Northern Saskatchewan Summer High Water Update – September 4, 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 has come in the months of June, July, and August where accumulations at some sites have exceeded 200 per cent of normal.
Over the past week, rainfall accumulations through the Churchill River Basin ranged from 10-25 mm, with the highest accumulations near the Alberta boundary. Accumulations were higher near the Northwest Territories (NWT) boundary, with accumulations in excess of 30 mm near Lake Athabasca.
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. 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: 421.07 m
Levels at Lac Île-à-la-Crosse are beginning to show some declines; however, they will remain 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: 364.92 m
Observed Peak: 364.95 m (August 10-30)
While strong winds have made it difficult to get an accurate water level for the lake, it appears as if levels have shown some small declines over the past week. Levels will, however, remain high throughout the fall and could rise higher with additional rainfall. Our best estimate is a decline of just 0.15 m between now and freeze-up. This would be similar to conditions experienced in the fall of 2011.
Sandy Bay
Present Elevation: 8.96m (1960 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 1.2 m. Levels are now well below the 2005 peak. With the full effect of the August 19 flow reduction at the Whitesand Dam now being observed at Sandy Bay and flows further upstream on the Churchill River fairly stable, declines in the flow and level at Sandy Bay are expected to slow and remain fairly stable over the next two weeks.
Meeting Lake
With warm and dry conditions over the past month, levels at Meeting Lake have been dropping. Only 17 mm of rainfall was observed since August 1 at Spiritwood, the closest observations we have to Meeting Lake. Other sites in the area have observed 20-30 mm over this period.
Present elevation: 739.32 m – September 4, 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 2.0 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 receding Deschambault Lake has likely peaked and a peak at Amisk Lake can be expected 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
Showers are expected across northern Saskatchewan Saturday with an advancing surface low. Accumulations ranging from 5-25 mm are expected, with heaviest accumulations extending from Peter Pond Lake over to Deschambault Lake. Based on current forecast, this system is not expected to result in higher peak flows, but it could reverse some of the recent gains made at lakes within the Churchill River and Lower Saskatchewan River basins.
For more information, contact:
Patrick Boyle
(306) 631-6997
Patrick.Boyle@wsask.ca