Connecting the dots with airborne geophysics: Mapping aquifer structure at new scales in the Mississippi Alluvial Plain

The Mississippi Alluvial Plain hosts one of the most prolific aquifer systems in support of agricultural resources in the United States. The surficial aquifer, spanning more than 92,000 square kilometers in parts of seven states, provides over 9.2 billion gallons per day primarily for irrigation in an agricultural economy which generates $8 billion dollars annually in direct revenues. Despite its economic importance, there is insufficient knowledge of the belowground architecture of the aquifer system over this vast area with the spatial resolution needed for effective management of water resources. Here, we introduce the results of a large airborne geophysical survey that uses a combination of electromagnetic (AEM), magnetic, and radiometric sensors to map the aquifer system and deeper sediments at an unprecedented scale for a regional aquifer system in the United States. More than 40,000 flight-line-kilometers of airborne geophysical data supplement more than 9,000 existing borehole logs in the region to provide new three-dimensional insight into the three-dimensional arrangement of sediments that comprise the surficial aquifer and surrounding units. Interpretations of aquifer structure derived from the AEM data will be used to inform the development of regional groundwater models, and to guide decisions on where additional data are needed in the future.