Lake Winnipeg

Around the Lake Winnipeg Watershed

The vitality of Lake Winnipeg is in jeopardy. A central feature of our landscape, this body of water is an obvious point from which to begin a discussion of water issues in the province. Fondly dubbed our “prairie ocean”, the lake is home to a stunning variety of aquatic life, a source of water to the creatures that populate its shores, and is a major flyway for migrating birds.

A central feature of our landscape, this body of water is an obvious point from which to begin a discussion of water issues in the province. Fondly dubbed our ‘prairie ocean’, the lake is home to a stunning variety of aquatic life, a source of water to the creatures that populate its shores and is a major flyway for migrating birds. It is also a place rich in the history of the First Nations People and of the settlers who came later. Today it is held dear as a special place in the hearts of people as a spectacular holiday destination and natural retreat. Add to that its economic role in sustaining the largest freshwater commercial fishery in western Canada and its hydroelectric capacity, and it is easy to recognize its importance to life in Manitoba.

However, the vitality of Lake Winnipeg is in jeopardy. Scientists have alerted us to the fact that the health of this beautiful lake is seriously threatened. Indeed, its current state is comparable to that of Lake Erie in the 1970s. In a complex play of cause and effect these ills include: pollution, invasive species, loss of biodiversity, E.coli contamination, climate change, controlled water levels, erosion, and habitat destruction. And on top of all that there is an over riding threat: the lake is suffering from an overload of nutrients. Satellite images reveal massive blooms of algae covering vast stretches of the north basin and areas farther south. These sickly lime green patterns as seen from space are nothing short of alarming. Eutrophication, as this problem is known, is caused by human activities that result in an excess of phosphorus entering Lake Winnipeg. This phosphorus is generated from a multitude of sources, but comes primarily from municipal and industrial wastewater and intensive agricultural production throughout the watershed.

The Lake Winnipeg watershed (the area of land that drains into the lake) is vast. It covers nearly one million square kilometres, and reaches west to the Rockies, east almost to the Great Lakes and into four states south of the border. Within it are numerous sub-watersheds each draining an area of land into rivers that empty into the lake. What goes on in these smaller watersheds has a direct impact on Lake Winnipeg. Indeed, the consensus among government, academia and environmental groups is that the key to solving the issues facing Lake Winnipeg lies in the sustainable management of its watershed. In other words, the fate of the lake will be determined in the meadows, fields and forests well beyond its shores. With this holistic approach in mind let us take a closer look.

Basins The Lake Winnipeg Watershed is made up of six distinct river basins. Water flowing into Lake Winnipeg exits via the Nelson River, and eventually enters the ocean at Hudson Bay.

The Assiniboine River Basin

The Assiniboine River basin is approximately 42,000 km2 in size (excluding the Souris and Qu’Appelle river basins) and stretches from its headwaters in eastern Saskatchewan to the Red River at the Forks. Land use in the basin is dominated by agriculture. Manitoba’s potato industry, the second largest potato industry in Canada, is heavily reliant on the Assiniboine River during the summer months. In the late 1960’s the Shellmouth Dam was constructed on the river to provide downstream flood protection. The reservoir formed by the dam, called Lake of the Prairies, has also been an important supply of water for irrigation, industrial and municipal uses.

Ecological goods and services (EG&S) are benefits that arise from ecological functions of healthy ecosystems. Examples of ecological goods include clean air, clean and abundant fresh water and a diverse and healthy soil. Services include carbon sequestration, erosion control, purification of water and air, water retention and maintenance of biodiversity. In the Assiniboine River watershed, the Alternative Land Use Services (ALUS) is an EG&S pilot proposal designed by farmers for farmers. The project aims to conserve and restore Manitoba’s valuable natural capital on private lands, while respecting and rewarding the important role that farmers play in environmental management.

Incentives, in the form of a per acre financial payout are available to farmers who want to set aside land to protect wetlands, natural areas, ecologically sensitive lands and to increase the size of buffer zones along streams and rivers. Providing financial incentives are one approach to conserve and protect private environmental assets and can be carried out with existing programs of regulation, environmental farm planning, integrated watershed planning and tax rebates.

The Lake Manitoba Basin

Excess nutrient loading is a common problem in drainage basins with significant human populations, and the Lake Manitoba watershed is no exception. Livestock production around the lake and inadequate cottage sewage handling are two of the most important sources. A heightened phosphorous-to-nitrogen ratio in certain areas of the lake has lead to blooms of blue-green algae, which pose a variety of threats to the aquatic ecology. Not least among them is the production of microcystin, a toxin that was present in the lake at three times the recommended maximum level in 2001.

In addition to nutrient loading, the artificial control of its water levels is perhaps the most significant detriment to Lake Manitoba’s ecology. The lake’s marshlands, including the Delta and Netley-Libau marshes, have been given world-class designation. However, they are not as healthy as they used to be. The Fairford dam was constructed in the mid-1950s in response to lake-wide flooding. Artificial control of water levels over the last half-century has had an impact. Stable water levels can have a dramatic effect on marsh ecology.

Marshes require both floods and droughts to thrive. During droughts, seeds grow in exposed mudflats, replenishing and renewing the marsh vegetation. During floods, plants are drowned out of deep sites, preventing overgrowth. The control of water levels since the construction of the Fairford dam has interfered with these natural processes, diminishing the extent and quality of marshlands on the lake. Scientists have also observed declines in the commercial fish populations and the muskrat population since the construction of the dam.

