How long can Canada’s ‘Big River’ keep flowing? : Commentary

The Mackenzie River, (DehCho – Big River- in Slavey) runs nearly 1,800 km northwest from Great Slave Lake to its mouth at Kittigazuit in the Arctic. The Mackenzie is one of the few uncontrolled rivers in Canada, and drains almost a fifth of the country.

It is also in trouble.

Climate change is certainly a factor, but so too is long-term climate variability and human interference with the natural flow of rivers within its watershed. All of them impact the Mackenzie’s ability to sustain its role as a major transportation artery between southern Canada and the Arctic.

Climate-related factors

• Reduction in snow pack in the Rockies.
• Reduced glacier flow (likely little or none after 2030).
• Increased early-season temperatures. leading to more rapid snow melt.
• Degradation of forest cover by the Mountain Pine beetle because of milder winters.
• Forest fires in British Columbia resulting in faster spring run-off.

Human interference

• Increasing water demand on the Athabasca River due to the oil sands.
• Construction of the W.A.C. Bennett, Peace Canyon and Site C dams on the Peace River by BC Hydro.
• Agricultural demand with major water withdrawals from the Peace River in Alberta.

Long-term climate variability

• The 20th century has, generally, been unusually stable and moist, ie adequate, although declining, rainfall.
• In earlier centuries, severe droughts that lasted for decades were common. Captain John Palliser (Palliser Expedition 1857-1860) warned that water was scarce in the Prairie Provinces, and both the North West Company and the Hudson’s Bay Company reported water flow problems on principal rivers in the 18th and 19th centuries.

Navigation

The river has always been a major transportation artery. Cargo movements commenced when the Hudson’s Bay Company among others –  started running sternwheel riverboats (often with attendant barges) in the mid 19th century. Tug and barge operations became important in the mid 20th century with discovery of oil at Norman Wells, and radium and silver on Great Bear Lake. Large amounts of cargo were shipped in the 1950s in support of the DEW line, and also in the 1970s during the period when Canada was actively exploring the Arctic for oil and gas. This activity segued into resupplying oil and dry goods for isolated communities on the river, as well as the Western Arctic.

Today, service out of Hay River NT on Great Slave Lake is critical for petroleum products and dry cargo for three remote river communities, two in the Delta region, four-five in the western Arctic (Kugluktuk in Nunavut has alternative service out of the East), together with several North Warning System sites. In 2020 it was planned that tows from Hay River would move some 35,000 cubic meters of petroleum products and close to 6,000 tonnes of dry goods.

Hay River became the cargo service centre in 1964 when the railway line for the Pine Point mine was finished. Until then, cargo was transhipped from Fort Fitzgerald around the rapids on the Slave River to Fort Smith. However, in 2024, CN decided to abandon the rail line from Enterprise NT to Hay River because of forest fire damage to a 30-kilometer section. CN claims that traffic cannot support the $15 million repair cost.

To support navigation, it is not only the average quantity of water flowing in the river that is important; when it flows is critical.

As shown by the flow characteristics chart, the season is typically June 1 to sometime in October, or at best 140 days. There are seasonal variations in water depth that vary with winter conditions.  For example, a good snow year in the mountains will lead to better depths compared with a below- average year when the season may only last 120 days. Water depths tail off in late season and there have been difficulties in even returning light barges over Rampart Rapids in some years. In 2023, one of the tugs went aground in Providence Rapids at end season due to exceptionally low water.

That is a description of a typical season, but since 2023 seasons have been far from typical.

The Mackenzie, being a natural river, has several rapids sections that affect navigation by the tug and barge tows that move cargo on the river.

Rapids and Relay Distances

Even though some rapids have been dredged, tows cannot be safely taken through them as a unit, and the tugs will relay between one and three barges at a time, depending on channel characteristics, water levels and current speed. The relay is between safe mooring locations for barges on either side of the obstacle.

Under low water conditions, the most difficult of these rapids is the rock ledges of Rampart Rapids. For the last two years, there has been insufficient water to safely take tugs and barges through this set of rapids, although Providence Rapids have also been a problem. Communities south of Norman Wells could still be served from Hay River, but those from Fort Good Hope north have had to be served up river from Inuvik.

For 2025, it looks as if low water in Great Slave Lake is again causing navigation problems at Providence Rapids. As a result, barge operations for the upper part of the river may have to be handled from the ferry landing at N’Dulee at the Wrigley crossing.

At time of writing, no decision has been made as to how tug and barge transportation will be handled in 2025, and whether major logistical changes need to be made for future years.

The auguries do not look good.

Snow pack in the headwaters of rivers to the west of the Mackenzie – which provide 60% of its water – continue to be below normal (the Liard was the only region above normal in the 2024/25 winter). The NWT is in an ongoing state of drought, as is northern Alberta, and parts of Saskatchewan and Manitoba. Great Bear Lake is at record-low water levels, materially affecting water flows down the Great Bear River.

On top of this, the Site C dam on the Peace River is now operational, making 3 major dams that control – and effectively smooth –  water flow on the Peace, which via the Slave River and Great Slave Lake makes up about a quarter of the Mackenzie water supply (another quarter comes from the Liard at Fort Simpson.

So where do we go from here?

A lot depends on water levels in Great Slave Lake. These, in turn, largely depend on water flows in the Peace River, which makes about 50% of the lake’s supply. However, as of February 1, the Peace Region snowpack is only at 85% of normal, which does not bode well.

If there is insufficient water depth to get through the Fort Providence reach, then much of Marine Transportation Services (MTS) tug and barge fleet is trapped in Hay River; some of the fleet will have wintered in Tuktoyaktuk or Inuvik, so they could serve communities as far up stream as Fort Good Hope, as Rampart Rapids will likely be impassible. For the upper reaches, MTS will probably need to contract with Cooper Barging – who are based on the Liard River – for tug and barge capacity.

Thus, a solution for 2025 deliveries could be cobbled together. But if low water is the new normal, it’s anyone’s guess how future transportation on the river can be managed.

If the Mackenzie does close to through navigation, access to the Canadian western arctic is either a long haul around Point Barrow through US waters, or a sometimes fraught route via Lancaster Sound with a six-week window.

Christopher Wright is the former president of The Mariport Group Ltd, a marine and port consulting company that he formed in 1989. After retiring in 2013, Wright joined WorleyParsons Canada (now Advisian) as a marine logistics specialist.

He has written two books: “Arctic Cargo; A History of Marine Transportation in Canada’s North” (2016) and “Of Penguins and Polar Bears, a History of Coldwater Cruising” (2020).