GROUND WATER IN NORTH-CENTRAL TENNESSEE

*J12 GEOTJND WATEtt IN NORtH*CEN*RAL TENNESSEE
rather cavernous, as at Whitehurst Cave (No. 361, pi. 4), about 4
miles northeast of Franklin, and along the crest of the ridge crossed
by the Murfreesboro pike between 4 and 5 miles east-southeast of
Franklin. These cavernous zones, which occur approximately from
100 to 200 feet above the major valleys, were clearly formed before
the Nashville Basin stage of stream planation (pp. 20-22), for they
have been cut through by streams adjusted to that Stage and gener­
ally are completely drained. That along the Muffrfeesboro pike,
however, constitutes a natural reservoir and impounds Water, which
is exposed in several sink holes about 740 feet above sea level,
such as Armstrong's Pond (No. 374), and is discharged by several
perennial springs between 700 and 740 feet above sea level about the
periphery of the hilly tract. Presumably the principal outlets of this
cavernous zone are wholly or partly clogged with debris, else Water
could not be impounded in it. In these same hilly tracts some drilled
wells penetrate water-bearing beds between 40 and 200 feet below the
surface, although most wells are between 60 and 100 feet deep. Some
Wells that are close together find water at different depths. Generally
the Water associated with beds 100 feet or less below the surface con­
tains only a moderate amount of dissolved calcium bicarbonate and
other mineral matter and is not unduly hard. On the other hand, the
water associated with the shallower beds in a few places and with the
deeper water-bearing beds at most places is likely to be BO highly con­
centrated in sulp'hate or chloride and to have so much noncarbonate
or permanent hardness that it is quite unsuited for general use. Anal­
ysis 394 (pp. 116-117) is typical of the calcium sulphate waters. Fur­
thermore, some of the waters are reported to contain hydrogen sulphide,
as in well 378, or appreciable amounts of petroleum or natural gas, as
in wells 399 and 401. Both potable and highly mineralized nonpotable
Water are encountered by well 373 in beds that are approximately
40 feet and 200 feet, respectively, below the surface. The water from
this well is usable for domestic purposes only in the wet season, when
the static level of the ground water in the 40-foot bed is at its highest
and is considerably above that of the 200-foot bed. Furthermore,
many wells in the hilly tracts, such as Nos. 357, 363, 388, and 396, do
not find any Water-bearing beds even though they range from 40 to
225 feet or more in depth. Well 389 passed through a water"-bearing
bed that yielded 15 gallons a day about 40 feet below the surface but
found no other water-bearing beds to a depth of 300 feet. Among
the most reliable sources of water in the hilly areas are perennial
springs, such as Nos. 362 and 364, although none are known whose
minimum annual discharge is much more than 25 gallons a minute.
In the valleys of the east half of the county ground-Water condi­
tions also differ greatly from place to place. In general the Welife may
be divided into two groups those which obtain moderately coacfen-