Evaluating diffuse and point source phosphorus inputs to streams in a cold climate region using a load apportionment model

Rattan, K.J.; Bowes, M.J. ORCID:; Yates, A.G.; Culp, J.M.; Chambers, P.A.. 2021 Evaluating diffuse and point source phosphorus inputs to streams in a cold climate region using a load apportionment model. Journal of Great Lakes Research, 47 (3). 761-772.

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Variation in the timing and quantity of diffuse versus point-source inputs of phosphorus (P) to streams can be evaluated by examining P concentration-flow relationships. Diffuse load inputs usually increase with stream flow (due to increased delivery caused by precipitation); whereas, point-source concentrations decrease with rising river flow (due to increased dilution). This study tested the suitability of a load apportionment model (LAM), a power-law function of flow, to estimate contributions of diffuse and point inputs to P loads for eight sub-watersheds in the Red River Valley, a cold-climate rural region of Manitoba, Canada. For all but two sub-watersheds, annual and seasonal (snowmelt and summer) models of P concentration versus flow best fit a strictly diffuse source contribution. The models identified significant point-source inputs (in addition to diffuse sources) in two sub-watersheds, during summer in both watersheds (consistent with the fact that wastewater from sewage lagoons is discharged to upstream reaches between June and September) and during snowmelt for one watershed. Application of a LAM proved to be a simple and rapid method for nutrient source apportionment as well as detection of unknown sources for cold-climate, rural sub-watersheds. Such information is critical for developing the most effective mitigation strategies to reduce P concentrations and eutrophication risk.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: Water Resources (Science Area 2017-)
ISSN: 0380-1330
Additional Keywords: nutrient sources, eutrophication, Lake Winnipeg, concentration-flow relationships
NORA Subject Terms: Ecology and Environment
Date made live: 13 Jul 2020 11:12 +0 (UTC)

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