Assessing the Connectivity of a Regional Fractured Aquifer Based on a Hydraulic Conductivity Field Reversed by Multi-Well Pumping Tests and Numerical Groundwater Flow Modeling

Aquifer connectivity could greatly affect groundwater flow and further control the contaminant transport in fractured medium. However, assessing connectivity of fractured aquifer at regional scales is still a challenge because such connectivity is difficult to be measured directly. This study proposes a framework for assessing connectivity of a fractured aquifer, with Qitaihe area, Heilongjiang Province, northeastern China as an illustrating study area. The 3-D finite difference numerical models were established to interpret the results of three multi-well pumping tests and inversely estimate the distribution of hydraulic conductivity (K) in the fractured aquifer. A static connectivity metric of the minimum hydraulic resistance (MHR) was calculated, based on the optimized K-field, to evaluate the hydraulic connectivity in the aquifer, and the corresponding least resistance paths (LRPs) were identified. The results indicate a better horizontal connectivity in the fractured aquifer in the northeastern and middle parts than in the southwestern part of the study area. The identified LRP indicated that the preferential flow channels at regional scales were controlled mainly by aquifer connectivity instead of local high-K zones. The results of this study can provide a method for aquifer connectivity estimation at regional scales.

Automated summary

This study proposes a framework for assessing the connectivity of fractured aquifers, using Qitaihe area in northeastern China as an example. By using 3-D numerical models and pumping tests, the distribution of hydraulic conductivity (K) in the fractured aquifer was estimated. The minimum hydraulic resistance (MHR) was then calculated based on the optimized K-field to evaluate hydraulic connectivity, and the least resistance paths (LRPs) were identified. The results indicate that connectivity is better in the northeastern and middle parts of the study area compared to the southwestern part, and that aquifer connectivity plays a larger role in controlling preferential flow channels at regional scales rather than local high-K zones.