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Soggy Missouri Basin

Water levels rising again

Runoff from recent rainfall has significantly boosted the amount of water expected to enter the Missouri River system. So much so that the record basin inflow of 61 million acre feet of water that entered the system in the historic flood year of 2011 is within reach.

Based on record rains throughout the system in recent weeks, the U.S. Army Corps of Engineers has revised the expected runoff to 58.8 maf, an increase of 4 maf from the September 1 outlook which was already the second highest level on record. Furthermore, according to the National Weather Service, more heavy rains can be expected over the next several days.

Unlike 2011, when heavy runoff impacted the upper reservoirs on the Missouri – Fort Peck in Montana, Lake Sakakawea in North Dakota and Lake Oahe in both North and South Dakota, the bulk of this year’s runoff is primarily impacting the lower reaches of the Missouri River system. South Dakota, Nebraska and Iowa are all bracing for a possible third round of flooding this year. Kansas and Missouri could encounter high water troubles too.

In their latest update for Missouri Basin interests, the Corps announced that this year’s runoff has reached 232% of average with the latest round of heavy rainfall impacting an already high level of water in reservoirs throughout the system. The Corps cited some astonishingly high rainfall totals during the first two weeks of September.

Mitchell, S. Dak. received 7.6 inches of rain earlier this month where the norm is 0.96. Elsewhere, O’Neill, Nebraska received 5.15 inches of rain versus their long-term average of 0.94, Williston 6.13 inches versus a norm of 1.06 and Culbertson, Mont. 4.78 inches versus a norm of 0.47.

So much water has entered the system that the Corps reduced outflow from Gavins Point, Nebraska from 80,000 cubic feet per second to 60,000 cfs in an effort to reduce flooding impact downstream from that location. However, the reduction is only temporary with releases from Gavins Point to be increased to 80,000 cfs within the next few days.

“2019 continues to be a very wet year throughout the basin,” said John Remus, Corps of Engineers in Omaha, Neb.

Although high water levels remain in the Missouri River reservoirs, there’s ample storage remaining to contain any increased inflow due to rainfall in the coming days. However, the goal is to lower the reservoirs to specified target levels prior to freeze-up. If that cannot be accomplished there is a possibility that reservoir levels would be higher than ideal prior to next spring’s runoff season.

Despite the recent rains the levels of Fort Peck and Lake Sakakawea are expected to continue to decline over the coming days. So too is Lake Oahe. Lake Sakakawea stood at 1,846.55 feet Tuesday, several feet below what it was earlier this year.

The most recent projections from the Corps has Lake Sakakawea dropping to 1,845.4 feet by the end of Sept. with a release rate continuing at 46,000 cfs well into next month. 46,000 cfs is a higher than usual release from Lake Sakakawea at this time of year, as are release rates from other reservoirs in the system. The Corps is continuing efforts to evacuate water from the system to reach designated draw-down levels in the next several weeks.

More rain in forecast

1Another system of wet weather is bearing down on North Dakota. Even though the anticipated amount of precipitation has been reduced from earlier projections, significant rainfall is still expected to fall on ground already saturated from heavy September rains.

“We are still dealing with a fairly moist weather pattern, fairly unusual for this time of year,” said Bill Abeling, NWS meteorologist in Bismarck. “September is usually drying out time.”

The first of two doses of rainfall is expected to drop a quarter to a half-inch of rain across the state. Based on Tuesday’s projections, the second dose of rainfall will be much more significant.

“It’s another one of these slow moving, upper level troughs that will stay with us over the weekend,” said Abeling. “In western and central North Dakota, from Minot towards Bottineau, you could receive an inch to an inch and a half of rain.”

If realized, the rain could produce some new records for September rainfall in the region. Williston’s precipitation total for September has already passed the existing record. Williston recorded 6.13 inches of rain through Sept. 16, easily surpassing the old monthly record of 3.74 inches set in 1959. Normal for the Williston region is 1.06 inches.

A record seems certain to fall in Minot too. The City of Minot received 4.25 inches of rain from Sept. 1-16, 1.86 inches short of the all-time record year of 1971. The existing mark could be eclipsed by the system expected to reach the Minot area Friday. If not then, then perhaps on any one of the 10 days remaining in the month beyond Friday.

“We can start using the term unprecedented. We are getting close to all-time records for September,” remarked Abeling. “Highly unusual.”

Having too much moisture in the ground prior to freeze-up could have adverse implications next spring. The amount of snowmelt runoff is often affected by wet ground which has little or no room for additional saturation. Fortunately, there’s plenty of time remaining on the calendar to alleviate those concerns.

“We still have a lot left of this fall for drying things out,” said Allen Schlag, Bismarck NWS hydrologist. “This wet cycle can end as quickly as it started. I’m not real concerned at this point.”

–Kim Fundingsland

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