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Water Science & Technology Vol 64 No 11 pp 2185–2191 © IWA Publishing 2011 doi:10.2166/wst.2011.760

Application of nitrogen and phosphorus criteria for streams in agricultural landscapes

P. A. Chambers, G. A. Benoy, R. B. Brua and J. M. Culp

Environment Canada, 867 Lakeshore Road, PO Box 5050, Burlington, ON, Canada L7R 4A6 E-mail: Patricia.Chambers@ec.gc.ca
Environment Canada and Agriculture and Agri-Food Canada, Potato Research Centre, 850 Lincoln Rd., PO Box 20280, Fredericton, NB, Canada E3B 4Z7
Environment Canada, National Hydrology Research Centre, 11 Innovation Blvd, Saskatoon, SK, Canada S7N 3H5
Environment Canada and Canadian Rivers Institute, Department of Biology, University of New Brunswick, 10 Bailey Dr., PO Box 4400, Fredericton, NB, Canada E3B 5A3


ABSTRACT

Efforts to control eutrophication of water resources in agriculturally dominated ecosystems have focused on managing on-farm activities to reduce nutrient loss; however, another management measure for improving water quality is adoption of environmental performance criteria (or ‘outcome-based standards’). Here, we review approaches for setting environmental quality criteria for nutrients, summarize approaches developed in Canada for setting ‘ideal’ and ‘achievable’ nutrient criteria for streams in agricultural watersheds, and consider how such criteria could be applied. As part of a ‘National Agri-Environmental Standards Initiative’, the Government of Canada committed to the development of non-regulatory environmental performance standards that establish total P (TP) and total N (TN) concentrations to protect ecological condition of agricultural streams. Application of four approaches for defining ideal standards using only chemistry data resulted in values for TP and TN spanning a relatively narrow range of concentrations within a given ecoregion. Cross-calibration of these chemically derived standards with information on biological condition resulted in recommendations for TP and TN that would likely protect aquatic life from adverse effects of eutrophication. Non-point source water quality modelling was then conducted in a specific watershed to estimate achievable standards, i.e. chemical conditions that could be attained using currently available and recommended management practices. Our research showed that, taken together, short-term achievable standards and ultimate ideal standards could be used to set policy targets that should, if realized, lower N and P concentrations in Canadian agricultural streams and improve biotic condition.

Keywords: criteria; nitrogen; nutrients; phosphorus; streams; thresholds


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