Shallow Ground Water

Shallow ground water is one of the four flow components in the Wash. Just like rain, snow, lakes and rivers, ground water is part of the hydrologic cycle (see below). It is part of the continual movement of water between the earth and the atmosphere through evaporation and precipitation. As rain and snow falls to the earth, some of the water runs off the surface into lakes, rivers, streams and oceans; some evaporates; and some is absorbed by plant roots. The rest of the water soaks through the ground's surface and moves down through the open spaces in rocks and soil until it reaches the saturated zone or "water table." The water in this saturated zone is called ground water. In addition to the ground water that originates as precipitation, humans can accelerate these natural processes quite a bit by over irrigating our yards and other ornamental landscaping. When we talk about ground water that is beneath the entire city of Las Vegas, we usually refer to it as the "shallow ground water system." This ground water generally occurs within thirty feet of the land surface and is contributed to the Wash in the southeast part of the Valley. Shallow ground water is not used for drinking water.

So, why is this flow component important to the Las Vegas Wash? The water that flows beneath the surface (ground water) generally follows the same direction as water that flows on the surface. That means that even ground water in the shallow ground water system drains into the Wash. Although shallow ground water represents a very small percentage of the overall flows entering the Wash, it is very important to monitor because this water is usually very salty and it can increase the amount of dissolved solids in Wash water, both of which can adversely affect the growth of wetlands and have negative impacts to habitat. In addition, past land use practices have brought other water quality concerns.