Impact of Airborne Electromagnetic (AEM) Surveys in Groundwater Management in The Lower Platte South Natural Resources District, Nebraska, USA

Abstract

The Lower Platte South Natural Resources District has collected several thousand line kilometres of Airborne Electromagnetic (AEM) data during five surveys beginning in 2007 and continuing through 2016 to develop a hydrogeologic framework for priority groundwater management areas. Frequency domain systems were originally used in 2007 and 2008. A shift to time domain electromagnetics was required to increase the depth of investigation in areas of conductive glacial till beginning in 2013. The AEM surveys were collected as reconnaissance and block flight lines. Careful calibration and diligent inversions were required to maximize resolution of the AEM data. The AEM-improved hydrogeologic framework was the basis for changes to the management area boundaries and the type of management controls for many of the areas. The revised Dwight-Valparaiso-Brainard management area has experienced improvements in ground water levels and recent regulation changes have allowed an increase in groundwater pumping in the eastern region. Based on the AEM, a new recharge area was identified, and management controls were implemented to reduce non-point source pollution over the recharge area. The AEM-derived hydrogeological framework information has been used for the following: to vary management techniques based on the degree of aquifer confinement and in-season water declines; to determine the amount of groundwater in storage; to locate potential recharge areas; to guide the installation of monitoring wells; to locate and install surface water gages to understand groundwater-surface water relationships; to locate areas for vadose zone characterization; and, finally, to assist local public water suppliers with the management of limited aquifers.