GROUND WATER IN NORTH-CENTRAL TENNESSEE

EOBEETSON COUNTY 171
GROUND-WATER CONDITIONS
As in other parts of the Highland Rim plateau that are underlain
by the St. Louis limestone, most of those who reside in interstream
tracts of Robertson County derive their domestic water supplies from
cisterns. This condition is chiefly due to the absence of water-bearing
zones in the residual clay that mantles the plateau, so that dug wells are
generally inadequate. Relatively few tubular wells have been drilled
in the county, although such wells generally obtain adequate domes­
tic supplies in channeled zones in the limestone (see pp. 173-175)
from 30 to 105 feet below the surface. A few wells obtain potable
water in the limestone as much as 175 feet below the surface, but on
the other hand some deep wells have found no water-bearing strata
more than 100 feet below the surface. One typical well, No. 92
(pp. 173-174), found a small amount of water 20 feet beneath the sur­
face in cherty debris at the top of the solid rock but did not penetrate
any other water-bearing strata even though drilled to a depth of 311
feet. Several relatively deep wells, such as Nos. 78,93,94, 99, and 108
which have been drilled in search of oil or gas, have either been dry
holes below a depth of 100 to 200 feet or have encountered only highly
concentrated brine. No extensive permeable stratum is known to
exist beneath the county. So far as is known, none of the tubular
wells have been pumped more than 5 gallons a minute, and the total
capacity of some is much less than 5 gallons a minute.
In those parts of the county which are deeply trenched by the
streams ground-water conditions in the limestone differ greatly from
place to place; generally water-bearing beds are not found far below
the level of the perennial streams. Some of the beds in the upper
part of the Fort Payne formation, which crops out in the deeper valleys
south of Springfield, are sandy and appreciably permeable, but their
water-yielding capacity is not known. In these parts of the county
both seepage and tubular springs (pp. 90-95) are numerous, and many
of the domestic water supplies are derived from them. Some of the
tubular springs have relatively constant discharge and are by far the
most reliable sources of water in the county. Three of the typical
springs (p. 176) discharge 100 gallons a minute or more each, and the
discharge from one (No. 80) was about 725 gallons a minute on
August 26, 1927, when the ground-water discharge was nearly at its
seasonal minimum.
Most of the ground waters of Robertson County are moderately
concentrated and moderately hard calcium bicarbonate waters that
are suitable for any ordinary use, especially after they have been
softened. In a few places the water associated with the St. Louis
limestone and Warsaw formation is highly concentrated and very
high in noncarbonate hardness; it may also contain considerable
hydrogen sulphide. In other places, as in well 76, the ground water