Wyoming Groundwater-Quality Monitoring Network

The WGQMN samples wells to establish baseline groundwater quality in priority areas where groundwater has been identified as an important source of public or private water supplies, is susceptible to contamination, and is overlain by one or multiple land-use activities that could negatively impact groundwater resources (Bedessem and others, 2005). The WGQMN project area consists of 33 priority areas  identified by the Wyoming Department of Environmental Quality's Aquifer Prioritization for Ambient Ground Water Monitoring project in the 7 principal river basins of the state. Although the scope of this project is statewide, initial efforts have been limited to specific river basins. Priority areas were grouped together to be sampled based on principal river basins.

Objectives of the WGQMN are to:

• Measure water levels and collect groundwater samples from selected wells;
• Analyze groundwater samples for a variety of natural and man-made compounds;
• Report the results through publically available U.S. Geological Survey (USGS) reports, fact sheets, and water-quality web site.

Groundwater samples are collected from existing shallow wells. Wells are stratified by depth (less than 500 feet), and aquifer type (alluvial or shallow bedrock). Upon further evaluation of data, a subset of wells are selected to include in the WGQMN. All samples are analyzed for standard analytes including major ions, trace elements, nutrients, dissolved organic carbon, total dissolved solids, alkalinity, volatile organic compounds, gasoline range organics, diesel range organics, dissolved hydrocarbon gases (methane, ethene, ethane), hydrogen-2/hydrogen-1 and oxygen-18/oxygen-16 isotope ratios, and total coliform and Escherichia coli bacteria. Additionally, selected samples are analyzed for supplemental analytes waste water compounds, tritium, gross alpha and gross beta radioactivity, and radon-222.

Before sampling a well, the depth to water is measured, if possible. Wells are pumped (purged) until it is apparent that aquifer water, rather than water stored in the casing, is being sampled. If no pump is installed, a submersible pump is used for purging and sampling. Water temperature, pH, specific conductance, dissolved oxygen, oxidation-reduction potential, and turbidity are measured and recorded periodically during purging.

Samples are collected in accordance with specific USGS sampling protocols (USGS, 1997-present) to ensure a quality sample. Samples are containerized and preserved according to the analysis method's requirements, and shipped to either the EPA Region 8 Laboratory or a USGS analytical laboratory, depending on the analysis to be performed.

In addition to collecting samples, details about the well being sampled are useful for analyzing data. These data include photographs, geographic coordinates, water levels, and information about sampling conditions and well construction. All data are stored at the USGS office in Cheyenne, and much of the data are available on the internet under the data and tools tab.

Sampling by the USGS, in cooperation with the WDEQ, began in the Greater Green River Basin in December 2009 - including 4 additional wells sampled as part of the Wyoming Landscape Conservation Initiative. Sampling efforts moved to the Platte River Basin in November 2010 because of concerns about potential groundwater contamination from increased oil and gas development in the Niobrara shale formation. To date, sampling has been conducted in Albany, Campbell, Carbon, Converse, Crook, Goshen, Johnson, Laramie, Niobrara, Platte, Sheridan, Sublette, Sweetwater, and Uinta counties.

A fact sheet describing the WGQMN design and objectives, field procedures, and water-quality analyses was published in April 2011 and is available online at: http://pubs.usgs.gov/fs/2011/3041/. A scientific-investigations report describing the water-quality data through water year 2013 was published in 2014 and is available online at: http://pubs.usgs.gov/sir/2014/5130/.