Spring is setting in. Like every year, 400 kilometers northwest of Trois-Rivières, a Hydro-Québec employee manually opens the last valve of the old Gouin dam. The Saint-Maurice River is ready to receive water from the melting snow of a territory equivalent to Switzerland.

Between this work built in 1917 and the St. Lawrence River, a drop of water will take five days to cross the turbulent waters of the Saint-Maurice and will turn the turbines of 11 hydroelectric power stations.

Halfway through this nautical course, in La Tuque, the heat of the sun takes effect. The children straddle their bikes, the falls of the small Bostonnais river break their grip of ice and the lapping of the water is heard in the gutters, while the snow slowly disappears from the roofs.

“This noise is a sign that the melting is starting,” notes, amused, Rémi Robbe, water management engineer at Hydro-Québec. It is he who for more than a decade has been playing the balancing act there. It plans to close the gates and spillways of the Saint-Maurice dams to prevent flooding, maintain recreational use for residents during the summer and maximize the state-owned company’s electricity production.

Historically, the cycle was quite simple. HQ fills its reservoirs in the fall, turbines the water during the winter to heat our homes and empties them when spring arrives to fill them again during the spring flood. It can thus reduce the flow of rivers and control floods as much as possible.

Extreme events have always existed, but the climate is increasingly uncertain. Mr. Robbe can testify to that. In 2021, the Saint-Maurice experienced its weakest spring flood since reliable data on its flow were recorded in 1950. And in 2022, the third in importance. “What I want is good weather, not too hot, and without prolonged periods of rain,” he explains.

In La Tuque, we make the same observation. The city has had a taste of it in recent years. In 2017, the seventh largest flood since the data was compiled, Route 155, the umbilical cord that connects the industrial city to the south, was flooded. It is a shock, a “pivotal moment”. “It never happened,” said the mayor, Luc Trudel.

Hydro-Québec has adjusted: since then, it has been sharing water flow data with the city, which can thus see the rising waters coming. But that doesn’t solve everything.

In 2022, new floods occur. It’s the perfect storm: a historic rain is falling on the entire Saint-Maurice watershed, in the middle of a thaw. This time, a section of Route 155 is still under water and the 350 residents of the village of Parent, located 215 km from downtown La Tuque, in the middle of the woods, are completely cut off from the world because that the three forest roads that connect this sector are flooded. An airlift must be put in place urgently.

“We’re talking about a 100-year rain and it happens twice in 10 years. Hello ! You have to realize that it’s going to be a lot more frequent,” said City Manager Pierre Pacarar.

The City is asking for more funds from the Government of Quebec to repair the damage following an extreme weather event, but also to prepare for floods and forest fires. Meanwhile, La Tuque “hasn’t had a penny yet” of the $2 million it is claiming from the Quebec government for the 2022 floods.

In 2022, municipalities asked the Quebec government to put in place a “green pact” of 2 billion per year for 10 years to help them adapt to climate change. For the moment, the Legault government has not agreed to this request.

And the situation is likely to get worse with global warming. What seems certain: there will be more heavy precipitation, since the warmer air can store more water. “I did a literature review recently on the expected impacts on precipitation extremes. Out of 60 scientific articles, all said that the extremes of precipitation would increase,” explains Jean-Luc Martel, professor at the École de technologie supérieure and specialist in hydrological modeling.

During the summer, these heavy and sudden rains will be interspersed with more frequent low water levels caused by droughts. For cities, it’s dramatic: heavy rain in urban areas can cause flooding, as we saw in Longueuil and Montreal in September 2022.

But here, what matters is the melting snow. And it is more risky to predict the impact of climate change on spring floods. In southern Quebec, more frequent mild spells are expected during the winter which will deflate the flood, the main factor of which is the thickness of the snow cover in the spring.

But north of the St. Lawrence, in La Tuque, Saguenay–Lac-Saint-Jean, Abitibi or on the North Shore, the shorter winter could still be snowier.

The work of a dam manager, like Hydro-Québec, in this context, is all the more risky.

The state corporation knows it. In fact, in November 2022, it published its Climate Change Adaptation Plan. Hydro-Quebec has a lot on its plate, it must review, according to the renovations of the infrastructures, their “level of resilience” in the face of climate change.

“Taking climate change into account may require a review of the portfolio of investment projects over a 20-year or even 50-year horizon,” the report says.

This is already underway on the Saint-Maurice, where some structures are among the oldest in the network. Most of them were built before the nationalization of electricity.

The Gouin dam was built in the middle of the First World War and the reservoir of the same name was then the largest in the world. His erection is both a technical feat and a drama. The flooding of the territory had drowned the Opitciwan reserve and several Aboriginal people died after drinking water, which had become undrinkable after the flood, due to the carcasses of drowned animals that were there.

The safety of dams is not in question: “even in a context of climate change, their role is to manage extremes,” says Jean-Philippe Martin, sustainable development advisor at Hydro-Québec.

But now, Hydro-Quebec, when it begins a major refurbishment project, does analyzes “to ensure that this project is adapted to the future climate”.

Investments in Hydro-Québec infrastructure have reached $3.7 billion on average over the past five years. They will rise to 5 billion over the next five years.

