Budgeting for groundwater in the West Plains, Spokane County, USA
Faculty Mentor
Chad Pritchard
Presentation Type
Poster
Start Date
4-14-2026 2:00 PM
End Date
4-14-2026 4:00 PM
Location
PUB NCR
Primary Discipline of Presentation
Geosciences
Abstract
Groundwater budgets are a common way to understand inputs and outputs of groundwater in a region. Unfortunately, water levels in the West Plains have been decreasing (Burns et al., 2012, Spokane County Water Resources, 2013). Beyond calculating water budgets, this study also collected radiocarbon dating of groundwater in the West Plains, dating for the commonly used aquifers, the Columbia River Basalt Group (CRBG) aquifers. The about 16.2 million year old Grande Ronde Basalt is the deeper basalt aquifer and is semi-confined by the Latah Formation. The upper Wanapum Basalt is about 16 million years old and is an unconfined aquifer commonly accessed in shallower wells (<200 ft deep). However, looking at the West Plains holistically, there is not a good understanding of how the aquifers are recharged, though past studies document decreasing groundwater levels in CRBG aquifers and municipalities have lost water rights due to over pumping. Additionally, many areas in the West Plains have PFAS contaminated groundwater. Taking a more holistic approach, we test the potential of connection between basement and basaltic aquifers using groundwater age, groundwater budgets and a meteoric water line. Analysis of the Carbon-14 data and the estimated ages of groundwater within the basaltic aquifers, found a 16-26% decrease in age between 2012 and 2024. When comparing groundwater ages between basalt and basement aquifers there is a 1.25 magnitude difference, suggesting the basement aquifers have a separate hydrologic cycle from the basaltic aquifers. However during times in which the basement aquifer levels are high, springs can form as water spills out of the aquifer at the surface. These springs can feed the basalt aquifers of the West Plains. Additionally, younger groundwater is centralized around urban or residential areas of the West Plains, suggesting overuse of the aquifer, which increases gradients for downward recharge in those areas, which greater distributes PFAS contamination across aquifers. Due to groundwater contamination multiple locations now import drinking water, which results in groundwater budget with potentially increasing storativity and localized groundwater levels (mounding). This artificial recharge from Spokane may help dilute the PFAS, but also exacerbates the distribution of PFAS across the West Plains, affecting thousands of private well owners and a municipal well.
Recommended Citation
Meier-Grolman, Cadence, "Budgeting for groundwater in the West Plains, Spokane County, USA" (2026). 2026 Symposium. 8.
https://dc.ewu.edu/srcw_2026/ps_2026/p3_2026/8
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Budgeting for groundwater in the West Plains, Spokane County, USA
PUB NCR
Groundwater budgets are a common way to understand inputs and outputs of groundwater in a region. Unfortunately, water levels in the West Plains have been decreasing (Burns et al., 2012, Spokane County Water Resources, 2013). Beyond calculating water budgets, this study also collected radiocarbon dating of groundwater in the West Plains, dating for the commonly used aquifers, the Columbia River Basalt Group (CRBG) aquifers. The about 16.2 million year old Grande Ronde Basalt is the deeper basalt aquifer and is semi-confined by the Latah Formation. The upper Wanapum Basalt is about 16 million years old and is an unconfined aquifer commonly accessed in shallower wells (<200 ft>deep). However, looking at the West Plains holistically, there is not a good understanding of how the aquifers are recharged, though past studies document decreasing groundwater levels in CRBG aquifers and municipalities have lost water rights due to over pumping. Additionally, many areas in the West Plains have PFAS contaminated groundwater. Taking a more holistic approach, we test the potential of connection between basement and basaltic aquifers using groundwater age, groundwater budgets and a meteoric water line. Analysis of the Carbon-14 data and the estimated ages of groundwater within the basaltic aquifers, found a 16-26% decrease in age between 2012 and 2024. When comparing groundwater ages between basalt and basement aquifers there is a 1.25 magnitude difference, suggesting the basement aquifers have a separate hydrologic cycle from the basaltic aquifers. However during times in which the basement aquifer levels are high, springs can form as water spills out of the aquifer at the surface. These springs can feed the basalt aquifers of the West Plains. Additionally, younger groundwater is centralized around urban or residential areas of the West Plains, suggesting overuse of the aquifer, which increases gradients for downward recharge in those areas, which greater distributes PFAS contamination across aquifers. Due to groundwater contamination multiple locations now import drinking water, which results in groundwater budget with potentially increasing storativity and localized groundwater levels (mounding). This artificial recharge from Spokane may help dilute the PFAS, but also exacerbates the distribution of PFAS across the West Plains, affecting thousands of private well owners and a municipal well.
