Assessment and validation of confined aquifer vulnerability based on the VEBHAT method: a case study in Heilongjiang Province, northeastern China

摘要

Groundwater vulnerability assessment is an effective tool for groundwater pollution prevention and control. However, very few methods are available to address the vulnerability assessment of confined aquifers, though the risk of confined aquifer pollution has been increasing. This paper describes a method that integrates the vulnerability of the unconfined aquifer (V), extraction rate (E), aquitard thickness (B-t), head difference between unconfined and confined aquifers (H), aquitard media (A(t)), and transmissivity of the confined aquifer (T-c), i.e., VEBHAT, to assess the vulnerability of confined aquifers. Hydraulic connections between the unconfined and confined aquifers, the vulnerability of unconfined aquifers, and the properties of confined aquifers were explicitly considered in this method. Moreover, the FO-TOPSIS method was used, which integrates fuzzy set theory (FST), along with an optimization model of multi-objective programming (OMP) and the classical TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method, to determine the weights of assessment factors, and to reduce subjectivity of the weight assignment. To illustrate the applicability and reliability of the VEBHAT and FO-TOPSIS methods, they were applied to assess the vulnerability of confined aquifers in Zhaoyuan County, Heilongjiang Province, northeastern China. The Pearson correlation coefficient between the ammonium concentration data and the vulnerability assessment values was used to verify the validity of the methods. The results showed that the VEBHAT method and FO-TOPSIS method could be used to effectively assess the vulnerability of confined aquifers.