度大、原始数据较分散的净补给量、地下水埋深和包气带类型三项评价参数的权重值,剔除了影响不大且各评价单元原始数据相差很小的坡度参数。结果表明,天津市平原区第Ⅰ含水岩组地下水较低脆弱性分区、中度偏低脆弱性分区、中度偏高脆弱性分区、较高脆弱性分区和高脆弱性分区的面积比例分别为1.3%、22.3%、42.6%、31.2%、2.6%,具体分布与实际情况吻合较好。改进权重的DRASTIC方法可同时兼顾指标数据的分布特点和权重的经验性取值,对开展地下水脆弱性评价具有参考价值。

Study and assessment on vulnerability of groundwater from No.I aquifer group in plain area of Tianjin

The zoning assessment on groundwater vulnerability is an important basic work for reasonable development and utilization of groundwater resources and prevention of groundwater pollution. The conventional DRASTIC method has a certain defect， i.e. endowing the assessment parameters with fixed empirical weights. The method for determining the weights is modified with the method of integrating both the entropy weight method and the analytic hierarchy process （AHP） together， and then a case study is carried out by taking the groundwater from the No.I aquifer group in the plain area of Tianjin as the study object. The weight values of three items of assessment parameters， such as larger impacting degree， net recharge with more decentralized initial data， groundwater depth and aeration zone types， are protruded by the DRASTIC method with the modified weights， while the gradiemt parameters with less impact and less differences among the initial data in all the assessment units are omitted by the method as well. The result shows that the area ratios of lower groundwater vulnerability subzone， moderate-lower vulnerability groundwater subzone， moderate-higher groundwater vulnerability subzone， higher groundwater vulnerability subzone and high groundwater vulnerability subzone are 1.3%、22.3%、42.6%、31.2%、2.6% respectively， for which the specific distribution is better coincided with that from the actual condition. The DRASTIC method with modified weights can take account of both the distribution characteristics of the indicator data and the empirical values of the weights， thus has reference value for assessment made on groundwater vulnerability.