US Army Corps of Engineers
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image - construction at Folsom Dam

Coordinated dam releases key to reducing winter storm flood threat

Published Jan. 14, 2013
Advanced weather and channel flow data shared via instant communications between water management agencies is critical to California’s Central Valley during an active flood season. (U.S. Army photo illustration by Robert Kidd/Released)

Advanced weather and channel flow data shared via instant communications between water management agencies is critical to California’s Central Valley during an active flood season. (U.S. Army photo illustration by Robert Kidd/Released)

Looking eastward from over the Pacific, California’s Central Valley is carved out between coastal and western mountain ranges and includes some of the world’s most productive farmland.

Looking eastward from over the Pacific, California’s Central Valley is carved out between coastal and western mountain ranges and includes some of the world’s most productive farmland.

SACRAMENTO, Calif. – The weather and geography that make California’s Central Valley a world-class agricultural machine also fuel the potential for disastrous flooding – conditions constantly gauged by the water management section of the U.S. Army Corps of Engineers Sacramento District.

“Flood risk management is my group’s number one mission this time of year – helping protect life and property,” said Wayne Johnson, chief of the Sacramento District water management section.

Sacramento District water managers oversee the operation of 33 flood control reservoirs in California – 16 Corps-owned-and-operated facilities and 17 non-Corps reservoirs ranging from Shasta Lake in the north to Isabella Lake in the south and from the Sierra Nevada mountains to the Russian River basin. The District is also responsible for overseeing the operation of eight non-Corps flood control reservoirs in the Great Basin of Utah and seven non-Corps flood control reservoirs in the upper Colorado River basin of Utah and Colorado.

During flood season, typically November through April, Corps water managers constantly communicate with the National Weather Service, California Department of Water Resources, U.S. Bureau of Reclamation, U.S. Geological Survey and a host of regional water agencies, sharing information regarding current stream flows, weather forecasts and timing of specific reservoir releases.

Johnson and 14 more Sacramento district personnel focus on two tasks – gathering data and analyzing that data to manage reservoir operation and storage.

“Each of the reservoirs we manage has its individual operating plan, but during a critical high-water event we closely coordinate reservoir releases to help manage all the downstream watersheds,” said Johnson. “During a heavy rain event or a major snow melt, many uncontrolled streams and tributaries are also feeding California’s water systems.”

When a potential flood event develops, communication intensifies between the major water agencies. “Depending on intensity of storms and current reservoir levels, our team may work around the clock,” said Johnson.

Open, honest, out-of-the-box communication between federal, state and local agencies was pivotal in averting disaster during the floods of 1986 in Northern California. Joe Countryman, currently a member of the Central Valley Flood Protection Board, was chief of the Sacramento District’s engineering civil design branch at the time.

As storm waters threatened to overwhelm Folsom Dam, Sacramento’s primary flood defense, Countryman represented the Corps in discussions with DWR and the Bureau of Reclamation.

“Our agencies came together and jointly agreed to increase the release rate from Folsom Dam beyond prescribed operating limits, because of the crucial threat we faced,” said Countryman. That difficult decision made under extreme pressure was pivotal in preventing loss of life and destruction in the region.

“That same spirit of honest, open communication between local, state and federal water agencies has continued to protect the region, leading directly to the improvements made through the Joint Federal Project at Folsom Dam,” said Countryman.

The district is currently working with the board and USBR to build a new spillway at Folsom Dam, allowing for more flexibility in releasing water during big storms.

“Our goal is to control dangerously high flow rates in our biggest waterways (the Sacramento, San Joaquin, Russian and Truckee Rivers) during flood events,” said Johnson. “During times of high flows, all reservoir operating agencies act together to lower flows as much as possible in the entire river system rather than operating each reservoir independently.”

Technology continues to improve the joint effort. Representatives of federal and state water control agencies in the Sacramento region are now tied together electronically, staging regular video conferences during active storm events.

Sacramento District also maintains approximately 120 gages collecting water flow and weather data in California’s Central Valley, coastal mountains and the Sierra Nevada.
USGS, in collaboration with the Corps and 850 other cooperators, operates a nationwide stream gage network that monitors the water level and flow of the nation’s rivers and streams. The National Weather Service, under NOAA, forecasts flooding using this stream gage data to reduce losses from flood damages. DWR and USBR also operate many of the largest flood control reservoirs in the region.
“During the rainstorms this past December, our reservoirs had plenty of extra capacity, so the primary concern for residents was localized flooding coming from creeks and other uncontrolled tributaries,” said Johnson. “We have ample capacity now, but we remain vigilant. That’s in the job description.”