HR: 0800h
AN: H11A-0150    [Abstracts]
TI: Taking the superconducting gravimeter to the field for hydrologic and other investigations
AU: * Wilson, C R
EM: crwilson@mail.utexas.edu
AF: Dept of Geological Sciences, Jackson School of Geosciences University of Texas Austin, Austin, TX 78712, United States
AU: Wu, H
EM: wuhongqiu@mail.utexas.edu
AF: Dept of Geological Sciences, Jackson School of Geosciences University of Texas Austin, Austin, TX 78712, United States
AU: Scanlon, B
EM: bridget.scanlon@beg.utexas.edu
AF: Bureau of Economic Geology, Jackson School of Geosciences University of Texas Austin, Austin, TX 78712, United States
AU: Sharp, J M
EM: jmsharp@mail.utexas.edu
AF: Dept of Geological Sciences, Jackson School of Geosciences University of Texas Austin, Austin, TX 78712, United States
AB: We have adapted the GWR superconducting gravity meter to a transportable configuration for field studies in support of hydrologic and other investigations. The gravimeter has a precision in the 10-nanogal range, and a nominal drift of a few microgals per year. Although the GWR instrument has been in production for about three decades, operations have been restricted previously to laboratory and vault environments. A ground water gravity signal has often been apparent, but complex hydrologic conditions have made quantitative interpretation difficult. By making the instrument transportable, one is able to choose sites where better-defined hydrologic problems can be investigated, and to consider tectonic, volcanic, and other applications. Technical advances have reduced the size of the helium dewar and solved the helium replenishment requirement via a compact refrigeration system. With the ability to cool to 4 K, it is possible to maintain a full dewar indefinitely. With support of NSF EAR Instrumentation and Facilities, we procured a GWR gravimeter and developed the system to be transportable, self contained within two enclosures, and accessible via cell-phone internet service. A bracket system allows the helium dewar containing the gravity sensor to be locked to the frame and transported without disassembly. Initial application is to hydrologic investigations in karst and desert alluvial aquifers. The goal is to understand hydrologic signals at a level near one microgal, equivalent to the attraction of a 2cm layer of water. Instrument precision exceeds this, but the variety of sources in the atmosphere makes it difficult to identify hydrologic signals with greater precision. Companion weather and well observations are used to observe and interpret gravity variations in terms of infiltration and storage changes, and GRACE satellite gravity observations enable separation of regional and local influences.
DE: 1218 Mass balance (0762, 1223, 1631, 1836, 1843, 3010, 3322, 4532)
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 1243 Space geodetic surveys
DE: 1294 Instruments and techniques
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting