Corn ethanol and Water in the US Part 1 - by Robb

(Graphic from Robert Service 2004)

I'd like to discuss corn ethanol because it is a perfect example of a proposed solution that isn't as good as it seems. It also serves as a good model for examining personal resource use as it impacts so many areas of our lives; food, water, transportation. I'll attempt to cover this in 2 or 3 posts.

Transportation contributes 33% of total GHG in the US. At only 18% or less efficient well to wheel, light truck and automobile traffic contribute 60% of that total. If the ratios of US GHG emissions stay the same, in order to achieve the carbon reduction goals as set forward by the Contraction and Convergence limits of 450ppmv by 2050, personal transport contributions need to be reduced by 4/5’s.

The Bush Administration believes that corn based ethanol is part of the solution. A shift to ethanol is being subsidized to achieve a target of 36 billion gallons of production by 2022 as mandated by the Energy Independence and Security Act of 2007. Approximately 1/3 of that is set to come from corn.

Water and climate change in the US
In a 2003 freshwater report the Government Accounting Office (GAO) found that of the 50 states,

“36 states anticipate water shortages in localities, regions, or statewide in the next 10 years..... When shortages occur, economic impacts to sectors such as agriculture can be in the billions of dollars.”

In the case of drought the number of states expecting shortages rises to 46. Georgia, Alabama, and Florida are embroiled in a legal struggle to control the Appalachicola-Chattahoochee-Flint River basin. South Carolina is suing North Carolina over diversion of water from the Catawba river basin. The city of Las Vegas has struck deals with most of the neighboring states for their water or storage capacity. These types of conflict and brokering are common all over the US.

Snow-melt accounts for 75% of all water in streams in the west. The Cascades of Washington, Oregon and Canada will likely see snow-pack reductions of 60% or higher by 2050.This would reduce stream flows in the summer by 20 to 50%, directly affecting over 9 million people 8 in cities from Vancouver to Portland west of the mountains not to mention the big cities east of the mountains. As cities rely on this water for domestic supply this places them in increasing competition with agriculture. (Robert Service 2004)


Most of the water coming off the mountains is stored in reservoirs. The 2003 GAO freshwater report states that,

“........the amount of water available for use from these reservoirs is continually being reduced by sedimentation.....the total reduction resulting from the buildup of sediment is estimated at about 1.5 million acre-feet per year.”

To the corn belt of the midwest, climate change will bring more rain in the winter, before planting, and late spring during planting. This rainfall will likely be more intense, risking the flooding of fields during planting time. Summers will see less rain and lower reservoirs. (Cromwell, Smith and Raucher 2007) As of 1997 only 15% of the total US corn crop was irrigated (Christenson 2002), but irrigation is becoming more common which has significant impacts on groundwater resources.

Groundwater constitutes more than 25% of the US water supply. Farmers used 2/3’s of the 28 trillion gallons of groundwater pumped in 1995.(Hoekstra and Chapagain 2007) Major aquifers are in serious decline. The Oglalla aquifer, one of the largest in the nation is a well known example,

“......... 6% of the aquifer has dropped to an unusable level that can no longer be pumped. If irrigation continues to draw water from the aquifer at the same rate, about 6% of the aquifer will be used up every 25 years.” (Worm 2004)

Groundwater is relied upon for domestic, industrial, and agricultural uses. When we’ve outstripped it’s ability to recharge we are in trouble.