Citation:

Lin, J., J. Compton, J. Baron, D. Schwede, S. Bittman, D. Hooper, P. Kiffney, N. Embertson, B. Carey, H. MacKay, R. Black, G. Bahr, J. Harrison, AND E. Davidson. Nitrogen input inventory in the Nooksack-Fraser Transboundary Region: Key component of an international nitrogen management study. AGU, New Orleans, LA, December 11 - 15, 2017.

Impact/Purpose:

Nitrogen (N) is an essential biological element, so optimizing N use for food production while minimizing the release of N and co-pollutants to the environment is an important challenge. The Nooksack-lower Fraser Valley, spanning a portion of the western interface of British Columbia and Washington state, and the Lummi Nation and the Nooksack Tribe, supports agriculture, fisheries, diverse wildlife, and vibrant urban areas. This study brings together local, state, regional and international stakeholders to contribute to a current, comprehensive quantification of N inputs to the Nooksack-lower Fraser basin. The information on cross-boundary N inputs to the landscape will be coupled with stream monitoring data and existing knowledge about N inputs and exports from the watershed to estimate the N residual and inform N management in the search for the environmentally and economically viable and effective solutions. This abstract contributes to SHC 4.61.

Description:

The Nooksack-Abbotsford-Sumas (NAS) Transboundary Watershed, spanning which spans a portion of the western interface of British Columbia, Washington State, and the Lummi Nation and the Nooksack Tribal lands , supports agriculture, estuarine fisheries, diverse wildlife, and urban areas. Excess N has contributed to surface and ground water pollution, shellfish closure, and impaired air quality (such as haze or smog) in some areas in the watershed. The goal of this project is to determine the distribution and quantities of N fluxes of the watershed using site-specific and high-resolution data on N that originates from energy use, transportation, fertilization, wastewater treatment plants (WWTP), animal feeding and manure production, crops and more. This project is one of seven international demonstration projects contributing knowledge of regional N budgets and collaborative approaches toward N management as part of the International Nitrogen Management System (INMS). Successful N reduction relies on the partnership of all stakeholders with appropriate institutions to integrate science, outreach and management efforts. This project will reach out to other stakeholders on both sides of the international border for a first comprehensive, quantitative characterization of all N inventories and fluxes across this international watershed. Using crop-specific fertilizer application rates and wind-shield-survey land use data, we estimated that the annual fertilizer N input to the U.S. portion of the watershed was about 3779 metric tons (MT), which is very close to the USGS estimate of 3955 MT. Based on county level animal census data, we estimated total excretion N from major livestock (cattle) to be 7895 metric tons on the U.S. side. Using existing model results from other studies, we estimated that the annual N loading on the U.S. side was about 351 MT from point sources, 527 MT from atmospheric deposition, and about 7 MT from alder fixation. The preliminary results demonstrate an important role for N from the agricultural sector in the watershed. The results will be refined by improving current estimations, adding other N sources and the Canadian portion, and including high-frequency ground and surface water monitoring data and knowledge about N transfers to estimate the residual/retention N.

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