Statewide Ground Water Quality Monitoring (GWQM)

Background Information

The Ground-Water Quality Protection Act (Senate Bill #1269), passed by the Idaho State Legislature in 1989, authorized a comprehensive approach for maintaining and improving Idaho's ground-water quality. The Act resulted in the formation of the Ground-Water Quality Council, which developed the Idaho Ground-Water Quality Plan in 1992. The monitoring component of the plan outlined the need for statewide, regional, and local ground-water quality monitoring. In 1990, the Idaho Department of Water Resources (IDWR), with help from other state and federal agencies, began the Statewide Ground Water Quality Monitoring Program. The Statewide Program provides valuable information about Idaho's groundwater quality to private citizens, consulting companies, and governmental entities, and also provides data into the EDMS database.

Program Objectives

The objectives of the Statewide Program are to:

1. Characterize the ground-water quality of the state's major aquifers.
2. Identify trends and changes in ground-water quality within the state's major aquifers.
3. Identify potential ground-water quality problem areas.

Program Responsibilities

For 18 years, IDWR and the U.S. Geological Survey (USGS) worked as partners in the Statewide Program. Due to the economic challenges that arose in the country in 2008, IDWR assumed full responsibility for the Statewide Program in 2009. These responsibilities include collecting the data samples, analyzing the data, provided public access to the data, and writing interpretive reports. IDWR would like to recognize and sincerely thank the USGS for their many years of dedication to the Statewide Program.

From 1990 to Present

The Statewide Ambient Ground-Water Quality Monitoring Program (Statewide Program) began in 1990 with a limited prototype network of 97 monitoring sites (IDWR, 1991). In 1991, the funding was increased significantly both from the State of Idaho and Federal (USGS). This funding enabled the State to sample about 400 sites to the network each year from 1991 through 1994. By the fall of 1994, the Statewide Program network included over 1,500 monitoring sites.

Every year, about 400 monitoring sites are sampled. Most sites are sampled once every five years. Water quality results include: bacteria, nutrients, common ions (calcium, magnesium, etc.), trace elements (iron, arsenic, lead, etc.), pesticides, volatile organic compounds, and radioactivity.

About 100 sites are sampled every year; these are called Annual Sites. Annual sites serve two main purposes. First, they allow for more rapid data collection so that trend analyses can be conducted quicker on those sites (as opposed to waiting 15 or 20 years for enough data to be collected at sites that are sampled less frequently). Second, the collection frequency at Annual Sites may be useful for determining whether concentration changes are associated with long-term trends or are being affected by unique events or conditions such as precipitation extremes or patterns.