NWT Water Monitoring Bulletin – July 9, 2024 (Mackenzie Mountains Rainfall Forecast)

News Type: 
Water monitoring bulletin

YELLOWKNIFE (JULY 9, 2024) — Environment and Climate Change Canada (ECCC) has issued a Weather Notification regarding a storm system expected in the southern part of the Mackenzie Mountains between July 10 and July 12.

This water monitoring bulletin interprets what this could mean for rivers and people in the NWT.

The situation

  • There is high confidence there will be a large rainfall event (60 to 80+ mm) in the southern Mackenzie Mountains.
  • The heaviest rainfall is predicted to start falling in the afternoon of July 10, and will last into the morning of July 12.
  • There is less confidence on which river will receive the heaviest rainfall – however, forecasts suggest the South Nahanni River basin could see very significant rainfall. A rise in water level of over one metre is possible if the rainfall is concentrated in one basin.
  • When compared to historic data for the general area, this means that over one month’s worth of rain could potentially fall within one day.

Why it matters

This could impact people on the land. Rivers flowing into the Liard and Mackenzie rivers from the Mackenzie Mountains – such as the South Nahanni River, North Nahanni River, Root River, and Redstone River – are strongly affected by rainfall in the Mackenzie Mountains. This level of rainfall could mean rapid rises in water levels and flow along these rivers. 

The rise in water levels will depend on where the precipitation falls. If heavy rainfall falls within the South Nahanni Basin as forecast, there is the possibility of rapid rises in water levels and flow on the South Nahanni River and in the community of Nahanni Butte.

This level of rainfall in a short period also has the potential to cause challenges for infrastructure like roads and drainage systems.

What to do

  • The community of Nahanni Butte should be aware of this system, monitor conditions closely, and assess any risks to their community based on those conditions.
  • Those planning to be out on-the-land this week should be aware that this storm system may cause rapid rises in water levels and flow. Be prepared with communication methods before you go out on-the-land, know the conditions, and be prepared to leave your cabin, camp, or cabin on short notice should flooding become imminent.
  • In all flood-prone communities, including Nahanni Butte, it is always important for individuals to be ready for emergencies. That means having an emergency plan for you and your household, having an emergency kit ready to go, staying up-to-date with the latest information from your community, and following instructions from local officials should the time come.

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