Lake Winnipeg

Category: Inland Aquatic Biomes.

Geographic Location: North America.

Summary: This relatively pristine freshwater habitat is under stress from anthropogenic sources of excess nutrients, invasive species, and climate change.

Lake Winnipeg is the largest lake in the Canadian province of Manitoba, and a valuable source of hydropower, commercial fishing, and recreation for the region. Its name is from the Cree term for muddy waters. The watershed is almost 40 times greater than the surface of the lake; it is shaped by environmental forces and human activities in an extensive area spanning Canada and the United States. The water quality and aquatic biodiversity of Lake Winnipeg are threatened by excess nutrients, invasive species, and climate change, while the large size and multiple jurisdictions of the watershed present further challenges for water management and policy decisions.

Among the largest freshwater lakes in the world (tenth in terms of surface area), Lake Winnipeg measures 270 miles (435 kilometers) north to south and spreads across approximately 9,460 square miles (24,500 square kilometers). It is the largest remnant of ancient Lake Agassiz, formed by glacial retreat in North America about 12,000 years ago. Lake Winnipeg consists of a large north basin and a smaller, comparatively shallow south basin; these are separated by a narrow channel that carries water from the south basin northward. Compared with other large lakes, Lake Winnipeg is relatively shallow, with an average depth of 39 feet (12 meters). This contributes to a fairly short water residence time of three to four years for the lake as whole, and further affects the water temperature, volume, and ecosystem functions.

The Lake Winnipeg watershed is nearly 386,000 square miles (1 million square kilometers), stretching from the Rocky Mountain foothills to within a few miles (kilometers) of Lake Superior and covering parts of four provinces (Manitoba, Ontario, Saskatchewan, and Alberta) and four US states (North Dakota, South Dakota, Minnesota, and Montana). River flow is the most significant source of water to the lake, which is fed by three major river systems: the Saskatchewan River from the west, the Red River from the south, and the Winnipeg River from the southeast. The Winnipeg River contributes nearly half of the total inflow to Lake Winnipeg, followed by the Saskatchewan River (25 percent), Red River (16 percent), other tributaries, and precipitation. The only outlet from the lake is the Nelson River, flowing northward to Hudson Bay, with evaporation also contributing to water loss.

Biodiversity

Walleye and whitefish are the most commonly fished species in the lake, accounting for the bulk of commercial fishing. Winnipeg was also once the main source of goldeye. Other native fish include sauger, yellow perch, troutperch, berbot, freshwater drum, lake cisco, and emerald shiner. Fish designated as at risk (by the Committee on the Status of Endangered Wildlife in Canada) include silver chub, bigmouth buffalo, shortjaw cisco, and chestnut lamprey. The lake supports not only commercial and recreational fishing, but subsistence fishing for the local indigenous population.

Several introduced species in the lake are having considerable influence on ecological relationships, by competing with native species for food and other resources. Aquatic invasive animal species known to occur in Lake Winnipeg include the common carp, rainbow smelt, white bass, Asian tapeworm, and a zooplankton species (Eusbomina coregoni). Rainbow smelt are now the dominant prey fish species in the north basin of the lake, and scientists are investigating their effect on the harvest and production of walleye, an important commercial native species.

A particularly notable invasive species is the zebra mussel, which made its way to the lake from the Red River watershed by 2013. A boom in zebra mussels in the lake in 2015 had major environmental impacts, with scientists conceding that little could be done to reverse the invasion. The mussels are considered a major disruptor of ecosystems due to their quick breeding and consumption of microorganisms, and also a detriment to recreation due to their sharp shells covering the lake bed. By 2019, the zebra mussel problem had escalated, as the species had made its way to the lake’s shores. In some spots, the mussel’s sharp shells completely covered parts of the shoreline. Another threat was the spiny water flea, which was identified downstream from Pointe du Bois Dam on the Winnipeg River in 2010. Managers remain concerned about these invasive species migrating up- or downstream, as they may further affect ecosystem health and economic activities in Lake Winnipeg.

Human Impact

Lake Winnipeg provides important socioeconomic benefits to the region. It is one of the world’s largest hydro-reservoirs, and supplies Manitoba Hydro, the Crown Corporation hydroelectric utility, with majro portions of its storage and generating capacity. Regulated since 1976, water flows around Lake Winnipeg now create hundreds of millions of dollars’ worth of electrical power each year, with close to 75 percent of that revenue resulting from exports to other Canadian provinces and the United States.

This aquatic ecosystem also supports the most important commercial fisheries in Manitoba; in 2021, an estimated 800 commercial fisheries operated on the lake. Prior to the 2020 COVID-19 pandemic, recreation and tourism around Lake Winnipeg generate more than $100 million per year, as the area’s beaches, parks, and cottages are popular destinations. Additionally, more than 23,000 permanent residents along the shoreline in 30 communities, as well as populations downstream, rely on the water quality of the lake for drinking water.

Water quality in Lake Winnipeg has deteriorated during the late twentieth century, primarily from excess nutrients loaded into the lake through watershed sources. The catchment is dominated by agricultural use; it supports approximately tens of millions of livestock and millions of people. Monitoring of watershed nutrient sources has revealed that cropland fertilizers carry the largest amounts of phosphorus to the lake through surface runoff and flooding, mainly through the Red River. Human and livestock wastes contribute additional loads.

