An estimate of the volume of water stored in the alluvial aquifer was made by calculating the simulated thickness of the saturated zone and multiplying by the specific yield. The volume of water in 2007 stored in the alluvial aquifer was estimated to be approximately 536 million acre-feet (equivalent to 10.7 feet of water covering the entire study area). Cumulative storage change within all the aquifers simulated in the MERAS model indicates overall depletion of 140 million acre-feet (equivalent to 2.8 feet of water covering the entire study area, and most of the water is from the alluvial aquifer) from 1870 (fig. 2). Therefore, the total amount of water removed from aquifer storage to date in the Mississippi embayment equals approximately 26 percent of the amount stored only in the alluvial aquifer.