View of Oahe Dam, located six miles north of Pierre, S.D. On August 17, 1962, President John F. Kennedy spoke at Oahe’s ‘Power on the Line’ dedication ceremony. The first of Oahe’s seven 85,000 Kilowatt generators was put into operation in March 1962 and the final generator went into operation in June 1963. The largest electricity producer on the river, Oahe produces 2.8 billion Kilowatts annually.
An overview of the construction The new dam flooded the farms, homes and businesses of a lot of people, many of them were Native Americans.
|Street View, Aug 2009|
|USACE-image, Photo by Cheryl Moore|
Oahe Dam Surge Tanks
Located near Pierre, South Dakota, the surge tanks at Oahe Dam are each 70 feet in diameter. There are two tanks per penstock. The surge tanks help regulate water flow to the power house turbines.
"Oahe’s generators were upgraded in the 1980s and are now capable of producing 112,290 Kilowatts each, for a total potential output of 786,000 Kilowatts. Oahe is the largest power producer on the Missouri River, producing 2.8 billion Kilowatts annually" [USACE-hydro]
|USACE via SDdigitialarchives|
This Power Plant at the Oahe Project near Pierre, S.D., is nearing completion by the U.S. Army Corps of Engineers. The surge tanks, each 145' high and 70' in diameter, help to control flows of water from the reservoir above the turbines below.
|Street View, Sep 2008|
I wonder what discharge rate causes flooding downsream.
In 2011, the USACE ignored advice about a big snow pack melting late in the year because of a long Winter, saturated soils and heavy rains; and they did not open spillways early. So later in the year they had to open the spillways even further creating an even bigger flood.
|ArgusLeader (paycount 5)|
The release volumes on the six dams also were moving up aggressively. By May 26, officials forecast releases of 100,000 cfs by mid-June and 110,000 cfs by early July - amounts well above previous records. And amounts that would mean major flooding for Pierre, Fort Pierre and Bismarck....
Concerns also grew for Oahe Dam. The last time the dam experienced high water, the earthen embankment moved south. The corps dispatched geotechnical staff to begin taking instrument readings. It was an area of concern that needed to be watched.
Officials also were working on models of potential release volumes from the dams. Farhat noted May 28 that, "Just adding one rainfall event like the one two weekends ago pushed the releases up to 150,000 (cfs)."
And that's what happened. More rain came.
Later that day, the corps issued a news release stating that five of six dams would ramp up to 150,000 cfs by mid-June.
[So if 110,000 cfs would cause major flooding, what did 15,000 cfs do?]
In a June 8, 2011 photo, sightseers look at water pouring from the outlet tunnels at Oahe Dam near Fort Pierre, S.D. The U.S. Army Corps of Engineers has opened the tunnels to help get rid of heavy rains and an impending snowmelt upstream in the Missouri River basin. The result is a pectacular show. (AP Photo/Chet Brokaw)
[So in June the snowmelt is still impending.]
USACE posted five images with the comment:
Yesterday [posted Sep 11, 2018], crews at Oahe Dam on the Missouri River opened one regulating tunnel. Releases are flowing from the power plant and regulating tunnel during scheduled maintenance to two units at the Oahe power plant.
Today's project orders at Oahe are for releases at 45,000 cubic feet per second. The current river stage on the Missouri River at Pierre is 10.87 feet (Sept. 11, 10 am) down from 12.26 on Sunday night. (Sept. 9)
[That is an impressive hydraulic jump.]
construction video That page also has a video about the 2011 floods. (A YouTube version of the 2011 flood video)
(new window) June 18, 2011, at 155,000 cfs June 19, 20011, at 160,000 cfs
(new window) spillway outlet footage Big Bend spillway
(new window) A lot of 85,000 cfs action