The work was to get value of acceleration due to gravity (g) from different areas around the city of Tucson. Value of 'g' relative to different places in the city is used to measure water table within the study area. That day, we headed towards the east Tucson. We went to one of the sites of USGS where an artificial well was built. The well visited was numbered ' C 022A'.
Well
Well Number: C 022AThe task was to get a relative value of acceleration due to gravity using a gravitometer.
GravitometerThis value obtained was later compared with the absolute value of 'g'. The fluctuations in the value of 'g' is used to monitor the water table in the area under study. The 'g' value here is measured in mGal (Gal referred "galileo" and is equal to 1 centimeter per second squared, source).
Reading in gravitometerColorado river is the major source of water for Tucson city and measuring water table in Tucson illustrates the input and extraction going on in the Colorado river. Knowing water table is also useful for locals at the work site.
However, our work on that day was not much fruitful. Due to an earthquake that had occurred 17 hours ago, earth was continuously shaking, though in very negligible extent to be felt. Because of the shake we could not get a precise value for 'g'. Data showing the earthquake can be viewed from here.
Though being interrupted by an earthquake, I had an informative exposure towards how acceleration due to gravity can be used to measure water table of an area and how it is actually being carried out in the field. A similar work like this by USGS had been done before at Lancaster, Antelope Valley, California, from November 1996 through April 1997. The report can be accessed from here. Different works by USGS, Arizona Water Science Center can be accessed through their link.
I hope to join Brandon again next time and illustrate more about how it works.
My sincere thanks to
Brandon Forbes
&
USGS family !!
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