The Lake Winnipeg Basin

In eastern Manitoba, Lake Winnipeg’s watershed encompasses Canadian Shield country that is characterized by dramatic rock outcroppings, magnificent boreal forests and spectacular waterways such as the Winnipeg River. The trees of the boreal forest anchor the soil and absorb rainwater. When these forests are impacted by logging or wildfire, water quality is affected. Once the trees are logged or burned less water is absorbed. It ends up filtering down through the soil, leaching nutrients into streams and rivers. Where soils are shallow and the land is steeply sloped, erosion occus. Both leaching and erosion have the effect of introducing dissolved organic matter and nutrients into the water. Phosphorus is one of these nutrients, and once it makes its way into the lake, it causes an increase in blue-green algae. Other effects of leaching and erosion can be increased turbidity or “muddiness”, lower oxygen levels and higher levels of harmful metals such as lead, cadmium and copper.

The Manitoba Model Forest (MMF) has been conducting research on water quality in this area for the past three years. One of their goals is to develop a forest management design that minimizes the negative impact that forestry has on Lake Winnipeg. Next year MMF will be initiating a project to look at the effects of logging on riparian areas from the perspective of water quality, wildlife and vegetation. While it is encouraging that MMF has made water quality and Lake Winnipeg a focus of its work, concerned citizens will be watching with the hope that this body of research leads to regulations on logging activity to promote healthy waterways and a healthy lake.

The Red River Basin

The Red River basin is a complex watershed characterized by a very flat valley surrounded by relatively steep escarpments to the east and west. This has resulted in numerous spring time flood events over 1000’s of years since the last ice age.

According to scientists at the Department of Fisheries and Oceans Canada, loadings of phosphorus from the Red River Basin have increased by over 50% in the last 10 years. The largest geographic source of phosphorus to Lake Winnipeg is the Red River basin. The largest anthropogenic source of phosphorus in the Red River basin is derived from the agricultural sector.

Since the early 1970’s, phosphorus concentrations have increased by 194% in the La Salle River and 188% in the Seine River, both tributaries of the Red River. Manitoba’s “hog alley” is situated mostly in the Seine River watershed, whereby saturated fields with manure can run-off into the surface water after heavy rainfall events and spring run-off.

South of the international border, the North Dakota government is proposing a project similar to the old Garrison Diversion. The Red River Valley Water Supply Project would divert water from the Missouri River across the continental divide into the Red River. This proposed inter-basin transfer of water has major implications for Manitoba’s fisheries through the possible introduction of invasive species that can alter the ecology of Lake Winnipeg.

The Saskatchewan River Basin

Canada has been blessed with relatively abundant supplies of fresh water. This can cause us to take our lakes and rivers for granted. David Schindler, renowned Canadian ecologist and educator, wants to issue a wakeup call. His studies of Canada’s lakes and rivers have lead him to some disturbing conclusions about the future of our waterways that have implications for the Saskatchewan River.

Dr. Schindler’s research indicates that the prairies face significant water supply issues. He points out that much of Canada’s ‘plumbing’ is located in the north where it is not accessible and that even the water supply we can tap into is dwindling. Climate change will alter precipitation patterns across the prairies, and may lead to regional droughts. Taken in historical perspective, the 20th century was very wet on the prairies. The rainfall levels over the last 100 years can be considered a climatic aberration, and cannot be expected to continue into the future. Furthermore, global warming is causing the ancient glaciers to shrink at an alarming pace. The Saskatchewan Glacier, which is the source of the headwaters of the North Saskatchewan River, receded an astounding 1.5 kilometres between 1924 and 2002. Decreased flows have already been observed in many rivers. Across the land large human withdrawals are further taxing the supply of fresh water.

What are the potential impacts on Lake Winnipeg? Decreased water quantity will affect water quality because it will result in a higher concentration of nutrients. ‘Most people worry about doubling the input of nutrients because it will cause more algal blooms, but if you halve the volume of flow it has the same effect.’ (Climate and Water Issues in the Athabasca River Basin: Presented by David Schindler) Knowing that the Saskatchewan River contributes a significant amount of the lake’s total inflow (about 20%) and knowing that nutrient overloading is a serious threat to Lake Winnipeg, this is an issue we cannot afford to ignore. Water conservation combined with a reduction in greenhouse gas emissions must become priorities.

The Winnipeg River Basin

The Winnipeg River drainage basin is the most significant of Lake Winnipeg’s sub-basins, contributing 45% of total inflow, 25% of nitrogen loading, and 12% of phosphorous loading. In turn, the Lake of the Woods sub-basin, straddling the border between Ontario and Minnesota, is the most important of the Winnipeg River’s drainage areas, contributing half of its flow.

The Minnesota Pollution Control Agency (MPCA) recently completed a multi-year assessment of the nutrient and algae conditions on the Lake of the Woods. The results of the assessment may lead to the MPCA adding the lake to its draft list of “impaired” waters. Similarly, on the Canadian side of the border, the occurrence of algal blooms on the lake has lead the Lake of the Woods Water Sustainability Foundation to initiate a nutrient budget study of the lake.

In addition to agricultural runoff, cottage development is among the suspected sources of Lake of the Woods’ nutrient loading. One of the adverse impacts of nutrient loading is the production of toxic microcystin by the blue-green algae present in the lake in elevated numbers. Last summer it was found that microcystin was present in the lake at levels that posed a high risk for recreational use.

Mercury contamination is also a concern on Lake of the Woods. The heavy metal naturally occurs in the bedrock beneath the lake. However, the Minnesota Pollution Control Agency reports that most mercury entering lakes in the region comes from the atmosphere, as air-borne emissions from coal-fired power plants, mining sites, and manufacturing facilities. In light of the elevated levels of mercury found in fish in Lake of the Woods, The Guide to Eating Ontario Sport Fish recommends limits on the size and number of fish consumed for a number of species. More stringent limits are recommended for children and women of childbearing age.