Nutrients in Lake Winnipeg

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Phosphorus and Nitrogen Levels in Lake Winnipeg

High phosphorus and nitrogen levels can result in harmful algal blooms in Lake Winnipeg. In 2013, phosphorus levels in its North and South basins and the Narrows were above the water quality guidelines for the protection of freshwater plants and animals most of the time. Nitrogen levels in each basin were generally below water quality guidelines.

Both phosphorus and nitrogen levels were consistently above water quality guidelines for the protection of freshwater plants and animals in the Red River, and always below the guidelines in the Winnipeg River. Just over 44% of phosphorus samples in the Saskatchewan River were above the guidelines for the 2011 to 2013 period while nitrogen samples were always below the guideline values.

Status of phosphorus and nitrogen levels in Lake Winnipeg, Canada, 2013; and in three tributary rivers, Canada, 2011 to 2013

Map - See long description below.
Long description

The map shows the status of phosphorus and nitrogen levels in the North and South basins and Narrows of Lake Winnipeg for 2013. In 2013, the phosphorus status was red because phosphorus levels in the North and South basins and the Narrows of Lake Winnipeg were above water quality guidelines for the protection of freshwater plants and animals. Nitrogen status was green because levels were at or below water quality guidelines.The map also shows the status of phosphorus and nitrogen levels in three tributary rivers for the 2011 to 2013 period: the Winnipeg River; Saskatchewan River; and Red River. In the Winnipeg River, fewer than 10% of samples were above the guideline and the phosphorus status was green. The phosphorus status was yellow in the Saskatchewan River because between 10% and 50% of samples were above the guideline. It was red in the Red River because more than 50% of samples were above the guideline. Nitrogen status was green in the Winnipeg and Saskatchewan rivers and red in the Red River.

Data for this map
Status of phosphorus and nitrogen levels in Lake Winnipeg, Canada, 2013
Lake Winnipeg Phosphorus water quality guideline
(milligrams of phosphorus per litre)
Phosphorus level
(milligrams of phosphorus per litre)
Phosphorus level status Nitrogen water quality guideline
(milligrams of nitrogen per litre)
Nitrogen level
(milligrams of nitrogen per litre)
Nitrogen level status
North Basin 0.025 0.033 Red 1.0 0.49 Green
South Basin and Narrows 0.025 0.108 Red 1.0 0.72 Green

Download data file (Excel/CSV; 752 B)

Status of phosphorus and nitrogen levels in three tributary rivers, Canada, 2011 to 2013
River Phosphorus water quality guideline
(milligrams of phosphorus per litre)
Proportion of phosphorus levels above the guideline
(percentage)
Phosphorus level status Nitrogen water quality guideline
(milligrams of nitrogen per litre)
Proportion of nitrogen levels above the guideline
(percentage)
Nitrogen level status
Saskatchewan River 0.050 39 Yellow 1.0 5 Green
Red River 0.050 100 Red 1.0 99 Red
Winnipeg River 0.050 0 Green 1.0 0 Green

Download data file (Excel/CSV; 770 B)

How this indicator was calculated

Note: Status colours for the North Basin and the South Basin and the Narrows of Lake Winnipeg were determined by comparing seasonally weighted average total phosphorus and total nitrogen levels in lake water collected from across the basins to the appropriate water quality guidelines for the protection of aquatic life. For the Red, Winnipeg and Saskatchewan rivers, the total phosphorus and total nitrogen water quality status was determined based on the frequency with which water quality monitoring data were above the guideline values.Footnote [1],Footnote [2]
Source: Manitoba Conservation and Water Stewardship and Environment and Climate Change Canada.

Lake Winnipeg is Canada's sixth-largest freshwater lake and the world's third-largest reservoir, generating hydro-electric power for all of Manitoba.Footnote [3] The lake is home to over 30 communities and supports a large commercial fishery, as well as recreation. Lake Winnipeg is composed of a large, deeper North Basin and a smaller, shallower South Basin. The two basins are separated by the Narrows, through which water from the South Basin flows northward. With an average depth of 13 metres in the North Basin and nine metres in the South Basin, the lake is shallow compared to the Laurentian Great Lakes. At 953 240 square kilometres, the lake's drainage basin is the largest drainage basin of all lakes in Canada, covering four provinces and four U.S. states. The shallow waters and large volume of water flowing in from the rivers draining into the lake are major influences on water quality in the lake.

