The lower Gavins Point releases helped ease flooding on the lower river and benefited the Missouri River mainstem reservoir system, according to Larry Cieslik, chief of the Corps water management office in Omaha, NE. The water stored in the system is extremely low because of the current drought, in its eighth year in the upper basin, he said.
Gavins Point releases have remained extremely low this spring because of good downstream runoff, Cieslik said. The releases were cut even further after heavy rain fell across large portions of South Dakota, Nebraska, Kansas, Iowa and Missouri the weekend of May 5-6, he said.
Areas of eastern South Dakota received as much as 10 inches of rain that weekend, creating James River and Vermillion River flooding. The flood water will eventually dump into the Missouri River downstream from Gavins Point.
"Releases from Gavins Point Dam so far in May have averaged only 8,600 cubic feet per second (cfs), a record low level for this time period. And they have been only 8,000 cubic feet per second since May 7," Cieslik said in a press release.
The release required to provide minimum service navigation support at this time of year normally ranges from 22,000 cfs to more than 25,000 cfs, Cieslik said.
Reduced releases from the system resulted in lower downstream river stages, Cieslik said. The move resulted in reduced flood damages and will allow flooded areas to drain sooner as the flows recede, he added.
Runoff from rainfall in the Dakotas, coupled with the record low releases, allowed for a significant rise in reservoir pools, he said.
"We estimate that our record low releases in May alone will save about a foot and a half of water in each of the upper three reservoirs: Fort Peck in eastern Montana, Garrison in central North Dakota and Oahe in central South Dakota," Cieslik said in the press release.
Rising reservoir levels at this time of year are particularly important because of the on-going forage fish spawn, according to Corps officials.
Spring pulses from Gavins Point were added to the water management plan in 2006 to benefit the endangered pallid sturgeon. But the plan also "precludes" the spring pulses in the event of low system pool levels or high downstream flow.
Neither the March nor the May spring pulses were implemented because of low reservoir levels. The plan would also have precluded the May spring pulse because of high downstream flows.
With record low releases at Gavins Point, Yankton has become "Ground Zero" for upstream and downstream battles. Yankton officials are watching the impact of the record low releases but report no problems with meeting the city's water needs.
"So far, we haven't had to add anything. It was at 6,000 (cfs) for a short time, but it was a brief time and we didn't notice a difference," said Jerry Busby, superintendent of the Yankton water treatment plant.
"We are in close contact with the Corps, with our intakes downstream of the dam. Basically, we are the only water system between here and close to Omaha that has municipal intakes."
Busby checks daily river releases on the Corps' Web site, which helps him make adjustments if needed. But so far, he hasn't seen major differences.
"There's not really any changes for us. (The record low release) has decreased the amount of flow into the plant, but we don't have the demand that requires extra steps," he said. "On an annual (basis), we average 2.6 million gallons a day, and right now we are at the 2 million mark. In the winter, we average 1.8 million gallons a day. In the summer, it goes up to 6 to 7 million gallons a day."
Why the difference? Irrigation and other seasonal changes in water usage, Busby said.
"Right now, we are going up a little bit," he said. "We are getting up there to the 2.5 million mark pretty easily."
The city has handled Gavins Point releases currently running at a fraction
of normal for this time of year, Busby said.
"We are pretty close to the maximum pumping capacity. If the river level does come up, it's not a problem," he said. "Right now, it has only changed 100 gallons a minute."
While Yankton can meet its water needs, the community does see the impact of upstream sediment and downstream scouring of the river bed, Busby said.
"We have got two intake buildings and four pipes in the river," he said. "One of our intake structures is not usable because of the scouring of the river."
Yankton officials are talking with the South Dakota congressional delegation about Missouri River management and its impact on the community, said Kevin Kuhl, the Yankton public-works director.
Yankton city manager Jeff Weldon spoke with federal officials during the annual Yankton Area Chamber of Commerce trip to Washington, DC, Kuhl said.
"It's something that weighs heavily on their (city leaders') minds," Kuhl said of the river management. Weldon could not be reached Wednesday for comment.
The construction of the new Missouri River bridge at Yankton will take into account the city's water needs, Kuhl said.
"Thank goodness, there is an updated extension as part of the bridge project that pumps from depths lower than in the past," he said. "We are making use of that facility, and we are grateful that we are able to accomplish more."
This year's low releases from Gavins Point are not new, Kuhl said.
"In 1993, when the huge flooding event occurred downstream, we were in the
opposite situation," he said. "We had a record low flow for this segment of the river. They nearly shut the dam off to relieve flooding downstream from Sioux City."
The same situation has recurred in 2007, Kuhl said. "This year, they are conserving water (in the reservoirs), so they are keeping (releases) very low," he said.
The influx of floodwater into the Missouri River doesn't appear likely to change anytime soon. The National Weather Service (NWS) flood warning continues for the James River near Scotland until further notice. At 8 a.m. Wednesday, the stage was 18 feet. Major flooding is occurring, and major flooding is forecast.
The flood stage near Scotland is 13 feet. The James River rose above flood stage near Scotland on May 6 and crested at 19.22 feet at 5 p.m. May 11. The river is projected to fall below flood stage near Scotland around June 8.
According to the NWS, the 19.22 feet level was the sixth-highest recorded in the river's history at the Scotland station. Mitchell saw its second-highest level ever at 24.35 feet May 10, while Huron and Forestburg saw their fourth-highest levels.
Moderate to major flooding along the James River will continue for an extended period of time, with many locations from Mitchell to Yankton not falling below flood stage until early June, the NWS predicted. And more rain may be on the way.
According to the NWS forecast, the threat for thunderstorms with some severe
weather will increase Monday into early Tuesday across the region. These thunderstorms will also be capable of producing heavy rainfall later Monday, into Monday night.