An Analytical Model With a Generalized Nonlinear Water Transfer Term for the Flow in Dual-Porosity Media Induced by Constant-Rate Pumping in a Leaky Fractured Aquifer

In the past, many mathematical models based on the dual-porosity (DP) concept were developed to describe the groundwater flow in fractured aquifer systems. Most of them seemingly have problems in predicting accurate drawdown at the early and/or intermediate times as compared with field measured data. Thus, this study proposes a new analytical model with a generalized transfer term (GTT) to describe the flow induced by pumping in such systems. The new model is nonlinear because the GTT representing the matrix-to-fracture flux gives different weights to the fracture and matrix drawdowns. The GTT reduces to the existing first-order transfer term if the weight equals zero and second-order term if the weight is one. The present model also includes a leakage term accounting for flow from the overlain or underlain aquitard. The drawdown solution of the model is developed based on the Laplace transform method and integration by parts formula and then verified through the comparison with the finite-element solution. The effect of different weight values in the GTT on the DP flow is investigated. Additionally, the sensitivity analysis is performed to assess the impact of the change in each of the aquifer parameters on the flow. Furthermore, the present solution is used to analyze two sets of pumping drawdown data from test sites in Canada and India. We found that the drawdown predictions from the present solution fit field measured data very well, suggesting that the present model can adequately describe the real-world DP flow system.

Automated summary

A new analytical model with a generalized transfer term (GTT) is proposed to describe groundwater flow in fractured aquifer systems, addressing previous issues in predictive accuracy. Investigation of different weight values in GTT and sensitivity analysis of aquifer parameters provide insights into the impact on DP flow. The model's drawdown predictions fit field measured data well, suggesting its adequacy in describing real-world DP flow systems.