Lake Winnipeg

On August 12, 2021, Manitoba and Canada announced a renewed "Canada-Manitoba Memorandum of Understanding Respecting Lake Winnipeg and the Lake Winnipeg Basin". The agreement details how the provincial and federal governments will continue their work to understand and protect the water quality and ecological health of Lake Winnipeg and its basin, including reducing nutrient loading.

With its beautiful beaches and wide open waters, Lake Winnipeg is one of Manitoba's greatest freshwater resources. Lake Winnipeg, the world's 10th largest freshwater lake by surface area, plays a critical role in tourism, recreation, commercial and sport fisheries, and hydroelectric generation in Manitoba. Over 23,000 permanent residents live in 30 communities along the shores of Lake Winnipeg, including many First Nation and Métis communities. Lake Winnipeg's world-class beaches attract many visitors to the province and offer many opportunities for swimming, paddling, sailing, and windsurfing on the east and west shores of the south basin. Each year, approximately 800 commercial fishers operate on Lake Winnipeg, catching a variety of species including world-class walleye, goldeye, sauger, whitefish, plus others. Sport anglers find many places to fish while enjoying the lake's beauty. Lake Winnipeg is also the world's third largest reservoir, generating hydroelectric power for all Manitobans.

Manitoba is proposing a Nutrient Targets Regulation under The Water Protection Act that would establish nutrient loading targets for the four major tributaries (Red, Winnipeg, Saskatchewan, and Dauphin Rivers) flowing into Lake Winnipeg and nutrient concentration targets for total phosphorus and total nitrogen in Lake Winnipeg. The proposed nutrient targets will provide important guidance for nutrient reduction activities and provide science-based benchmarks to track and evaluate progress over time. Key information to support the proposed regulation includes:

  • Plain Language Summary of the proposed Nutrient Targets Regulation
  • Report on Setting Phosphorus and Nitrogen Targets to Improve Water Quality
  • Report on Application of a Water Quality Model to Draft Nutrient Targets for Lake Winnipeg
  • Public consultation on the proposed Nutrient Targets Regulation was conducted through the Manitoba Regulatory Consultation Portal. The comment period closed on February 26, 2021 and feedback received is being considered by the department. Manitoba Environment and Climate Change thanks everyone who provided comments during the public consultation period.


    About the Lake

    • The Lake Winnipeg watershed is the second largest watershed in Canada and includes parts of four provinces and four U.S. states.
    • The Lake Winnipeg drainage basin is nearly 1,000,000 km2 in size and is home to more than 7 million people.
    • Lake Winnipeg, the last remains of glacial Lake Agassiz, lies on the boundary between the low-relief Interior Plains and the southwestern Canadian Shield.
    • Several major rivers flow into Lake Winnipeg including the Red, Winnipeg, and Saskatchewan rivers. These three rivers make up on average more than 60% of the total river flow into Lake Winnipeg.
    • Some of the other rivers that flow into Lake Winnipeg include the Poplar, Berens, Pigeon, Manigotagan, Dauphin, Fisher, and Icelandic rivers.
    • Only one river flows out of Lake Winnipeg, the Nelson River. The outflow of the lake has been regulated for hydro-electric power generation since 1976 making Lake Winnipeg the third largest hydro-electric reservoir in the world.
    • Water moves through Lake Winnipeg over a period of on average about 3 to 5 years. This is relatively fast compared to other large lakes such as Lake Superior where the water residence time is 191 years.
    Physical Characteristics
    • Lake Winnipeg is the 10th largest lake in the world by surface area.
    • The surface area of Lake Winnipeg is about 23,750 km2 and covers about 3.7% of the surface area of the province.
    • Lake Winnipeg is about 436 kilometres in length and about 111 kilometres across at its widest point.
    • On average, the lake is about 12 metres deep but at a point off the northeast shore of Black Island, Lake Winnipeg reaches its maximum depth of about 36 metres.
    • With its many bays, harbours, and points, the shoreline of Lake Winnipeg is about 1,750 kilometres long.
    • The volume of Lake Winnipeg is 284 cubic kilometres.
    • Lake Winnipeg consists of a large, deeper north basin and a smaller, comparatively shallow south basin. Lake Winnipeg is shallow relative to other large lakes, with an average depth of 9 metres in the south basin and 13.3 metres in the north basin. The two basins are separated by the Narrows through which waters from the south basin ultimately flow northward.
    • Because of its shallow depth, the water column of Lake Winnipeg is typically not stratified with bottom waters within 1 to 2° Celsius of surface water temperatures.
    Eutrophication, Water Chemistry, and Aquatic Life
    • Nutrient loading to Lake Winnipeg and concentrations of nutrients in Lake Winnipeg have increased over the past several decades.
    • Nutrient increases in Lake Winnipeg in the 1990s led to a doubling of phytoplankton biomass and a shift to cyanobacteria (blue-green algae) dominance of the phytoplankton community.
    • Phosphorus concentrations are almost three times higher in the south basin on Lake Winnipeg as compared to the north basin.
    • Nitrogen concentrations are slightly higher in the south basin of Lake Winnipeg as compared to the north basin.
    • Higher nutrient concentrations generally occur at the very south end of the lake and decline moving northwards. Elevated nutrient concentrations at the southern end of Lake Winnipeg are likely associated with the nutrient-rich inflow of the Red River.
    • Several aquatic invasive species, including zebra mussels are known to occur in Lake Winnipeg. Although it can be difficult to predict impacts to Lake Winnipeg, aquatic invasive species may potentially alter ecological relationships among native species, affect ecosystem health and function, the economic value of ecosystems, water-related infrastructure including water intakes, and human health. For more information on aquatic invasive species, visit:
    Economic Value
    • More than 23,000 permanent residents live in 30 communities along the shores of Lake Winnipeg, including 11 First Nations communities.
    • In 2013/14, 816 licensed fishers and their helpers were employed in the commercial fishery on Lake Winnipeg.
    • During the 2013/14 season, 4,457,390 kg (round weight) of walleye were caught by commercial fishers on Lake Winnipeg. Harvests of lake whitefish and sauger were 1,335,641 and 313,326 kg (round weight), respectively.
    • In 2013/14, the total landed value of commercial fish production of Lake Winnipeg was $15,714,994.