Water quality in Lake Winnipeg has been deteriorating for many years, putting the health of the lake at serious risk. Before European settlement in the region, the lake had moderate levels of phosphorus and nitrogen. Since then, the levels of these nutrients have been affected by a range of human activities. With the opening up of the West, livestock and crop production began contributing phosphorus and nitrogen from manure and fertilizer to the drainage basin. The westward expansion also resulted in the draining of thousands of wetlands that dotted the Prairies, which received and processed nutrients running off the land. Growing cities have also generated more nutrients and changed how water flows across the land.

The excess amount of phosphorus and nitrogen flowing into Lake Winnipeg contributes to increasingly large, frequent, and potentially toxic, algal blooms. The highest levels of phosphorus and nitrogen are typically found in the South Basin near the inflow from the Red River, with levels declining as the water flows north. Without a reduction in nutrients, water quality in the lake will continue to deteriorate.

Phosphorus and nitrogen are key nutrients for plant growth in lakes and rivers. Rock weathering and the natural decomposition of plants and animals are natural sources of phosphorus. Nitrogen is naturally added to the environment by bacteria that convert nitrogen gas in the air into forms plants can use for their growth. Too much or too little in the environment, however, is harmful. Phosphorus and nitrogen from human activity enters Lake Winnipeg through municipal and industrial wastewaters, agricultural runoff, and air pollution. When phosphorus and nitrogen levels in water become too high, aquatic plant growth can become excessive and harmful. The decay of excess plant material can reduce the amount of oxygen available for fish and other aquatic animals. High nutrient levels can also lead to harmful algal blooms, which can kill animals that use the water and affect human health.

Reducing Phosphorus Loads to Lake Winnipeg

As of March 2016, stewardship projects supported by the Lake Winnipeg Basin Stewardship Fund were preventing an estimated 22 200 kilograms of phosphorus per year from entering Lake Winnipeg and its tributary rivers. The drop in the amount of phosphorus reaching Lake Winnipeg reflects reductions of almost 6500 kilograms of phosphorus per year from projects undertaken between April 2008 and March 2012 and just over 15 700 kilograms of phosphorus per year for projects completed between April 2012 and March 2016. In addition, the bio-remediation of a decommissioned municipal wastewater lagoon in 2015 prevented 21 300 kilograms of phosphorus from ever reaching Lake Winnipeg.

Cumulative, estimated reduction in the amount of phosphorus reaching Lake Winnipeg due to stewardship projects, April 2008 to March 2016

Column chart - See long description below.
Long description

The column chart presents estimates of the amount of phosphorus prevented from entering Lake Winnipeg's watersheds from April 2010 to March 2016. For Lake Winnipeg, an estimated 22 200 kilograms of phosphorus per year has been diverted from the lake, as well as a one-time reduction of 21 300 kilograms from a bio-remediation project in 2015, between April 2008 and March 2016.

Data for this chart
Cumulative, estimated reduction in the amount of phosphorus reaching Lake Winnipeg due to stewardship projects, April 2008 to March 2016
Year Estimated phosphorus removal
(kilograms of phosphorus)
Estimated one-time phosphorus removal
(kilograms of phosphorus)
Total estimated phosphorus removal over all years
(kilograms of phosphorus)
2010-2011 4907 not applicable 4907
2011-2012 1586 not applicable 6493
2012-2013 0Footnote [A] not applicable 6493
2013-2014 122 not applicable 6615
2014-2015 8194 not applicable 14 809
2015-2016 7404 not applicable 22 213
2015-2016 not applicable 21 300 43 513

Download data file (Excel/CSV; 1.09 KB)

How this indicator was calculated

Note: The estimate of reduced phosphorus load represents projects with final reports submitted by March 2016. Figures for each project type are rounded and then summed to give the total.
Source: Environment and Climate Change Canada (2016) Lake Winnipeg Basin Initiative.

Environment and Climate Change Canada, Manitoba Conservation and Water Stewardship and other partners are working closely together to more fully understand the relationships between phosphorus and nitrogen levels and nuisance algal growth in Lake Winnipeg, as well as the impacts of the recent arrival of zebra mussels (Dreissena polymorpha). While this work continues, they are also engaging citizens, scientists, and domestic and international partners to reduce phosphorus pollution by supporting stewardship projects, such as erecting fencing to prevent livestock from entering lakes and rivers, stabilizing river banks and lake shorelines, restoring wetlands and planting native shrubs, plants and trees. This work will help Manitoba achieve its long-term goal of reducing phosphorus concentrations in the lake to pre-1990 levels of approximately 0.05 milligrams of phosphorus per litre.

Pristine lakes and rivers image

Pristine lakes and rivers

These indicators support the measurement of progress towards the long-term goal of the 2016-2019 Federal Sustainable Development Strategy: Clean and healthy lakes and rivers support economic prosperity and the well-being of Canadians.

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