Manageable Souris runoff expected
The National Weather Service issued their latest Flood Potential Outlook for the Souris River Basin on Thursday. The conclusions are that there is a minimal chance for the Souris to reach major flood stage in North Dakota or cause significant problems.
The Flood Potential Outlook issued in early February caused some concern, especially when considering the heavy snowfalls that occurred early in the winter season. However, the past several weeks have been nearly snow free with unseasonably warm temperatures, good news for river watchers.
“The take home message from this outlook is that there is no big change from the previous one,” said Allen Schlag, Bismarck NWS hydrologist. “You will continue to hold on to the vast majority of the water equivalent you are sitting on already.”
Areas south and west of Minot have experienced considerably more melting of snow than has the Minot region. The area snowpack still is significant and carries enough moisture to be of concern, particularly if untimely precipitation should occur once the melt gets underway. However, says Schlag, the current weather outlook favors a very manageable runoff.
“It still looks to me like a real long, gentle melt season for most of North Dakota,” said Schlag. “There’s good reason to be optimistic. We’re still expecting above normal temperatures through most of next week, then more seasonal. That’s how we will start March.”
Warm soil conditions, says Schlag, are one of the favorable factors figured into the latest runoff outlook. It is expected that a portion of this spring’s runoff will infiltrate into the soil. If the ground was frozen with considerable frost, runoff would be increased because very little water would be able to be absorbed into the ground.
Thursday’s outlook shows a slight increase in water levels for the Souris at the Sherwood Crossing where minor floor stage is 1,623 feet. There is now a 75 percent chance of reaching that level at Sherwood. While minor flood stage causes almost no significant problems at that location it may raise the level of concern for residents further downstream at Mouse River Park which is located on the banks of the Souris.
A key measurement location on the Souris is Minot’s Broadway Bridge where minor flood stage 1,551 feet. According to the latest outlook, there’s only a 25 percent chance the Souris will reach that level. It should be noted that minor flood stage generally occurs well below the level of protection at many locations along the Souris. Major flood stage at the Broadway Bridge is 1,557 feet and, says the outlook, there’s only about a five percent chance that level will be reached this spring.
Lake Darling, the reservoir on the Souris northwest of Minot, is currently releasing about 260 cubic feet per second of water into the Souris as part of an effort to lower the reservoir to 1,594 feet prior to the major runoff season. Lake Darling was at 1,559.6 feet and declining slowly Thursday.
“One of the positives right now is that Alameda is moving to increase storage,” noted Schlag. “It has already been releasing water, clearing out the Souris River all the way to Lake Darling.”
Alameda Reservoir is located on Moose Mountain Creek near Oxbow, Saskatchewan. Moose Mountain Creek is a major tributary of the Souris. Snow on the ground in that drainage is similar to what has fallen in the Minot region, enough for authorities to take the precaution of lowering Alameda beyond usual spring target levels in order to accommodate what potentially could be higher than normal runoff.
Little has changed regarding runoff into the the Des Lacs River from the outlook issued earlier this month. Thursday’s outlook concludes the Des Lacs should remain below flood stage unless conditions should change.
“It’s a pretty complicated little stream,” said Schlag. “There’s still a lot of water coming through the Des Lacs.”
Schlag said he was “hoping” the flows in the Des Lacs would remain as predicted “unless something noticeable” happens, which could be in the form of additional snow or rainfall during the upcoming runoff period.
Flood Potential Outlooks were also issued yesterday for the James and Missouri River basins along with other drainages in North Dakota. No major problems are anticipated. The outlook noted the current warm weather has been beneficial in lowering flood risk at several locations.
“This relatively early melt should be viewed as favorable overall in the overall reduction of risk for widespread problematic flooding,” says the outlook. “In particular, enough moisture should come off the Knife, Heart, Cannonball, Apple Creek, Beaver Creek and the James River below Jamestown watersheds to lower their overall risk during the effective period of this outlook.”
The bulk of Missouri River Basin runoff generally comes from snowmelt in two regions defined by the U.S. Army Corps of Engineers – total snowfall above Fort Peck, Montana and total snowfall from Fort Peck to Lake Sakakawea. The latter is considered the Yellowstone River drainage.
The latest report on snow water content in the Montana mountain snowpack has increased significantly in one week. The above Fort Peck reach is now estimated at containing 92 percent of average snow water equivalent, up from 83 percent just seven days earlier. The SWE for the Yellowstone increased to 132 percent of average as compared to 117 percent the previous week.
Lake Sakakawea is expected to reach 1,845 feet in July. The lake stood at 1,837.47 feet Thursday.