GROUND WATER IN NORTH-CENTRAL TENNESSEE

222 GROUND WATER IN NORTH-CENTRAL TENNESSEE
the surface, so that wood or steel tanks are used to store rain water.
In these same areas storm run-off is generally impounded in small
natural or artificial ponds for the watering of stock.
Among the most reliable sources of ground water in the county are
the perennial tubular springs (pp. 92-95), such as those which issue
at the heads of the perennial creeks (Nos. 323, 329, and 342, p. 233),
and the underground streams that are exposed where the roof of a
large solution channel has collapsed (Nos. 331 and 338). The course
of one such underground stream from 15 to 25 feet or more below the
surface is indicated in a general way by a belt of sink holes that trends
northwestward through Blindfish Cave (No. 338); through Cave
Spring, which is on the fair grounds at the western edge of Lebanon;
and through the unused City Spring, in the public square at Lebanon.
The solution channel through which this stream flows is a part of what
seems to have been an extensive system of channels draining much of
the Nashville Basin peneplain before its dissection. Hence, some of
the tubular springs that issue from channels of this system may drain
large bodies of limestone and be correspondingly less variable in
discharge than those whose catchment area is small. The discharge
of most of the tubular springs is extremely variable, increasing notably
a few hours after a heavy rain and decreasing greatly in the summer.
Consequently, the reliability of any spring can be determined only by
periodic measurements of the discharge during several years.
The drilled wells from which domestic water supplies are drawn on
the Nashville Basin peneplain of Wilson County range in depth from
22 feet to about 200 feet, although most of them are between 50 and
75 feet deep. Generally, the portions of the strata that are permeable
are not continuous, for wells at adjacent sites may be drilled to very
different depths in order to find water. Generally the tested capacities
of the wells are not more than 5 gallons a minute, and for some the
capacities are less than 1 gallon a minute. A few wells, such as No.
348 (pi. 4, also pp. 230-232), have tested capacities exceeding 10 gallons
a minute, but unsuccessful wells have been drilled at many places, espe­
cially on the crests of the ridges. The difficulties that are encountered
in obtaining a large amount of water from drilled wells are shown by
conditions at Horn Springs (No. 326), where 30 or more wells have
been drilled in an effort to obtain an adequate water supply for a resort
hotel with outdoor swimming pool. It is reported that each of these
wells would have yielded enough water for a single household, although
the chemical character of some of the ground water obtained was
unsatisfactory, and all but four of the wells have been abandoned as
inadequate. Several wells that were drilled near the hotel within 200
yards of Horn Spring No. 2 (No. 326), about 570 feet above sea level,
range from 35 to 95 feet in depth; all found rather highly concentrated
water at depths between 17 and 35 feet but no water below. The