Submitted Photo As indicated in this graphic, February snowfall has pushed existing snowpack over the Missouri River drainage above normal levels with several weeks of winter remaining.

The mountain and plains snowpack throughout the Missouri River drainage increased considerably during February, a month in which record or near-record snowfall occurred in many regions of the northern United States. Increased snowfall has led to an increased snowmelt runoff forecast for the Missouri River basin.

The latest projections of the U.S Army Corps of Engineers is that runoff for the entire Missouri River system is expected to reach 112 percent of average. However, cautioned the Corps during a conference call Thursday, the runoff outlook can change significantly in the coming months and there is growing concern about ice jams and spring rainfall that could further increase expected high water levels.

The March runoff forecast calls for 28.4 million acre feet of water to enter the Missouri River system this spring. That is a large increase from the February projection of 25.6 maf. The reason, says the Corps, is heavy snowfall over much of the basin during February.

Doug Kluck, National Weather Service regional forecast center, explained that it is “relatively wet across most of the basin as a whole” and that “Montana, as far as we know right now, is relatively wet.” The Missouri and Yellowstone Rivers enter North Dakota from the west where “things have gotten wetter,” said Kluck.

Despite the increased runoff forecast the projected peak elevation of Lake Sakakawea this summer changed less than two feet from a month ago. Sakakawea is now expected to reach 1,843.9 feet in July. That compares to 1,842.2 feet in the outlook issued Feb. 1.

The entire reservoir system on the Missouri has been lowered to allow for annual spring runoff. John Remus, chief of water management division for the Corps’ Omaha, Nebraska office which oversees the Missouri River system, stated Thursday that “flood management remains the Corps’ number one priority” and that “flooding can occur due to ice jams and rainfall” and not just snowmelt alone.

Fort Peck Reservoir in Montana is expected to peak this summer at 2,242.1 feet, well within the flood control pool of 2,234 to 2,250 feet. Similarly, Lake Sakakawea’s current projected peak of 1,849.9 feet would be above the base elevation of the flood control pool of 1,837.5 feet and well below overflow of 1,854 feet.

Worth noting is that colder than usual weather could last late into the spring season and then be followed by a rapid snowmelt. That scenario, along with what the NWS describes as “relatively wet” conditions, could trigger another increase in runoff projections in the upper reaches of the Missouri Basin.

According to the NWS there is already concern about too much runoff in the lower reaches of the Missouri River with major flooding expected to occur along tributaries throughout South Dakota and Iowa.

Mountain snowpack water content above Fort Peck in Montana was measured at 107 percent of normal Thursday. The area considered to be the plains snowpack, basically the region between Fort Peck and Lake Sakakawea, was measured Thursday at 103 percent of normal.

Generally by March first about 80 percent of the total accumulation of snow has occurred but this year, says the NWS, that average may not hold true because of cold weather that seems likely to extend the snowfall season a few weeks later than usual.