Despite Slight Improvement, Forecast Still Calls For Low Runoff In Missouri Basin
The latest runoff forecast from the Corps of Engineers’ Missouri River Basin Water Management Division, released June 8, shows slight improvement, but 2022 is still shaping up to be much drier than normal.
The updated basin runoff forecast for this year is 18.3 million acre-feet (maf.), which is just 71 percent of average. The forecast is 0.5 maf. higher than the forecast a month ago, but, if realized, that runoff amount would rank as the 25th lowest calendar year runoff since 1898, the Corps said.
“A wet April and May in North Dakota resulted in wetter soils in the state, but dry soils remain in the rest of the basin,” said John Remus, chief of the division. “Drought conditions persist but have improved over the last month. Over 20 percent of the basin is drought-free, and only 8 percent of the basin is left in extreme drought conditions, mostly in the state of Montana.”
Due to the ongoing drought and the amount of water stored in the reservoir system, water conservation measures will likely continue through the remainder of 2022 and into 2023, the division said.
Mountain snowpack in the upper Missouri River Basin has been melting at slower-than-average rates due to cooler-than-normal temperatures during the spring and early summer, which has also allowed for additional late season accumulation. As of June 1, 60 percent of the annual peak remained above Fort Peck Dam, and 68 percent of the annual peak remained above Garrison Dam. The mountain snowpack peaked above Fort Peck on April 29 at 85 percent of average, while the mountain snowpack in the Fort Peck to Garrison reach peaked on May 3 at 92 percent of average. Mountain snowpack normally peaks near April 15.
Gavins Point Dam releases will be set to provide minimum-service navigation flow support at all four target locations (Sioux City, Omaha, Nebraska City and Kansas City) through July 1, the Corps said. Flow targets may be missed to conserve water if there is no commercial navigation in a given reach. Minimum-service flow targets range from 25,000 cfs. at Sioux City, Iowa, to 35,000 cfs. at Kansas City, Mo.
Flow support for the second half of the navigation season, as well as the navigation season length, will be based on the actual system storage on July 1. The current forecast indicates that minimum service flow support will be required throughout the navigation season, and flow support may be shortened by slightly less than two weeks.