Thursday, September 11, 2014

Have You Seen Groundwater?

by Ann Bleed, Groundwater Foundation Board Member

Groundwater is one of the most difficult natural resources to manage because it is so hard to see and observe. In fact, most people never see groundwater, although some can say they have seen it, at least momentarily, as it is transformed to surface water at a groundwater spring or artesian well. Some may have felt it as a sudden area of cold water caused by a groundwater spring flowing into a river or lake.

Even scientists have trouble observing and understanding groundwater. In most cases the best a groundwater scientist can do is build a groundwater model to try to describe how an aquifer works. Because groundwater flow varies depending in part on the type of subsurface materials through which it flows, the first step toward understanding how groundwater moves is to map the horizontal area and vertical depth of the subsurface layers of gravel, sand, silts, and clays in the aquifer.

Until recently, scientists have had to rely on drilling test holes and describing the various subsurface layers in each hole, a very costly and laborious process. Because of the cost, test holes are usually far apart, leaving the task of determining what the aquifer is like between test holes to a geologist who makes the best guess possible of what might be going on between the test holes.

Today, however, there is a new technique that makes exploring an aquifer more precise and less costly. Airborne electromagnetic or AEM surveying, uses a sophisticated sensor towed by a helicopter to identify and evaluate the geology within an aquifer. To the unknowing citizen the sensor may look like a bomb, so before the Lower Platte South Natural Resources District in Nebraska used AEM to survey one of its aquifers, the District made sure it issued press releases to tell the public what was going on.

This technique is fascinating to watch and already has provided a great deal of valuable information all over the world. And, thanks to the Lower Platte South Natural Resources District, the Nebraska Educational Telecommunications network and QUEST, a joint-venture science program affiliated with PBS, you can watch a seven-minute video of how this system works at

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