Declining Water Levels Pose Challenges for Eastern Idaho Aquifer Monitoring

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IDAHO FALLS, Idaho —Last summer, water levels reached all-time lows in 177 wells used to monitor the eastern Snake River Plain aquifer at and near the Idaho National Laboratory. As the region goes through its third year of drought, U.S. Geological Survey scientists, working in cooperation with the U.S. Department of Energy, have assessed factors influencing water-level declines and how future declines might jeopardize some wells in the monitoring network. They published their findings today.

Scientists examined how close water levels were to the depth of well pumps, a level at which the wells would no longer be usable. They also analyzed geophysical data for the wells to determine how future declines might affect well productivity, the amount of water that could be pumped.

The monitoring well network is essential to the U.S. Department of Energy’s ability to meet its compliance and surveillance objectives, as well as federal and state regulations.

Key findings from the USGS study include:

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• Two monitoring wells have gone dry in the past year. While the study was underway, the water level in one well dropped below the well’s pump. A second well south of the INL dating back to the early 1920s is completely dry.
• Water levels in 11 other monitoring wells are within 10 feet of well pumps. These wells are at risk of becoming unusable if the region experiences an extended drought similar to the period between 2000 and 2005 when aquifer water levels declined about 10 feet.
• Water levels in an additional 28 monitoring wells are within 20 feet of well pumps. This depth is significant because water levels in some wells in the northern part of the INL site have declined as much as 20 feet in the last 14 years.
• Production wells used for water supply at the INL site are not at risk of running dry because of their greater depths.

“Declining water levels could affect our ability to monitor and understand the aquifer,” said Roy Bartholomay, scientist in charge of the USGS project office at the INL. “To keep some of these wells active, we may need to deepen the wells and pumps, which could be very expensive. We may need to decide whether to keep some wells in the monitoring network.”

Data from the INL monitoring well network are available on the USGS INL Project Office website.