Field Permeability Tests with Inward and Outward Flow in Confined Aquifers

Abstract

Field permeability tests gave the local hydraulic conductivities (K) at three different sites. Constant head (CH) and variable head (VH) tests were performed using 33 monitoring wells (MWs) installed in confined aquifers. Each test method was conducted with either an inward flow from aquifer to pipe or outward flow from pipe to aquifer, which makes a total of four types of tests: discharge and injection tests (CH) and rising and falling head tests (VH). The MWs were developed soon after their installation to remove the fine particles that were close to the screen areas. This article first explains various test results at different sites. For MWs in perfect condition, two opposite flows should yield equivalent K values. However, the tests with inward flow and outward flow gave different K values, which is due to some clogging of the screen or internal erosion of the filter pack. In addition, the K (CH tests), which are frequently lower than the K (VH tests), are more accurate because the CH test lasts longer and has a larger influence radius. The article also provides recommendations for estimating reliable K values for a confined aquifer.