Thursday, October 17, 2013

Lunar Cycles And Groundwater Level Fluctuations In Confined Aquifers From S. India

Interesting paper in Current Science (Open Access) - Impact of Earth’s crustal tides on groundwater regime in confined sedimentary aquifers of Andhra Pradesh, India - Umamaheswara Rao Bollimunta

Water being less rigid deforms more easily due to the Moon's and Sun's gravitational attraction, manifested as the familiar ocean tides. However, the earth's crust too deforms slightly. So, there are crustal tides daily just like ocean tides. The magnitude of deformation is quite small, about 2 feet across the diameter of the earth. U.R. Bollimunta in this paper demonsrates that water levels in two piezometric wells i.e. wells which puncture confined aquifers show cyclical variations in water level tracking lunar phases. When the moon's pull is the strongest as on full moon the water levels drop. This is because when the moon's tidal attraction is maximum the overburden load on the aquifer is reduced allowing it to expand every so slightly.  During times of less lunar attraction the aquifer compresses causing water levels to rise again.

Fascinating stuff-


Signatures of the Earth’s crustal tides are recorded in the groundwater regime, particularly in confined aquifers in the form of rise and fall of its piezometric surface. Though this phenomenon is universal, and exists in the entire groundwater regime, the recording at a few places and in some rare situations is doubtful. An attempt is made here to study the conditions required for recording this phenomenon along with its basic principles. The Central Ground Water Board has constructed 115 piezometer wells and monitored piezometric heads with high frequency digital water level recorder. The impact of Earth tide on ground- water regime is clearly recorded at two sites namely, Kothagudem (Khammam district) and Mangapet (Warangal district). The wells at these sites are constructed in the confined aquifer of Kamthi sandstone in Godavari valley which is nearly 200 km inland from the east coast. Analysis of the data reveals that the piezometric level heads fluctuate in a cyclic manner and the variations for each lunar cycle of 13–14 days with high peaks on new Moon and full Moon days. The peaks observed in the piezometric heads gradually decline coinciding with the lunar phase. Distinct changes in piezometric heads are observed for each phase of the Moon in both of the above-mentioned places. An account of impact of lunar and solar attraction forces on piezometric level heads of ground- water, the ideal conditions required for recording this phenomenon along with a comparison of these hydro- graphs with examples from the literature are provided in the present study.

And No Astrologers.. this slight crustal expansion and compression does not cause big earthquakes.

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