Low Risk, Changes Likely
BISMARCK — As the winter snowpack in the region continues to develop, so too does analysis of its possible impact on river flows in the spring.
The National Weather Service has issued a Flood Potential Outlook for the Souris River Basin. It does not contain any language or data that can be considered alarming, quite the opposite, but it does note that several weeks of winter remain and that conditions are almost certain to change over that period.
When people see snow building up in the region, it is understandable that thoughts turn to what will be the impact on the drainage when the snowmelt gets underway this spring. The Souris River has ample history of flowing out of its banks, most recently in the historic flood of 2011 that led to the ongoing flood control project in Minot and other points along the Souris today.
This year though, at least to date, the NWS concludes that the Souris will behave itself, saying, “In general, lower than normal risk of flooding exists in the western portion of the Souris River basin in North Dakota.”
The Flood Potential Outlook adds that the flood risk on the Souris increases “to near normal” downstream from Minot. However, the NWS rates the risk of major flooding at most locations on the Souris, including Minot, at less than 5%. It adds a precautionary statement that, “Roughly two months remain of the normal snow accumulation season for the Souris River basin.”
As for snow water equivalent, the NWS says it varies greatly from one locale to another, sometimes without much distance separating one area from another.
The NWS says less than an inch of water is in the snowpack in Williams and Divide Counties, but more than four inches in portions of McHenry, Bottineau, and Rolette Counties. Average for this time of year is 1.5 inches.
A number of factors can affect the spring runoff. It should be noted that much of the area now covered in snow was mired in drought last summer, meaning there is ample room for moisture to be absorbed into the ground. Other factors to consider include frost depth, speed of melt, storage available in potholes, spring rain, and contributions from various tributaries.
For Minot, Souris River flows are closely tied to the amount of water being released through the Lake Darling Dam. That facility, working in conjunction with two major dams on the Souris drainage in Canada, helps regulate spring flows. Below Lake Darling, at Burlington, the Des Lacs River flows into the Souris. That water source has the potential to significantly add to Souris River flows, but generally for a period of only a few days.
Further downstream the Wintering River and Willow Creek enter the Souris, both with the potential to impact flows. Willow Creek drains the most substantial area, flowing south out of the Turtle Mountain region, joining the Souris near Upham, and adding to the northbound flow of that river.
The next NWS issuance of a Flood Potential Outlook for the Souris River is scheduled for February 10.