OPG’s hydro operations preparing for whatever spring has in store
At a glance
- OPG’s hydroelectric operations are once again preparing for spring freshet, the annual increase in water flows from melting snow and rainfall.
- This preparation work includes snow surveys, drawdown of water at storage reservoirs, and pre-freshet training exercises.
- OPG is also working with communities and other agencies to prepare for everything and anything this spring.
Freshet may be weeks away, but OPG’s hydroelectric operations and employees are already preparing for the annual deluge of water.
Each spring, rivers across Ontario experience higher flows from melting winter snow and increased rainfall – a phenomenon known as freshet.
With 240 dams operated on 24 river systems, 27.6 billion cubic metres of total storage capacity, and roughly 600 billion cubic metres of water managed across the province, OPG works to help mitigate the impacts of freshet each year for the benefit and safety of communities.
“Freshet is truly a period where we are all hands on deck,” said Melissa Vogl, a Water Manager in OPG’s Eastern Operations who helps oversee the Ottawa and Madawaska River watersheds. “We’re continually monitoring conditions every hour and every minute as it’s always changing. We’re also monitoring those conditions all year round. We get all the real-time data, watch the trends, and have our set strategies in place pre-freshet. We’re always thinking about the risks around this time and trying to be cautious, as safety is paramount when it comes to freshet.”
Despite popular misconceptions, OPG can’t predict the weather and the future. While water managers can rely on data and modelling to get an idea, each spring’s water levels will vary based on snow melt, temperatures, and rainfall.
Freshet is truly a period where we are all hands on deck. We’re continually monitoring conditions every hour and every minute as it’s always changing. We’re always thinking about the risks around this time and trying to be cautious, as safety is paramount when it comes to freshet.Melissa VoglWater Manager in OPG’s Eastern Operations
And while the province has several principal reservoirs at its disposal to accommodate spring flows, when those major reservoirs are at capacity, that’s it, Vogl said.
“At that point, we have no more storage available and we will have to deal with what mother nature gives us,” she said. “A lot of how we respond to freshet is making decision as it happens, in the moment. We have to work with nature.”
But there are strategies in place to help OPG prepare for whatever spring has in store.
This yearly work begins with snow surveys taken across OPG’s hydro regions starting in January. These surveys, along with data from similar work conducted by the Ontario Ministry of Natural Resources and Forestry (MNRF), weather forecasts, and satellite-derived snow cover maps, help OPG’s water managers estimate the spring runoff potential by looking at the snow’s water content.
Did you know? On large river systems like those in Ontario, spring freshet can take up to several weeks. Regardless of water levels, please be safe around rivers and dams as water levels can change in an instant.
In parallel to this, OPG’s storage reservoirs begin their winter drawdown of water levels from January to March, in accordance with provincially mandated water management plans. The drawdown lowers a reservoir’s operating level from its summer maximum to the target winter water level to accommodate the spring snowmelt and rainfall. It’s a process that can take months for large reservoirs, and days or weeks for smaller ones.
“Think of reservoirs as a big bathtub. We need to drain them so we get to bottom elevation. We’ll make sure we’re at the bottom and wait to fill them back up over the spring,” said Vogl. “We’re really trying to attenuate the peak flows by holding back some of the water. And we strategize how quickly we fill up our reservoirs. The timing of that is a key piece.”
Finally, OPG’s hydroelectric operations and staff conduct pre-freshet preparation exercises from February to March. These exercises include training, equipment tests, and communication protocols to ensure everything and everyone is ready to respond to every potential outcome of freshet.
In all of this, OPG doesn’t act alone, as it takes a community effort to prepare for freshet.
Each year, OPG meets and communicates with local leadership, the MNRF, partner agencies, conservation authorities, and other river operators. This coordinated effort to managing the inflows makes the best use of storage capacity and spill capability at OPG and facilities owned by others.
As with all things, it pays to be prepared. And these early efforts are helping OPG, its operations, and communities across Ontario be ready for anything this spring.
To learn more about how OPG prepares for freshet, visit these resources below.
How OPG works with nature to manage water
Our Story: What you need to know about spring freshet
Our Story: Snow surveys help OPG’s hydro operations prepare for freshet
Our Story: Winter drawdown helps OPG prepare for spring freshet
Our Story: Tabletop exercises helping OPG’s hydro operations prepare for spring freshet
Our Story: OPG’s hydro operations managing the impacts of “fall freshet”
We work with nature
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