In late July 2011, Brigadier General John McMahon, (who oversees the entire Missouri River) decided not to lower the Missouri River reservoirs below the traditional base level of 56.8 million acre feet (MAF) at the start of next year’s runoff season. That base level only frees up 22% of the reservoir system’s storage capacity. In 2011, the Army began the runoff season at that level. We now know that level did not provide enough storage space to capture this year’s flood.
For months, McMahon insisted on maintaining the status quo in the operation of the reservoirs. He likely held firm to this position because he had the backing of the majority of the basin’s senators and other government representatives. Those officials almost certainly recognized that a lower reservoir system base level threatened the monetary benefits of the Army’s hydraulic system. Less water behind the big dams in 2012 would mean fewer financial benefits derived from hydropower generation, Missouri and Mississippi River navigation, reservoir recreation, and the apportionment of water to downstream municipalities and power plants.
But McMahon’s decision ran up against fierce public resistance. To a large segment of the basin’s citizenry, it appeared as though McMahon and his political backers were willing to put the economic interests of a select few in the energy sector and the navigation industry above the general public’s need for flood control.
After confronting stiff opposition to its plans, the Army decided to grant the public a small concession. On November 4, the corps’ Omaha District released a statement to the press. It stated, “…the corps will take an aggressive stance with winter and spring releases.” In other words, if runoff conditions warrant it, the Army will dump water into the lower valley to open up enough space in the upstream reservoirs to avert a repeat of the 2011 deluge. Jody Farhat, who is the Army’s reservoir operations manager, went even further. She said, “We will get as much water out of the system as possible as weather permits and the repair work allows.” But Farhat did not specify just how much water the Army hoped to evacuate from the reservoirs. Nor did she commit to lowering the reservoirs below the 56.8 MAF base level. She remarked, “…we may be able to start the runoff season with more than 16.3 million acre feet [of available storage space].”
The corps’ new Missouri River management policy of “flexible response” is a step in the right direction. But will it be enough to avert a future disaster? That is the question on everyone’s mind.
If “flexible response” only frees up an additional 750,000 acre feet of reservoir storage behind Garrison Dam (the Dalrymple proposal), there will be almost no extra flood protection for Missouri Valley residents next year. That amount of storage just isn’t going to stop a super flood. But if the Army opens up another 4.6 MAF in the reservoirs (to take the base level down to 52.2 MAF) before March 1st – it will substantially reduce the risk of a flood next year. The Army’s own hydrological studies indicate that had it had 4.6 MAF of added reservoir space in early 2011, and altered its reservoir release schedule, it could have shaved 60,000 cubic feet per second (cfs) off of the peak flows exiting Gavin’s Point Dam. Gavin’s Point Dam’s record releases would have been 100,000 cfs rather than 160,000 cfs. The 100,000 cfs discharge rate would have decreased the river’s flood crest at Sioux City by at least 6 feet. With such a reduction, the Missouri would not even have reached flood stage at that location.
Dropping the reservoirs is only a first step in reducing the flood risk along the Missouri Valley. Other actions must be taken. Most notably, the water storage capacity of the Missouri Valley south of Ponca, Nebraska, should be increased through the use of non-structural flood reduction techniques.
Dismantling the navigation channel, letting the Missouri into its former floodplain, reestablishing bank side wetlands, reopening the river’s side channels, reconnecting the old oxbow lakes to the main river, and establishing floodways through former channel areas are non-structural solutions to flooding south of Ponca. These actions will increase the water storage capacity of the lower valley, diminish the height of the river’s flood crests, and slow the Missouri’s destructive currents during the next flood.
If the lower basin states refuse to modify the lower valley environment to enhance its ability to mitigate floods, then the upstream reservoirs will have to be kept low indefinitely, since the navigation channel and lower valley will remain flood-prone. But to keep the reservoirs low will have detrimental effects on hydropower production, the reservoir fishery, and the water supply needs of upper and lower basin municipalities and power plants. It does not make economic sense to sacrifice the system’s largest money earning purposes (such as hydropower production) to maintain it’s least economically justifiable purpose – the navigation channel. The lower basin states have to provide more space in the Missouri Valley to store floodwater – just as the upper basin is now being required to create more storage space in the reservoirs.