Promise and Problems of Real-Time Nitrate Monitoring to Inform Watershed Management in the Nooksack Basin
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Promise and Problems of Real-Time Nitrate Monitoring to Inform Watershed Management in the Nooksack Basin. David Hooper1, Rich Sheibley2, Craig Senter3, Jana Compton4
1Western Washington University, 2USGS Washington Water Science Center, 3USGS Pacific Islands Water Science Center, 4US EPA, Pacific Ecological Systems Division
From its headwaters in the northwestern Cascade Mountains, the Nooksack River drains approximately 809 mi2, comprising most of western Whatcom County, including agricultural areas and the developed lowlands surrounding the towns of Deming, Everson, Lynden, and Ferndale. The Nooksack River enters the Lummi Indian Reservation at its eastern extent, which contains most of the river delta before it discharges into the marine waters of Bellingham Bay. The Nooksack River is also the primary source of freshwater into Portage Bay, which is located approximately 5 miles southwest of the Nooksack River delta. Nonpoint nutrient pollution is a growing water quality problem in the United States, particularly from mixed urban and agricultural areas such as the Puget Sound area. The Nooksack River basin contains some of the most productive farmland in Washington State, as well as a high rural residential population on septic systems, making it an ideal location to study temporal and spatial dynamics of nutrient delivery to surface water. The Portage Bay Partnership, a collaboration between Whatcom County dairy farmers and the Lummi Nation to improve water quality in the basin, was formed in 2017 to primarily address bacterial pollution in surface water. The data collected from this current project will help add to the partnership’s efforts on controlling bacterial pollution by providing a detailed dataset on nitrate concentrations at key locations within the basin. EPA’s Safe and Sustainable Water Resources Program supported continuous nitrate sensor monitoring through a cooperative agreement with Whatcom Conservation District (WCD), to track real time nitrate loads in streams and rivers of the Nooksack River basin. This type of data is invaluable for better understanding sources of nutrients to the nearshore waters of the northern Salish Sea. The USGS supported WCD to monitor continuous nitrate using both SUNA and OTT nitrate sensors at three locations in the basin. The continuous nitrate sensors will be deployed until December 31, 2021. Continuous nitrate monitoring will take place at three locations in the Nooksack Basin. The first site, located on Fishtrap creek (site ID 12212050), a tributary to the Nooksack River, drains farmland from Washington and Canada and is in an important location for monitoring nutrient loads into the mainstem of the Nooksack River. Data collection started in June 2018. At a second tributary site, Kamm Creek (site ID 12211390), continuous monitoring began in January 2019. The third location is at the mouth of the Nooksack River near Ferndale, WA (site ID 12213100). Monitoring continued through December 2021. These three sites allow partners to study how tributary inputs of nitrate influence mainstem nutrient loads over annual timescales. Existing flow USGS flow gages at the Nooksack at Ferndale and Fishtrap Creek in Lynden, and supplemental gauging by cooperators at Western Washington University (WWU) allow for the calculation of nitrate loads during the monitoring period.
The team used the data to construct export nitrate loads within the basin and compare the sensors and different loading estimation methods. This presentation shares the results of this monitoring effort with the Nooksack-Fraser Transboundary Nitrogen (NFT-N) project team and other federal, state and local partners interested in nitrogen transport within and beyond the Nooksack River Basin. The presentation also seeks to obtain feedback about the utility of these data and suggestions for improvement in future efforts.