GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
GROUND WATER IN NORTH-CENTRAL TENNESSEE
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
SPE<strong>IN</strong>GS 89<br />
blank sample of water should be taken from each of the observation<br />
wells and springs and preserved as a standard of comparison. Sam<br />
ples are then taken at regular intervals at each of the observation<br />
points and compared with the corresponding blank sample, and the<br />
collection of samples is continued until the arrival and passing of the<br />
uranin have been noted. From the interval of time between the<br />
dosing of the ground water and the appearance of the dye at a point<br />
a known distance away the rate of movement can be computed. This<br />
is usually determined from the interval between dosage with the dye<br />
and its first appearance at the point of observation, the resultant<br />
figure being probably a minimum value. Though a positive result<br />
from a field test with uranin gives useful information, a negative<br />
result is not conclusive, for the uranin commonly advances as a very<br />
narrow band,63 which may pass between two observation wells and<br />
thereby escape detection.<br />
An instructive example of the use of uranin in tracing the flow of<br />
ground water in limestone has been described recently by Crouch.64<br />
A disappearing stream was traced to springs as much as 5 miles distant,<br />
and the rate of movement was found to be about 160 to 185 feet an<br />
hour.<br />
SPR<strong>IN</strong>GS<br />
GRAVITY SPR<strong>IN</strong>GS<br />
GENERAL FEATURES« ' ' ' '' '<br />
Many localities in north-central Tennessee have no perenjajal<br />
streams of consequence, and hence the springs are an impor^ajpti<br />
present and future source of water supply for municipal and industrial?<br />
uses. The value of any spring for these purposes is determined by<br />
the amount and variability of its discharge, by the temperature of<br />
its water, and by the amount and character of the dissolved and sus<br />
pended matter in its water.<br />
Most of the springs in this region are gravity springs that is, they<br />
percolate from permeable beds or flow from large openings in the rocks<br />
under the force of gravity, much as a stream flows down its channel.<br />
In such springs water does not issue under artesian pressure. These<br />
gravity springs may be further classified as seepage springs, in which<br />
the water percolates slowly from the many small interstices of a<br />
permeable material; as fracture springs, in which the water flows from<br />
one or more joints or other fractures in the rocks; or as tubular springs,<br />
in which the water issues freely from large tubelike channels that are<br />
> Stiles, O. W., and others, op. cit., p. 73.<br />
« Crouch, A. W., The use of uranin dye in tracing underground waters: Am. Waterworks Assoc. Jour.,<br />
vol. 19, No. 6, pp. 725-728,1928.<br />
68 For a full discussion, see Meinzer, 0. E., An outline of ground-water hydrology, with definitions: U. S.<br />
QeoL Survey Water-Supply Paper 494, pp. 60-53,1923. Bryan, Kirk, Classification of springs: Jour. Geol<br />
ogy, vol. 27, pp. 522-561, 1919.<br />
100144 32 7