When La Presse arrived at the Rapide-Blanc site – a power plant commissioned in 1934 when Louis-Alexandre Taschereau was Premier of Quebec – workers were cutting out a giant gate, the water intake valve, intended discarded. Its weight of 30 tons made it too big to be moved.

Meanwhile, workers were diving into a watertight shaft glued to the outer surface of the dam, allowing them access to the river bed, 80 feet under water, to repair foundations, concrete and prepare for changing turbines. . The work of more than 610 million aims to change the six turbine-alternator groups. “The new turbines should have the same lifespan as the old ones [90 years],” says Carl Morin, project manager for the refurbishment of the Rapide-Blanc generating station, who shows us around the facilities. It must therefore be adapted to the climate of 2100.

The state-owned company also assesses the capacity of the structure’s spillway, used when the water supply in the Saint-Maurice is too great. Studies are in progress.

After Rapide-Blanc, another nearby power station, La Trenche, will be renovated. HQ is planning the refurbishment of the six turbine-generator groups with an increase in installed power of 48 MW, as well as an increase in the evacuation capacity for the passage of a probable maximum flood taking into account the impact of climate change. .

This is not the only risk that Hydro-Québec must be wary of. Specialists predict more wind, and more waves on large reservoirs. Erosion will affect the dikes and embankments that contain the water, and this is without taking into account the increasingly rapid freeze-thaw cycles that will damage the concrete of the infrastructures. “That means more repair work,” notes Jean-Philippe Martin.

According to Ouranos, by 2050, the increase in average annual flows will be around 12% in Nord-du-Québec and around 5% in the southern portion. “However, not all of this water will necessarily be turbinable, it will all depend on where and at what time of the year this precipitation will materialize,” said Francis Labbé, spokesperson for Hydro-Québec.

It’s not just Hydro-Québec that manages dams. The Ministry of the Environment has hundreds under its responsibility, and the Legault government will commission a study to find out the impact of climate change on the safety of these structures.

“For us to have their light, to have their insight into what the impact of climate change on security might be, or the scope or the need for dams, is information that will be useful to us,” said the Minister of Environment and the Fight against Climate Change, Benoit Charette, in an interview with La Presse.

This report will allow the Ministry to “adapt its practices” and aims to “combine predictability and safety of dams”. Mr. Charette will give this mandate, still in preparation, to the Ouranos consortium, to better understand the impact of the coming climate on these structures that dot the cities and villages of Quebec.

The Minister is well aware of the risks posed by water. He was marked by the floods of 2017 and 2019, which ravaged his riding of Deux-Montagnes, in the northern crown of Montreal.

The minister points out that the Legault government’s thinking on the impact of climate change on flooding goes much further than “simple dam safety”. “A safe dam in good condition, at times, if the water pressure is too high, you have to open the valves and you have to think where this water will end up,” he explains.

He remembers the episode of the Chute-Bell dam, in Grenville-sur-la-Rouge, in the lower Laurentians. “The pressure was so strong that we feared for a time that the dam literally gave way. We had to open the floodgates, and yes, that had an impact on the floods. »

Mr. Charette believes that in southern Quebec, the issue of dams is inseparable from the reflection on land use planning made necessary by the floods of 2017 and 2019. At this time, a “transitional regime” is in place . It restricts, in riverside municipalities, the territories where it is possible to authorize the construction of buildings. We want to avoid having to compensate people who are flooded repeatedly.

“In the future, the frequency is going to be higher. In Deux-Montagnes, in 2017, in all transparency, I was not Minister of the Environment and I did not have the knowledge that I have today. I had a third of the city completely flooded. And I was told, ‘Benoit, we won’t see this again in our lifetime. It’s exceptional,” he said.

At the same time, Mr. Charette affirms that he has strengthened the Dam Safety Act, with the adoption of Bill 102 in 2022. He thus responded to criticisms formulated in… 2015 by the Commissioner for Sustainable Development.

The law gave the power to municipalities to carry out work on private dams whose owners “do not feel the obligation to do minimum maintenance”, explains the minister. They can then pass the bill on to him.

Then the Ministry cleaned up the real importance of the dams under its control by quantifying it. “A small dam can be of real importance [for example if there are cottages downstream]. We came to qualify that,” he explains. Some dams may also be of importance to municipalities, as they give increased land value to residences or hotel complexes. Without dams, lakes would disappear, he explained.

In 2015, the Commissioner for Sustainable Development, Jean Cinq-Mars, filed a report very critical of the Ministry, which was failing to ensure the maintenance of the dams. The report pointed out that almost 20% of dams did not have emergency measures plans, or that they were not in compliance. The bill has “added regulations so that dams have a compliant plan before December 31, 2023,” said Minister Charette’s office.

The Ministry of Environment has 918 dams under its responsibility.

Hydro-Québec operates more than 550 dykes and dams. This is without counting the dams owned by companies, municipalities and private individuals.

The directory of dams in Quebec lists 8089 “dams” in total. Some are only very small dikes, others, like the Hydro-Québec structures, are gigantic, and they are not all subject to the Dam Safety Act.