Gavins Point Dam

The spillway releases at Gavins Point Dam west of Yankton have been reduced greatly since this past Sunday. On Tuesday, overall discharges at the dam were increased to 30,000 cubic feet per second, in part because of the record runoff in the basin in December.

Already-elevated releases at Gavins Point Dam are being increased by the U.S. Army Corps of Engineers (USACE) in order to evacuate more water from the Missouri River storage system after heavy runoff in December.

During a webinar held Tuesday, Jan. 7 to offer an update on the Missouri River basin, John Remus, chief of the Missouri River Water Basin Management in Omaha, Nebraska, said releases at the Yankton dam are being upped from 27,000 cubic feet per second (cfs) to 30,000 cfs.

Normally, discharges at Gavins Point Dam range from 12,000-17,000 cfs during the winter months.

“Warmer temperatures and the continued high (flows) on many of the tributaries have significantly limited the amount of water we have been able to evacuate from the system,” Remus said. “Over 700,000 acre feet of water is stored in the flood control pools, so (Tuesday, Jan. 7) morning, we increased releases from Gavins Point Dam as part of our efforts to evacuate the 2019 runoff and restore the full 16.3 million acre feet of flood control storage. More increases may be possible.”

He added, “Even with the system increase, all of the flood control storage may not be evacuated.”

The current long-range plans for increases at Gavins Point Dam call for about 33,000 cfs starting in March and running through the summer, then moving to 42,000 cfs by the fall.

Due to the warm temperatures and heavy precipitation in some locations, the basin saw its highest December runoff on record, according to Kevin Low of the National Weather Service (NWS).

It’s a case of cause and effect after a soggy 2019, he noted. “When soil moisture is high, the potential for runoff is much higher,” Low said.

Last month, South Dakota Gov. Kristi Noem and Sen. Mike Rounds sent a letter to USACE officials requesting that flows at Gavins Point Dam be increased by more than 7,000 cfs to reduce the flood threat in South Dakota, but Remus said that was not the reason behind the new increase.

“We got that letter from Sen. Rounds and Gov. Noem. We were evaluating that, but it was really overtaken by events,” Remus said. “The record runoff (in December) limited our ability to evacuate water. Increasing releases (even more) is really not in the cards unless things turn around drastically in the next 30 days.”

He said the request from the South Dakota officials “has become a moot point right now.”

The basin is coming off one of the wettest years ever. In fact, Doug Kluck of the NWS said that the period from January-November was the wettest on record for the Dakotas.

Particularly hard hit were areas of eastern North Dakota and eastern South Dakota, which has resulted in prolonged flooding on the James River, which feeds into the Missouri River below Gavins Point Dam and thus can’t be directly regulated by the Corps.

“There are some places on the James that are approaching their 300th consecutive day of flooding,” Low noted.

Overall, Missouri River basin runoff above Sioux City, Iowa, in 2019 was the second highest on record at 60.9 million acre feet (MAF). The record was 61 MAF in 2011.

The outlook for 2020 calls for runoff to continue higher than normal.

“We’re expecting runoff to be about two times the average in January and February,” said Kevin Grode of the USACE. “We’re also expecting March and April runoff to be very high — more than two times the average.”

He said higher-than-normal runoff is expected through the summer.

The Corps projects that the 2020 runoff will be 36.3 MAF, which, if realized, would be the ninth highest on record.

But there are plenty of variables in all forecasts, the NWS officials said, noting that there are no major climate phenomena such as an El Nino or La Nina impacting the weather patterns.

In terms of snow impact, Low noted the snowpack in the mountains is running just slightly above average at this point. However, the snow cover on the plains is running ahead of last year’s pace. There is about 2-4 inches of liquid content in the snow cover in portions of eastern South Dakota, he noted.

Remus said the Corps will remain on top of the situation.

“In 2019, a near-record upper basin runoff made managing in the Missouri River basin very challenging,” he said. “The Corps is well aware of the damage this year’s flooding has caused, and we are doing all we can to reduce the impacts and assist in the recovery.

“As we begin the New Year, I want to assure everyone in the basin that the Corps remains committed to our flood-control reduction mission,” he added.

Follow @kelly_hertz on Twitter.

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