Science Center Objects

The Flaxville aquifer is present in the northern and central parts of the Fort Peck Indian Reservation and consists of sand and gravel that forms extensive plateaus and topographic benches used for dryland farming.  Because many residents rely on groundwater as their primary water supply on the Reservation, the Flaxville and underlying aquifers are important sources of groundwater.  The goal of this project is to better understand the possible changes in groundwater quality in the Flaxville and underlying aquifers as a result of changing land use and land management practices as related to farming and energy development. Well inventory and reconnaissance work will take place over the summer of 2019.  Water quality samples will be collected over the course of 2020-2021.

Location of Study Area (Includes Flaxville Aquifer and Lustre Oil Fields) and Sampling Sites From Previous USGS Studies

Location of Study Area (Includes Flaxville Aquifer and Lustre Oil Field) and Sampling Sites From Previous USGS Studies

(Public domain.)

This project focuses on the extent of the Flaxville aquifer and includes the aquifers that underlie the Flaxville aquifer.  The project also includes an area of energy development called the Lustre Oil Field.  Tasks include:

  • Evaluate the current status and sampling feasibility for all 112 previously-sampled wells and springs. Field inventory about 100 of these sites.
  • Collect water samples from a total of about 60 previously-sampled sites that were inventoried in FY19.
    1. Analyze for major-ion chemistry and nitrate concentrations in water samples from all 60 sites.
    2. Use current age-dating techniques in water samples from about 12 sites to re-evaluate age of groundwater in different areas of the reservation.
    3. Analyze for nitrogen isotopes in water from about 12 sites in order to evaluate potential source(s) of continuing contamination.
  • Collect seasonal samples (summer, fall, winter, spring) from about 16 sites with nitrate concentrations near or above the EPA’s Maximum Contaminant Level.
  • Identify about 20 sample sites for evaluation of effects of energy development.
  • Collect water samples at about 20 sites in energy-development area.
    1. Analyze for major-ions, trace elements, and selected halides in water samples from all 20 sites.
    2. Analyze for strontium-isotope ratios in water samples from about 10 sites.
  • Present results to pertinent Tribal, local, and state agencies.
  • Publish a U.S. Geological Survey report with the results from the sampling investigations.
  • Prepare a fact sheet on nitrate and groundwater and how changing land-use practices have altered (or not) groundwater quality based on findings from report.
  • Prepare a fact sheet about groundwater quality as related to energy development in the study area.