Purpose

Aquifer evaluations are conducted for various purposes including water supply development as well as groundwater contamination and remediation situations. They can range from fairly intense evaluations involving test drilling, geophysical investigations, installation of monitoring or observation wells, test pumping, physical and chemical water quality analyses, analytical and digital modeling to rapid evaluations based on existing data.

Elements of an Aquifer Evaluation

Basic elements of an aquifer evaluation involve delineation of the extent and thickness of the water bearing unit as well as characteristics such as composition and grain-size distribution, permeability/transmissivity, storage and may involve any or all of the following:

   - Evaluation of existing data
   - Test drilling
   - Installation of monitoring or observations wells
   - Geoprobing and/or hydroprobing
   - Geophysical investigations
   - Geophysical borehole logging
   - Groundwater gauging
   - Groundwater sampling and analyses
   - Test pumping
   - Slug testing
   - Analytical and digital groundwater modeling
   - Solute transport modeling
   - Groundwater monitoring

The drawing above illustrates some of the components of a pumping test (aquifer test). It shows how a discharging well effects the water-level in the aquifer and causes a "cone of depression" and drawdown in nearby observation wells and diverts groundwater that formerly discharged to a stream.

In some cases groundwater modeling is warranted as a part of an aquifer evaluation, especially where predictions of future conditions are needed relative to water quality and/or quantity.