Interpreting a Pumping Test Influenced by Another Well in an Anisotropic Aquifer

Abstract

In confined aquifers the influence of neighboring active wells is often neglected when interpreting a pumping test. This can, however, lead to an erroneous interpretation of the pumping test data. This article presents simple methods to evaluate the transmissivity tensor and storativity of an anisotropic confined aquifer when there is an interfering well in the neighborhood of the tested well. Two methods have been developed depending on whether the tested well or the interfering well is the first in operation. These new methods yield better estimates of the hydraulic parameters than when the influence of the interfering well is neglected. These methods have then been used on data obtained from numerical models with an interfering well and the results have been compared to an analytical method that neglects the influence of the interfering well. The methods require knowledge of the pumping rate of the interfering well and the time elapsed since the pumping started in each well. If the interfering well started pumping before the tested well, the method does not require knowledge of the aquifer piezometric level at the beginning of the test, which is often unknown in this case. As for the method without interference, at least three monitoring wells (MWs) are needed, the position of which influences the accuracy of the estimated parameters. Some recommendations concerning MWs position have been given to get more accurate results according to the sought parameter.

Estimation of Aquifer Transmissivity From Analysis of Long‐Term Monitoring With the Thiem Solution

“…By regressing nearby water levels against known withdrawal rates at the subject well, the method also discounts potential interference resulting from competing groundwater withdrawals (Rushton 1985; Weber and Chapuis 2013; Weber et al 2014). Both examples presented here are near large municipal withdrawals, and the background variability in aquifer water levels was captured in the LTM datasets.…”

Analysis of Groundwater Time Series With Limited Pumping Information in Unconfined Aquifer: Response Function Based on Lagging Theory

“…The existing response function for aquifer pumping depends on specific information about pumping, such as pumping rates and spatial distribution. In previous literature (e.g., Rushton, 1985; Weber & Chapuis, 2013; Weber et al., 2014), it has been found that employing typical analytical solutions (like Theis (1935) solution or Jacob and Lohman (1952) approximate solution) to describe single‐well pumping activities applied to field data can lead to incorrect parameter estimation values in many areas with interfering wells. To achieve more accurate parameter estimations, it is essential to first obtain the pumping rates of interfering wells and the duration of pumping for each well (Weber & Chapuis, 2013).…”