subhead

Water levels update, flooding this spring unlikely

With water levels along the Ottawa River deemed relatively normal for the time being, Mayor Maxime Pedneaud-Jobin said that, barring any dramatic shift, spring flooding shouldn’t be a significant issue this year.

Announced during Gatineau’s Executive committee meeting on April 7, the Mayor explained that the Ottawa River Regulation Planning Board (ORRPB) conducts daily water level updates regarding the probabilities of spring flooding. He added that the general tendency along the length of the Ottawa River of late has been a constant reduction of water flow and levels. The Mayor added that a combination of recent warm weather during the day and cold weather in the evenings has also helped stabilize water levels and considerably reduced flood risks in riverside communities. “We don’t want to say that it’s impossible when there is still a small probability,” he added. “But there is very little snow left, and there’s no expected important precipitations in the coming days. So, it’s very positive.”

As another positive sign, the Mayor noted that the ORRPB ceased conducting daily flood level updates on April 9 since the level of alertness for spring flooding this year is considerably low compared to previous years. “It’s not completely over,” Pedneaud-Jobin said. “But for now, it’s going very well from the point of view of an eventual flood … we already have enough sources of concern. If one gets reduced, I think that’s good for everyone.” More information about Ottawa River water levels in Gatineau is available on the Gatineau website.

On March 31, Hydro Québec conducted a technical briefing on water flow and management of the Ottawa River watershed with an update on the probabilities of spring flooding in the Outaouais this year. While the situation can change very quickly between now and May, Hydro Québec hydraulic resource engineer Pierre-Marc Rondeau said that flood risks in the Outaouais this spring are very low – calling conditions typical. “We don’t see it as an issue,” Rondeau said, stating that around 50 per cent of snow along the river has melted so far. With two-thirds of it located in Québec and the other third in Ontario, he explained that the Ottawa River watershed stretches all the way from Abitibi-Temiscamingue to the Montreal metropolitan region. “The river has one of the largest complexities of any in all of Québec,” Rondeau said.

Measured at around 1,100 kilometres long, Rondeau said a drop of water can take around three weeks to flow from one end of the river to the other. The river includes multiple hydraulic dams and reservoirs, managed by either Hydro Québec, Ontario Power Generation, the Québec government or the federal government, Rondeau said. “There are four main dam operators,” Rondeau said, stating that they play important roles in helping mitigate flood risks in the region and producing electricity. He added that a number of rivers are known to spill into the Ottawa River, including the Gatineau River where Hydro Québec operates two reservoirs – Baskatong and Cabonga – which also contributes to water levels fluctuating.

Emphasizing that dams are important tools to reduce the impact of spring flooding by adjusting water levels of certain reservoirs, Rondeau noted that they don’t have the power to completely eliminate them. “When it goes well, it’s nature’s doing,” Rondeau said. “But when it goes wrong, it’s Hydro Québec’s fault.”

The two main actions dam operators can do to reduce flood risks are to perform daily meteorological predictions to see how weather will impact snow melt, and to prepare the region’s reservoirs ahead of time. “We don’t have a crystal ball that says exactly what’s going to happen,” Rondeau said. “Snow is the first indicator that spring will either be long or be short. But snow accounts for just 30 per cent of what causes spring flooding. The rest is the quantity of rain we will receive.”

Despite advancements in technology and enhanced knowledge about water level management, Rondeau noted that the spring floods of 2017 and 2019 were the largest in the Outaouais in 140 years – pointing out the cause to be extraordinary levels of snow and rain. But without the region’s dam operators, Rondeau said those floods would have been significantly more devastating. “It would have been way worse,” Rondeau said.

While the region’s southern portions are more densely populated, Rondeau said that the Ottawa River’s hydraulic dams are located in the northern parts of the Outaouais. Since 1983, the ORRPB has been responsible for managing the Ottawa River, including spotting and mitigating flood risks.