2013-02-21 / Top News

Corps gives Missouri River forecast

The updated runoff forecast for the upper Missouri River basin continues to indicate less-than-normal runoff in 2013.

Based on the current soil moisture and snowpack conditions, 2013 runoff in the Missouri River basin above Sioux City, Iowa, is forecast to be 19.9 million acre feet (MAF), 80 percent of normal.

Runoff is typically slowed during winter months as rivers freeze over and cause temporary reductions in inflows into the reservoir system. However, warmerthan normal temperatures, plains snowmelt and rainfall runoff above Sioux City, Iowa, resulted in slightly above normal runoff during January.

“Based on the current forecast, the total volume of water stored in the mainstem reservoir system at the start of the 2013 runoff season is expected to be 8.3 MAF below the top of the Carryover Multiple Use Zone,” Jody Farhat, Chief of the Missouri River Water Management Division, said.

The Carryover Multiple Use Zone is designed to provide service to the eight Congressionally authorized purposes, though at reduced levels, through a 12-year drought like that of the 1930s and early 1940s.

Releases from Gavins Point are currently being scheduled at 14,000 cfs throughout the month of February.

“As a water conservation measure, releases are being scheduled at the lowest level possible this winter while still serving the needs of the municipal, industrial and powerplant water intakes along the lower river,” Farhat said.

Weather and river conditions will continue to be monitored, and additional release increases may be necessary on a temporary basis if extremely cold temperatures return.

Releases from Gavins Point will be stepped up in mid-March for the 2013 navigation season, which will open on April 1 at the mouth near St. Louis. The current forecast indicates that minimum service flow support will be provided for navigation and other downstream uses during the first half of the navigation season. The Corps will set the level of flow support and season length for the second half of the navigation season following the system storage check on July 1. Minimum-service flow targets range from 25,000 cfs at Sioux City, Iowa, to 35,000 cfs at Kansas City, Mo., and are designed to provide a navigation channel that is 8 feet deep by 200 feet wide. Full service navigation flows providea9by300feetchannel. As a result, barges may be required to haul lighter loads.

Mountain snowpack is currently 96 percent of normal in the reach above Fort Peck and 89 percent in the reach between the Fort Peck and Garrison. Typically 64 percent of the peak mountain snowpack accumulation has occurred by February 1.

“The Corps will continue to monitor both the plains and mountain snowpack throughout the winter, as well as basin soil conditions to fine tune the regulation of the reservoir system based on the most up to date information,” Farhat said.

Reservoir forecasts

Gavins Point releases averaged 14,800 cfs during the month of January. Releases were temporarily increased to 16,000 cfs in early February due to an ice jam on the Missouri River above Sioux City. No flooding resulted during the jam. The ice jam caused a temporary reduction in flows downstream of the jam, which resulted in a drop in stages. The current release rate of 14,000 cfs will continue in February. The reservoir behind Gavins Point dam ended January at elevation 1207.3 feet msl. The reservoir will gradually be lowered to elevation 1206 by the end of February to make room for potential spring runoff.

Fort Randall releases averaged 12,100 cfs during January. Releases are expected to average near 11,000 this month, and will be adjusted as necessary to maintain the desired elevation at Gavins Point. The reservoir ended January at elevation 1346.2 feet msl, up 6.2 feet during the month. It is expected to rise 3.8 feet by the end of the February. The refill of the reservoir is designed to provide increased winter hydropower generation at Oahe and Big Bend.

Big Bend releases averaged 16,700 cfs during the month of January. They are expected to average 14,700 cfs this month. The reservoir will remain near its normal elevation of 1420 feet msl during February.

Oahe releases averaged 17,300 cfs during the month of January. Releases are expected to average 14,700 cfs this month. The reservoir ended January at elevation 1594.7 feet msl, up 1.1 feet during the month. The reservoir is expected to climb about two feet during the month of February.

Garrison releases averaged 21,500 cfs in January. Releases were gradually increased from 17,000 cfs in late December to 23,000 cfs by mid-January as part of normal operations to balance system storage in the upper three reservoirs. Releases will remain at 23,000 cfs during February. The reservoir ended the month at elevation 1828.2 feet msl, down 1.2 feet from the previous month. It is expected to decline about a foot during February.

Fort Peck releases averaged 12,300 cfs in January. Releases were increased from 11,500 cfs to 12,500 cfs in early January to better balance storage in the upper three reservoirs and to provide additional winter hydropower. The reservoir ended the month at elevation 2224.0 feet msl, down 2.1 feet from the previous month. It is forecast to drop nearly two feet during February.

The six mainstem power plants generated 634 million kilowatt hours of electricity in January. Typical power generation for the month of January is 714 million kWh. The power plants are projected to generate 7.9 billion kWh of electricity this year, compared to the normal of 10 billion kWh.

To view the detailed threeweek release forecast for the mainstem dams, go to: www.nwd-mr.usace.army.mil/rcc/ reports/twout.html.

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