The typical Nebraska corn crop can easily consume 1,800 gallons of irrigation water to produce a single bushel of corn.

That’s not a typographical error. You can do the math yourself based on an acre foot, or 325,000 gallons water, applied to support an average yield of about 185 bushels.

Extrapolate that out over this year’s expectations for 1.5 billion bushels and you get a better idea of why Environmental Defense is raising concerns about the impact of rapidly increasing ethanol production on the Great Plains and the Ogallala Aquifer.

Tim Male, a senior scientist at the public interest group’s Washington, D.C., headquarters, tried to make the case for more soil and water conservation Thursday in unveiling a new report that examines the impact of biofuels on natural resources.

More specifically, Male called for keeping grassland intact, keeping acres in idled status in the Conservation Reserve Program, and guiding ethanol plant builders toward locations where there’s the best chance of water sustainability.

“We are very concerned that not enough of these environmental considerations are being included in the decision-making process of where these plants are going today,” he said.

Nebraska is perched over the deep end of a vast Ogallala formation that stretches into Colorado, Kansas and all the way to Texas and New Mexico.

But even at the north end, there are ethanol plants in operation and ethanol plants proposed in areas that have experienced substantial declines in groundwater levels in recent years.

Looking at things from a multi-state perspective, the Environmental Defense report notes that many of the plants being built to respond to a biofuels mandate are in places where water levels have dropped as much as 40 feet in recent years.

Environmental Defense economist Martha Roberts called those “local hot spots of depletion,” and said a new Nebraska ethanol plant at Madrid was an example of questionable siting.

The report’s executive summary underscored her point. “In the areas of highest Ogallala Aquifer depletion, new corn ethanol plants currently under construction or planned will increase the region’s ethanol production capacity by 900 percent.”

That means more water consumed by ethanol plants and much larger quantities likely to be consumed in raising the corn in the same area to make ethanol.

“This dramatic expansion of ethanol production,” said the report, “has substantial implications for already strained water and grassland resources in the Ogallala Aquifer region.”

Some quick figuring by Ken Cassman, director of the Nebraska Center for Energy Sciences Research at the University of Nebraska-Lincoln, confirms the possibilities for using almost 2,000 gallons of water to grow a bushel of corn.

“It’s phenomenal how much water a crop uses,” Cassman said.

But he offered some context for corn’s thirst. “Realize that irrigated agriculture globally produces 40 percent of the food supply on 18 percent of the arable land. So there’s a value in intensive production on an acre of land, so we don’t spread agriculture out all over the place,” he said.

Part of the Environmental Defense concern is that millions of acres enrolled in the federal government’s Conservation Reserve Program might be withdrawn by farmers over the next few years because of high corn prices.

In Nebraska and elsewhere, that would mean more irrigation and possibilities for more soil erosion.

Lavaine Moore, a conservation specialist with the Farm Service Agency in Lincoln, said 10-year contracts will expire at the end of this month on about 159,740 CRP acres in Nebraska.

But Moore said there’s no sign of a large-scale CRP exodus by farmers so far involving a total inventory of about 1.35 million acres. “They’re not knocking down our door and wanting out,” she said.

Reach Art Hovey at (402) 523-4949 or at ahovey@alltel.net.