The 2005 commercial navigation season was shortened by 48 days, the most since the system of reservoirs first filled in 1967. The season ended on Oct. 14 at the mouth of the river near St. Louis. In addition, releases from the dams have been cut far below normal levels. The release rate at Gavins Point Dam was reduced 75 percent, from the average of 36,100 cubic feet per second (cfs) to only 9,000 cfs.
Runoff above Sioux City, IA, in October was 1.2 million acre feet (MAF), 102 percent of normal. "There has been enough downstream tributary inflow to allow us to maintain lower releases from the reservoirs, while continuing to meet the needs of water supply intakes on the lower river" said Larry Cieslik, chief of the Water Management office in Omaha.
The current runoff forecast for 2005 is 20 MAF, 80 percent of normal, compared to the normal of 25.2 MAF.
System storage ended October at 36.3 MAF, an increase from the 35.7 MAF recorded last year at this time. The amount of water currently stored in the reservoirs is 19.5 MAF below average.
The draft 2005-2006 Annual Operating Plan was released Oct. 20 for public review and comment. It proposes two "spring pulses" to satisfy the requirements of the Endangered Species Act, provided there is sufficient water in the reservoir system. To conserve water, the pulses would be delayed until 2007 if there were not at least 36.5 MAF of storage on March 1 and May 1. Increased reservoir levels are dependent on rain this fall and snow on the plains and in the mountains this winter.
The draft plan maintains the same level of "flood control constraints" currently in the Master Water Control Manual. These are the flows that act as triggers for reducing releases from Gavins Point during higher downstream river levels.
The plan also describes the overall management plan for the dams and reservoirs. It anticipates that there will be only minimum flows for the 2006 navigation season and it could be shortened 15 to 58 days, depending on runoff this winter and spring. A final determination season length will be made July 1, 2006.
Steady to rising reservoir levels during the spring fish spawn are likely if there is normal or above normal runoff. However, continued drought conditions may not make that possible at all the upper three reservoirs. To the extent reasonably possible, the Corps will set releases at Garrison Dam to result in a steady to rising pool during April and May. The ability to provide such conditions depends on the volume, time and distribution of the runoff from melting snow on the plains and in the mountains of Montana and Wyoming.
The draft 2005-2006 Annual Operating Plan with a detailed description of the spring pulses is posted on the Northwestern Division website: www.nwd.usace.army.mil and is also available in hard copy by writing to: Water Management Division, U.S. Army Corps of Engineers, 12565 West Center Road, Omaha, NE 68144. Comments on the draft plan and the supplement to the Master Water Control Manual will be taken during public meetings, in writing, and via e-mail through Dec. 1.
Gavins Point reservoir will remain near elevation 1207 feet above mean sea level (msl) during November. Releases averaged a record low 12,300 cfs in October compared to the normal 36,100 cfs. They were gradually reduced 9,000 cfs by Oct. 19, where they were held until early November. The previous record low average release for October was set at 14,100 cfs. Releases were slightly increased on Nov. 3. Further adjustments may be necessary depending on downstream conditions.
Fort Randall releases averaged 10,400 cfs in October, also a record low. They will average 7,000 cfs in November as needed to maintain Gavins Point reservoir near its desired elevation. Fort Randall reservoir ended October at 1341.2 feet msl. The reservoir will end November near elevation 1340 feet msl.
Big Bend reservoir will remain in its normal elevation range of 1420 to 1421 feet. Releases will be adjusted to meet hydropower needs.
Oahe reservoir rose a foot during October, ending the month at elevation 1573.9 feet msl. It will rise two feet in November, ending the month 24 feet below average. The reservoir is slightly less than a foot lower than it was last year at this time.
Garrison releases averaged 12,600 cfs during October, compared to the normal 19,600 cfs. They will average 13,000 cfs through November. Garrison reservoir remained essentially level in October, ending the month at elevation 1814 feet msl. It will remain steady in November, ending the month 24 feet below average. The reservoir is a foot higher than last year at this time.
Fort Peck releases averaged 4,300 cfs in October, compared to the normal 8,500 cfs. They will remain near that level through November. The reservoir rose half a foot in October, ending the month at elevation 2202.6 feet msl. It will remain level in November, ending the month 30 feet below average. It is currently 2.8 feet higher than last year at this time.
The six main stem power plants generated 314 million kilowatt hours (kWh) of electricity in October, 37 percent of normal because of reduced releases from the dams. This was the second lowest October generation on record, just slightly higher than last year's record low of 310 million kWh. The forecast for 2005 energy production is 5.5 billion kWh, compared to a normal of 10 billion kWh.