IOWA CITY, IA – (May 29) Recent heavy rainfall over portions of north central Iowa has increased runoff into Coralville Reservoir. To maintain water storage and flood risk management capability, reservoir outflows were increased to 10,000 cubic feet per second (cfs) this morning, May 29.
Increased inflow into the Coralville Reservoir on the Iowa River is causing the pool level to rise significantly. Today, the Coralville Lake level is at 698.80 feet and is continuing to rise. Inflow into the reservoir is forecast to raise the pool level to slightly below the spillway crest of 712' on June 7. This level represents use of approximately 98 percent of storage capacity with a pool level 1 foot below the spillway at 712 feet. The record high level at Coralville Lake was 717.02 feet on June 15, 2008.
In an effort to reduce downstream flooding and prevent the pool level from overtopping the spillway, the Corps is anticipating the need to increase outflows from 10,000 cfs to 12,000 cfs on May 30, followed by an additional increase to 13,000 cfs on June 1.
If levels overtop the spillway, significant flooding can be expected in the Iowa City area. To reduce the risk of this occurring, the Corps is anticipating the need to increase outflows from 10,000 cfs to 12,000 cfs on May 30, followed by an additional increase to 13,000 cfs on June 1. Additional increases in release rates above 13,000 cfs may be implemented to ensure water levels remain below the spillway.
Coralville Reservoir inflow at 6 a.m., Wednesday, May 29, was 16,700 cfs with an average outflow of 6,300 cfs. At 3 p.m., today, Coralville is storing 153,940 acre feet of water (50.16 billion gallons) and is at 32.04 percent storage capacity.
The increased release is necessary to evacuate the water stored in the reservoir as quickly as possible to accommodate current and forecasted inflow. Downstream residents should be alert to rising water levels as the reservoir outflow is increased.
Updated information about Coralville Reservoir is available on the Web by visiting http://www.mvr.usace.army.mil/About/Offices/EmergencyManagement/2013Flood.aspx.
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