Qu’Appelle System Lake Levels – Update
The Water Security Agency (WSA) is providing an update on lake levels along the Qu’Appelle System.
Above normal snowpack and rapid runoff within the Qu’Appelle System has contributed to higher-than-normal lake levels along the system. All lakes within the system are between 30 and 60 centimetres (approximately 12 to 24 inches) above their summer levels. This includes Last Mountain, Pasqua, Echo, Mission, Katepwa, Crooked and Round lakes. Buffalo Pound is now at its typical summer operating level.
Releases from the Qu’Appelle River Dam at Lake Diefenbaker will be limited to what is needed to supply irrigators on the Upper Qu’Appelle River, and to offset the evaporative, industrial and municipal use at Buffalo Pound Lake. To minimize the flow within lower portions of the system, releases from Buffalo Pound Dam will be limited to about 1.1 m3/s, which is the flow needed to operate the fishway at Buffalo Pound Dam.
Current lake levels, their peaks, upper desirable operating ranges, and estimated time to return to normal summer levels are shown in the table below. Significant precipitation could delay the return to desired levels and could result in additional peak levels that may exceed those previously observed.
|Lake||2023 Peak Elevation (m)||Peak Date||May 18 Elevation (m)||Top of Summer Operating Range (m)||Timing to Reach Operating Range|
|Last Mountain||490.64||May 12||490.63||490.27||Early August|
|Pasqua-Echo||479.55||May 4||479.43||479.15||Late June|
|Mission-Katepwa||478.72||April 28||478.67||478.38||Early August|
|Crooked||452.50||May 5||452.28||451.71||Early July|
|Round||443.09||May 9||442.95||442.42||Early July|
Peak lake levels throughout the system were about one in four-year events. High flows in the system resulted from rapid snowmelt in early April and flows remained elevated into May as a result of the melt of the April 19/20 snowfall.
Flows on the Qu’Appelle River below Craven will remain high into July as water from Last Mountain Lake is released to the system; it will be late June before the downstream lakes start to drop into their desired operating range.
Control structures at Craven, Echo Lake and Crooked Lake will remain fully open until lakes they control reach desirable summer levels.
During spring runoff, to allow for a natural split of the Qu’Appelle River flow arriving at Craven, the Craven Control Structure was fully open. A portion of the water arriving at the Craven area on the Qu’Appelle River was flowing into Last Mountain Lake up to May 11, at which point, in response to receding flows on the Wascana Creek and the Moose Jaw River, water started exiting Last Mountain Lake.
While flows and levels remain high in the Qu’Appelle River System, WSA will continue to monitor conditions and will provide further updates as needed.