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Nebraska City News-Press - Nebraska City, NE
  • Missouri River reservoirs ready for 2014

  • Based on the current soil moisture and snowpack conditions, runoff in the Missouri River Basin above Sioux City, Iowa, is forecast to be 26.1 million acre feet (MAF) in 2014, up slightly from the 25.1 MAF recorded in 2013. Normal runoff is 25.2 MAF.
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  • Based on the current soil moisture and snowpack conditions, runoff in the Missouri River Basin above Sioux City, Iowa, is forecast to be 26.1 million acre feet (MAF) in 2014, up slightly from the 25.1 MAF recorded in 2013. Normal runoff is 25.2 MAF.
    “Although drought conditions in the Missouri River Basin improved significantly in 2013, the Missouri River mainstem reservoir levels remain below normal due to the lingering effects of the 2012 drought,” said Jody Farhat, Chief of the Water Management Division. “Improved runoff into the reservoir system in 2013, in combination with the drought conservation measures that were implemented, increased the total volume of water stored in the reservoirs by 2 million acre-feet since last year at this time. However, the upper three reservoirs, Fort Peck in eastern Montana, Garrison in North Dakota, and Oahe in South Dakota, remain 5 to 11 feet below the desired operating levels.” 
    The near-normal runoff in 2013 was the product of below normal plains and mountain snowmelt runoff offset by above normal summer and fall precipitation in the Dakotas and eastern Montana. “Wet soil conditions in the Dakotas will likely contribute to spring runoff in 2014,” said Farhat. “However, because the reservoirs levels are below normal, the reservoir system is in excellent condition to capture high runoff this spring should that occur.”
    In addition to the normal flood control capacity of 16.3 MAF, the latest reservoir forecast indicates that an additional 6 MAF of storage capacity will be available in the carryover multiple-use zone on March 1, near the start of the runoff season. That effectively increases the total flood control capacity available by more than 35 percent. The carryover multiple-use zone, which is often referred to as the reservoir system’s “bank account for drought,” contains 38.5 MAF of water when full. It’s designed to serve the eight Congressionally authorized purposes, though at reduced levels, through a 12-year drought like that of the 1930s and early 1940s. Those purposes are flood control, navigation, water supply, irrigation, hydropower, recreation, water quality control, and fish and wildlife.
    To conserve water in the mainstem reservoir system, winter releases from Gavins Point are scheduled at the lowest level possible while still serving the needs of the municipal, industrial, and powerplant water intakes along the lower river. “Gavins Point releases have ranged from 13,000 cubic feet per second (cfs) to 18,000 cfs so far this winter to ensure intakes remain operational as cold temperatures moved through the region building ice on the river,” said Farhat. Releases have been above the target rate of 12,000 cfs to offset water lost to ice formation. “We will continue to monitor river ice conditions and adjust releases as necessary to ensure water supply is served to the extent reasonably possible.”
    Due to the below normal system storage, it is likely that the Corps’ flow support for Missouri River navigation will be between minimum and full service for the first half of next year’s navigation season as a drought conservation measure. Minimum service flow support is designed to provide an 8-feet-deep by 200-feet-wide navigation channel rather than the 9 feet by 300 feet supported with full-service flows. The actual service level will be set based on the total volume of water stored in the reservoir system on March 15 in accordance with guidelines in the Master Manual. Flow support for the second half of the navigation season, as well as the navigation season length, will be set based on the actual July 1 system storage.
    Page 2 of 2 - As of Jan. 1, the mountain snowpack was 110 percent of normal in the reach above Fort Peck and 113 percent of normal in the reach from Fort Peck to Garrison. Light-to-moderate plains snowpack has accumulated over much eastern Montana, North Dakota, and eastern South Dakota.
    “The Corps will continue to monitor the plains and mountain snowpack through the winter and into spring, as well as basin soil conditions to fine tune the regulation of the reservoir system based on the most up-to-date information,” said Farhat.

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