USGS Groundwater Information: Branch of Geophysics
F.D. Day-Lewis (email@example.com) (1); K. Singha (2); R.J. Versteeg (3); C.D. Johnson (1); M.D. Petkewich (4); A. Richardson (3); T. Rowe (3); and J.W. Lane, Jr. (1)
(1) U.S. Geological Survey, Office of Ground Water, Branch of Geophysics, 11 Sherman Place, Unit 5015, Storrs, CT 06269 United State
(2) Dept. of Geosciences, Pennsylvania State University, 311 Deike Building, University Park, PA 16802 United States
(3) Idaho National Laboratory, PO Box 1625 , Idaho Falls, ID 83415-2025 United States
(4) U.S. Geological Survey, 720 Gracern Road, Columbia, SC 29210 United States
Aquifer storage and recovery (ASR) is used increasingly as a water-resources management tool, particularly in arid and coastal areas. ASR involves subsurface freshwater injection and storage during periods of water surplus and subsequent extraction during periods of water deficit or high demand. In coastal areas, injection into brackish-to-saline aquifers creates freshwater zones, the shapes and extents of which are controlled by aquifer heterogeneity and ground-water flow. ASR efficiency is limited by a lack of information about (1) the spatial and temporal distribution of injected freshwater and (2) possible degradation of aquifer properties resulting from injections. Without such knowledge, ASR managers cannot optimize injection and extraction schemes, nor can they predict or prevent breakthrough of brackish water at pumping wells. In this study, we examine the potential of hydrogeophysical monitoring as a management tool for ASR operations. In August-September 2005, time-lapse electrical resistivity tomography (ERT), combined with conventional chemical and hydraulic sampling, was conducted during a pilot-scale ASR experiment in an Atlantic Coastal Plain aquifer in Charleston, SC. The field site consists of 4 wells including three observation wells arranged symmetrically around a central injection/extraction well at radial distances of about 9 m. The wells are 140-155 m deep. Sand and limestone sections of the Santee Limestone/Black Mingo aquifer served as target zones for injection, storage, recovery, and ERT monitoring. We acquired time-lapse ERT data sets every 2.5 hours during 120 hours of injection, 48 hours of quiescent storage, and 96 hours of extraction. A key aspect of this work was the use of an autonomous remote monitoring system developed by Idaho National Laboratory (INL), which controls data collection, automated data upload to a central server, and parsing of the data into a relational database. In addition, this system provides a web interface for browser-controlled data visualization and analysis. Near real-time data visualization revealed the influence of preferential transport pathways within the productive zones of the aquifer consistent with borehole geophysical logs and hydraulic testing observations. The timing, locations, and relative magnitudes of resistivity changes were consistent with the results of direct chemical sampling at observation wells; these results demonstrate the feasibility of ERT for monitoring the spatial and temporal distribution of freshwater injected for ASR projects, providing information about transport processes between boreholes where direct chemical measurements are unavailable.
Final copy as submitted to the American Geophysical Union for publication as: Day-Lewis, F.D., Singha, K., Versteeg, R.J., Johnson, C.D., Petkewich, M.D., Richardson, A., Rowe, T., and Lane, J.W., Jr., 2005, Toward real-time continuous, automated hydrogeophysical monitoring of aquifer storage and recovery-results of a pilot-scale experiment, Charleston, South Carolina [abs.]: EOS Transactions, American Geophysical Union Fall Meeting, San Francisco, California, 5-9 December, 2005, v. 86, no. 52, abstract H44C-01-INVITED.