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Open-File Report 2010–1229

Unintended Consequences of Biofuels Production: The Effects of Large-Scale Crop Conversion on Water Quality and Quantity

By Heather L. Welch, Christopher T. Green, Richard A. Rebich, Jeannie R.B. Barlow, and Matthew B. Hicks

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Introduction

In the search for renewable fuel alternatives, biofuels have gained strong political momentum. In the last decade, extensive mandates, policies, and subsidies have been adopted to foster the development of a biofuels industry in the United States. The Biofuels Initiative in the Mississippi Delta resulted in a 47-percent decrease in cotton acreage with a concurrent 288-percent increase in corn acreage in 2007. Because corn uses 80 percent more water for irrigation than cotton, and more nitrogen fertilizer is recommended for corn cultivation than for cotton, this widespread shift in crop type has implications for water quantity and water quality in the Delta. Increased water use for corn is accelerating water-level declines in the Mississippi River Valley alluvial aquifer at a time when conservation is being encouraged because of concerns about sustainability of the groundwater resource. Results from a mathematical model calibrated to existing conditions in the Delta indicate that increased fertilizer application on corn also likely will increase the extent of nitrate-nitrogen movement into the alluvial aquifer. Preliminary estimates based on surface-water modeling results indicate that higher application rates of nitrogen increase the nitrogen exported from the Yazoo River Basin to the Mississippi River by about 7 percent. Thus, the shift from cotton to corn may further contribute to hypoxic (low dissolved oxygen) conditions in the Gulf of Mexico.

First posted October 19, 2010

For additional information contact:
Director
U.S. Geological Survey
Mississippi Water Science Center
308 South Airport Road
Jackson, MS 39208-6649

http://ms.water.usgs.gov

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Suggested citation:

Welch, H.L., Green, C.T., Rebich, R.A., Barlow, J.R.B., and Hicks, M.B., 2010, Unintended consequences of biofuels production—The effects of large-scale crop conversion on water quality and quantity: U.S. Geological Survey Open-File Report 2010–1229, 6 p.



Contents

Why has the Production of Biofuels Become Important?

The Mississippi Delta—Consequences of Biofuels Production from a Local Perspective

Increased Withdrawals for Corn and Soybeans Are Accelerating Groundwater Declines in the MRVA Aquifer

Increased Agrichemical Application Rates Have Affected Groundwater Quality

Nitrogen Export to the Gulf of Mexico Has Increased

Stream Ecosystem Health Is Affected by Declining Water Quality and Quantity in Delta Streams

Summary—How Has the Biofuels Initiative Affected Conditions in the Mississippi Delta?

References Cited


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