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Progress Report on the Lake Winnipeg Basin Initiative 2012–13 and 2013–14

Threats to the Health of Lake Winnipeg

Satellite imagery shows green algal blooms in the north and south basins of Lake Winnipeg.

Lake Winnipeg is the tenth largest freshwater lake in the world and the sixth largest in Canada. Although Lake Winnipeg is located entirely within Manitoba, its vast (almost 1 million km2) basin is the second largest in Canada and encompasses parts of four provinces and four American states. The scale of the basin and the size of the lake make it a freshwater body of international significance.

The water quality in Lake Winnipeg has been deteriorating for several years. This has put the health of the lake at serious risk. The chief concern is an increasing amount of nutrients, such as phosphorus and nitrogen, which are a food source for algae in the lake. These nutrients originate mainly from agricultural runoff and municipal waste water and are carried into Lake Winnipeg by rivers and streams. Nutrient loading is made worse by the extended wet-cycle in the Red River basin, which has resulted in higher spring runoff and floods such as those experienced in 2009, 2011 and 2014. More than 50% of the nutrient loading to Lake Winnipeg originates from beyond Manitoba’s borders, and the Red River is the largest source.

The basin covers approximately one million square kilometres extending over four provinces (Alberta, Saskatchewan Manitoba and Ontario) and four states (Montana, North Dakota, South Dakota and Minnesota).

Approximately half of the phosphorus in Lake Winnipeg comes from the Red River, making it the largest source of phosphorus to the lake. On average, the Red River contributes approximately 7150 tonnes of phosphorus per year to Lake Winnipeg.

Lake Winnipeg’s suffering health is evident in satellite images taken over the past decade, which indicate an increasing trend in the frequency and size of algal blooms. Some of the algal blooms cover thousands of square kilometres of the lake and have been three times bigger than the province of Prince Edward Island. Algal blooms clog fishing nets, foul beaches and, under certain conditions, produce harmful toxins.

Map showing the area of the Lake Winnipeg Basin

More concerning, though, is that algal blooms are evidence that the lake is in an advanced state of eutrophication due to high concentrations of nutrients. Eutrophication means that healthy freshwater has become so over-enriched with nutrients that algal blooms and other decaying organisms may eventually deprive the lake of its oxygen. The situation is comparable in many respects to that of Lake Erie in the 1970s and again in recent years.

Map of the phosphorus load coming from the Red River

Image showing a boat docked at Hecla Village Harbour on Lake Winnipeg

Lake Winnipeg is also facing threats from several invasive fish and other aquatic species. These non-native species are thriving in the nutrient-rich waters of Lake Winnipeg and pose a threat to the native species in the lake. In 2013, zebra mussels were found in several harbours in Lake Winnipeg. Efforts to eradicate them in the infested harbours were successful, but undetected seed populations survived outsided the treated habours and will continue the infestation of the lake. The presence of zebra mussels in Lake Winnipeg has potentially severe negative implications for its ecosystem health. They affect how energy and nutrients move through the food chain, they aggressively compete with native species for food, and their biological processes often result in more algal blooms.

The ongoing eutrophication of Lake Winnipeg and the threat from invasive species have potentially serious repercussions. The lake plays a vital role in Manitoba’s economic prosperity and well-being by supporting an annual $50-million freshwater commercial fishery and a $110-million tourism industry. Without a reduction in nutrients, deterioration in the lake’s water quality will continue towards severe eutrophication with potentially irreversible negative impacts on the aquatic ecosystem and on the livelihood of those who depend on a healthy lake.

The problems and solutions to the challenges faced by Lake Winnipeg are interprovincial and international in scope. Any solutions for improving the health of the lake will require the coordinated efforts of multiple stakeholders. The Government of Manitoba and its neighbouring jurisdictions are already taking action and developing strategies to reduce nutrient loading to local waterways that drain into Lake Winnipeg. Since 2007, the Government of Canada has collaborated with other governments and stakeholders, conducted science and monitoring, and supported local stewardship action through the Lake Winnipeg Basin Initiative. This increased coordination of efforts across Lake Winnipeg’s vast basin will help governments to better synchronize action, share innovative solutions and pool research findings. Although progress has been made, continued collaboration is needed to improve the health of Lake Winnipeg and its basin.

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