Lake Winnipeg faces four types of often-interrelated problems:
The first is a chemical problem in that we have been adding more chemicals to the lake than it can get rid of through its outflow down the Nelson River to Hudson Bay. For example, one of the most troublesome of these chemicals is the element, phosphorus.
Algae need phosphorus to survive and grow (just like we do). About 8,000 tonnes of phosphorus enter the lake each year but only about 2500 tonnes flow out. The rest accumulates in the lake. Algae need other elements too, especially nitrogen and carbon and small amounts of several others like sulfur and iron. Algal nutrients are not the only chemical problems. Back in 1970 the commercial fishery was closed for a season because levels of mercury in the fish were found to exceed guidelines set to protect human consumers. This was probably a natural occurrence and the levels are lower now but the reasons for this are not clear.
Many other chemicals like pesticides, PCBs, heavy metals, hydrocarbons and radioisotopes from the testing of nuclear bombs have been detected in the lake but levels have been low and the fishery was not affected. Recently industrial chemicals like synthetic fire retardants added to many household products have turned up in the lake but again levels have been low; ongoing surveillance will be needed to keep them low. Interest is growing in a number of household personal care products and medicines but data remain very limited.
The ongoing addition of growing quantities of phosphorus from sources like sewage, fertilizers and erosion of soils containing it has resulted in the second problem, namely blooms of algae. Lake Winnipeg has probably always had algal blooms even back before we began to add chemicals to the lake. However, satellite images have show that blooms have been occurring more and that they cover greater areas of the lake.
The algae that form blooms are typically blue-green algae, a specialized type of bacteria that can use sunlight to drive the photosynthesis like land plants. One of the unusual things about blue-green algae is that they can obtain the nitrogen they need from nitrogen in the air. Other kinds of algae need their nitrogen supplied in the water. Consequently, it is difficult to control these algae by reducing the nitrogen supply to them. They just make their own nitrogen compounds. Blue-green algae can also produce protein-like substances that are very toxic to vertebrates including ourselves. When algae die and sink down to the bottom of the lake, their decomposition consumes oxygen in the water and may cause it to fall so low that other organisms suffocate.
Algae are not the only biological problems facing the lake. We have the invasion of lake by species not native to it, most spectacularly by the rainbow smelt, and the loss or potential loss of native species. A major fear is the potential invasion by zebra mussels with effects like those found in the lower Great Lakes.
The lake has been affected by a number of physical changes. The most frequently mentioned of these is the control of water flows by Manitoba Hydro. In effect, Lake Winnipeg is a giant hydroelectric reservoir and as such it produces hundreds of millions of dollars in electrical power. The byproduct of this is a change in the seasonal flow characteristics leading to questions of biological implications and questions of shoreline stability to erosion.
A smaller scale example of changes to flow patterns is represented by the Hecla causeway. Perhaps the most pervasive physical change underway is warming due to planetary climate change and the implications that has for water dynamics and biological processes. Over the past years, flows in the Winnipeg and Red Rivers have been increasing while that in the Saskatchewan has been decreasing.
With the growth of agriculture throughout much of the lake’s million-sq-km catchment basin, we have seen widespread efforts to drain farmland rapidly in the spring so that the land can be worked as early as possible. This drainage facilitates the rapid transport of water and anything it carries from agricultural fields to local waterways and ultimately to the lake.
The lake is situated in a difficult spot politically. The lake itself is in Manitoba but the drainage basin that controls it extends to about a million square km. In addition to much of Manitoba, its catchment extends to Alberta, Saskatchewan and Montana in the west, North Dakota, Minnesota and even a little bit of South Dakota in the south, and Ontario almost to Thunder Bay in the East.
With parts of its drainage in both Canada and United States, the two national governments also have interests and responsibilities. That adds up to two national governments, seven state or provincial governments and many more local and First Nations governments. Obviously reaching anything like consensus on issues facing the lake will be difficult, especially when costs occur in one jurisdiction and benefits in another.
Many diverse public and private agencies have interests in the lake. Our web site will help you locate many of them and their web sites will lead you to even more.
In spite of all the problems facing the lake, it remains a beautiful place to be. We hope to help restore it in those areas where it has deteriorated and to keep it healthy for the future. Thank you for your interest in Lake Winnipeg