It's corn planting time in the US Plains, and that means Kansas corn farmer Merl "Buck" Rexford is worrying about the weather - and hoping there is enough water.
Rexford plans to start seeding his 7,000 acres near Meade, Kansas, this week and he is relishing a recent heavy snowstorm that dropped several inches of much-needed moisture.
Like corn farmers throughout the US, Rexford hopes to grow a healthy crop yielding more than 150 bushels an acre this year. Much of his crop will wind up at a nearby ethanol plant.
And that puts the 65-year-old Rexford at the centre of a bitter divide over biofuels, particularly corn ethanol.
Critics argue that precious water resources are being bled dry by ethanol when water shortages are growing ever more dire. Federal mandates encouraging more ethanol production don't help.
Proponents say corn ethanol for transportation fuel is far better for the environment, national security and the economy than oil, and the first step toward cleaner fuel sources.
"We really have to ask ourselves, do we want to be driving with renewable fuels or with gasoline made from petroleum resources," said Brent Erickson, executive vice-president at the Biotechnology Industry Organisation, which backs ethanol.
Corn ethanol's future is already muddied by concerns that it requires a substantial amount of energy to produce and that heightened demand makes corn more costly in human food and livestock feed. Now, with climate change concerns mounting and drought becoming more of a problem in many areas, the water-intensive nature of creating ethanol also is a growing concern.
"Biofuels are off the charts in water consumption. We're definitely looking at something where the cure may be worse than the disease," said Brooke Barton, a manager of corporate accountability for Ceres, a group backed by institutional investors focused on the financial risks of climate change.
Corn is a particularly thirsty plant, requiring about 20 inches of soil moisture per acre to grow a decent crop, but most corn is grown with rain, not irrigation. Manufacturing plants that convert corn's starch into fuel are a far bigger draw on water sources.
Water consumption by ethanol plants largely comes from evaporation during cooling and wastewater discharge. A typical plant uses about 4.2 gallons of water to make one gallon of ethanol, according to the Institute for Agriculture and Trade Policy.
The ethanol industry pegs that at about three gallons of water to one gallon of fuel.
Washington lawmakers and the White House have been encouraging the use of ethanol as an alternative fuel to help lighten the nation's costly dependence on foreign oil. But the moves are meeting opposition from many groups who fear that population growth and climate change are combining in ways that will leave not only the United States, but the world, with too little water.
Many ethanol plants are located in agricultural areas - close to the corn, but also close to other users who need a lot of water to operate, such as hog farmers and cattle ranchers.
"We're headed in the wrong direction and this problem is not going away," said Mark Muller, program director at the Institute for Agriculture and Trade Policy. "This water issue is like the financial crisis... and I'm afraid something awful is going to happen."
The group says much of the Corn Belt stretching through Iowa, Illinois, Nebraska, Minnesota and Indiana has enough water for all, but water availability could challenge the ethanol industry in areas including greater Chicago, western Iowa and Nebraska, and generally west of the Missouri River.