Canada's Water Security Agency issued its March outlook for runoff potential on Monday, including the Souris River basin. In response, the amount of water being released from Lake Darling Dam is scheduled to be increased from 70 cubic feet per second to 150 cfs on Wednesday and then to 250 cfs this weekend.
The immediate impact will be weakening of river ice, perhaps even opening the river channel through the city of Minot and beyond in the week ahead. Anyone venturing onto the river in the coming days is encouraged to exercise extreme caution due to an expected deterioration of the ice pack.
The increases through the gates at Lake Darling are considered minimal and well within the norm for this time of year. In addition, there is little cause for alarm for Souris River interests contained in the new WSA outlook. While large areas of Saskatchewan have received well above normal snowfall, regions influencing runoff into the Souris River basin are not among those that have received abnormal amounts of snow. As a result, spring runoff is expected to be contained without any difficulty.
According to the WSA, "In the Long Creek, Souris River and Moose Mountain Creek basins, below normal fall precipitation occurred. Winter precipitation varies from well above-normal along the northern portions of the basin to near-normal along the International Boundary. Above normal runoff is expected in spring 2013."
Even though "above-normal" runoff is forecast, it is not expected to challenge the amount of storage available in Rafferty Reservoir on the Souris near Estevan, Sask., nor at Alameda Reservoir on Moose Mountain Creek near Oxbow, Sask.
As of March 1, Rafferty Reservoir was at an elevation of 1,802.66 feet and is scheduled to be drawn down to 1,802.17 feet prior to spring runoff. Runoff is expected to raise Rafferty about five feet this spring to a peak of 1,807.74 feet.
According to the WSA, Alameda Reservoir is not scheduled to release any water at this time. The level at Alameda on March 1 was 1,840 feet with a projected peak of 1,843.83 feet. Should Alameda or Rafferty exceed projected levels, considered normal for the summer period, releases would begin.
Boundary Reservoir, which is fed by Long Creek and connected to Rafferty Reservoir by a diversion channel, is kept at relatively stable levels for the purpose of supplying water to a shoreline power plant. Boundary was at 1,836 feet March 1 and is forecast to reach 1,840.55 this spring. Normal summer operating level for Boundary Reservoir is 1,838.90 feet. If excess inflow occurs, that water will be diverted into Rafferty.
Lake Darling's level on Monday was 1,596.04 feet. Increased releases this week are expected to draw down the reservoir slightly in anticipation of similar flows entering the Souris from Canada. According to Monday's WSA outlook, all points along the Souris River should remain well within the river's banks. The projected peak flow at Sherwood is expected to reach 1,765 cfs. That compares with a peak flow of 26,520 cfs during the record flood year of 2011.
The information contained in the WSA outlook was included in the recent Souris River Flood Outlook issued by the National Weather Service. The NWS outlook also showed that only minor flows are anticipated along the Souris this spring unless significant changes in temperatures or precipitation should occur. The WSA intends to issue another Spring Runoff Potential survey in April. The NWS is expected to update the Souris River Flood Outlook later next week.