GROUND WATER IN NORTH-CENTRAL TENNESSEE

GROUND WATER IN NORTH-OfeNTRAL TENNESSEE
Small steeply tilted blocks also occur about 2 miles east 6f Cum­
berland City, although the structural Conditions are not fully known
and can not be delineated on the scale of Plate 4.
QROUND-WATEB, CONDITIONS
In Stewart County, as in other parts of the Highland Rim plateau
where the bedrock consists of the St. Louis limestone^ the residual clay
mantle on the upland tracts contains little coarse material and gen­
erally yields very little ground water. Hence, most residents of the
upland store rain water in cisterns for domestic supply and impound
storm run-off in small artificial ponds for watering stock. On the
other hand, a few derive water from rather deep dug Wells or from
drilled wells that enter the limestone. No wells are known to find
potable water more than 175 feet below the surface or water of any
character more than 350 feet below the surface, as in well 34 (pi. 4 and
pp. 194-195), which is 1,636 feet deep. On the plateau remnantsin the
deeply dissected western part of the county the channeled zones in
the upper part of the limestone may be drained, so that it is impossible
to obtain an adequate water supply even for domestic purposes by
drilling. The Eutaw and Tuscaloosa formations, which underlie a part
of the plateau (pi. 4), contain beds of permeable material that should
yield water freely where they are not drained by the valleys of tribu­
tary streams. However, the part of the plateau that is underlain by
these formations is in general very sparsely populated and is covered
with a dense growth of timber, so that nothing is known of the actual
water-bearing conditions.
In the stream valleys and on the lower slopes of the dissected areas
many dug wells derive water from alluvium or from hill wash.
Ground-water conditions in the underlying limestone differ greatly
from place to place, although drilled wells usually find water less than
100 feet below the surface. In general, however, water-bearing beds
are not likely to be found far below the level of the near-by perennial
streams. Probably the most reliable sources of ground water in the
dissected parts of the county are the tubular springs that issue from
the limestone (pp. 92-95), many of which are used for domestic supplies
and for stock. The discharge of some of these springs is relatively
invariable; that of others may vary greatly from season to season,
even though the minimum discharge may be large. Hence the relia­
bility of a spring can be determined only by periodic measurements of
its discharge over a term of several years. Large springs of this sort
seem to be especially numerous at two levels on the lower reaches of
the tributary streams from 25 to 50 feet above the Tennessee and
Cumberland Eivers, and near the heads of the tributaries not far
below the remnants of the Highland Eim plateau. Many seepage
springs (pp. 90-92) of relatively small discharge also issue from the hill