The Field Measurement Dilemma   

Geologic field measurements and how to make them often confront geoscientists and engineers in what can be called "the field measurement dilemma".   Much of what we are interested in is "out of sight" in the subsurface.    Techniques such as test drilling or geophysics are needed to investigate rocks, structures, or groundwater that are in the subsurface.   Test drilling by several methods is generally the preferred method of exploring the subsurface because samples of materials can be collected as the drilling tools penetrate beneath the crust of the earth.   Monitoring or observation wells can be installed in borings to sample and test groundwater.   When investigating water in the subsurface (groundwater), numerous accurate water level measurements are required.   Monitoring or observation wells are often completed at very small diameters to reduce the expense of subsurface investigations.  

Making accurate water level measurements is often a challenge in small-diameter wells.   This subject is explored further on our "Groundwater Depth Measurement" and "Small-Diameter Well Quandry" pages where Heron water level meters are introduced.    One common problem occurs where the measurement probe and/or the tape adhere to the walls of a small-diameter well.   This condition happens most commonly when the walls of the well are moist.   There are a number of solutions to this problem.    The most successful solution to this "dilemma" is to add additional weight to the measurement probe.

The evaluation of aquifer permeability (or hydraulic conductivity) is often critical for solving this dilemma.   Pumping tests and slug tests are often used to evaluate aquifer permeability.   Obtaining accurate and often rapid water level measurements is necessary in these evaluations.   Heron water level meters and their new data-logger can help in the conduct of these tests.

Continued...