Water Releases To Increase From Fort Peck Lake
Saturday, May 7th 2011
Omaha, Neb.– The U.S. Army Corps of Engineers Water Management Division announced today that it plans to gradually increase releases out of Fort Peck Reservoir this month.
"The reservoir ended the month at the highest end-of-April level since the spring of 1996," said Jody Farhat, Chief of the Water Management Division here. "Higher release rates are necessary to evacuate water already stored in the reservoir from the melt of plains snowpack and runoff that is yet to come from the above normal mountain snowpack."
Normally, the mountain snowpack peaks in mid-April, however this year it continued to accumulate into early May. Although it appears to have peaked recently at 141 percent of normal in the reach above Fort Peck and 136 percent of normal in the reach between Fort Peck and Garrison, cool weather coupled with additional snow could push those figures even higher.
The Corps plans to gradually increase releases from Fort Peck from the current rate of 9,000 cfs to 20,000 cfs by mid-May. Releases will remain at that rate through June and July.
Increased releases are necessary as the reservoir level is currently less than 5 feet from its exclusive flood control zone. The exclusive flood control zone, which extends from elevation 2246 feet to the top of the spillway gates at elevation 2250 feet, is maintained exclusively for flood control. Water is released from this zone as quickly as downstream channel conditions permit so that sufficient storage remains available for capturing future inflows. Fort Peck reservoir is expected to crest this summer 2 feet into the exclusive flood control zone at elevation 2248 feet. The top of the dam is at 2280.5 feet.
When all the generating units and transmission facilities are available, the release capacity of the powerplant is 15,000 cfs. However, current on-going maintenance efforts are limiting releases to approximately 10,000 cfs through the powerplant. Releases above the powerplant capacity will be made through the spillway. The Fort Peck spillway has not been used since 1997.
"Releases haven't been this high in more than 10 years so we are asking the public to be cautious in and around the river. "There is also the potential for bank erosion adjacent to the river," said John Daggett, Fort Peck Operations Manager.
Daggett advised irrigators to monitor irrigation pumps regularly as changes in releases may affect pump intakes. "As releases are increased, the stages on the river below Fort Peck are expected to rise several feet. However, once they reach the desired rate only minimal fluctuations in daily stages are expected."
Fort Peck rose by 2.2 feet in April, ending the month at elevation 2240.9 feet. It is expected to increase by 2.2 feet in May, ending the month near elevation 2243 feet. The reservoir is currently 16 feet higher than it was a year ago at this time. Fort Peck was the last of the Corps' mainstem dams to recover from the drought. The reservoir, which had been low since 1999, reached the normal operating level in July 2010.
Similar conditions are being experienced throughout the mainstem reservoir system. Three other Corps' dams on the Missouri River (Garrison, Oahe and Fort Randall) have significant volumes of flood water to evacuate, and all six mainstem reservoirs will see much higher releases in the coming days. The other two Corps' dams on the Missouri River (Big Bend and Gavins Point) have little to no flood control storage and essentially pass inflow.
"Our goal is to evacuate the water as quickly and as safely as possible so that we are ready for the next flood event," Farhat said. "Public safety is our number one concern."