The prolonged drought in the central U.S. is starting to worry farmers of corn and soybeans, and even commercial shipping has started to be affected. Several barge operators have begun lightening their loads to keep vessels from scraping the bottom of the Mississippi and Illinois rivers.

If river levels don't rise soon, the U.S. grain industry "will have significant delays," said the president of the American River Transportation Company.

But that's not all-both rivers are major transport routes for commodities such as salt, petroleum products, and cement-making materials.

So far, the economic fallout from the prolonged drought isn't as broad as the impact of the 1988 dry spell, which shrank the U.S. corn harvest by 31 percent and speeded the consolidation of American farms.

Nonetheless, Illinois state authorities report that tens of thousands of farmers already have lost one-third of their potential crops.