For U.S. Rep. Steve King, the arithmetic of Missouri River flood control is simple addition and subtraction.
Here's the western Iowa Republican's formula:
Permanently subtract water from the river system's three largest reservoirs. Add permanent capacity for more runoff and rain. The sum of those actions equals enough space to control the largest Missouri River flood since at least 1881.
King's calculation of how to prevent a repeat of the unprecedented flooding unleashed this year from the nation's largest reservoir system is rippling across the basin.
Some governors and Capitol Hill colleagues have endorsed the plan — now a bill in both the House and Senate — or picked up the concept of creating more reservoir capacity for floodwater.
Upriver resort operators and biologists are watching to see how any changes could affect recreation and fishing. Downstream barge and towing interests warn that King's solution could damage their industry.
King is convinced the new high-water mark set in 2011 requires an adjustment of the Army Corps of Engineers' river operating policies.
"Congress has no choice but to redirect the Army Corps of Engineers, because they seem unwilling to embrace the reason . why the dams were built in the first place — flood control," he told The World-Herald.
King's bill would require the corps to amend its Master Manual — its river operating bible — to recalculate the total amount of flood-control storage space within six federal reservoirs stretching from Montana to Nebraska along the upper Missouri.
U.S. Sens. Chuck Grassley, R-Iowa, and Mike Johanns, R-Neb., recently introduced a similar bill in the Senate. Both bills call for creating enough free space behind the dams to control a flood of the size that hit this year.
The latest corps projections forecast a record 60.8 million acre-feet of runoff to flow into the Missouri above Sioux City, Iowa, this year. The previous record was 49 million acre-feet.
King said the legislation would not change any of the congressionally authorized purposes for which the corps operates the river: flood control, navigation, hydropower, water supply, water quality control, irrigation, recreation, and fish and wildlife, including endangered species.
"This bill merely aims to ensure the corps has the ability to continue to meet its flood-control responsibilities in light of this year's historic flooding," he said.
The corps says that flood control has been and remains its top priority in operating the river but that historic May rainfall over the northern Plains overwhelmed its reservoirs.
The reservoirs were designed with 16.3 million acre-feet of flood-control storage. That represents about 22 percent of the storage behind the dams. The corps is studying how much more reservoir space might be reserved for flood control.
King said corps officials have told him his proposal would require setting the pre-runoff spring elevations of the system's three largest reservoirs — Fort Peck in Montana, Garrison in North Dakota and Oahe in South Dakota — 6 feet lower than the current Master Manual.
That change, however, would have little impact on the reservoirs' average elevations, King said. The corps' target elevation at Oahe Dam for spring runoff is 1,607.5 feet above sea level. King's plan would lower it to 1,601.5 feet, which is 1.3 feet higher than the historic average.
The barge and towing industry, flooded off the middle Missouri this year, is wary of plans to lower reservoir levels.
Kevin Holcer, towboat manager for AGRI Services of Brunswick in Missouri, said flood control and navigation are the most important uses of the river.
"We understand that they need to lower the reservoirs some to make room for flood control, but not low enough that it hinders navigation," he said. "There's got to be a happy median."
Holcer, whose company has floated barges to Nebraska City and Blair since flooding ended in September, said most barges had no trouble adjusting to lower flows during the depths of last decade's drought. They could do so again, he said.
But the Waterways Journal, a weekly barge industry trade publication in St. Louis, said King's bill could reduce water available for navigation and recreation.
The Missouri River reservoirs also created some of the nation's premier fisheries and a recreation industry in the Dakotas valued at upward of $100 million.
Kelly Sorge, owner of Indian Hills Resort on Lake Sakakawea in North Dakota, survived recent dry years and isn't eager to see lower water levels again.
"I think the answer is to take it slow," she said. "Don't overreact."
Mark Fincel, senior fisheries biologist for South Dakota Game, Fish and Parks in Pierre, said the impacts of lowering reservoirs vary.
Reservoir water levels need to be steady or rising in the spring for a successful spawn of rainbow smelt, the primary bait fish in Oahe. A collapsing smelt population would trigger poor reproduction and growth in walleye, the lake's primary game fish.
Fincel said lower lake elevations also increase the chances that the lake's water temperature would rise, destroying valuable cold water fisheries below the dam.
"It all depends on timing," he said.
Most basin governors — including Dave Heineman of Nebraska and Terry Branstad of Iowa — supported a request to the corps by North Dakota Gov. Jack Dalrymple to lower Lake Sakakawea by 2.5 feet this year to make room for greater water storage next spring.
The corps declined, saying it was more important to keep downstream river flows low enough this fall to allow flooded land to drain and to begin inspecting and repairing damaged levees.
The North Dakota plan was drafted by Todd Sando, the state's water commissioner. Sando said King's proposal probably would affect other river uses such as recreation, supplying water to cities and generating electricity, especially during droughts.
"To react to this year's flood with a permanent lowering of the reservoirs probably isn't very prudent," he said. "You need flexibility. It makes sense in wet years, but not in normal or dry years. Our weather patterns are very cyclical and they come in strings of wet and dry years."
Sando said soils are saturated this year and the region is in a wet weather cycle.
"We definitely need more flood storage now," he said. "The water will come back."
Terry Steinwand, director of the North Dakota Game and Fish Department, supported Sando's plan to lower Sakakawea this fall.
"We don't want to see another year like this year," he said.
A Johanns spokesman said the prospects and need for the legislation most likely hinge on the corps' success in preparing the reservoirs for next year's runoff. Grassley says he wants to capitalize on the unity following this year's flooding.
Although the corps does not plan to lower its big storage reservoirs more than usual by next year's runoff season, water managers said they will be more flexible this fall and early winter in releasing as much water as possible. They also plan to be aggressive with winter and spring releases.
King said basin residents from Montana to Missouri have lived through dry and wet climatic swings more dramatic than anything his bill would do to the reservoirs.
"It's a no-cost bill, a no-brainer bill," he said. "The system was built to protect us from floods, and that's how it needs to be managed."
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