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Information Bulletin – April 13, 2023
Regional Direction of Civil Security and Fire Safety of the Outaouais

Monitoring spring freshet conditions 2023

Flood expertise table

During the spring freshet, the Ministère de la Sécurité publique (MSP) coordinates a flood expertise table to allow authorities to monitor the situation and anticipate any issues that may arise. This table, which meets weekly, is made up of experts from various departments of the Quebec and Canadian governments, as well as organizations such as Hydro-Québec (HQ) and Hydro-Météo.

Following the meeting of Thursday, April 13, here is the important information that the experts had to transmit to us for the greater Outaouais region.

Weather conditions

According to experts at Environment Canada, the temperatures forecast for the next 3 to 4 days will be above seasonal norms, both during the day and at night, which will significantly accelerate the melting of the snow. Fortunately, no precipitation is expected on Friday, Saturday and Sunday. As of Monday, April 17, a system from Ontario will bring precipitation (in the order of +/- 25mm) which may affect the St. Lawrence Valley more. The Outaouais should be relatively unaffected, but we can still expect to receive light precipitation during the day on Monday. The rain will be accompanied by a drop in temperature, which will slow down the melting of the snow. I invite you to consult the temperature forecast table for the next 2 weeks (reference point = Maniwaki):

In terms of longer-term temperature forecasts (next 4 weeks), the week of 17-24 April 2023 is the most likely period to see above-normal temperatures. The following weeks will be mostly within the seasonal normals.

Predicted probabilities (%) of above and below normal temperatures. Left: week 17-24 April, right: week 24 April-1 May.

Predicted probabilities (%) of above and below normal temperatures. Left: week of May 1 to 8, right: week of May 8 to 15.

On the precipitation side, the next week, April 17-24, will be marked by the weather system mentioned above, but the probabilities are that the following weeks will be marked by precipitation at or below the seasonal norm.

Predicted probabilities (%) of above and below normal precipitation. Left: week 17-24 April, right: week 24 April-1 May.

Predicted probabilities (%) of above and below normal precipitation. Left: week of May 1 to 8, right: week of May 8 to 15.

Impacts on watercourses and reservoir management

In the region, the snowmelt expected in the next few days is likely to have a significant impact on rivers where the response is more rapid. Peak flood levels could approach or exceed the minor flood thresholds for the Picanoc (Saturday) and Petite-Nation (Sunday) rivers. The consequences that can be anticipated for these sectors are :

  • Flooding on some streets (or roads), land (low-lying areas) and parks that are located in areas that are normally prone to flooding;
  • Few or no residences (or buildings) are affected by this level.

Rivière Petite-Nation Station 040406

Rivière Picanoc Station 040840

ALL major reservoirs have completed their draining and are ready to receive snowmelt water (Mitchinamecus, Kiamika, Poisson-Blanc, Dozois, des Quinzes, Cabonga, Baskatong, etc.). The Dozois and Cabonga reservoirs are completely closed and will remain so until May in order to store the water from the melting snow. The Baskatong reservoir reached its lowest level yesterday and will begin filling today.

Hydro-Quebec informs us that the vertical inflows to be received for the next few days will be closely monitored and that the water flows drawn down will be adjusted so that Maniwaki, and other downstream municipalities, are kept below minor flooding thresholds. Should the melt over the next few days prove to be very intense, the Baskatong reservoir will be closed to store the excess water.

Note: The Ottawa River Regulation Planning Commission has begun publishing its hydrological forecasts, as well as those for certain stations on the Ministère de la Sécurité publique’s Vigilance platform. We invite you to consult them regularly in order to be aware of possible issues in your municipal territory. You will find the links to access them below.

Other relevant information

The MSP would also like to remind you that a wide range of relevant information on spring flooding is available on the Government of Quebec’s web portal in the “Safety and Emergency” section.

You will also find an information and awareness kit designed to help municipalities prepare for the next spring flood. The kit contains information, awareness, preparedness and steps to take in the event of a disaster.

You are also invited to consult the various tools provided by our partners, which are made available to you so that you can be aware of changes in river and reservoir water levels, stream flow, snow cover conditions, upcoming weather conditions, etc.

Finally, don’t forget that the Government Operations Centre receives, processes and transfers to the appropriate responders calls from government and municipal emergency lines to report a civil security emergency, 24 hours a day, 7 days a week. If you have noticed a natural disaster such as a flood, a landslide or any other event that could compromise the safety of people or essential infrastructures in your municipality, do not hesitate to contact the GOC.

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