The Superconducting Gravimeter as a Field Instrument Applied to Hydrology

We describe development of a transportable version of the Superconducting Gravimeter (SG) and its test in a field experiment to monitor storage in a karst (limestone) aquifer in central Texas. The SG is contained within two aluminum enclosures, one holding the SG in its 35 liter helium dewar, plus electronics; and the second for refrigerator and power supply. In the field test, the SG was supported on threaded steel rods cemented into limestone, and surrounded by weather-protecting sheds. The steel rod design was not completely satisfactory, and in most field settings a concrete floor will probably be required. Field operation requires wired electric power, but is managed remotely using wireless internet. The experiment south of Austin Texas was designed to monitor ground water level, precipitation, and other variables, and observe mass variations associated with storage changes in the aquifer. Drought conditions prevailed, limiting conclusions about the aquifer, but the experiment demonstrated the feasibility of remote unattended operation for periods of many months.