Parched farmland soaked up moderate rain in parts of Iowa on Friday, Ohio officials warned of the possibility of mandatory water conservation, and barges sat idle near shallow sections of the busy Mississippi and Ohio rivers.

"I don't think the public understands the gravity of this problem," Ohio Lt. Gov. Paul Leonard said Friday. "They think this is a great summer. From the beach point of view, this may be a great summer. But from a water availability point of view, this could be a dangerous summer."In the South, reservoirs on the Savannah River in South Carolina are at low levels comparable to their status during the severe droughts of the 1930s and 1950s, the Army Corps of Engineers says.

Several points in northwestern and north-central Iowa received half an inch or more of rain Friday, but other areas got nothing more than clouds when a warm front made its way southeast through the region.

"This is probably our last chance for rain for a week," said Chuck Myers, forecaster for the National Weather Service in Iowa. He said weather patterns would shut off any moisture from the Gulf of Mexico; Friday's rain came from a weak weather system that came all the way from the Pacific.

Iowa State extension climatologist Elwynn Taylor said Friday's rain barely made a dent in the amount of moisture needed. He said dry counties in northeastern Iowa need five inches of rain to get back to normal growing conditions. The rest of the state needs between two and four inches.

In other developments, Iowa ordered irrigators and other heavy water users along the Winnebago, English and Little Cedar rivers and a section of the Cedar River to stop pumping, with officials saying similar action is being considered to protect other low-flowing streams.

The weather service has predicted a continuation of the unusually dry Midwestern weather through at least July 15, raising the possibility of a 20-25 percent loss in corn yields as opposed to the 10 percent loss suffered to date.

Futures traders on Chicago, Kansas City and Minneapolis commodities exchanges have been bidding up prices for future delivery of grains and soybeans. On the Chicago Board of Trade, corn futures have risen about 40 percent since May 1 and soybeans have advanced about 35 percent, and cash prices have followed suit.

About 1,000 barges were halted on the Mississippi near Greenville, Miss., while nearly 700 barges were stranded on the Ohio near Mound City, Ill., authorities said, with water down to 7 feet deep in spots, 2 feet too shallow for loaded barges.