There are two types of geologic materials in the Walla Walla Subbasin that contain groundwater. Some wells draw water from sediments like sand and gravel, while other wells access the basalt that lies below the sediments in the valley and at the surface in the uplands. Groundwater levels have dropped up to 40 feet in the sediments and up to 150 feet in basalt aquifers since 1940. These declines indicate that the groundwater use in the basin exceeds natural recharge. Action is needed to stabilize groundwater levels and ensure that water is available to meet future needs. The Department has presented more detailed information regarding the water level trends, hydrogeology, and management options for basalt aquifers in the Walla Walla Subbasin during several public meetings.
Additional Documents and Presentations