An estimated 12 million acre-feet per year (11 billion gallons per day) of groundwater was pumped in 2005 from aquifers in the Mississippi embayment. Irrigation constitutes the largest groundwater use, accounting for approximately 11 million acre-feet per year (10 billion gallons per day) in 2005 from the alluvial aquifer in Arkansas, Louisiana, Mississippi, and Missouri, and to a lesser extent in Illinois, Kentucky, and Tennessee. Cumulative groundwater pumpage from 1870 through 2007 from the alluvial aquifer amounts to over 280 million acre-feet (enough to cover the entire study area with more than 5 feet of water) or approximately 87 percent of the total cumulative amount pumped (fig. 3). Cumulative pumping is greater than the cumulative change in storage because some of the demand for pumping is offset by recharge or inflow through streambeds. The amount pumped from the alluvial aquifer is more than nine times that from the middle Claiborne aquifer, which is the second largest producer of groundwater in the Mississippi embayment. Cumulative groundwater pumped from the middle Claiborne aquifer made up approximately 9 percent of the total, while combined pumping from remaining aquifers made up 4 percent.
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MERAS study