Northern Saskatchewan Summer High Water Update – September 22, 2020
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 has come in the months of May, June, and July, where accumulations at some sites have exceeded 200% of normal.
Most of the north received less than 5 mm of rainfall over the past week. Only southern portions of the Churchill River Basin, including the Meadow Lake and Lac La Ronge headwater areas, received higher amounts with accumulations of 42 mm near Big River and 34 mm near Waskesiu. These amounts are not expected to result in any higher peak flows or levels than what has already been observed.
Flows and Lake Levels:
High river and lake levels can be expected for the remainder of fall and in some cases, such as the mainstem of the Churchill River, into the winter. The observed peaks throughout the system were 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, exceed previous historical highs.
Below are specific conditions at various locations as well as projected future peak levels:
Ile a la Crosse:
Present elevation: 420.98m
Levels at Lac Ile a la Crosse are continuing to decline; however, they will remain higher than normal for the remainder of the open water season and vulnerable to additional rainfall events and wind events. Based on historically similar years, levels prior to spring snowmelt in 2021 are expected to be 0.4-0.5 m higher than normal on Lac Ile a la Crosse.
Lac La Ronge:
Current elevation: 364.87 m
Observed Peak: 364.95 m (August 10-30)
Over the past week, 3 mm or rainfall has been observed at La Ronge and accumulations ranging from 5 to 34 mm were observed over headwater near Montreal Lake. While this slowed inflow recessions some, the lake continued to decline. The expectation remains that Lac La Ronge will go into winter at a level similar to what was experienced in 2011.
Present Elevation: 8.55m (1820 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 1.6 m. Levels are now well below the 2005 peak. With flows upstream showing some slow declines, flows and levels at Sandy Bay will continue to decline slowly over the coming week. Flows are expected to be down below 1800 m3/s by the end of the month.
With warm and dry conditions over the past month, levels at Meeting Lake have been dropping. 17 mm of rainfall was observed on September 20 at Spiritwood, the closest observations we have to Meeting Lake. This likely resulted in a small increase in the lake level
Present elevation: 739.26m – September 18, 2020
Observed peak: 739.48 m – July 27, 2020
A system is expected to bring some showers to the north late in the work week. Current model guidance is indicating that heaviest accumulations will occur in the northeast, near Reindeer Lake, where accumulations of 20-30 mm are expected. Minimal rainfall is expected over upper portions of the Churchill River Basin over the next 5-days.
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