2023 Spring Water Level Outlook and Snow Surveys: Near normal snowpack and water levels across most of the NWT; Potential For Break-Up Flooding Remains

The Government of the Northwest Territories (GNWT) has completed snow surveys and the 2023 Spring Outlook has been released. The technical report is available online.

Key takeaways from the technical report

Current water levels

• Overall, as the spring melt season begins, water levels across the territory as of April 18, 2023 are generally between average and below average, with some exceptions.
• The weather experienced during the coming weeks in river basins will have a large impact on the flood risk at break up.

Snowpack

• Snowpack across the territory in the winter of 2022-23 was approximately average, with exceptions being higher than normal snowpacks in the Sahtu region and Peel River basin, and a much lower than normal snowpack in the Snare River basin in the North Slave region.

River Ice

• Winter air temperatures in 2022-23 in the NWT were slightly warmer than average, which, in part, means ice may be thinner than usual.
• Ice jams during break up typically form on north-flowing rivers, where warm weather and snowmelt cause ice to break up earlier on the southern reaches of a river. As this ice flows north (downstream), it may meet a more solid ice cover.
• When this happens, sheets of floating ice run into the solid ice and can form a dam (an ‘ice jam’), which may cause water levels to rise rapidly behind it.

Flood Risk

• As always, it is difficult to predict in advance how break up will occur – and if ice jams will form.
• The weather experienced during the coming weeks in river basins will have a large impact on the flood risk at break up.
• Ice-jam flooding can happen in any year regardless of pre-existing water levels and snowpack SWE.

Hay River Basin

• Flooding in Hay River last year was a result of high pre-existing moisture conditions in the basin (so there was limited room for the ground to hold snowmelt water), higher than average pre-existing water levels in the Hay River, higher than average snowpack, a later-than-normal spring, and an extreme precipitation event that fell on the basin during break up.
• Water levels on the Hay River are currently below average and much lower than last year at this time. Warm weather in early April has helped to initiate early snowmelt in the basin, but as always, the weather experienced in the Hay River basin over the coming weeks will have a large impact on the flood risk at break up.
• Snow surveys show snowpack in the basin is average – specifically, 100% of the normal level – as of late-March 2023. This includes an analysis of snow surveys completed in Alberta and British Columbia – where 94% of land feeding the basin is located.

Peel River Basin and Inuvik Region

• Snow survey data for the Peel River basin show that snowpack values are above average at 125% of normal.
• Water levels on the Peel River are currently much higher than average. Data will continue to be watched closely over the next weeks.
• Water levels on the Mackenzie River at Tsiigehtchic and throughout the Mackenzie Delta are average for this time of year.

Dehcho and Sahtu Regions

• Prior to the floods in Fort Simpson, Jean Marie River, and Fort Good Hope in 2021, water levels and flow rates on the Mackenzie River were the highest on record for that time of year, a contributing factor to the flooding experienced.
• In the Liard River basin, Yukon snowpack data for April 1st indicate that the snowpack in the upper Liard basin is generally average at 102% of normal.
• Further downstream, data from British Columbia show that the snowpack is below average (81% of normal), while snow survey data in the lower Liard basin in the NWT show average values at 101% of normal.
• Snow in the remainder of the Dehcho region (outside the Liard River basin) indicate that snowpack in the region is average at 104% of normal.
• Flows on the Liard River over winter have been about average and have been since summer 2022. Recent increases in flows are due to the response of an early snowmelt event in early April.
• Further north in the Sahtu region, snow surveys found that snowpack values are above average at 124% of normal.
• Currently, water levels on the Mackenzie River at Fort Simpson and Norman Wells are below average.

Great Slave Lake

• Water levels on Great Slave Lake receded to average levels over the summer of 2022 after being extremely high since the summer of 2020.
• Snowpack values in the North Slave region will likely result in lower flows and levels on local rivers and lakes but will not have a strong impact on water levels on Great Slave Lake as the vast majority (~75-80%) of the water in Great Slave Lake comes from the Slave River to the south.

Taltson and Tazin River Basins

• • Poor weather conditions during late March and early April prevented safe access to remote snow survey sites.

• Flows on the Taltson and Tazin rivers are currently below average and have dropped substantially since extreme record high flows in 2020 and 2021. Water levels on Tazin Lake are about average.

Quote

“With spring break up comes the potential for ice jams and flooding. Government of the Northwest Territories staff work to provide expert analysis on snow, and real-time updates on water and ice conditions, and to share that information with emergency managers across the territory. Our government is committed to supporting residents and communities as they prepare for the upcoming spring melt season.”

– Shane Thompson, Minister of Environment and Climate Change; Municipal and Community Affairs

Quick facts

• The Department of Municipal and Community Affairs maintains a list of communities considered to be at-risk of flooding during spring break up each year. For these communities — and all communities — it is crucial to take steps to prepare for flooding before it happens.
  • For 2023, these communities include:
    • Hay River (Hay River)
    • Kátł’odeeche (Hay River)
    • Nahanni Butte (South Nahanni River, Liard River)
    • Fort Liard (Liard River)
    • Fort Simpson (Liard River, Mackenzie River)
    • Aklavik (Mackenzie River)
    • Fort Good Hope (Mackenzie River)
    • Tulita (Mackenzie River)
    • Jean Marie River (Mackenzie River)
• For harvesters and trappers who may be impacted by floods outside of communities – including their cabins, traplines, and other equipment essential for traditional practices – the Hunters and Trappers Disaster Compensation program may be able to help recoup costs.

Related links

• Read the Spring Outlook Technical Report (in English only)
• Get Snow Surveys and Water Monitoring Bulletins
• Get emergency preparation tips and information: Be Ready – For Floods
• Hunters and Trappers Disaster Compensation

For media requests:

For information on water levels, flow, and snow survey data

Mike Westwick
Manager, Public Affairs and Communications
Environment and Climate Change
Government of the Northwest Territories
Mike_Westwick@gov.nt.ca

For information on emergency response, preparedness, and flood risk assessments

Jay Boast
Communications Specialist
Municipal and Community Affairs
Government of the Northwest Territories
Jay_Boast@gov.nt.ca

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