History of Regulation – Lake Winnipeg
The history of settlement around Lake Winnipeg shows high lake levels and overland flooding were recurring problems, prompting ongoing calls for government action.
- The Lakes Winnipeg and Manitoba Board concluded that regulation of Lake Winnipeg for flood and recreation benefits was not practical as the costs would be too high for the benefits received; however, regulation of Lake Winnipeg for Nelson River power development could become economical within a few decades.
- Canada and Manitoba enter into the first of a series of cost-sharing agreements to investigate the feasibility of hydroelectric development on the Nelson River, including works to regulate and control the levels of water of Lake Winnipeg and the outflow to the Nelson River.
- Canada and Manitoba agree to jointly undertake the development of the hydroelectric potential of the Nelson River. The federal government's role was to finance the direct current transmission line facilities to bring the power from northern to southern Manitoba.
- Premier Schreyer announces plans to proceed with development of Lake Winnipeg for flood control and the regulation of Lake Winnipeg for power purposes.
- Manitoba Hydro is granted an interim licence under the Manitoba Water Power Act to regulate Lake Winnipeg outflow. The project begins with the construction of 3 channels.
- Construction of Jenpeg Generating Station begins.
- Construction is completed.
The Lake Winnipeg Regulation project included construction of:
- diversion channels built to substantially increase the winter outflow potential of the lake;
- Jenpeg Generating Station and Control Structure;
- a dam at the outlet of Kiskitto Lake to prevent water from backing up into that lake.
The Diversion Channels
To bypass natural constrictions in the Nelson River, 3 diversion channels were required:
- 2-Mile Channel: Helps to "unplug" Lake Winnipeg by augmenting the natural outlet at Warren Landing. The channel cuts across the narrowest point of land between the north end of Lake Winnipeg and Playgreen Lake, about 10 km northwest of Warren Landing. The bottom width of the channel averages 112 m.
- 8-Mile Channel: Connects Playgreen Lake with the southernmost end of Kiskittogisu Lake, just north of the 54th parallel. The channel increases the flow of water from Playgreen Lake. The bottom width of the channel ranges from 130 m to 300 m.
- Ominawin Bypass Channel: Built to avoid natural constrictions in the Ominawin Channel, which is the most northerly outlet of Kiskittogisu Lake to the west channel of the Nelson River. The excavation is 2,300 m long with a centre rock groin dividing it into 2 channels, each with a bottom width of 172 m.
Each channel has a depth of approximately 7.6 metres (m). The amount of material excavated for the 3 channels totalled over 37 million cubic metres.
Jenpeg Generating Station
Jenpeg Generating Station and Control Structure is located on the Upper Nelson River at the point where the west channel of the Nelson River flows into Cross Lake.
- Primary purpose: To regulate the water outflow from Lake Winnipeg into the Nelson River.
- Secondary purpose: To take advantage of a 7.3-m operating head (waterfall) at the site to produce electricity.
Its powerhouse and spillway control the outflow from Lake Winnipeg. It has a capacity of 135 megawatts.
The Kiskitto Dam
With the construction of the diversion channels and Jenpeg, water levels increased along the Nelson River upstream. The dam prevents water from backing up into Kiskitto Lake.
The Kiskitto Dam is 600 m long, with a maximum height of 15 m. Kiskitto lake is regulated within its natural range, and water levels are controlled to provide maximum benefit for fish, wildlife, and recreational activities.
A total of 16 separate dykes with a length of 14 km protect the lake from the higher levels of the Nelson River's west channel.
A gated culvert was installed to supply water from the Nelson River's west channel, while a small channel and control structure were built to keep the lake from exceeding normal levels during periods of high precipitation.
The Cross Lake Weir
Lake Winnipeg Regulation reversed the historic pattern of water levels and fluctuations at Cross Lake. With regulation, the lake level tends to drop in the spring and rise in the fall, instead of the reverse under natural conditions. Also, the range of water levels on Cross Lake is greater than before regulation.
Manitoba Hydro and the community worked together over a number of years to find a way to restore as far as possible the former environment. In 1990, agreement was reached on the mitigation measures to be taken to raise the minimum water levels on Cross Lake. The measures included the construction of a $9.5-million rock weir and a channel excavation project at the outlet of Cross Lake. The construction of the Cross Lake Weir took place in 1991.
The weir gradually raised the minimum water level on Cross Lake by nearly 1.4 m. The weir was constructed to also flow more water out of Cross Lake during flooding. As a result, season to season, fluctuations are more moderate and gradual than in the past. The effectiveness of the Cross Lake Weir continues to be monitored.