2016 NGWA Groundwater Summit

Accuracy Testing of New and in-Use Electric Groundwater-Level Measurement Tapes

Tuesday, April 26, 2016: 12:00 p.m.
Platte River Room (The Westin Denver Downtown)
Rod Sheets , Department of Interior, US Geological Survey
Janice Fulford, Dr. , Dept. of Interior, US Geological Survey, Stennis Space Center, MS
William L. Cunningham , Office of Groundwater, U.S. Geological Survey, Reston, VA
James Dubuisson, Dr. , Department of Interior, U.S. Geological Survey, Stennis Space Center, MS

The U.S. Geological Survey (USGS) measures the water level in more than 15,000 wells each year and, increasingly, these measurements are done with electric tapes.  Approximately 650 electric water-level tapes are in use by the USGS and USGS standards require regular calibration of these and all instruments used for hydrologic measurement. 

Electric water-level measurement tapes are generally assumed to be accurate to ±0.01 foot (ft), but little information is available from the manufacturers and USGS field office calibration and initial calibration studies by the USGS Hydrologic Instrumentation Facility (HIF) indicate that this accuracy is seldom attained. This study was designed initially to determine the accuracy of six models of new, unused electric groundwater tapes often used by the USGS for routine water-level measurements and groundwater studies. A tape-calibration system was designed and built at the HIF. The tape-calibration system compares the length of each electric tape to a calibrated-steel reference tape and measures each probe’s activation accuracy. The tape-length accuracy combined with the probe-activation accuracy gave the overall measurement accuracy of the tape.  Results demonstrated that none of the electric-tape models tested consistently met the suggested accuracy of ±0.01 ft, and that most tapes were accurate to approximately ±0.05 ft per 100 ft without additional calibration.  Precise calibration of in-use tapes is necessary to gain the required accuracy.  Comparisons between results at established metrology laboratories and the tape-calibration system at the HIF indicate that the HIF system is adequate for calibration of USGS electric tapes, and a program has been established to retrieve all USGS field electric water-level tapes for evaluation and calibration. Results of this ongoing evaluation and calibration of in-use USGS electric tapes will be presented.

Rod Sheets, Department of Interior, US Geological Survey
Rod is a groundwater specialist for the Office of Quality Assurance. Prior to that, I was a hydrologic technician, hydrologist, and groundwater specialist for the USGS Ohio Water Science Center, working on a variety of projects and tasks, including those related to surface/ground-water interaction, aquifer testing, surface and borehole geophysics and ground-water flow modeling. Before joining the USGS Water Mission Area, I worked as a geologist and geologic technician for the USGS Office of Earthquakes for a short time/ (started as a NAGT student). I still drill an occasional water well.

Janice Fulford, Dr., Dept. of Interior, US Geological Survey, Stennis Space Center, MS
Director Hydrologic Instrumentation Facility

William L. Cunningham, Office of Groundwater, U.S. Geological Survey, Reston, VA
Bill Cunningham is the Chief of the U.S. Geological Survey Earth Systems Processes Division. This office is the single focal point for disciplinary and interdisciplinary process studies research and development. Prior to joining the ESPD, Bill was the Chief of the Office of Groundwater, and prior to that he worked on groundwater science investigations in the Ohio and North Carolina Water Science Centers. Cunningham also serves as Co-Chair of the Subcommittee on Ground Water for the Federal Advisory Committee on Water Information. He received undergraduate and graduate degrees from The Ohio State University.

James Dubuisson, Dr., Department of Interior, U.S. Geological Survey, Stennis Space Center, MS
Blu Dubuisson is an expert hydrologic technician who designed and built a tape calibration system at the Hydrologic Instrumentation Facility.