One challenge faced by Manitoba Hydro is that water flows are greatest in spring and summer while demand for electricity is greatest in winter. Seasonal water flows do not match seasonal energy demand. This dilemma is compounded by the lack of a means to store large amounts of electricity.

Lake Winnipeg Regulation (LWR) aimed to address this by reversing the seasonal flows in the Nelson River system.¹ By means of the Jenpeg Dam, Hydro planned to hold water back in Lake Winnipeg during spring and summer, to be released down the Nelson River in winter (see maps). In this way, Lake Winnipeg–the 11th largest freshwater lake in the world²–could function as a gigantic battery for Manitoba, with Jenpeg as the on-off switch.

Southern Indian Lake, Cedar Lake, and other smaller lakes serve as storage reservoirs in a similar fashion.

Manitoba Hydro’s 1970s booklet, Power from Nelson, describes how the company intended to use LWR.

Change
Recently, Manitoba Hydro has indicated (in direct communication with our Task Force) that, in fact, it has not needed to significantly alter seasonal flows from Lake Winnipeg into the Nelson River system. Instead, the utility has used summer flows to sell power to the U.S.–where peak demand is in summer–and then buy power back in winter (at lower rates) as required. According to the company, average seasonal levels of Lake Winnipeg have not changed significantly, as per information on Hydro’s website.

35-year Interim Licence
For almost 35 years, Lake Winnipeg Regulation has operated under an interim Water Power Act licence. On December 22, 2010, Manitoba Hydro requested a final licence for LWR.³

For more detailed information about Lake Winnipeg Regulation see Manitoba Hydro’s own description of the project here.

Notes

1. The following description of Lake Winnipeg Regulation appeared at <http://www.hydro.mb.ca/corporate/water_regimes/lake_wpg_regulation.shtml&gt; as of January 14, 2011:“Regulation is necessary because the natural flow pattern from Lake Winnipeg into the Nelson River is opposite to the energy needs of the province. Manitobans use more electricity in winter than in summer, while the water flow into the Nelson River from Lake Winnipeg in its natural state is less in the winter and more in the summer. In addition, the flow out of the lake depends upon the water level and during the winter upon the degree of obstruction by ice of the Nelson River channels. It was, therefore, necessary to be able to decrease the water outflow from Lake Winnipeg in the spring and early summer in order to make available more outflow in the fall and winter. The Lake Winnipeg Regulation project guarantees winter outflows to ensure that the winter demand for electricity can be met.”Manitoba Hydro’s 1970s booklet, Power From the Nelson, similarly describes the intent of LWR.
2. Source: Manitoba Hydro webpage on LWR.
3. Source: Letter from Manitoba Hydro to Manitoba Water Stewardship, December 22, 2010. See more about Lake Winnipeg Regulation licensing on the Manitoba Water Stewardship licensing websection.
4. Source: “The response of Lake Winnipeg to the cumulative impacts of  nutrient enrichment, lake regulation, exotic species, and climate change,” a presentation by A. Salki, M. Stainton, W. Franzin, G. McCullough, and H. Kling to the 30th Congress of the International Association for Theoretical and Applied Limnology, Montreal, Canada, 2007, as referenced on the Climate Change Connection website, note 13 (accessed January 2011).
5. Source: “Restoring the Health of Lake Winnipeg: Technical Annex – Report of Lake Winnipeg Implementation Committee,” Terry Duguid and N. Brandson, 2005, page 4.