August 25th, 2009 - The U.S. Army Corps of Engineers announced today the flood control storage has been nearly evacuated at Jamestown and Pipestem Reservoirs and releases from the projects are approaching normal summer levels. 

“The flood control zone at Jamestown Reservoir reached its base of 1431 feet msl on Aug. 9,” said Col. David. C. Press, Omaha District Commander. The reservoir will be held at that level until early September and then gradually reduced to the normal winter level of 1429.8 feet. The current release is 50 cfs, which matches the reservoir inflows.    

At Pipestem Reservoir, the flood control zone is 1.1 percent occupied, with a current pool elevation of 1444.3 feet and a release of 200 cfs. On August 26 the release will be reduced to 150 cfs. 

By the end of this week the reservoir pool is expected to reach an elevation of 1443.7 feet, at which point the gates on the outlet works will be set to a fill-and-spill operation, where the flow is regulated by an overflow weir in the outlet works.  After that adjustment, releases will gradually decrease.  The reservoir should reach 1442.9 feet by Sept. 15 when releases will match expected inflows of 30 cfs. Releases will continue to diminish this fall as inflows decrease.

Pipestem Reservoir peaked on April 23 at a record level of 1492.3 feet, which was 4 feet below the crest of the emergency spillway and 5.3 feet higher than the previous record of 1487 feet set in May 1997. Jamestown Reservoir peaked on April 26 at a record 1454.1 feet, 0.1 feet above the crest of the emergency spillway and 8.2 feet higher than the previous record of 1445.9 feet, also set in May 1997.  

The peak daily inflow into Jamestown was 10,800 cfs and into Pipestem it was 9,200 cfs. Without the dams in place, the total discharge in Jamestown would have been 20,000 cfs. It is estimated that the dams prevented $70 million in damages in the city. The flow volume at the Jamestown gage for 2009 is expected to be 520,000 acre feet.  This far exceeds the previous record flow volume of 420,000 acre feet in 1997.