Ground water is vulnerable to contamination. Once ground water becomes contaminated, it is very difficult to clean up. Because ground water often moves very slowly, the contamination may exist for a very long time. The contamination may impair ground water for use as drinking water and other beneficial uses and may affect the quality of the surface waters where it discharges.

DEQ is responsible for protecting the quality of ground water in Idaho, but does not undertake this task alone. DEQ monitors and protects ground water in Idaho through partnerships with the Idaho Department of Agriculture, Idaho Department of Water Resources, and many other state, local, and private agencies, organizations, businesses, and individuals. The roles of DEQ, the Idaho Department of Agriculture, and the Idaho Department of Water Resources are delineated in the Idaho Ground Water Protection Interagency Cooperative Agreement (pdf 2.3 mb, 21 pages).

The Idaho Statewide Ground Water Quality Monitoring Program is designed to assess the current condition of Idaho's ground water quality, identify potential problem areas, and detect trends in ground water quality. The program is a cooperative effort between the Idaho Department of Water Resources and the U.S. Geological Survey's Water Resources Division.

DEQ conducts regional and local ground water quality monitoring when the statewide program or other government agencies detect potential problem areas. DEQ also initiates its own evaluations and conducts regional and local monitoring in conjunction with other agencies. DEQ chairs the Idaho Ground Water Monitoring Technical Committee that includes membership from other Idaho state agencies, Idaho Health Districts, the Idaho Water Research Institute, Idaho's universities, and federal agencies.

Idaho's ground water quality monitoring program results show that significant levels of ground water degradation have occurred in specific areas across the state. This negatively impacts water quality and potentially threatens domestic water supplies, aquaculture, agriculture, mining, industrial, and other ground water beneficial uses. With input from other agencies, DEQ has established a statewide priority list of areas of significantly degraded ground water. This list is based on levels of nitrate (read more about nitrate in ground water) and is used to prioritize the development and implementation of management strategies to improve ground water in specific degraded areas.

In addition to the statewide monitoring program and DEQ's ground water monitoring program, the Idaho State Department of Agriculture addresses ground water issues that involve pesticides, fertilizers, animal waste, and other potential agricultural contaminants. The agency conducts regional and local agricultural ground water quality monitoring.

View reports on DEQ's ground water quality monitoring studies.

"Managed recharge" is a process where water is applied to the land surface specifically to allow it to sink into the ground to add water to (recharge) an aquifer.  It is one of several solutions to restore declining water levels in some aquifers.  Before water can be land-applied for managed recharge, a ground water quality monitoring program must be reviewed and approved by DEQ. DEQ provides guidance for developing monitoring programs to be used with managed recharge projects. The monitoring must demonstrate that a recharge project will not adversely affect water quality. Learn more: Frequently Asked Questions About Managed Recharge.

It is DEQ's job to protect the quality of ground water in Idaho. It is illegal in Idaho to cause or allow the release of a contaminant (anything that does not occur naturally or naturally occurs only in very small quantities) into the environment in a manner that it:

• Causes a ground water quality standard to be exceeded
• Injures a beneficial use of ground water
• Is not in accordance with a permit, consent order, or applicable best management practice, best available method, or best practical method

One potential source of contamination of ground water is land application of wastewater (spent or used water from a home, community, farm, or industry). To assure ground water is protected, DEQ requires anyone wishing to land-apply wastewater to obtain a wastewater reuse permit. Septic systems can also contaminate ground water. Applicants for all large soil absorption septic systems and for central septic systems located in nitrate priority areas or in areas of "sensitive resource" aquifers must complete a nutrient-pathogen evaluation of the proposed wastewater system as part of their application for a permit. This evaluation helps predict whether effluent from the treatment system will be diluted enough to prevent ground water contamination.

Learn about regulatory measures to protect ground water quality.

If ground water is already contaminated, DEQ's role is to help restore ground water quality and prevent further degradation (see DEQ's policy for addressing degraded ground water quality areas). In coordination with other agencies, DEQ assists local ground water quality advisory groups to develop ground water quality management strategies (compiled into ground water quality management plans) for high priority areas.

The strategies focus on understanding the dynamics of the ground water and contaminants in a high priority area, preventing contamination, protecting current quality, and remediating contaminated water to maintain or improve water quality.

Specific strategies may include:

• Collecting additional data

• Evaluating hydrogeology, water quality, water use, land use, and population projections

• Determining if the contamination is the result of historical practices or natural causes

• Applying voluntary and/or regulatory control measures designed to protect the area (e.g., best management practices)

• Applying remediation techniques

• Coordinating with other agencies

DEQ periodically reviews the effectiveness of the strategies and may remove a high priority designation when management strategies have proven to be effective. In instances where management strategies are ineffective, additional strategies may be employed or the strategies may be changed to be more effective. If additional protective measures are necessary, an aquifer or portions of it may be re-categorized as a sensitive resource aquifer.

Local input is extremely important in implementing these strategies. View a map (pdf 1.5 mb, 1 page) of the status of ground water management plans or contact your local DEQ regional office to learn if a plan is underway in your area and how you can become involved. Completed plans area available online (listed under the county the plan covers).

Remediating contaminated ground water is time consuming and expensive. Fortunately, preventing ground water contamination doesn't have to be. Properly disposing of hazardous materials such as paint, bleach, and cleaning products; carefully using pesticides and fertilizers (DEQ Brochure, October 2007: pdf 143 kb, 2 pages); watering your lawn wisely; and maintaining your septic system all help protect ground water for you and for generations to come. Read A Citizen's Guide to Ground Water Protection (pdf on U.S. EPA Web site) to learn more about what you can do to protect ground water.

(DEQ Brochure, Updated October 2007: pdf 143 kb, 2 pages)

Idaho's Ground Water Quality Rule (IDAPA 58.01.11)

(pdf on Department of Administration Web site)