Chehalis River Basin

Science Center Objects

The Chehalis River flows approximately 125 miles in southwestern Washington north-northwesterly to Grays Harbor and the Pacific Ocean, draining an area of approximately 2,700 square miles. The Chehalis River Basin is the second largest basin in Washington State. It is bounded on the west by the Pacific Ocean, on the east by the Deschutes River Basin, on the north by the Olympic Mountains, and on the south by Cowlitz River Basin. The basin includes portions of Grays Harbor, Lewis, Mason, and Thurston Counties and the Cities of Aberdeen, Centralia, Chehalis, and Hoquiam, and the Confederated Tribes of the Chehalis Reservation. Population in the Chehalis River Basin was about 141,000 in 2000.

Increasing demands for water for municipal, fisheries, agricultural, industrial, and recreational uses will affect the water resources of the basin. A better understanding of the ground-water flow system and its relation to rivers and streams is needed to effectively manage the basin's water resources.

9722-DYB-T2 - Data Analysis and Watershed Characterization, Chehalis River Basin, Washington - Completed FY2011

Problem — In recent years, increased use of ground- and surface-water supplies in the Chehalis River Basin of Washington State has created concern that insufficient water resources remain for fish and other uses. Additionally, flooding in the Chehalis River Basin in 1996, 2007, and 2009 damaged public and private property, forced the closure of major transportation corridors, and displaced residents throughout the area. Water-resource managers and emergency management officials in the Chehalis River Basin need information to assist in the development and implementation of a long-term, basin-wide watershed management plan for normal to extreme hydrologic conditions.

Objectives — The major objectives of the study are to characterize the hydrogeologic setting of the Chehalis River Basin and the interaction of groundwater and surface-water features in selected representative areas.

Relevance and Benefits — This study addresses two water-resource issues identified in the USGS Science Strategy document: hydrologic hazards (flooding) and hydrologic system management. This study also is consistent with the water-resource issues identified in the USGS Washington Water Science Center’s Science Plan. This study will provide information that advances the understanding of hydrologic processes in the basin and also will provide resource managers in the Chehalis River Basin with information needed to mitigate the impacts of hydrologic extremes.

Approach — Groundwater and surface-water data will be compiled and the data will be entered into the National Water Information System (NWIS) database, and geospatial data will be compiled and entered in a newly created Geographic Information Systems (GIS) database. These data will be evaluated and analyzed to characterize the hydrogeology and generalized groundwater flow system of the basin.

9722-DYB00 - Data Compilation, Collection, and Evaluation in Support of the Characterization of the Water Resources of the Chehalis River Basin, Washington - Completed 2011

Problem - In 1998, the Washington State Legislature established the Washington State Watershed Management Act (codified under RCW 90.82) to address diminishing water availability and quality and the loss of critical habitat for fish and wildlife. Watershed planning under this Act was started in 1998 in the Chehalis River Basin Water Resources Inventory Areas (WRIAs 22 and 23) by a group of Initiating Governments. Upon completion of the Technical Assessment, and during preparation of the Watershed Management Plan, some members of the Initiating Governments and other project partners concluded that data gaps in the Technical Assessment would limit the usefulness of the plan. Chehalis Basin Partnership members and stakeholders have asked the USGS Washington Water Science Center to design and conduct a data-collection study, including the compilation and evaluation of existing information, to address data gaps and assist in the development of a long-term watershed management plan for the Chehalis River Basin.

Objectives - The major objectives of the study are to compile, collect, and evaluate data pertinent to the characterization of the hydrologic and hydrogeologic setting of the Chehalis River Basin, with a focus on interactions between groundwater and surface-water resources. This study also will create project management tools to facilitate communication between project partners and stakeholders, and to establish consistent methods and practices among project participants for project data collection, quality assurance/quality control (QA/QC), and archiving of project data.

Relevance and Benefits -This study is consistent with the national USGS mission and goals identified in the USGS Science Strategy document (USGS, 2007) and with water-resource issues identified in the USGS Washington Water Science Center’s Science Plan. The study addresses groundwater availability and sustainability, and surface-water/groundwater interactions as related to water-resource management. The study will provide information that advances the understanding of hydrologic processes and also will provide resource managers in the Chehalis River Basin with information needed to assist in the development of a long-term watershed management plan that meets the needs of current and future water demands within the watershed, while also working to protect and improve its natural resources.

Approach - Existing hydrologic and hydrogeologic data will be compiled and entered into the appropriate databases. New hydrologic data will be collected, compiled, and evaluated to support the future characterization of the flow system. Geospatial data will be compiled and entered in a newly created Geographic Information Systems-based database.

9722-9EU-T10 - Potential Scope of Work to Assess the Water Resources of the Chehalis River Basin - Completed FY2008

Problem - In recent years, increased use of ground- and surface-water supplies in watersheds of Washington State has created concern that insufficient instream flows remain for fish and other uses. The Chehalis Basin Partnership is working to develop a long-range sustainable watershed plan to meet the needs of current and future water demands within the watershed, while also working to protect and improve its natural resources. The ground-water flow system is not understood well enough on a watershed scale to effectively plan and manage the use of this resource.

Objectives - The broad objective of this study is to develop a better understanding of the ground-water/surface water interaction of the Chehalis River Basin. To achieve this objective, synoptic streamflow measurements were collected to evaluate gaining and losing reaches of the main-stem Chehalis River and selected tributaries.

Relevance and Benefits - The proposed project supports the USGS mission to provide information on water resources for management activities and decisions. It also addresses water availability and ground-water/surface-water interactions, which are major water-resource issues identified in the USGS Washington Water Science Center's Science Plan. The USGS has already established the desired stream-gaging in the basin.

Approach - A seepage run (synoptic streamflow measurements) was conducted during September 2007 in the Chehalis River Basin. The seepage run identified gaining and losing reaches of the Chehalis River and its major tributaries. The USGS will continue operation and maintenance of 19 surface-water stations and 1 real-time ground-water monitoring wells.