GW vulnerability assessment based on entropy and fuzzy method

Groundwater vulnerability assessment and mapping are basic tools for groundwater environmental protection. The Drastic index system is the most popular in the world but many details still need to be improved. This paper introduces an entropy weight fuzzy optimisation method to a groundwater vulnerability assessment coupled with a geographic information system. Weights are not needed for anthropogenic influences, and the result could be continuous in this approach, which avoids the subjectivity of assigning weights of indicators and the discontinuity in assessing groundwater vulnerability. Taking the Huangshuihe River catchment as an example, the entropy weight of Drastic parameters and the optimal membership degree of overlay area were calculated. Thus, the groundwater vulnerability of Huangshuihe River catchment was divided into three grades: high (0·0091–0·1499), medium (0·1500–0·7400) and low (0·7401–0·9917), respectively corresponding to about 19·3%, 29·7% and 51% of the whole area. Compared with the traditional Drastic method, good results were obtained and the approach seems to be a good improvement on the classic method. A sensitivity analysis showed that topography is the most sensitive to vulnerability.