YANKTON, S.D. (AP) - Because of prolonged drought, the U.S. Army Corps of Engineers said it may consider water conservation measures later this year in the Missouri River basin.
At this point, the Corps doesn’t anticipate the need to take such measures, according to John Remus, chief of the Missouri River Basin water management division in Omaha.
In contrast to 2019 flooding, most of the basin - including the Yankton region - is now classified as abnormally dry or in moderate or severe drought. An area northeast of Yankton is listed as being in extreme drought.
The latest 2021 Spring Outlook suggests that odds favor slightly drier-than-normal conditions across much of the Missouri Basin, the Yankton Press and Dakotan reported.
“At this point, the basin is much drier than in the current past,” Remus said during a conference call. “As of now, the reservoir storage is in very good shape from the standpoint of flood control and flow support for navigation. But if the dry conditions persist or worsen, we may be in for water conservation measures later this year.”
The Gavins Point Dam releases near Yankton averaged 18,300 cubic feet per second (cfs) during the past month. Gavins Point currently releases 17,000 cfs, which will be increased around March 19 to provide full-service navigation flow support on the lower Missouri River.
Fort Randall Dam releases at Pickstown averaged 15,100 cfs during the past month. Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point and to back up Gavins Point releases.
Remus said he wasn’t seeking to alarm anyone because the basin currently contains adequate water. However, he wanted to provide advance notice of possible changes in releases should drought conditions persist.
“If we have a really dry spring and summer, and we get down to a minimum flow of 12,000 cfs, it can be problematic for water intakes,” he said.
Now is a good time for intake operators to review or update their needed measures in case of low releases and water conservation measures, Remus said. “They may need to dust off their contingency plans,” he said.
Any water conservation plans, if necessary, wouldn’t be taken until this summer, he added.
“We wouldn’t implement anything until July 1, when we do our storage checks,” he said. “Those storage checks are based on the total amount of water stored in the system.”
Because of the drought conditions, inflows in the Missouri River basin above Sioux City were well-below average in February. The 2021 calendar year runoff forecast for the upper basin remains below average.
February runoff in the upper Basin was 0.8 million acre-feet, 70% of average. The 2021 calendar year runoff forecast for the upper Basin is 21.8 MAF, 84% of average.
The Corps has evacuated all of the flood water in the Missouri River reservoirs in preparation for the 2021 runoff season. System storage is currently 55.6 MAF, 0.5 MAF below the base of the annual flood control zone.
The mountain snowpack ranges in the normal to below normal category, according Kevin Low, the Missouri River Basin forecast center hydrologist. By this point, the mountains have usually accumulated 80% of its snow water equivalent (swe).
The March 1 mountain snowpack in the Fort Peck and the Fort Peck to Garrison reaches was 94% of average. Mountain snowpack normally peaks near April 15. Currently, plains snowpack in the upper basin remains light.
The plains snowpack is non-existent, and the soils are extremely dry. The river ice threats are limited to the northern tier, Low added.
During the past several years, the focus has been on the evacuation of stored flood water, he said. Moving the water supply hasn’t been an issue this year.
Those sentiments were echoed by Doug Kluck, the NOAA Central Regional Climate Services director in Kansas City.
“We have no plains snowpack, especially Montana, North Dakota and South Dakota this time of year,” he said, noting the unusual conditions.
The next week doesn’t contain any forecast of major precipitation, Kluck said. However, any moisture could provide relief with dry conditions and wildfires in parts of the basin, he said.
“Later in the seven-day period, there is another (weather) system across the northern part of the basin but nothing to write home about,” he said. “We hope this accumulates in the mountains and we can tamp down the dust and wildfires in the dry areas where they desperately need something before it gets too warm.
The 8- to 14-day outlook calls for below-normal precipitation in Montana, Wyoming and the plains. Looking ahead to March-May, much of the basin could continue seeing above-average temperatures. He foresees a fading of the La Nina weather pattern, which generally favors cool and wet weather.
“We’re trying to avoid going into spring, and especially summer, with this kind of pattern. The only thing summer does is dry things out more, and summer is hotter,” he said.
“We’re hoping for a good spring and a wet season across the Missouri Basin, especially the upper basin and Colorado. But the drought outlook isn’t favorable. The precipitation folks are saying there isn’t going to be a lot of change through the end of May.”
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