Lower Winnipeg River Basin Discussion Sheet Series Sheet #4 | Water Quallity and Nutrient Loading

This briefing sheet from the International Institute for Sustainable Development (IISD) summarizes water quality and nutrient loading in the lower Winnipeg River basin (LWRB) based on data from 2018 and 2019. It details assessments of four monitoring sites, highlighting exceedances in total phosphorus and certain metals, and analyzes the river's role as a major nutrient contributor to Lake Winnipeg.

• The lower Winnipeg River is characterized as isothermic, with temperatures consistent throughout the water column. Recorded near-bottom temperatures of 23°C may impact the growth, survival, and reproductive success of aquatic organisms. Dissolved oxygen levels are generally high, with a mean concentration of approximately 10 mg/L across four assessed sites, exceeding the Canadian Council of Ministers of the Environment guidelines of 5.0 to 9.5 mg/L.
• Total phosphorus (TP) concentrations in the lower Winnipeg River frequently exceed the Manitoba Water Stewardship guideline of 25 μg/L. Exceedance rates vary by site: 41% in Eaglenest Lake, 57% in Lac du Bonnet, 81% in Pine Falls Forebay, and 85.3% in Pointe du Bois Forebay.
• Several metals exceed the Manitoba Water Stewardship protection of aquatic life (PAL) guidelines, particularly at the Pine Falls Forebay. Aluminum showed the highest overall exceedance across all sites, with 100% of samples in Pine Falls exceeding the 100 μg/L guideline. In Pine Falls Forebay, nearly 50% of iron samples exceeded the 300 μg/L guideline, and 58% of copper samples exceeded the 4.53 μg/L guideline.
• The Winnipeg River is the second largest absolute contributor of nutrients to Lake Winnipeg, providing approximately 25% of the total nitrogen (TN) and 15% of the total phosphorus (TP) loads. Nutrient exports and loads increase downstream from Pointe du Bois to Pine Falls, with the reach between these two sites producing nutrient exports nearly three to four times higher than at the individual sites.
• The reach between Pointe du Bois and Pine Falls is estimated to contribute about 3% of the total phosphorus load to Lake Winnipeg, based on an average annual phosphorus load of 265 tonnes from that reach against a mean annual total load of 7,830 tonnes (1994–2001). The specific source of these nutrients is unknown but may include human activity, erosion, cabin development, tributaries, or the surrounding watershed.
• Nutrient loading from the Winnipeg River is heavily influenced by water flow; 97% of the variation in TN and 79% of the variation in TP loading to Lake Winnipeg are attributed to river flows. Climate projections for the 2050s suggest a potential increase in mean annual precipitation (6.9%) and runoff (3.3%) into the basin, which could impact downstream nutrient loading.
• Water quality data reliability is limited because four monitoring sites are managed by three different organizations using varying sampling periods and analytical methods that have changed over time.

APA

International Institute for Sustainable Development (n.d.). Lower Winnipeg River Basin Discussion Sheet Series Sheet #4 | Water Quallity and Nutrient Loading. https://www.iisd.org/system/files/2021-06/winnipeg-river-basin-sheet-4-water-quality-nutrient-loading.pdf

Chicago

International Institute for Sustainable Development. Lower Winnipeg River Basin Discussion Sheet Series Sheet #4 | Water Quallity and Nutrient Loading. n.d. https://www.iisd.org/system/files/2021-06/winnipeg-river-basin-sheet-4-water-quality-nutrient-loading.pdf.

Wikipedia

{{cite report |author=International Institute for Sustainable Development |title=Lower Winnipeg River Basin Discussion Sheet Series Sheet #4 | Water Quallity and Nutrient Loading |url=https://www.iisd.org/system/files/2021-06/winnipeg-river-basin-sheet-4-water-quality-nutrient-loading.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{internationalinstituteforsustainabledevelopmentndlower, author = {{International Institute for Sustainable Development}}, title = {{Lower Winnipeg River Basin Discussion Sheet Series Sheet \#4 | Water Quallity and Nutrient Loading}}, institution = {International Institute for Sustainable Development}, url = {https://www.iisd.org/system/files/2021-06/winnipeg-river-basin-sheet-4-water-quality-nutrient-loading.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }