Common Methods of Groundwater Detection in California

People have been searching for groundwater for thousands of years. Of course, we’ve come a long way since the days of water diviners and the use of forked twigs! There are some more modern methods that are used these days to more accurately determine the presence of groundwater so well diggers don’t start digging in the wrong place, wasting time, energy and resources.

Let’s take a quick look at today’s most common methods of groundwater detection in California.

Two main methods

Today there are two main methods used to locate aquifers with much greater precision and efficiency. These are:

• Topography: This is the analysis of local vegetation and maps to determine the presence of water. In large-scale groundwater investigations, a global geological analysis can be performed by interpreting satellite images or aerial photos, which depict the presence of some significant geological outlines indicating the presence of groundwater in certain areas.
• Hydrogeophysics: Geophysical methods are the most popular method of discovering underground aquifers, and there are multiple subtypes of geophysical methods. Using these methods, scientists can study the physical properties of the soil, paying special attention to its electrical properties.

Aquifers are most commonly found between layers of rock. All rocks are able to conduct a certain amount of electricity, with that conductivity varying based on the type of the rock, its compactness and the presence of permeable or impermeable structures. Scientists can measure the conductivity or resistivity (the opposite of conductivity) as a means of determining where aquifers are located beneath rock layers.

There are a couple ways to do this:

• Measuring electrical resistivity using direct currents: This is the most commonly used method, as it applies to the widest variety of circumstances. In this method, the analyst sends a direct electrical current into a geological structure at a site—usually anywhere between 50 and 400 volts—using a pair of electrodes.
• Measuring electrical activity through magnetism: The use of Slingram, VLF and other magnetic methods are actually easier to implement than direct current methods. However, because they are not nearly as versatile as direct currents and because they are incapable of discovering aquifers that are located 20 meters or more below the surface, they are not as commonly used. In this method, there is no direct contact required with the ground, and thus no electrodes. Instead, analysts measure electromagnetic signals that occur through the phenomenon of magnetic induction.

These groundwater detection methods can all help people to avoid some extremely costly errors in groundwater investigation, saving both time and money. However, hydrogeophysical analysis is still costly, and is typically only realistic for large-scale water extraction facilities. In other cases, different types of groundwater detection methods might be needed. A person who is building a cabin in the woods, for example, should not expect hydrogeophysical analysis to be used to determine the best spot to place his well.

This provides you with some general background information about today’s most common methods of groundwater detection in California. Contact National Groundwater Surveyor Inc. today for more information.