Phosphorous and nitrogen are the two major nutrients contributing to the increased frequency and intensity of algal blooms that threaten the Lake Winnipeg biome. More than 80 percent of the algae that form blooms in the lake during the ice-free seasons are blue-green algae or cyanobacteria, of particular concern because of their detrimental effect on the ecosystem. Cyanobacteria are a less desirable food source than other algae types for organisms in the lake, leading to species accumulation and dominance. When these algae die and sink down to the bottom of the lake, their decomposition by bacteria consumes oxygen in the water; this reduces the available oxygen necessary for fish and other organisms in the food web. In addition, cyanobacteria have the potential to produce potent toxins that may pose health risks to humans and other animals. These water-quality changes can affect the lake’s ecosystem sustainability, safety for the public, and aesthetic appeal.

Climate change has the potential to alter water temperatures and further affect ecosystem structure in the lake. From 1909 to the early twenty-first century, August water temperatures in the south and north basins of Lake Winnipeg increased by 3.4 degrees F and 1.8 degrees F (1.9 degrees C and 1 degree C), respectively. Global climate models predict that the south basin’s summer water temperatures could rise 9 degrees F (5 degrees C) by 2085. Research also suggests that the diversity of aquatic species in the lake will decline as water temperature rises.

Increased temperatures in central Canada will likely exacerbate the establishment of invasive species in Lake Winnipeg from southern regions, and favor species that thrive in higher water temperatures. From 1969 to 1990, the algal species composition during warm months shifted from a diverse assemblage to significant dominance of blue-green species with a tolerance for higher temperatures. Earlier spring melt and later freezes would lengthen the duration of the open water season and create warmer water temperatures, which could have detrimental effects for more than twelve coldwater fish species, including the commercial species of whitefish. Temperature-sensitive life cycles of aquatic insects may be sufficiently altered to cause shifts in abundance and species composition that disrupt food web functioning on a large scale.

In 2003, the Manitoba provincial government announced the Lake Winnipeg Action Plan, which aims to reduce phosphorous and nitrogen loading to Lake Winnipeg through several strategies. The plan strives to protect riparian growth, address fertilizer applications, introduce new sewage and septic regulations, reduce shoreline erosion, and engage other jurisdictions on nutrient management within the watershed. The Lake Winnipeg Stewardship Board was also initiated under this plan to identify necessary actions and make recommendations for reducing nutrient conditions by 10 percent. The board members represented a variety of interests, including fishing; agriculture; urban land use; First Nations; federal, provincial, and municipal government; and nongovernmental organizations.

Scientific research has also been advanced through intensive federal, provincial, collaborative, and independent research and monitoring programs. In 2008, Environment Canada and Manitoba Water Stewardship partnered in the Lake Winnipeg Basin Initiative, an effort to summarize accumulated scientific knowledge of the physical, chemical, and biological characteristics of the lake and its basin. The plan initially allocated $2.4 million to fund more than forty projects throughout the basin. Phase II of the plan began in 2012 with $18 million in funding to encourage scientists and the public to take a more active role in protecting the lake. In 2010, Manitoba and the federal government signed a memorandum agreeing to work together for the environmental health of Lake Winnipeg. The agreement was extend for five years in 2015 and extended again in 2021.

Bibliography

"Lake Winnipeg Basin Initiative." Government of Canada, 16 Aug. 2018, www.canada.ca/en/environment-climate-change/services/water-overview/comprehensive-approach-clean/lake-winnipeg/reports-publications/basin-initiative.html. Accessed 17 Aug. 2022.

"Lake Winnipeg Basin Stewardship Fund (LWBSF)." Environment and Climate Change Canada, Government of Canada, 8 Sept. 2016, ec.gc.ca/eau-water/default.asp?lang=En&n=D7134110-1&pedisable=true. Accessed 29 June 2018.

"Lake Winnipeg Quick Facts." Manitoba, www.gov.mb.ca/waterstewardship/water‗quality/lake‗winnipeg/facts.html. Accessed 29 June 2018.

Mann, Mark. "Anger and Indifference on Lake Winnipeg." The Walrus, 13 July 2017, thewalrus.ca/anger-and-indifference-on-lake-winnipeg/. Accessed 29 June 2018.

McGinn, Roderick A. "Lake Winnipeg." The Canadian Encyclopedia, Historica Canada, 4 Mar. 2015, www.thecanadianencyclopedia.ca/en/article/lake-winnipeg/. Accessed 29 June 2018.

North/South Consultants. “Literature Review Related to Setting Nutrient Objectives for Lake Winnipeg.” Winnipeg, Manitoba: North/South Consultants, 2006.

Sandford, Robert W. Saving Lake Winnipeg. Rocky Mountain Books, 2013.

Schindler, D. W. “The Cumulative Effects of Climate Warming and Other Human Stresses on Canadian Freshwaters in the New Millennium.” Canadian Journal of Fisheries and Aquatic Sciences 58 (2001).

"Zebra Mussels Multiplying in Lake Winnipeg, Now Found on Shorelines." Water Supply Association of B.C., 18 Aug. 2019, wsabc.ca/zebra-mussels-multiplying-in-lake-winnipeg-now-found-on-shorelines/. Accessed 17 Aug. 2022.