South Fork Nooksack River Basin Groundwater and Surface-water Interactions and Processes Completed

WA - Characterization of Groundwater Processes and Groundwater/Surface-water Interactions of the South Fork Nooksack River Basin, Whatcom County, Washington - Completed FY2015

Problem - High water temperatures and low instream flows during the summer have been identified as some of the key limitations for the viability of South Fork Nooksack River salmon populations including summer and spring-run Chinook salmon. Restoration strategies including the placement of engineered log jams, the restoration of floodplains and wetlands, and instream flow negotiation have been developed by river managers to address high water temperatures and low instream flows. The relationship between the groundwater-flow system, wetlands, and streams within the South Fork Nooksack River basin remains poorly understood and the contribution of wetlands to summer baseflow and stream temperature is not well defined. To inform salmonid restoration actions, managers of the South Fork Nooksack River need information and tools to understand the current groundwater-flow system, and its relationship to surface-water features such as wetlands and streams.

Objectives - The objective of this study is to characterize the contribution of wetlands to the baseflow and temperature of the South Fork Nooksack River and to develop a hydrogeologic framework for the South Fork Nooksack River basin in preparation for the future development of a basin-wide groundwater-flow model.

Relevance and Benefits - The objectives of this study are consistent with the national USGS mission and goals identified in the USGS Science Strategy. The study addresses groundwater availability and sustainability, and surface-water/groundwater interactions as related to water-resource management. This study is appropriate for the role of the USGS in the Cooperative Water Program because it advances analytical methodology for understanding hydrologic processes and will contribute to the scientific basis for understanding groundwater flow in the South Fork Nooksack River basin. This study will provide resource managers in the South Fork Nooksack Basin with the information needed to assist in the development of a long-term watershed management plan to meet the needs of current and future water demands within the watershed, while also working to protect and improve its natural resources.

Approach - Existing and new groundwater and surface-water data will used to characterize the hydrogeologic framework and flow system in the South Fork Nooksack River basin. The temperature and baseflow contributions of wetlands to the South Fork Nooksack River will be assessed using fiber-optic distributed temperature sensing, temperature gradients in shallow piezometers, and synoptic streamflow measurements. These data along with an exploratory numerical groundwater flow model will be used to inform future development of a fully-calibrated groundwater-flow model.