Hydraulic conductivity tests

Determination of the water permeability, also called hydraulic conductivity, is important for environmental soil research, as it helps to determine the extent of the spreading of potential pollution. Hydraulic conductivity should be measured in the field. A number of different field methods exist. Nevertheless, slug or recovery tests can be used and are generally accepted. These tests yield only local values of horizontal hydraulic conductivity, within a close proximity to the wells were they are performed.

The procedure involves either adding or removing (by means of known volume disposable bailers) a measured quantity of water from a well rapidly, followed by making a rapid series of water-level measurements at regular intervals of time in order to assess the rate of water-level recovery; either rising-head or falling-head.

The type of procedure that is used to evaluate a well is normally determined by the conditions of the respective aquifer. Extraction of a known volume of water may be conducted in aquifers that are poorly transmissive and require many minutes to recover after they have been bailed.  However, it is difficult or impossible to test a highly transmissive aquifer by extracting water because of rapid water level recovery.

Water level changes within the boreholes are generally measured with pressure transducers and data are registered by data-loggers. Standard level probes can also be used to record water level variations and verify transducer lectures.