U.S. Army Corps of Engineers’ reservoirs ready for spring

Published Feb. 28, 2011

ROCK ISLAND, Ill. – In anticipation of spring snowmelt and rainfall, the U.S. Army Corps of Engineers, Rock Island District, is ensuring its three Iowa reservoirs are ready for increased inflows to assist in reducing the risk of downstream flooding.

 

Saylorville Lake in Johnston, Iowa, is currently at 836.32 feet (0.35 percent of flood storage used); approximately one-third foot above its normal pool elevation of 836 feet due to increased inflow into the reservoir.  As inflows decrease, the reservoir level will be maintained at the normal pool elevation in anticipation of spring rain and snowmelt runoff.  The normal conservation pool represents 11.5 percent (23.9 billion gallons) of Saylorville Lake’s total storage capacity of 184.7 billion gallons.  Fluctuation of the pool level will result from snowmelt and rainfall entering the reservoir.

 

The Saylorville Lake project encompasses 25,515 acres of land and water and provides 13 recreation sites.  An estimated 1,300,000 visits occurred in fiscal year 2010 with an economic impact of approximately $27,000,000.  Since its completion in 1977, the reservoir has prevented more than $183,500,000* in flood-related damages.

 

Coralville Lake in Iowa City, Iowa, is currently at 681.1 feet; approximately 2.1 feet above its spring conservation pool elevation of 679 feet and is being lowered to reach that elevation.  As inflows decrease, the reservoir level will be maintained at the spring pool elevation in anticipation of spring rain and snowmelt runoff.  The spring pool is four feet below Coralville Lake’s normal (summer) pool elevation of 683 feet and provides approximately 4 billion gallons of additional flood storage.  The spring pool represents 3.7 percent (5.11 billion gallons) of Coralville Lake’s total storage capacity of 128 billion gallons.  Fluctuation of the pool level will result from snowmelt and rainfall entering the reservoir.

 

The Coralville Lake project encompasses 24,591 acres of land and water and provides 11 recreation sites.  An estimated 1,138,090 visits occurred in fiscal year 2010 with an economic impact of approximately $22,400,000.  Since its completion in 1958, the reservoir has prevented more than $184,000,000* in flood-related damages.

 

Lake Red Rock in Knoxville, Iowa, is currently at 734.36 feet (0.0 percent of flood storage used); approximately 7.6 feet below its normal pool elevation of 742 feet.  The pool level was lowered to replace the dam’s Tainter gate cables and complete additional construction work to bring the reservoir to its full functional capability.  As inflows increase, the reservoir level will be maintained at the normal pool elevation in anticipation of spring rain and snowmelt runoff.  The normal conservation pool represents approximately 11.6 percent (61.59 billion gallons) of Lake Red Rock’s total storage capacity of 467.92 billion gallons.

 

The Lake Red Rock project encompasses 50,300 acres of land and water and provides 11 recreation sites.  An estimated 741,250 visits occurred in fiscal year 2010 with an economic impact of approximately $14,300,000.  Since its completion in 1969, the reservoir has prevented more than $559,000,000* in flood-related damages.

 

Reservoir pool levels are maintained for authorized project purposes which include flood control, water supply (Saylorville Lake only), low flow augmentation, fish and wildlife management and recreation.  Lowering pool levels an additional amount in the spring could result in bank sloughing, increases the risk for fish kills and significantly increases the potential for ice jams at the controlling works which could impact reservoir releases and cause pool levels to rise more rapidly.  Additionally, lowering reservoirs beyond their authorized level does not afford significant flood storage capacity as empty reservoirs would fill to flood storage capacity within 18 to 33 hours during flood events similar to 2008.

 

For more information about the District’s reservoir operations, visit the reservoir website on the WWW @: http://go.usa.gov/gAn.

 

* Flood-related damages are not indexed for 2011 price levels.  Figures are representative of the year in which they occurred.

 

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EDITOR’S NOTE:  Please contact the following individuals at each reservoir for additional information:

 

Coralville Lake:  John Castle, Operations Manager, (319) 338-3543 x6304, John.C.Castle@usace.army.mil

Saylorville Lake: Jeff Rose, Operations Manager, (515) 276-4656 x6504, Jeffrey.W.Rose@usace.army.mil

Lake Red Rock: John Holt, Assistant Operations Manager, (641) 828-7522 x6404, John.F.Holt@usace.army.mil


Release no. 11-03-09