Public Notices

Unofficial translation

Watch for spring flood conditions in 2023

Flood expertise table

During spring flooding, 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 27, 2023, here is the important information that the experts had to transmit to us for the greater Outaouais region.

Weather conditions

According to the experts at Environment Canada, a succession of two low-pressure systems is approaching, one from the United States and the other from western Canada. Due to an atmospheric blockage that has been stagnating over Quebec for the past week, the two systems that are currently making their way towards us will be slowed down and will remain over our regions over the weekend. This will be the main cause of the significant amount of precipitation to be received.

The first, smaller phase of precipitation will begin around Saturday (Apr 29) for the Outaouais. It will be followed by a second precipitation impulse that should begin on Sunday night (30 Apr-1 May) and will be more significant in terms of quantity.

Until Sunday evening, the probability of 15mm of rain falling on the southern Outaouais is between 80% and 100%.

From Sunday evening to Tuesday evening, considering that this is a rapidly changing system, the different models used by meteorologists show a great divergence in terms of quantity. While the European model tends towards total amounts of 15 to 25mm, the Canadian model predicts amounts between 30 and 60mm. It is therefore difficult to predict with any certainty the total amount expected. The high level of uncertainty, both in terms of quantities and the trajectory of this system, makes hydrometeorological forecasts very difficult and uncertain.

The good news is that following the passage of these systems, mild and drier weather is expected for the rest of next week. So, little precipitation in sight, so far.

Premier système

Deuxième système

Snow Cover

In terms of snow cover, although the situation has been resolved in the southern Outaouais, there are still significant amounts of snow (water equivalent of snow on the ground) in the north, in Abitibi-Témiscamingue. The cooler temperatures of the last few days have favoured a slower and more gradual melting of the snow. As a result, the rivers in most areas began to recede.

Consequences for rivers and reservoir management

As far as the rivers are concerned, the watchword has been the same for several days, namely stability. All the rivers have seen a stability or a drop in level over the last week. Considering the still very uncertain amounts of precipitation to be received for the weekend, the impact is difficult to predict, but we can expect the rivers to start reacting as of Monday.

With respect to the management of the large reservoirs, although there is a decrease in almost all of the unregulated portion of the Ottawa River watershed, levels remain stable due to increased withdrawals (outflows) from headwater reservoirs such as Quinzes, Kipawa and Lake Timiskaming. On the Lièvre River, all reservoirs are closed, except for Poisson-Blanc reservoir, which also increased its withdrawal. The same message applies to the Baskatong reservoir, which saw its withdrawal rate increase following consultation with various partners.

This general strategy used by the dam managers is intended to allow the large reservoirs to maintain an acceptable margin of manoeuvre in anticipation of the rains expected over the weekend. Thus, the more water they pass now, the more room they will have to store the significant amount of inflow expected.

As for the dams at Chelsea and Rapides-Farmers, no change is expected. The flow will remain at +/- 1000m3/sec.

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 of our partners, which are made available to you to enable you to be aware of changes in the water level of rivers and reservoirs, the flow of watercourses, the state of the snow cover, future 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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