Central Truckee Meadows Remediation District
What is groundwater?
When rain falls to the ground, the water does not stop moving. Some of it collects and flows along the surface in storm drains, streams, rivers, or lakes. Some evaporates and returns to the atmosphere. Some of this water sinks or infiltrates into the ground. Imagine pouring a glass of water onto a pile of sand. Where does the water go? The water moves into the spaces between the individual sand particles.
Even though we may not realize it, groundwater can be found almost everywhere. Groundwater is the water found underground in spaces between soil, sand, and gravel particles, and within pores or fractures in other geologic materials. The volume of ground where these spaces are filled with water is called the saturated zone. The top of the saturated zone is called the water table.
The water table can be found right at the ground surface or it may occur hundreds (or thousands) of feet beneath the ground surface. The water table can rise or fall in response to many factors. Heavy rains or melting snow can cause the water table to rise, or an extended period of dry weather or groundwater pumping can cause the water table to fall.
Groundwater is stored in (and moves through) porous and permeable layers of soil, sand and other geologic materials. These materials are permeable because they have relatively large inter-connected spaces that water can flow through. The rate at which groundwater can move or flow through these layers depends on the size of the spaces in the aquifer and how well the spaces are inter-connected.
(Above) Central Truckee Meadows aquifer materials exposed
above the ground surface in a road cut along West 4th Street.
Groundwater can discharge at the land surface naturally as a spring or as discharge into lakes, streams, and rivers. Groundwater can also be extracted from the ground using a well drilled into the aquifer. A well is a pipe or conduit in the ground that fills with groundwater. This water then can be brought to the surface using a pump. Some wells do not need a pump because of natural pressures that force the water up and out of the well. These are called artesian wells.
Groundwater used to meet water demands can be replenished, or recharged, by infiltrating rain and snow melt. People in areas where groundwater is being used faster than it can be recharged or replenished face water shortages. Water shortages can also occur in areas where groundwater has been contaminated by human activities, making it unusable.
(Above) Schematic representation of water movement during the hydrologic
cycle along with the various components making up the water budget.
Groundwater is used for drinking water by more than 50% of the people in the United States. In the Truckee Meadows, groundwater is a vital component in our water supply. While much of the local water demand is met using surface water from the Truckee River in a typical year, during times of low river flows (such as under drought conditions) or times of high suspended sediment loads in the Truckee River, we can be entirely dependent on groundwater. In the central Truckee Meadows, up to 30% of our drinking water is currently derived from groundwater in a given year. As growth in southern Washoe County continues and water demands increase, groundwater will only become more important.
What can be done to protect groundwater?
Recognizing its significance, it is important for all of us to learn how to protect our groundwater.
"When the well's dry, we know the worth of water."
Benjamin Franklin (1706 - 1790)
We also come to appreciate the value of water when, during a time of need, we are faced with the costs of cleaning up or remediating groundwater that has been impacted and made not suitable for human consumption. In areas where infiltration can reach an existing aquifer, contaminants released into the environment as a result of:
- The accidental or negligent release or inappropriate use or disposal of industrial chemicals (like PCE);
- Landfill seepage;
- Septic tanks;
- Leaking underground storage tanks; and,
- The inappropriate use of fertilizers and pesticides can impact groundwater and make it unsuitable for human consumption.
One of the best ways we can most effectively protect our groundwater is by not allowing it to become contaminated in the first place. As stated in the State of Nevada, Wellhead Protection Program Guide, "It must be realized that it requires much less effort and money to protect drinking water supplies than to clean them up once contamination has occurred." If groundwater becomes contaminated, it will no longer be safe to drink unless activities (such as the creation of the Central Truckee Meadows Remediation District) are conducted to make it so.
To keep groundwater from becoming contaminated, we need to be aware of and utilize safe and effective practices at home and at work when conducting activities that may represent a risk to groundwater. This includes the proper storage, use, and disposal of potentially hazardous and/or toxic materials. Click here for additional information on safe and effective practices to protect groundwater.
We can also increase our awareness of wellhead protection areas. These are areas where any water at the ground surface (from rainfall, snowmelt, or irrigation) that infiltrates to the water table is predicted (typically using computer simulations) to be captured by a nearby water supply well. Any hazardous or toxic materials present within a wellhead protection area pose a risk to such a well if not properly stored, used, or disposed of.
(Above) In order to promote the awareness of wellhead protection,
you may soon see signs such as this in the central Truckee Meadows.
(Above) The integrity and security of monitoring wells used to assess the movement
and quality of groundwater must be maintained so that these wells don't
become conduits for groundwater contamination.
Groundwater wells must be protected or abandoned in accordance with
State regulations to eliminate the possibility that they will become
conduits for groundwater contamination.
Sources of information include:
Well related information: Nevada Division of Water Resources (NDWR).
Hazardous materials: Washoe County District Health Department (WCDHD).
Groundwater protection: the U.S. Environmental Protection Agency (EPA) and the
Nevada Division of Environmental Protection (NDEP).