    Monitoring and Research

    Considerable water quality work is being undertaken on Lake Winnipeg to better understand its existing condition, evaluate impacts to aquatic life and to assess long-term changes in water quality.

    Excessive concentrations of nitrogen and phosphorus in Lake Winnipeg are causing changes in the lake's water quality and biological communities. Nutrients are contributed from virtually all of our activities in the lake's watershed. These nutrients are directly associated with the production of nuisance growths of algae - affecting fish habitat, recreation, drinking water quality, and clogging fishing nets. Some nuisance growths of blue-green algae can also produce toxins.

    Since 2000, water samples are collected four times per year at locations around the lake and analysed for a wide variety of variables including nutrients such as nitrogen and phosphorus, chlorophyll a (a measure of algae biomass), metals, pesticides, dissolved oxygen, and others. Work on the lake is conducted in cooperation with other participants in the Lake Winnipeg Research Consortium. The organisms living in the sediments at the bottom of the lake are examined once per year at each location as an indicator of ecosystem health.

    Reporting and Assessment

    State of Lake Winnipeg Report

    The Province of Manitoba and the Government of Canada recently released the second edition of the State of Lake Winnipeg report. The report, led by Manitoba Environment and Climate Change and Environment and Climate Change Change Canada, is a collaborative effort by many researchers from government, universities, and non-governmental organizations. The report provides an update to the first comprehensive assessment of the physical, chemical, and biological characteristics of Lake Winnipeg released in 2011.

    The updated State of Lake Winnipeg report serves as a reference to measure progress towards reducing nutrient loading, will help in the assessment of the overall health of the lake, and also provides key information to support current and future research on Lake Winnipeg. The report is available as both an extended technical report and a highlights report.

    The first report is also available:

    Lake Winnipeg: Nutrients and Loads

    Excessive phosphorus and nitrogen contribute to the development of harmful and nuisance algal blooms in Lake Winnipeg. Nutrients arise from a number of natural and anthropogenic sources across the one million square kilometer Lake Winnipeg Basin. The reports below summarize nutrient conditions in Lake Winnipeg, nutrient loads from major tributaries flowing into the lake, and nutrient reduction actions underway.

    Lake Winnipeg Indicators

    Comprehensive, understandable and scientifically defensible indicators are required to provide assessments of the health of Lake Winnipeg and its watershed and to track progress and change over time. Manitoba Environment and Climate Change and Environment and Climate Change Change Canada have produced the first two factsheets as a part of the Lake Winnipeg Basin Indicator Series:


    On May 31, 2011, the Province of Manitoba released a report prepared by Dr. Peter Leavitt, Canada Research Chair in Environmental Change and Society (Department of Biology, University of Regina) and his colleagues Dr. Lynda Bunting and others on the paleolimnology of Lake Winnipeg.

    What you can do

    The future health and productivity of Lake Winnipeg, one of Manitoba's most valuable resources, is everyone's responsibility. Excessive concentrations of nitrogen and phosphorus are directly associated with the production of nuisance growths of algae that can clog fishing nets and negatively impact fish habitat, recreation, and drinking water quality. Some nuisance growths of algae can also produce toxins.

    Since nutrients are contributed from virtually all of our activities in the Lake Winnipeg watershed, there are lots of things that you can do to help reduce nutrient levels and thereby improve water quality in Lake Winnipeg.

    Here are some things that you can do to help reduce nutrients in Lake Winnipeg:

    • Leave uncut vegetation at the water's edge and plant native plants and shrubs.
    • Keep shorelines in their natural state.
    • Do not use fertilizers next to water.
    • Use phosphate-free soaps and detergents.
    • Do not use soap or shampoo in the lake.

    The Water Protection Handbook was written for cottage associations, river stewardship organizations, conservation districts, environmental organizations, waterfront residents, and other Manitobans who are interested in keeping our water clean. The handbook is a reference book that can be used by you and your family for many years to come.

    The Clean Water Guide outlines practical things we can do in our homes, our yards, at our cottages and when we are camping, to preserve and protect our water. It's up to all of us.

    Also, you can buy Lake Friendly cleaning products. Lake Friendly products are Ecologo certified, therefore helping you protect Lake Winnipeg and its watershed.



    Questions? Contact:
    Water Quality Management Section
    Manitoba Environment and Climate Change Water Branch
    Box 10 - 14 Fultz Blvd
    Winnipeg Manitoba, R3Y 0L6

    Telephone: (204) 945-0002
    Fax: (204) 948-2357
    Toll Free: 1-800-282-8069 (ext. 0002)