Northern Saskatchewan Summer High Water Update – August 28, 2020
Rainfall
Northern Saskatchewan has received extremely high cumulative precipitation since April 1, 2020, resulting in very high flows and lake levels across the Churchill River and Lower Saskatchewan River basins. Much of this rainfall fell in the months of June and July.
Over the past week, the majority of the north received precipitation accumulations that ranged from 10 to 35 mm. The exception is in the northwest along the Alberta border below Lake Athabasca, and portions of the North Saskatchewan River Basin, where up to 45 mm was received.
Flows and Lake Levels:
High river and lake levels can be expected for the remainder of summer and in some cases, such as the mainstem of the Churchill River, into the fall and winter. Many locations have stabilized or are declining. The expected peak or observed peak throughout the system is generally slightly lower than previous historical highs. However, flows and levels in the Lower Churchill River, including Reindeer River and Churchill River near Sandy Bay, have exceed previous historical highs.
Below are specific conditions at various locations as well as projected future peak levels.
Ile a la Crosse:
Present elevation: 421.1 m
Levels at Lac Ile a la Crosse remain high, and are expected to stay higher than normal for the remainder of the open water season and vulnerable to additional rainfall events and wind events.
Lac La Ronge:
Current elevation: 364.94 m
Observed peak: 364.97 m on August 22, 2020
While surface water inflows are declining, levels on Lac La Ronge have been holding steady near 364.95 m. It is postulated that subsurface inflows could be increasing and offsetting the declines in surface water inflows, holding the lake level relatively steady over the past two weeks. It is our expectation that declines in the lake level will be observed in the coming days unless additional rainfall is received over the basin.
Sandy Bay
Present Elevation: 9.28 m (2080 m3/s)
Observed peak: 10.15 m (2420 m3/s) on August 4
Water levels at Sandy Bay reached a peak on August 4 and are now down about 0.9 m. Levels are now down below the 2005 peak. Flows and levels are expected to remain relatively steady for the next week.
Meeting Lake
Only 13 mm of precipitation has been recorded in the region so far this month, which has resulted in a decrease in levels at Meeting Lake.
Present elevation: 739.35 m – August 28, 2020
Observed peak: 739.48 m – July 27, 2020
Meeting Lake has reached its outlet and is confirmed flowing into outlet channel. There is not significant flow moving through the outlet currently as it is congested with thick vegetation. Berms around the lake should now be built to WSA recommended standard (739.83-740 m).
Cumberland House
Cumberland Lake has peaked and is receding. The lake is now down 1.47 m from the peak observed in late July. Forecasted levels for Cumberland Lake are part of WSA’s 10-Day Saskatchewan River Forecasts, which can be found here: https://www.wsask.ca/Lakes-Rivers/Provincial/
Jan, Amisk, and Deschambault Lakes
Jan Lake peaked in late July — 54 mm above 2017 levels.
While we do not have any current information for Deschambault or Amisk lakes, with the Sturgeon Weir River at Leaf Rapids appearing to be at its peak, Deschambault Lake has likely peaked and a peak at Amisk Lake can be expected prior to the end of the month or in early September.
Like Jan Lake, peaks that are slightly above 2017 levels are expected at Deschambault and Amisk lakes, unless significant, additional precipitation is observed.
Future Rainfall
Throughout the weekend, the far northwest corner over Lake Athabasca is expected to receive 25 to 50 mm, with the bulk of precipitation excepted late Saturday and into Sunday. The remainder of the Lake Athabasca Basin and the northeast portion of the Churchill River Basin, including Reindeer Lake, is expected to receive 10 to 15 mm over the weekend. The remainder of the north is expected to receive 5 to 10 mm.
The greatest concern at this time is at Lac La Ronge, which, based on current forecasts, is expected to receive about 10 mm of rain over the coming days. While the forecasted rain will slow the recession of high water across the north, it is not expected to result in any higher peaks than what has already been observed. The exception is likely to be Lac La Ronge where direct rainfall on the lake is expected to result in slightly higher levels.
For more information, contact:
Patrick Boyle
(306) 631-6997