The Trent-Severn Waterway is an interconnected series of lakes, improved river channels and artificial canal cuts stretching for 386 km through the heart of Ontario. The water in the system comes from two major watersheds: Trent and Severn. The Trent River is the largest river in Southern Ontario while Lake Simcoe in the Severn watershed is the largest lake. The Waterway, including its tributary lakes and rivers, is an important economic, environmental and recreational resource used by thousands of boaters, shoreline residents, businesses and vacationers every year. It also provides water for power generation, municipal water supplies, and agriculture and supports a tremendous variety of fish and wildlife.
Water levels and flows throughout the Trent and Severn drainage basins are managed by Parks Canada an Agency of Environment Canada.
The Trent-Severn Waterway is divided into four administrative areas, with offices in Campbellford, Lakefield, Kirkfield and Haliburton. Waterway Headquarters is in Peterborough.
The Trent River basin encompasses some 218 lakes in the Haliburton Highlands region, 37 of which are directly controlled by Waterway dams. Water from these lakes flows south along either the Gull River, Burnt River, Nogies Creek, Mississauga River, Eels Creek or Jack Creek systems into the Kawartha Lakes. The Kawarthas drain down the Otonabee River into Rice Lake and on to Trenton on Lake Ontario via the Trent River. The Crowe River drains the eastern-most lakes in the Trent Watershed. Lake Scugog drains northward from the Oak Ridges Moraine to Sturgeon Lake.
The Trent River basin drains more than 12,000 km2 of Central Ontario. The neighbouring Severn River watershed drains an area just over 6,000 km2. Included in this watershed are the Canal Lake - Talbot River system, the Holland River, the Lake Simcoe - Couchiching basin, the Black River and the channels of the Severn River below the hamlet of Washago.
Because of the differing topography of these watersheds, they react differently to seasonal climatic variations. The fertile farmland of the Trent River and Lake Simcoe areas retains and releases water gradually following precipitation or a spring thaw. The shallow soils of the Canadian Shield which characterize the Haliburton Highlands and The Black River cannot absorb much water, resulting in more rapid runoff.
What is Water Management?
Water management on the Waterway is the regulation of water levels and flows to:
- permit safe boating
- lessen flooding of agricultural, residential and commercial property
- provide water for recreational activities
- protect fish and wildlife habitat
- help maintain water quality
- generate hydro-electric power
When establishing water flows and levels, Waterway staff must weigh the risks and requirements of these various uses to arrive at optimal levels. They must also take into account variables over which no control is possible such as topography and allow for variations in climatic conditions (rain, snowfall, temperature, etc.) based upon records of trends, extremes and averages. Daily readings from automatic water level recording stations and from streamflow and precipitation gauges are evaluated at Waterway headquarters to guide the engineers' decisions about dam settings, levels and flows. Directions are then communicated to operations staff in each of the four administrative areas who make the agreed changes at the dams.
During the Fall and Winter, the Haliburton and Kawartha Lakes are lowered by increasing their outflows. This drawdown prepares the lakes for the spring snowmelt and reduces the threat of high water and ice damage. Snow course sites throughout the Trent and Severn drainage areas are surveyed regularly beginning in January. Information about the depth and water content obtained from these surveys aids in forecasting the total volume and peak runoff for the upcoming spring freshet.
March, April and May are critical months for Waterway hydrologists as melting snow and rain fill waterway lakes. Attention focuses on the weather. Both heavy rainfall and prolonged warm temperatures will cause rivers and lakes to rise suddenly. The historical record shows this often results in more than one peak during spring freshet. Efforts to control this flooding are hampered by narrow channels, insufficient storage capacities in some lakes and the differing abilities of soils throughout the drainage basins to absorb water. While flood mitigation is a primary spring-time concern of waterway staff, care is also taken to ensure that water flows and levels are adequate to protect fish spawning sites and for use in the following summer.
During the summer, attention shifts to preserving water levels and flows. Navigable depths on the Waterway must be maintained while minimizing the requirement for water from the reservoir lakes. Although minimum flows are maintained to sustain water quality, the main cause of water loss is evaporation from the surface of lakes. The weather, particularly temperature, humidity and rainfall, determines the rate at which water from the reservoir lakes is needed.
While summer water management generally means conserving water supplies, unusually heavy rainfall at any time during the season can increase the risk of flooding. At these times, levels rise and flows are increased to move water out of the system. This may sometimes result in closures to navigation until flows and levels return within safe navigation limits.
The Haliburton Lakes Then and Now
Many of the earliest dams in the Haliburton Highlands were built by the lumber companies to prolong the spring runoff. Log drives were then done to float logs easily to their sawmills. Subsequent to the British North American Act, Orders in Council in 1905 and 1906 gave the Federal Government the necessary water rights and authority to construct a few new dams and reconstruct many others. These engineering works retained meltwater in the lakes providing water for the maintenance of navigation levels and the generation of electricity. Summer water quality improved and spring flooding was reduced. Water was drawn throughout the navigation season, beginning in the uppermost lakes and working down throughout the storage lakes as more water was needed later in the summer.
With the growth of cottage development in the Haliburton Highlands, a different procedure for drawing water was derived. Water is now drawn from each of the lakes on an equal percentage basis according to the storage range established for each lake. For example, when a lake with a relatively large storage range of 3.0m is drawn down 50%, its level will be at 1.5m, while a lake with 1.0m of usable storage will be lowered to 0.5m. Several times a week, staff read water levels at dams and make the necessary log changes ensuring that lowerings are proportional.
The Severn Basin
In the Severn River drainage basin, Lakes Simcoe and Couchiching are managed using a rule curve in effect since 1918. These very large lakes react more slowly to climatic conditions and stop-log changes at dams than other parts of the system. The rule curve serves as a target or guide for water levels throughout the year. Shoreline residents, farmers in the Holland Marsh, public utilities and boaters all have differing needs, which must be accommodated. Flows from these lakes must also be coordinated with flows on the Black River to reduce the threat of high water on the Severn River and Sparrow Lake.
Co-operation: The Key Ingredient
In 1978 the provincial and federal governments signed the Canada-Ontario Flood Damage Reduction Agreement. This agreement (which ended in about 1991) set aside funding for floodplain mapping, flood reduction and forecasting and warning systems. Some municipalities availed themselves of the programme and had these maps drawn for flood-prone areas to show the shoreline residents the level of hazard where they live. Anyone contemplating property in such areas could benefit from asking to see them.
The Trent-Severn Waterway works co-operatively with the Ontario Ministry of Natural Resources and the Federal Department of Fisheries and Oceans to protect fish spawning areas and other wildlife habitat and with conservation authorities to reduce flooding. Several Conservation Authorities operate dams on tributary portions of the watersheds. The Waterway also keeps in daily contact with Ontario Power Generation, other public utilities and private interests, which operate and maintain generating stations within the drainage basins.