Well above normal March snowfalls have increased the runoff potential across Saskatchewan according to the April spring runoff forecast released by the Water Security Agency.
However the forecast for the Southwest corner ranges from well below normal to above normal.
April’s forecast is significantly different from the February 1 runoff potential forecast which had the entire Southwest in the well below normal to below normal range.
The extreme Southwest corner of the province, primarily near Eastend to Val Marie, is now gearing up for above normal potential runoff. They noted the area south of the Cypress Hills and Frenchman River received above average accumulations over the past number of weeks.
The Swift Current Creek will experience near normal runoff, but much of the rest of the Southwest is anticipating well below normal runoffs.
The Water Security Agency adds that well below normal temperatures in early April have already pushed back the start of runoff past its normal start.
Their April update reminds that some agricultural water supply issues began to emerge in late summer 2017. In the areas where well below average 2018 snowmelt runoff is projected, these water supply shortages may intensify and expand to additional areas.
Most reservoirs and dugouts went into winter at slightly below average levels, so in areas of below normal runoff, there could be surface water supply concerns.
The snowpack over the eastern slopes of the Rocky Mountains is generally well above average for this time of year. Lake Diefenbaker is currently 0.7 metres below its normal level for this time of year, but is expected to be at desirable summer operating levels by July.
Winter inflows to Lake Diefenbaker were below normal this winter, but the lower water levels are attributed in part to a late runoff from the plains portion of the Saskatchewan River Basin.
Frenchman River: Runoff yields from the basin’s headwaters and areas south of the Frenchman River are expected to be higher than lower portions near Val Marie. The current expectation is for Eastend Reservoir as well as Huff and Newton Lakes to fill in 2018. Diversion into Cypress Lake from Belanger Creek are anticipated.
Maple Creek: Some runoff occurred with in the Maple Creek Basin in March with near normal yields. Thus far McDougald is the only reservoir in the basin to fill. Some snow still remains in the trees and coulees, so slow runoff is still likely in this areas.
Swift Current and Rush Lake Creeks: The snowpack in the basin’s headwaters near Shaunavon is heavier than near Reid Lake and the City of Swift Current. While above normal runoff is expected from the headwater areas, near normal runoff yields are expected from lower portions of the basin. Reid Lake is currently at 80 per cent capacity with a normal winter release of about 0.6 metres cubed per second. The focus initially at Duncairn Dam will be on storage during the snowmelt period.
Highfield Reservoir is near 50 per cent capacity following the release to the Rush Lake backflood project in late March. Diversions to Highfield Reservoir via the Swift Current Main Canal were occurring in March, but with the return of below normal temperatures, they were discontinued in late March. This action prevented the canal from freezing up, which would have hindered further diversion during spring runoff. Transferred water from Swift Current Creek was not used for the backflood on the Rush Lake Project.