Runoff in the Missouri River basin above Sioux City, Iowa, last year (2021) was 59% of average.
The US Army Corps of Engineers says 2021 was the 10th lowest annual runoff for the Missouri River Basin in 123 years of record-keeping. With no relief in sight for the ongoing drought, the Corps expects runoff into the mainstem reservoir system will remain below normal.
Based on current runoff trends, soil moisture and plains and mountain snowpack, the 2022 runoff in the Missouri River basin above Sioux City, Iowa, is forecast to be 84% of average (21.7 million acre-feet). The Corps says mountain snowpack in the upper basin is accumulating at a below-average rate, but more than half of the mountain snowfall typically occurs from Jan. 1 to mid-April, peaking near April 15.
At the start of the 2022 runoff season, which typically begins around March 1, the Corps anticipates the total volume of water stored in the mainstem reservoir system will be 48.2 MAF– which is 7.9 MAF below the top of the carryover multiple use zone. The mainstem Missouri River reservoir system is designed to use the water contained within the carryover multiple use zone to provide service to the eight Congressionally authorized purposes during extended droughts. Those purposes are flood control, navigation, water supply, irrigation, hydropower, recreation, water quality control, and fish and wildlife.
Service to the authorized purposes will be reduced to conserve water in the reservoir system should drought conditions persist. Primary drought conservation measures outlined in the Master Manual include reducing winter releases and flow support for navigation. Flow support to navigation was reduced on July 1, 2021. A significant portion of the water stored in the multiple use zone was used in 2021 to serve the authorized purposes and resulted in implementation of water conservation measures.
To further conserve water in the Missouri River Mainstem reservoir system, minimum releases from Gavins Point Dam (at Yankton) are scheduled this winter while still serving the needs of the municipal, industrial and powerplant water intakes along the lower river. Find more information in the final Annual Operating Plan for the Missouri River Basin for 2021–2022, posted at https://www.nwd.usace.army.mil/MRWM/Reports/.
Infographic credit US Army Corps of Engineers.
Infographic credit US Army Corps of Engineers.
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