Officials from the Water Security Agency say a large volume of water is entering Crooked Lake and will likely raise the lake level by 11 cm.
The water is coming from Pearl Creek, which had backed up behind the embankment where Highway 22 crosses the creek near the community of Killaly.
Officials said the water breached the embankment Friday afternoon and quickly rushed to the Crooked Lake.
The surge of water follows record-breaking rain that fell in southeast Saskatchewan days earlier and began entering the Qu'Appelle system of streams and lakes.
Dozens of properties at Crooked Lake have been inundated with water.
The agency is also keeping a close watch on a body of water further upstream that is currently being held back by an old railway crossing.
Officials say if that crossing fails, the amount of water that could enter the lake would raise its level by an additional 55 cm. But the agency noted the crossing "appears to be secure".