As if high temperatures, wildfires, and shriveled up crops weren't enough, the drought plaguing the United States is now crippling the nation's largest river.

Water levels on the Mississippi are so low that barges are having trouble getting through. Delays in shipping crucial goods can cost hundreds of millions a day.

Not-So-Mighty Mississippi

The Mississippi River is one of the nation's main arteries of commerce. More than 500 tons of grain, coal, and other goods pass along its banks every year.

But the drought of 2012 is shrinking the mighty Mississippi. In some places, it's been reduced to half its size.

"We need about 10 to 12 feet of water to get back to our normal stage," Barry Alderman, a manager at Mississippi Marine, said.

The Army Corp of Engineers is struggling to keep water levels at nine feet, the legal level to keep the Mississippi open for traffic.

"We're coming up with different approaches to meet these challenges and keep business going, which is what we all have to do," Greenville Port Director Tommy Hart said.

River levels haven't been this low since the late 1980s, and they're getting dangerously close to breaking the all-time low record.

In one stretch of the Mississippi, several barges got stuck. The situation prompted the U.S. Coast Guard to close an 11-mile section of the river, stranding 97 boats and barges.

Dredge operators are hard at work trying to make the water deep enough for the barges to pass through.

"I'm running what you may call a big vacuum," dredge operator David Woods explained.

Shoppers Feeling the Strain

If the Mississippi is forced to close, it will cost the U.S. economy $300 million a day and food prices will skyrocket.

Consumers are already feeling the strain at the grocery store.

Corn and soybean prices are at record highs. The price of corn is up 68 percent from June and soybean prices are up 39 percent.

Meanwhile, barges are already being forced to modify their loads.

"They're having to go to a smaller draft, but we've been able to keep the channel open and keep industry running," one dredge operator explained.

Carrying lighter loads helps the barges navigate the shallow waters. But the less they carry, the more consumers pay. More than 400,000 jobs depend on the flow of traffic in the Mississippi River.