Ottawa RiverRegulationPlanning BoardCommission de planificationde la régularisationde la rivière des Outaouais

The Ottawa River Basin

In early years, the Ottawa River was used mainly for navigational purposes. It was the route of explorers and fur traders’ to the interior of the continent and a part of the inland route between Montreal and Kingston. Later, it carried great rafts of logs to mills for processing.

The first reservoirs on the river were built to aid navigation, augment low flows during dry years and provide some flood control. Later, more reservoirs were established with hydroelectric energy production their primary purpose.

With the rapid urbanization in the 20th century and changes in needs of the basin’s population, there has been a change in the use of the river. Today’s greatest needs are for hydroelectric energy generation, domestic water supply and effluent dilution (wastewater) and recreational boating. Environmental protection has also become a major cause for concern.

Fortunately, many uses of the waters are compatible. Storage of waters in reservoirs operated primarily for the benefit of power generation, can reduce flood flows, similarly, release of these waters during drought periods augments flows.

Characteristics of the Basin

From its source east of the Dozois Reservoir to its confluence with the St Lawrence River, the Ottawa River has a length of more than 1,130 kilometres. For most of its length, it forms the boundary between the provinces of Ontario and Quebec. Its basin has a total area of 146,300 square kilometres, 65 per cent of which is in Quebec and 35 per cent in Ontario.

Principal Reservoirs in the Ottawa River Basin

(having more than 200 million cubic metres live storage)

The Ottawa River Basin

Outaouais Dozois (1) 1,863
Rapid VII (2) 371
Quinze (3) 1,308
Timiskaming (4) 1,217
des Joachims (5) 229
Montreal Lady Evelyn (6) 308
Kipawa Kipawa (7) 673
Madawaska Bark Lake (8) 374
Gatineau Cabonga (9) 1,565
Baskatong (10) 3,049
Lievre Mitchinamecus (11) 554
Kiamika (12) 379
Poisson Blanc (13) 625

The Ottawa River Basin

The ottawa river basin

The Flood Problem

Because of the basin’s size, shape and topography, highly varied meteorological conditions result in equally varied responses in water levels from some tributaries. Different times of response of the main tributaries generally combine to produce two distinct flood peaks, about three weeks apart.

The first flood peak in the Ottawa River originates from unregulated flows from its southern tributaries. The second peak results from a combination of high flows from the tributaries of the north shore together with flows from headwater areas, and is partially regulated. While the first peak is generally the lesser of the two, it can cause considerable flood damage since ice is still in the river and ice jams can occur.

A continuous monitoring of hydrometeorological conditions in the basin helps to forecast the occurrence of floods and droughts, but the current state of meteorological scientific and technical knowledge still leaves a substantial degree of uncertainty.

Costs associated with flooding are not only monetary but also have a human element as families are uprooted from their homes and transported to temporary quarters until floodwaters that have enveloped their homes subside.

There are no simple solutions to the flood problems of the Ottawa River basin. For example, the southern portion of the basin is unregulated and reservoir storage has a limited effect on the first flood peak, which occurs about mid-April. The second peak, about three weeks later, is strongly influenced by reservoir operations.

Normal operations at the principal reservoirs can ensure that a significant portion of the spring runoff is stored. This can substantially reduce the magnitude of the second peak.