Northern Saskatchewan Summer High Water Update – August 18, 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 and July.
Conditions have been warm and dry over the past few days, resulting in increased evaporative losses and declining flows across the north. Rainfall over the past three days has been less than 5 mm across the north.
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 saw an increase in flows and levels in response to the rainfall that occurred over the past weekend (August 8-10), but have since 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: 421.10 m
Levels at Lac Ile a 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: 364.95 m
Projected peak: 364.95 m on or near August 21, 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 6-days. It is our expectation that declines in the lake level will be observed later this week.
Sandy Bay
Present Elevation: 9.56 m (2190 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 0.6 m. Levels are now down below the 2005 peak. Flows and levels are expected to remain relatively steady for the next week. A reduction of 300 m3/s in the Whitesand Dam outflow on the Reindeer River is planned for August 19. This reduction will help to lower water levels further at Sandy Bay mid-week next week.
Meeting Lake
- With warm and dry conditions over the past week, levels at Meeting Lake have been dropping.
- There has been no new precipitation recorded in the area since August 9
- Present elevation: 739.38m – August 18, 2020
- Observed peak: 739.48m – July 27, 2020
- Meeting Lake has reached its outlet and is confirmed flowing into outlet channel
- There is not significant flow moving through 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 1.4 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. 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
While hot and predominantly dry conditions are expected to persist over the north for the next three days, current forecasts are suggesting accumulations ranging from 20-50 mm over much of the northern half of the province over the upcoming weekend. WSA will be monitoring these weather forecasts as they evolve and assessing impacts on the hydrological forecasts.