Department of
Environmental Quality

Ground water supplies 95% of Idaho's drinking water, so the quality of Idaho's ground water affects nearly everyone in the state. Although the quality of ground water in Idaho is generally good, ground water quality monitoring shows that in specific areas of the state, Idaho's ground water has been significantly degraded. This localized degradation negatively impacts water quality and potentially threatens domestic water supplies, aquaculture, agriculture, mining, industrial, and other ground water beneficial uses.

Nitrate is one of the contaminants responsible for this degradation and is one of the most widespread ground water contaminants in Idaho. High levels of nitrate in drinking water are associated with adverse health effects in humans and livestock. High levels of nitrate also adversely affect fish and surface waters such as lakes and rivers.

Identifying Degraded Ground Water Areas

DEQ regularly conducts regional and local ground water quality monitoring. When routine monitoring results show exceedances of state or federal standards, DEQ follows up with ground water quality investigations in the area of the detection, then summarizes the results. With input from other agencies, DEQ establishes a statewide priority list of areas with significantly degraded ground water. This list is used to prioritize the development and implementation of management strategies to improve ground water in specific degraded areas. 

Ground Water Quality Improvement (Management) Plans

If ground water is already contaminated, DEQ's role is to help restore ground water quality and prevent further degradation. In coordination with other agencies, including the Idaho State Department of Agriculture and the Idaho Department of Water Resources, 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 nitrate priority area ranking is used to prioritize the development and implementation of strategies to help reduce nitrate loading from land-use activities. In coordination with other agencies, DEQ assists local ground water quality advisory groups in developing ground water quality management strategies for nitrate priority areas. 

Ground Water Quality Management Strategies

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 of the status of ground water management plans in Idaho or contact your local DEQ Regional Office to learn if a plan is underway in your area and how you can become involved.