Major Impact from Snowmelt Unlikely
MINOT – There’s still several weeks of the winter season remaining, to be followed by potential spring rains, but current conditions throughout the Souris River Basin do not equate to undue concern for excessive spring runoff.
The amount of snow in southern Saskatchewan, and the condition of key reservoirs on the Souris River drainage, are of great interest to forecasters and citizens alike throughout the basin. Conditions along the Souris River Basin, which has its beginnings in southern Saskatchewan, presently favor the Souris River remaining within its banks during spring runoff.
However, it should be noted that many variables that can affect spring runoff remain unknown – such as how much snow will fall the remainder of this winter, how much rain will fall and when, and will the melt be fast, moderate, or slow.
The Saskatchewan Watershed Authority issued their initial runoff outlook earlier this month. It contained no undue alarm, cautioning that snow surveys conducted in late February will help establish further runoff projections closer to the traditional snowmelt season.
At present, said the WSA, “Both Rafferty Reservoir and Grant Devine Lake are below their prescribed February 1 drawdown elevations. With drier than normal conditions at freeze-up in 2022 and what is estimated to be a near to slightly above normal snowpack, the snowmelt runoff response is expected to be near normal above the three reservoirs and above normal in the area below the reservoirs to Sherwood Crossing.
Additional drawdown of the reservoirs is not expected, and it is anticipated that reservoir releases during the spring runoff period will be limited to amounts required to meet international apportionment obligations.”
The outlook added that Rafferty Reservoir, located near Estevan and the largest impoundment on the Souris, “is not expected to fill from snowmelt inflows in 2023.”
The WSA will be developing an additional outlook on or near Feb. 15, with additional forecasts near the first and fifteenth of each successive month as needed. All WSA forecasts can be found on wsask.ca.
The National Weather Service also issued what they call a “Spring Flood and Water Resources Outlook” this week. It does not contain any cause for alarm for Souris River Basin residents, many of whom know the reality of spring flooding.
According to the NWS, “The flood risks within the Souris River Basin of North Dakota can be split into two distinct areas this year. The first includes the Souris River near Sherwood, down through Minot, and roughly to the area near Velva. In this stretch of the Souris River, flood risks are slightly below to near normal this year as snowpack and its associated Snow-Water Equivalent (SWE) tends to decrease the farther north and west one looks from Minot. This near normal risk of flooding includes the Des Lacs watershed.”
The NWS says from Velva and going downstream on the Souris, all the way to Westhope, the snowpack and snow water equivalent are above normal, including the Wintering River and Willow Creek watersheds.
However, notes the outlook, “exceptionally dry and warmer than normal soils are underlying the snowpack” and are “expected to allow infiltration of a much larger than normal fraction of meltwater generated and rainfall received during the critical spring melt season.”
The NWS cautions that unforeseen ice jams remain a significant risk for flooding.
Of great interest to river watchers is the amount of water contained in Souris River Basin reservoirs above the population center of Minot. To date, the level of those reservoirs is lower than usual.
“Lake Darling above Minot along with the Canadian reservoirs behind Grant Devine and Rafferty Dams have near normal to somewhat below normal water levels for this time of year,” reads the outlook.
The 3-month weather outlook, February-April, favors below-normal temperatures and slightly above-normal precipitation. A somewhat later than normal spring melt season is anticipated.
The next Spring Flood Outlook from the NWS will be issued on Feb. 23.