Groundwater is located below the surface of the earth and occurs naturally as a result of snowmelt and rainfall in the nearby mountains. About 10 percent of Southern Nevada’s water supply comes from groundwater sources.
Groundwater in the Las Vegas Valley comes from three major aquifer zones generally located from 300 to 1,500 feet below land surface. This drinking-water supply is protected from surface contamination by a layer of clay and fine-grained sediments throughout most of the valley.
Occasionally, news reports mention that contaminants such as pesticides and fertilizers have been found in groundwater. These reports typically refer to water in the shallow groundwater system, which is water that lies within 50 feet of land surface. It is separated from the primary producing aquifers by thick layers of clay and fine-grained sediments. This water is not used for drinking water at this time.
Who uses groundwater?
In Southern Nevada, the primary users of groundwater are the Las Vegas Valley Water District, the City of North Las Vegas, and thousands of single-family domestic and private well owners. Groundwater is important in managing peak demands by all SNWA municipal water providers in the summer.
Precipitation, including snowmelt, in nearby mountains creates the valley’s groundwater basin. All groundwater in the Las Vegas Valley comes from the mountain ranges surrounding the valley. Rain and snow seeps into the ground and may travel for thousands of years before reaching the center of the valley.
The sediment in the valley is several thousand feet thick. These sediments vary in their ability to transmit water. Units that transmit water poorly are called aquitards or confining units. Units that transmit water well are called aquifers. Groups of aquifers and aquitards are called “aquifer systems” or “groundwater systems.”
Most of the wells in the Las Vegas area draw water from the confined aquifer system, which is several hundred feet thick. Because this is the most important part of the aquifer system, it’s sometimes called the “principal” aquifer. This aquifer system is confined by an aquitard, which is about 200 feet. Water within the upper 30 feet of this aquitard comes from landscape irrigation and is very salty. This upper 30 feet of sediment is called the shallow zone or shallow system.
Because this salty water is close to the land surface, it can dissolve foundations and be a problem for construction excavations.
Although this water is not a good source of drinking water, the Southern Nevada Water Authority and private parties are researching methods to extract, treat and use this water.
The shallow aquifer is located underground in central, eastern and southeastern parts of the Las Vegas Valley. It is primarily created through excess irrigation.
Water runoff is trapped near the land surface by impermeable clay and caliche. The shallow groundwater lies within 50 feet of land surface. Recent groundwater modeling shows that more than 100,000 acre-feet of irrigation water may be accumulating in this shallow zone each year.
Treating shallow aquifer water for other uses
The shallow aquifer water quality is poor with total dissolved solids exceeding acceptable drinking water standards in most locations. It is possible to treat shallow groundwater for drinking, but costs are still relatively high. As technology improves and other sources of water become more expensive, the use of shallow groundwater may be a viable option.
Recycling and reusing
The University of Nevada, Reno, in cooperation with the Las Vegas Valley Water District, conducted a study using shallow groundwater for landscape irrigation. Researchers blended shallow groundwater and drinking water to determine the response of grass irrigated with water with elevated salt concentrations–water in the shallow system contains high levels of salt. The results showed it was possible to blend the two water sources and maintain a healthy landscape.
Using it to our advantage
Shallow groundwater and water in the Las Vegas Wash have traditionally been viewed as a nuisance in the valley. However, the wetlands that surround the Las Vegas Wash serve as a vital link in the water cycle by filtering shallow groundwater and other flows before they reach Lake Mead. The wetlands also provide habitat for a variety of plants and animals.
There are different uses of groundwater wells in the Las Vegas Valley. Below are examples:
A domestic well serves a single home without a water right permit. Domestic well water usage may not exceed 1,800 gallons per day. Thousands of these wells exist in the Las Vegas Valley. One goal of the Groundwater Management Program is to involve domestic well owners in finding solutions to problems such as overdrafting.
A community well (also known as a quasi-municipal well) has a number of homes connected to it. Hundreds of these wells exist in the valley. A water permit for a community well allows 1,000 gallons per day, per home. Water usage may not exceed 365,000 gallons per year, per home. All quasi-municipal wells are required to have a meter, and accurate readings must be kept of all water pumped from the well. The goal of the Groundwater Management Program is to develop solutions that will benefit these well users and protect the long-term value of the local groundwater basin.
Commercial and industrial wells
Many golf courses and other commercial businesses own and operate wells. Although the amount of groundwater they use is typically limited by permit, these businesses and their employees rely heavily on that water for their economic livelihood. For this reason, the businesses have a vested interest in finding ways to protect the long-term quantity and quality of water in the groundwater basin.
Small water companies
In most cases, a small water company is another type of community well owner. There are many private water companies in the Las Vegas Valley and all of them are subject to the same issues and concerns experienced by other well owners.
Municipal water providers who own wells
In the Las Vegas Valley, city water is managed on a regional basis among several municipal providers. Two of these providers own and operate wells to help meet peak demands for water in the summer. This cooperation in managing supply and demand means the groundwater basin is an important resource that indirectly affects everyone in the valley, including residents who are on a municipal water system.