RESEARCH:  Analytical equations used in ground-water studies.

                           UNITED STATES
                    DEPARTMENT OF THE INTERIOR
                         GEOLOGICAL SURVEY
                     Water Resources Division
                        Washington 25, D.C.

In reply refer to:                             January 7, 1958
                                               Code 4051 0001


To:       District Chiefs and Staff Officials

From:     Chief, Ground Water Branch

Subject:  RESEARCH:  Analytical equations used in ground-water

The development of computational aids, such as a slide rule with
special scales, and the general progress of several research
projects (particularly Aquifer Analytical Methods) would be
greatly furthered by knowing which theoretical equations are being
used most frequently in analyzing ground-water hydraulics
problems.  Unquestionably the Theis nonequilibrium formula is used
more than any sought as to those equations that should be next in
order on a list arranged according to decreasing frequency of use.
It would appear, for example, that the drain and leaky-aquifer
formulas are used quite often, but their proper place on the list
can best be judged from the replies to this memo.

Each district supervisor and staff official is asked to provide
the Washington office with a selection of the equations and
empirical relationships which, in his experience in pursuing
ground-water investigations, have been most commonly used.  Kindly
restrict the selection to no more than 6 items arranged in order
from the most to the least frequently used.  Each item may be
presented as an equation name or number, complete with the page
and reference work where it can be found.  The Ground Water Notes
series, particularly Note No. 28, should be one of the handiest
reference sources and should be cited wherever possible.

In addition to listing the equations you adjudge most useful in
describing ground-water movement, your response to the following
questions would be especially helpful:

     1.)  Considering the investigations you are directing, or
          have directed, what ground-water hydraulics problems can
          you identify (and describe) which are not amenable to
          satisfactory analysis using presently available

     2.)  If your reply to question (1) embodies descriptions of
          several problems, how would you rank them in order from
          top priority to lowest priority?

It is not intended to burden the district supervisors and staff
officials with a detailed review of available quantitative
methods.  It is expected that the information and opinions sought
can be furnished readily by briefly reflecting upon drawing from
past field experience.  A prompt reply will be appreciated.

                               (s) A. N. Sayre

Distribution:  A, B, GS, GFO