GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
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164 <strong>GROUND</strong> <strong>WATER</strong> <strong>IN</strong> <strong>NORTH</strong>-<strong>CENTRAL</strong> <strong>TENNESSEE</strong><br />
above sea level. The south hall of the county is traversed by the<br />
somewhat meandering youthful valley of the Cumberland River, which<br />
at Clarksville is about 350 feet above sea level. Hence the total re<br />
lief within the county is about 350 feet.<br />
The massive crystalline beds of the St. Louis limestone and Warsaw<br />
formation, of Mississippian age, cover the greater part of the county,<br />
although there are few visible exposures of these rocks except in the<br />
youthful stream valleys. In the interstream areas bedrock is mantled<br />
by as much as 125 feet of clay and soil, which are residual from the<br />
chemical weathering of the limestone. Montgomery County is un<br />
like areas in which the cherty Fort Payne formation underlies the<br />
surface in that this residual clay contains comparatively few chert<br />
fragments. The Fort Payne formation, which crops out in the val<br />
leys of the Cumberland River and of Barton and Little Barton Creeks,<br />
in the southeast corner of the county, consists of thin beds of cherty<br />
and earthy limestone. The geologic map (pi. 4) shows the outcrop<br />
areas of these formations; the discussion of stratigraphy (pp. 33-37)<br />
treats of their lithologic character.<br />
<strong>GROUND</strong>-<strong>WATER</strong> CONDITIONS<br />
Most of the residents of the upland areas rely upon cisterns as a<br />
source of water, inasmuch as the residuum from the weathering of the<br />
limestone is generally not water bearing and dug wells are generally<br />
unsuccessful. Water for stock is generally impounded in natural or<br />
artificial ponds. Comparatively few tubular wells have been drilled,<br />
although they generally obtain sufficient water for domestic purposes.<br />
Most of the drilled wells are between 100 and 160 feet deep, and all<br />
derive their water from channeled zones in the limestone. (See pp.<br />
69-89.) A few wells, such as Nos. 49, 50, and 55 (pp. 166-167), have<br />
been drilled more than 200 feet deep in search of water, and several<br />
relatively deep holes have been drilled in search of oil or gas. So far as<br />
is known, however, the deepest water-bearing stratum disclosed in any<br />
of the upland tracts by these wells is 187 feet below the surface, If the<br />
experience of drilling in adjacent parts of the Highland Rim plateau<br />
is a sound basis for judgment, it seems likely that potable water will<br />
not be found more than 200 feet below the upland areas of Montgom<br />
ery County. In the more deeply dissected parts of the county ground-<br />
water conditions are relatively erratic, although many wells from 50<br />
to 100 feet deep yield sufficient water for domestic supply. Several<br />
wells in and near Clarksville, such as No. 52, are reported to find<br />
water about 300 feet below the surface in a sandstone or sandy<br />
limestone that occurs approximately at the horizon of the sandstone<br />
member of the Pegram limestone (pp. 41-43). However, there is no<br />
sound basis for making a definite correlation. This stratum is not<br />
water bearing in some wells that reach its horizon, as in well No. 55,