KANSAS CITY — It isn't so much the amount of water churning its way down the Missouri River that has people along the nation's longest waterway on edge. It's how long all that water will stick around.
The annual "spring rise" on the Missouri will last deep into this soggy summer, as a torrent of early season rains and winter snowpack flows through wide-open gates of South Dakota's Gavins Point Dam upriver and toward the confluence with the Mississippi River. The Missouri might start to crest soon, but it won't start to fall until August or later.
That constant pressure on the network of levees that protect farmland, roads, small towns and big cities from a river running well outside its banks is what worries folks downriver most as the high water heads south toward Kansas City and east toward St. Louis.
"The length of the flood will test levees like they've never been tested before," Missouri Gov. Jay Nixon said. "You're going to see levees which in essence may be tall enough but not strong enough."
That isn't the only worry as the summer of 2011 shapes up as the worst since 1993, when a Missouri River swollen by weeks of rain over the north-central United States led to flooding that killed 32 people, damaged an estimated 100,000 homes and caused $15 billion in damage.
There's also the prospect of flooded fields in five states that will keep farmers from planting some crops and harvesting others. Highways covered with river water will be as much a headache for drivers as the cash-strapped state and counties that must pay to fix them. Barge operators — and those who rely on them — face big losses if the river remains closed to navigation.
And then there is the greatest unknown in a river valley with no more room for any more water.
"One of my biggest concerns is simply rain," Nixon said. "I know that's no big public policy pronouncement, but that's a big worry."
The Missouri was already running higher than normal in the fall, when rains upriver combined with a heavy winter snow to fill the reservoirs in South Dakota and Montana and force the record-setting releases from dams the Army Corps of Engineers uses in most years to control the river's flow.
As evidence of how there is little margin for error this year, one need look only to this past week's rains in northern Missouri — 2 to 3 inches of rain pushed the Mississippi River up 6 feet within days near Hannibal. There is rain in the forecast in the upper Missouri and Mississippi rivers' valleys in the next several days and a long-range outlook for above normal rainfall this summer in the upper Missouri River region.
But for now, with the river already running high, the worries start with the levees.
So far, the river has breached just three levees on the Missouri River — a federally funded levee at Hamburg, Iowa; a small levee near Decatur, Neb.; and another small levee near Big Lake.
Army Corps officials think levees that protect the Kansas City and St. Louis areas are safe. But Jud Kneuvean, chief of emergency management for the Kansas City Corps office, said the corps projects water levels could reach the top of two federal levees near St. Joseph that protect Rosecrans Air National Guard Base. A federal levee near Glasgow could also see water near its top.
And many smaller levees protecting mostly agricultural land are in jeopardy between St. Joseph and Kansas City and in central Missouri, according to the corps. The flooding has already put hundreds of thousands of acres of farmland out of service, lost to wet ground, washed out crops and lost time in the fields.
Jon Hagler, director of the Missouri Department of Agriculture, said 570,000 acres in southeast Missouri were affected by the spring flooding along the Mississippi River. Another half-million acres are now in danger along the Missouri River, fertile land where corn and soybeans are already in the field.
"If it (flooding) stays through the summer, of course, that crop is gone," Hagler said.
The water washes away top soil, deposits sand and silt and causes scourging of the land, potential problems that will need to be addressed after the water subsides, Hagler said. The financial impact on agriculture won't be known for some time, but Hagler said it could reach the hundreds of millions of dollars.
The flooding has already closed several roads in northwest Missouri, most prominently a section of Interstate 29 at Rock Port. Beth Wright, a state maintenance engineer for the Missouri Department of Transportation, warned that other highways close to the river and its backwaters could be shut down for weeks as the river rises.
MoDOT officials declined to speculate on what other roads or bridges could be affected but said drivers should be prepared for detours in northwest and central portions of the state through the end of summer.
Once the floodwaters recede, MoDOT will begin assessing the damage and the cost to repair it, spokeswoman Melissa Black said. For now, she said, the agency is focused on keeping roads and bridges open and keeping motorists safe.
It isn't just roads. Nixon worries that the airport at Rosecrans could be affected. Rail lines running near the river could be shut down.
The river itself is a vital part of transportation that could be lost for months. Already, a 261-mile stretch of the upper part of the Missouri River is closed to all navigation. As floodwaters creep into Missouri, the key stretch from Kansas City to St. Louis could close, too.
While a far smaller player in barge traffic than the Mississippi River, the Missouri is a vital conduit for shipping things such as corn and soybeans, fertilizer, sand, gravel, asphalt and cement. Barge traffic on the Missouri has waned in recent decades, dropping from a peak of 3.3 million long-haul commercial tons in 1977 to 334,000 tons last year, according to the corps.
The biggest reason is the unpredictability of the Missouri's currents and water levels. Those factors only worsen as the river floods.
Lynn Muench of the American Waterways Operators, which represents the U.S. barge industry, said few barge operators are using the Missouri right now because of the flooding "and concerns of what could go wrong." Tugboat pilots steering the barges have a harder time maintaining control in high water that tends to move faster, and the wakes from passing barges may stress already fragile levees.
"Any kind of wake from us is not good," Muench said.