This has indisputably been a difficult year for those who manage Iowa’s waterways. Far more rain has fallen in 2019 than normal. While patterns have been less relentless in the past several weeks, Iowa is still getting more than its share of rain.
But, as Ottumwa passed the one-month mark for flooding earlier this week, it is fair to question why the river remains so high. The U.S. Army Corps of Engineers’ own regulations suggest it should have come down by now.
The corps’ standing instructions for Lake Red Rock, the reservoir immediately upstream of Ottumwa, are available on its website. There are two categories that bear special examination. The first is for normal operations. The second is for the reservoir’s operations during large magnitude flood events.
Normal operations, when the lake is above 742 feet but below 770 feet, vary depending on the time of year. That’s reasonable, given the importance of the river during the growing season. The guidelines on the corps’ website indicate between May 1 and Dec. 15 a lake level of 750 to 770 feet should trigger releases of 25,000 cubic feet per second.
The lake has hovered around 757 feet this week. Releases are currently around 35,000 cfs. That’s almost 40 percent more water coming through the dam than the corps’ guidelines say should be flowing under normal operations.
To the corps’ credit, it responded when the Courier asked about the difference. It said Red Rock is currently in large magnitude flood operations. The corps said it does not plan to reduce outflows until the lake is falling at a rate of at least one foot per day, and that recent inflows have been between 35,000-40,000 cfs.
Large magnitude events are defined as when the lake level is above or forecast to exceed 770 feet. Red Rock was at less than 760 feet this week. Records show it was last at 770 feet at 3 a.m. June 9, and there is no forecast we could find that shows it approaching 770 feet anytime in the foreseeable future.
The corps pointed out, correctly, that immediately cutting back on outflow when the lake dropped below 770 feet would simply cause Red Rock to rise above that mark again. It needs to gain some breathing space with the reservoir before heading back to normal operations. But even taking that into account, the guidelines don’t seem to be being followed.
Large magnitude flooding guidelines prescribe an outflow of 30,000 cfs at 770 feet. Outflows continue to be larger than that figure even as the lake itself is below the threshold. The corps’ data also contains a figure for the percentage of flood storage currently being used at Red Rock. That figure was zero and the same is true at Saylorville Lake, which is upstream from Red Rock.
All we can conclude from all this is that the corps is trying to lower the lake, which keeps the river above flood stage locally, even as it refuses to use the flood storage capacity upstream reservoirs were built for.
For the corps to have flood storage at zero, with outflows above those that appear to be prescribed in its guidelines, and continuing flooding in Wapello County because of those irregularities is mind-boggling. We hope the corps takes a hard look at why it has concluded flooding here is more reasonable than storing water at Red Rock, because that’s precisely what the current numbers mean.
The corps has a challenging job. This year has been particularly tough. But right now we have serious reservations about how things are being handled and whether the corps is following its own rules.