PUBLICATIONS--Reprint describing barometric effects on water levels in deep unconfined aquifers. UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY Water Resources Division Washington 25, D.C. In reply refer to: August 5, 1980 GROUND WATER BRANCH MEMORANDUM NO. 80.09 Subject: PUBLICATIONS--Reprint describing barometric effects on water levels in deep unconfined aquifers. Enclosed is a reprint entitled, "Barometric fluctuations in wells tapping deep unconfined aquifers," by E. P. Weeks. The report describes the mechanism causing such fluctuations and presents methods for correcting them. The report points out that the barometric efficiency method, commonly used to correct water-level data from confined aquifers, is inappropriate for correcting water levels in unconfined aquifers. This is true because the magnitude of unconfined water-level fluctuations is dependent on the rate as well as the magnitude of the barometric fluctuations. Also, under certain conditions, the magnitude of barometrically induced water- level fluctuations may exceed the magnitude of the barometric fluctuations themselves, an apparent paradox that cannot be explained in terms of barometric efficiency. The described methods for computing barometric effects should be useful to correct water-level data from aquifer tests on deep unconfined aquifers. Such fluctuations are potentially large and are inadequately described by previously existing theory. Because of the potential usefulness of the described concepts and methods, this report should be brought to the attention of persons in your district who are involved in ground-water studies. (s) Eugene P. Patten Acting Chief, Ground Water Branch Enclosure WRD Distribution: A (memo only) FOL (memo and enclosure)