The Investigation of Gravity Variations Near a Pumped-Storage Reservoir in North Wales
Continuous gravity measurements have been made for several months near the upper reservoir of the pumped-storage hydroelectricity scheme at Dinorwic, N Wales. A Lacoste and Romberg Earth Tide gravimeter, incorporating electrostatic feedback was installed 80 metres on the landward side of the reservoir and at a height of 10 metres above the maximum water level. Water level changes in excess of 30 metres were observed during the experiment involving the redistribution ~7.106 tonnes of water. A data set in excess of one month has been obtained and analysed in terms of the gravitational effects of the Earth’s body and ocean load tides in addition to the gravitational attraction due to the varying water level modelled according to Newtonian gravitational theory. The residual signal was examined in terms of non-Newtonian gravity and possible sources of systematic and random errors considered (e.g. uncertainty in lake geometry, gravimeter calibration and elastic properties of the local rock). The uncertainty in both the permeability and porosity of the rock in the vicinity of the gravimeter is found to be the dominant limiting factor in the overall accuracy of the experiment.
KeywordsPermeability Porosity Depression Europe Cross Correlation
Unable to display preview. Download preview PDF.
- Baker, T.F. (1980). Tidal gravity in Britain: tidal loading and the spatial distribution of the marine tide, Geophys. J.R. Astron. Soc, 62, 249–267.Google Scholar
- Baker, T.F., Edge, R.J. and Jeffries, G. (1981). High precision tidal gravity, Scientific report to U.S. Air Force AFGL-TR-81-0339, 26pp.Google Scholar
- Baker, T.F., Edge, R.J. and Jeffries, G. (1989). European tidal gravity. Geophysical Research Letters (in press).Google Scholar
- Clarke, S.P. (Editor), (1966). Handbook of Physical constants. Memoir 97, Geological Soc. of America.Google Scholar
- Edge, R.J., Baker, T.F. and Jeffries, G. (1986). Improving the accuracy of tidal gravity measurements. In, Proc. 10th Int. Symp. on Earth Tides, Consejo Superior de Investigaciones Cientificas, Madrid, 213–219.Google Scholar
- Kanngieser, E., Kummer, K., Torge, W., Wenzel, H.-G. (1983). Das Gravimeter-Eichsystem Hannover, Wiss. Arb. d. Fachrichtg. Vermessungswesen d. Univ. Hannover, 120, 95p.Google Scholar
- Tuck, G.J., Barton, M.A., Agnew, G.D., Moore, G.I., Stacey, F.D. (1988). A lake experiment for measurement of the gravitational constant on a scale of tens of meters, (preprint).Google Scholar
- Zumberge, M.A., Ander, M.E., Lautzenhiser, T., Aiken, C.L.V., Parker, R.L., Ferguson, J.F., Gorman, M.R. (1988). Results from the 1987 Greenland G experiment, EOS Trans. Amer. Geoph. Union, 69, 1046.Google Scholar