Nooksack River Ground-Water Bacteria

Science Center Objects

The lower Nooksack River Basin is located in Whatcom County, in the northwestern part of Washington. Within areas of the basin, the ground-water aquifer is shallow. Knowledge of how the surface water and the aquifer interact, and how this interaction affects the transport of bacteria and nitrates from agricultural fields to the ground-water system, is important to residents of the basin. This is true for the Nooksack and Lummi Indian Tribes, who have a large natural-resource interest in the area.

To help improve the understanding of how ground water and surface water interact in the basin, and to help resource managers plan for better water quality in the basin, the USGS is identifying areas where interactions occur and in which direction the waters are flowing. The USGS is also examining the ground- and surface-water quality.

9722-A4N - Transport and fate of bacteria and nitrate contamination in ground water of the Lower Nooksack River Basin - Completed FY2005

Problem - An improved understanding of the processes and pathways that affect concentrations of fecal coliform and nitrate in ground water of the lower Nooksack River Basin is needed to help decision-makers develop better plans to improve ground- and surface-water quality in the basin.

In particular, information is lacking about the source, location, temporal variation, and quality of discharging ground water, which is needed to answer questions regarding the fate and transport of fecal coliform and nitrate contaminants as they move from agricultural fields to the ground-water system and eventually to surface-water systems. Additional information about the extent of denitrification is also needed to provide realistic constraints on water-quality models that are used to make water-resource management decisions.

Objectives - The general objectives of this study are to improve the understanding of the interaction between surface and ground water in the shallow aquifer of the lower Nooksack River Basin and to better understand the transport and fate of bacterial and nitrate contamination within that aquifer.

Relevance and Benefits - An important part of the USGS mission is to provide scientific information to manage the water resources of the Nation, to enhance and protect our quality of life, and to improve our understanding of the environment and natural resources. A better understanding of ground-water and surface-water interactions and how they affect the transport of bacteria and nitrate is of value to residents and wildlife of the Nooksack River Basin and agricultural basins in other parts of the country. Locally, the data are very important to the Nooksack and Lummi Indian Nations, which have an extensive aquatic natural-resource interest in the study area. Study results are also relevant to State and Federal agencies and other parties that are charged with addressing issues that affect human and environmental health.

Approach - Stream locations will be identified where ground-and surface-water exchanges occur and flow directions between the ground- and surface-water systems will be determined. The quality of discharging ground water will be determined by analyzing fecal bacteria and a suite of constituents related to ground-water denitrification. Ground-water ages will also be determined. Ground- and surface-water samples will be collected over the course of a storm hydrograph for analysis of stable isotopes and bacteria to determine the relative proportion of surface runoff that constitutes streamflow during periods when surface-water bacteria concentrations are significantly elevated. Lastly, a laboratory microcosm experiment will be conducted to determine if ground-water denitrification can be enhanced by the addition of carbon, an electron source. All sampling results will be analyzed to meet the study objectives and results will be published in a USGS Water Resources Investigation Report or equivalent USGS publication.