‘A tale of two cities’: Nitrogen inventories in the Nooksack-Fraser Transboundary Watershed
Citation:
Lin, J., J. Compton, J. Baron, C. Clark, D. Schwede, S. Bittman, D. Hooper, B. Carey, P. Homann, H. Winter, P. Kiffney, N. Embertson, R. Black, G. Boggs, R. Sheibley, AND G. Bahr. ‘A tale of two cities’: Nitrogen inventories in the Nooksack-Fraser Transboundary Watershed. INMS case study meeting, Abbotsford, British Columbia, CANADA, October 13 - 14, 2018.
Impact/Purpose:
The Nooksack-Fraser Transboundary Nitrogen (NFT-N) project created a nitrogen (N) budget for the watershed spanning the border of U.S. and Canada. This effort represents the North American Case study for the International Nitrogen Management System (INMS) effort, and this presentation was given at a recent meeting with the INMS leadership team. The transboundary watershed has prolonged coastal eutrophication and contaminated groundwater issues due to excessive N. The team includes scientists and technical staff of federal, state/province, and local entities within the basin. hey found that livestock feed and fertilizer import were the two largest sources of N, accounting for 63% and 15% of total N input to the U.S. part of the watershed, respectively; food import for human and pets together accounted for 11% of total N input; deposition contributed 10% of N input to the watershed. About 25% of dairy manure N was lost as ammonia, and 8% via denitrification. Only 47% of manure N was directly available for plant uptake. Careful management of agricultural fertilizers and manures is key to improving water quality. Results will be refined by integrating with an existing Canadian N budget to achieve a complete budget, and applied to build an ecosystem model to simulate N outcome under various management scenarios.
Description:
Spanning the border of U.S. and Canada, the Nooksack-Fraser transboundary area (2639 km2) is home to the communities of Lynden, Washington, and Abbotsford, British Columbia, with a strong base in farming, fisheries and outdoor recreation. Balancing these uses is a key issue in the area, where nitrogen (N) loading contributes to coastal eutrophication and prolonged contamination of groundwater. The Nooksack-Fraser Transboundary Nitrogen (NFT-N) project had an initial goal of creating a N budget using data on energy use, transportation, fertilization, wastewater treatment, livestock operations, and fisheries. Using local data, we estimated that livestock feed and fertilizer import were the two largest N input sources to the U.S. part of the watershed, averaging 3472 and 1131 metric tons (MT) N yr-1, respectively. Atmospheric deposition was the third largest source of N to the watershed, averaging 527 MT N yr-1. The import of human and pet food added 655 MT N per year to the watershed. The returns of adult salmon brought in 6 MT N yr-1 to the watershed. N loss through volatilization of manure averaged 2035 MT N yr-1, and denitrification losses were approximately 204 MT N yr-1. N fluxes in surface and ground water will be estimated using load simulation and mass balance approaches. Preliminary results for the U.S. side demonstrate the importance of N inputs from agriculture sector, indicating that careful management of agricultural fertilizers and manures is key to improving water quality. Results will be refined by integrating with an existing Canadian N budget to achieve a complete budget for the watershed, and used to understand connections between inputs and N fates in ground and surface water. The budget will be used as a foundation to develop an ecosystem model for management scenario simulation.