U.S. Geological Survey scientists measure what often remains invisible – groundwater in the southeast Puget Sound region

TACOMA, Wash. - Together with partners, U.S. Geological Survey (USGS) scientists from the Washington Water Science Center have used cutting-edge tools to estimate groundwater, a critical regional resource for more than one million people in the southeast Puget Sound region of Washington.

Groundwater is water that flows through the soil and rocks underneath us. People use groundwater for about half of their water needs in the southeast Puget Sound region. These needs include public water supply, drinking water and household use, and agricultural water demands. Groundwater is crucial for communities; however, it can be an elusive resource for scientists and managers to measure and understand because it remains hidden underground.

"We gathered data from about 4,000 wells which gave information about the subsurface geology and patterns of groundwater flow," said lead scientistWendy Welch of the USGS. "We then built a 3-D numerical model that simulates how groundwater moves under different climate and water use scenarios representing potential drought and water-use changes."

The model is available so that other scientists and resource managers can use it to assess additional scenarios to inform management decisions. Resource managers may use the results of this study to evaluate the response of groundwater levels and stream base flows to potential changes in water use, drought, and other climatic conditions.

"This model gives us valuable information about groundwater throughout the Clover and Chambers Creeks region. It will help Pierce County in its mission to protect aquatic ecosystems and public health while also meeting surrounding community's needs" said Tim Hagan, Total Maximum Daily Load program manager for Pierce County Surface Water Management. "We value the USGS as a federal science agency and regional partner as we collaborate with other jurisdictions to develop regional-scale knowledge to help improve water resource management in the south Puget Sound".

The southeast Puget Sound groundwater investigation was conducted in close collaboration with 18 local and state water resource agencies. The model is regional in scale, covering an area of 887 square miles in central Pierce County and southwestern King County. This is an area that is more than half the size of the state of Rhode Island. The USGS holds expertise in developing large-scale investigations of water resources. The USGS is already using the published model to further overall understanding of groundwater topics in the region, including water table depths and groundwater flow paths. The model will support continued scientific applications to for managing surface and groundwater.

Learn more about the past work of USGS Washington Water Science Center, this study, and the partners involved here.

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