Impacts of Biofuel Production on a Municipal Water Supply in Ames, Iowa

Expansion of the biofuels industry in the Midwest has raised concerns about its impact on groundwater supplies. Ample water is needed because one gallon of corn ethanol requires from 3 to 6 gallons of water to produce. Iowa, the leading U.S. producer, will produce 3.6 BGY of corn ethanol by the end of 2008. Assuming a 4 gal H2O/gal ethanol ratio, about 14.4 BGY of groundwater will be pumped from aquifers underlying those corn ethanol plants. A collision of biofuels production and a muncipal water supply occurred recently between the cities of Ames (pop. 51,572) and Nevada (pop. 6,129) – both tap groundwater from the same alluvial/buried valley aquifer for drinking water. Nevada supplies raw water to Lincolnway Energy, a 50 MGY corn ethanol plant that uses about 200 MGY of groundwater. In October 2008, Nevada requested a 10-year permit from the Iowa DNR to increase withdrawals from 325 MGY to 800 MGY in order to accommodate the 329 MGY needed by the ethanol plant if it expanded. Thus, the plant's water requirement was nearly equivalent to the town's needs. Because Ames had proposed a new well field 1800 ft south of Nevada's well field, a finite-difference groundwater flow model was hastily assembled to simulate the impact of the pumping increase. Using a K of 696 ft/d from a pumping test at the site, the model predicted that pumping at 800 MGY would not affect drawdown in the Ames well field; however, pumping the aquifer at 2.2 BGY in the new Ames well field would lower the water table in the Nevada wells about 3 ft in 90 days. After a meeting of city officials, DNR granted the permit anyway, allowing Ames to stipulate its prior water right in writing. Similar biofuel/groundwater impacts are occurring elsewhere in Iowa and the Midwest.