Greater cultivation of crops to produce ethanol could harm water quality and leave some regions of the country with water shortages, a panel of experts is reporting. And corn, the most widely grown fuel crop in the United States, might cause more damage per unit of energy than other plants, especially switchgrass and native grasses, the panel said.

The panel, convened by the National Research Council, said improved agricultural practices, water recycling and other steps might reduce possible problems. But it added that "fundamental knowledge gaps" made it difficult to predict what would happen as the nation’s embrace of biofuel crops expanded. Meanwhile, it said, it would be "prudent" to encourage the use of ethanol sources other than corn.

Production of ethanol from corn kernels is on the rise, the panel said, adding that President Bush has called for the annual production of 35 billion gallons of ethanol by 2017, an amount that would account for about 15 percent of liquid transportation fuels in the United States.

But increased production could greatly increase pressure on water supplies for drinking, industry, hydropower, fish habitat and recreation, the report said. Facilities that turn plants like corn into liquid fuel would add to the pressure on water supplies, though these bio-refineries are relatively modest water consumers compared with agriculture, the panel said.

The research council, an arm of the National Academy of Sciences, issued the report yesterday. It is available at the academy’s Web site, nas.edu. It was financed by the National Science Foundation, the Environmental Protection Agency and other agencies and foundations.

The report noted that additional use of fertilizers and pesticides could pollute water supplies and contribute to the overgrowth of aquatic plant life that produces "dead zones" like those in the Chesapeake Bay, the Gulf of Mexico and elsewhere.