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)