Mauricie
Every year, we work hard to limit the impacts of the spring runoff well before it begins
Important reminder
In the event of a flood, contact your municipality. They will advise the Ministère de la Sécurité publique du Québec, which coordinates all flood-related activities.
In the Mauricie region, Hydro-Québec is mainly present in the Rivière Saint-Maurice watershed, which includes Gouin reservoir and its main tributaries, the Manouane, Matawin and Mékinac rivers. To operate our facilities, which are set up in sequence along the river, we have to take many constraints into account. A decision made for the north will impact areas further south and vice versa.
The Rivière Saint-Maurice watershed covers an area of 42,651 km2—about the size of Switzerland—and receives inflows from 100 tributaries and 36,000 lakes. In addition to Gouin reservoir, the watershed is home to several Hydro-Québec facilities, including Matawin dam, Mékinac dam, and the three Manouane dams (A, B and C). These structures regulate 40% of the natural inflows in the Saint-Maurice watershed. The remaining 60% flow directly into the river without being held back.
Hydro-Québec’s presence in Mauricie:
- 11 generating stations in 9 locations
- 4 reservoirs created by the Gouin, Manouane, Matawin and Mékinac dams
- 1 buffer area consisting of Blanc reservoir
- 1 river stretching some 400 km, from downstream of Gouin dam to the Fleuve Saint‑Laurent
- 1 watershed covering over 42,500 km2, or the size of Switzerland
Run-of-river generating stations do not have reservoirs and cannot retain water
Our 11 hydroelectric facilities on the Saint-Maurice—Chute-Allard, Rapides-des-Cœurs, Rapide-Blanc, Trenche, Beaumont, La Tuque, Grand-Mère, Rocher-de-Grand-Mère, Shawinigan-2, Shawinigan-3 and La Gabelle—consist of run-of-river generating stations. These types of stations are powered directly by the river’s flow and have virtually no storage capacity, except for Rapide-Blanc. In the latter facility, the generating station has a small amount of upstream storage (sometimes known as pondage), which acts as a buffer between upstream and downstream during spring flooding or when we expect heavy rain that could cause flooding in the most at-risk downstream areas. However, the volume of this storage is limited and it can only hold back water for a short period.
We store water in our reservoirs to reduce spring flooding
Every winter, Hydro-Québec draws down the level in its reservoirs in the Mauricie region to make room for spring runoff. Our reservoirs are then able to accommodate the water expected from snowmelt and rainfall. However, the duration, start date and extent of the drawdown varies from year to year depending on weather conditions.
During spring flood season, we manage the regulatable sub-watersheds judiciously to reduce the magnitude of the flood downstream. We proceed with caution, as some of our reservoirs can fill up very quickly, which can then lead to consequences downstream. The management of our facilities depends on the water levels expected. Our top priority is always public safety and the safety of our infrastructure.
Watch our expert explain how Hydro-Québec manages spring flooding along the Saint‑Maurice river.
We have access to various storage capacities:
- Multi-year reservoirs are very large reservoirs that regulate inflows over a period greater than one year. Their storage capacity is measured in weeks.
Gouin reservoir belongs to this category. Every spring, the gates of Gouin dam are the first to be closed by Hydro-Québec. At the peak of spring runoff, the flow discharged from the reservoir is as low as possible.Gouin reservoir acts as a headwater lake. One of its roles is to store excess water, which it will later release when the natural flow in the river becomes too low for the downstream generating stations to operate. For example, before Gouin dam was built, the flows in the Saint-Maurice varied between 170 m3/s during low-flow periods, and 5,700 m3/s during flood periods. Today, the flows are more evenly spread out throughout the year and are used to meet energy needs. - Annual reservoirs are emptied every year. Their storage capacity is limited to a few days, depending on water inflows.
In Mauricie, the reservoirs created by the Matawin, Mékinac and Manouane dams belong to this category. Aside from flood-management considerations, the operation of these reservoirs takes into account the effect of river levels and flows on riparian environments, as well as downstream water flow needs. These reservoirs also help reduce spring flooding. - The storage available upstream of some run-of-river generating stations is very limited—a few hours at most—and cannot be used to reduce spring runoff. The forebay of Rocher-de-Grand-Mère generating station is a good example of this type of storage.
Gouin dam (May 4, 2017). The water that flows from upstream to downstream runs through the mini-turbines that supply electricity to the dam's auxiliary systems and to nearby customers.
Trenche development (May 4, 2017). The spillways discharge excess water inflows that cannot be fed to the turbines. Spillways ensure the safety of both the public and the facility; without them, the water would spill over the facility and threaten its stability.
Mékinac dam and its watershed: A sub-watershed in the Saint-Maurice region that requires special attention
Mékinac dam is located at the southern tip of Mékinac reservoir/lake (Lac Mékinac), at the source of the Rivière Mékinac. Lac Mékinac is 16-km long and covers an area of 23 km2, while its watershed covers 880 km2. All the natural inflows in this watershed supply the Rivière Mékinac downstream of the dam. Lac Mékinac has little storage capacity for the size of its watershed. It requires close monitoring and frequent adjustments due to the high variation in its water inflows from rain, storm cells and snowmelt.
Lac Mékinac is an annual reservoir; it is filled by the water in its watershed and emptied over a one-year cycle. The water level in the lake is maintained by the dam’s stoplogs. These stoplogs can be added or removed manually to increase or decrease the flow discharged, which in turn changes the reservoir’s water level. The water that flows over the stoplogs spills into the Rivière Mékinac, where it helps sustain aquatic plants and wildlife.
The operating range of Lac Mékinac depends on the design criteria of the dam, which determine the maximum threshold that needs to be respected to ensure the safety of the dam and the public. The management of Mékinac dam is based on the water inflows anticipated. For example, if significant rainfall is expected in the coming days and the reservoir is already quite full, Hydro-Québec will need to release some of the stored water to accommodate the expected inflows. The safety of the public and our facilities is one of our core concerns and guides our every decision.
To learn more about the Saint-Maurice watershed, visit the website of the Bassin versant Saint-Maurice
organization (site in French only).
Diaporama
Le contenu qui suit est un diaporama d’images sur : Les normes
A tool that identifies flows and water levels
We are installing measuring instruments on rivers and reservoirs where we operate dams and generating stations. They provide flow, water level and meteorological data. This data is available to you through a simple tool, which can provide information about flows on rivers and water levels in reservoirs.
Learn more about the Tool
Questions on how Hydro‑Québec facilities are managed? Contact us at Affairesregionales@hydroquebec.com.