An aquifer test method is a controlled field experiment made to determine the approximate hydraulic properties of water-bearing materials. ASTM D4043-17 – Standard Guide for Selection of Aquifer Test Method in Determining Hydraulic Properties by Well Techniques, a newly-revised standard, provides guidance on the selection of an aquifer test method through the development of a conceptual model of a field site. It does not, however, establish a fixed procedure for determining hydraulic properties.
Groundwater is one of our most valuable resources, and aquifers – water-bearing rocks that readily transmit water to wells and springs – act as near-invisible, yet primary sources of agricultural and drinking water for many areas. Through the reliable estimation of the areas where ground is saturated with water, researchers are able to understand the transmissivity, hydraulic conductivity, and storativity of the water supply.
Choosing an Aquifer Test Method
The above video demonstrates a project funded by the University of Wisconsin Water Resources Institute, in which researchers experimented with pumping hot water into a well to measure the flow of groundwater. Technically, this could be considered a type of Slug Test Method, since it involves injecting a given quantity or slug of water into a well to estimate transmissivity.
As addressed briefly in the video, there are a variety of concerns that influence the decision of which aquifer test method to choose. This is because the hydraulic properties are dependent on the instrumentation of the field test, the knowledge of the aquifer system at the field site, and conformance of the hydrogeologic conditions at the field site to the assumptions of the test method. From these three factors, there are numerous considerations that can influence the choice of aquifer test method.
For example, sometimes the porous rock layers of an aquifer can become tilted within the earth. From this, there can emerge a confining layer of less porous rock both above and below the porous layer, creating what is known as a confined aquifer. Pressure factors for interacting with confined aquifers sometimes differ than other aquifers, since the internal pressure of the water source can be enough to push the water up the well and up to the surface without the aid of a pump. ASTM D4043-17 includes confined aquifers as a primary factor influencing the decision of the aquifer test method.
Some of the different aquifer test methods from ASTM D4043-17 are listed as follows:
- Constant Discharge
- Variable Discharge
- Constant Drawdown
- Slug Test Methods
- Leaky Confining Bed, Without Storage
- Leaky Confining Bed, With Storage
- Radical-Vertical Anisotropy
- Horizontal Anisotropy
- Test Methods for Multiple Aquifers
- Solutions for Fractured Media
The detailed procedure for selecting a suitable aquifer test method, along with the related ASTM standards used for calculating the hydraulic properties of aquifers after the method has been chosen and carried out, can be found in the ASTM D4043-17 standard.
ASTM D4043-17 – Standard Guide for Selection of Aquifer Test Method in Determining Hydraulic Properties by Well Techniques is available on the ANSI Webstore.