Daily reduction increments of 3,000 cubic feet per second (cfs) will be made until a rate of 10,000 cfs is reached on Oct. 13. Releases may be further cut to 9,000 cfs if tributary inflow below the reservoir system is adequate to allow municipal intakes to operate at lower release rate. Stages are expected to drop approximately 4 to 6 feet over the coming weeks as the lower releases move downstream and the tributary contributions fall off.
"Runoff throughout the basin continues to be extraordinarily low," said Larry Cieslik, Chief of the Water Management office in Omaha. "We expect to reach a record-low storage of 34.7 MAF by the end of the month, surpassing the previous record of 34.8 MAF set in January 2005. Reservoir storage fell by 1.2 million acre feet in September."
Because of drought-depleted reservoirs, the main stem powerplants are expected to produce nearly 40 percent less hydropower this year. To make up for the lower generation in September, the Western Area Power Administration, which markets the power produced by dams, had to purchase additional electricity to meet its contract obligations to utilities throughout the upper Midwest.
Releases from Gavins Point Dam will range from 25,000 to 9,000 cfs in October. The reservoir will remain near its current elevation of 1207.6 feet above mean sea level (msl). Releases averaged 27,600 cfs in September, compared to the long-term average of 36,300 cfs.
Fort Randall releases averaged 26,300 cfs in September. They will be adjusted in October as necessary to maintain Gavins Point near its desired elevation. The fall drawdown progressed slower than expected in September, resulting a lower than expected level in Oahe reservoir. Fort Randall ended the month at 1344.5 feet. It will continue its annual fall drawdown to provide storage space for winter hydropower releases and to prevent ice-related damage along the river, reaching 1339.5 feet by the end of this month and 1338.3 by the end of November.
Big Bend reservoir will remain in its normal range of 1420 to 1421 feet. Releases will be adjusted to meet hydropower needs.
Oahe reservoir rose just over a foot in September, ending at elevation 1571.4 feet msl. It was expected to rise nearly 3 feet. Lower releases in October will put the Fort Randall drawdown back on schedule and will result in Oahe rising about 2 feet, back to the level previously forecast. The reservoir will end the month near elevation 1573.5, 3.3 feet above its record low level of 1570.2 feet set on Aug. 30, and nearly 26.5 feet below normal. The reservoir is 1.5 feet higher than it was last year at this time.
Garrison releases averaged 18,100 cfs during September compared to the long-term average of 21,000 cfs. Releases were reduced from 24,000 cfs to 12,000 cfs in mid-month, where they will be maintained through October. Garrison reservoir fell 2.6 feet in September, ending this month at 1809.5 feet msl. It will continue its normal annual decline in October, falling 1.1 feet to 1808.5 feet, ending this month 28.7 feet below normal. The reservoir is 4.6 feet lower than last year at this time.
Fort Peck releases averaged 6,800 cfs in September, compared to the long-term average of 9,100 cfs, and will be maintained at 6,000 cfs in October. The reservoir fell a foot in September, ending at elevation 2202.6 feet msl. It will fall about half a foot in October, ending this month at elevation 2202.1 feet, about 30 feet below normal. It is half a foot higher than last year at this time. The reservoir is forecast to reach a record low of 2917.3 feet at the end of February, surpassing the previous record of 2198.3 feet set in January 2005.
The six main stem power plants generated 577 million kilowatt hours (kWh) of electricity in September, only 63 percent of normal because of lower pool levels and reduced releases from the dams. The forecast for energy production in 2006 is 6.2 billion kWh, compared to the average of 10 billion kWh.