GROUND WATER IN NORTH-CENTRAL TENNESSEE

GROUND "WATER IN NORTH-CENTRAL TENNESSEE;: 99
QUALITY OF GROUND WATER ,,. ,
The chemical character of the ground waters of north-central
Tennessee is shown by the analytical data tabulated on pages 110-119.
These data cover the analyses of 101 samples collected in 1927 by the
writer from representative wells and springs, at sampling points dis­
tributed as uniformly as possible within the region and from top to
bottom of the geologic column. Approximately half these analyses
were made by Margaret D. Foster in the water-resources laboratory
of the United States Geological Survey, and half by D. F. Farrar in
the laboratory of the Tennessee Geological Survey. All the analyses
were made after the methods outlined by Collins. 66
CHEMICAL CONSTITUENTS IN RELATION TO USE"
Total dissolved solids. The residue from complete evaporation of
a natural water consists mainly of the rock substances discussed below,,
with which may be included a small quantity of organic matter and
some water of crystallization. Most waters containing less than 500
parts per million of dissolved solids are satisfactory for domestic and
common industrial uses, except for the difficulties resulting from hard­
ness and occasional excessive iron or more rarely corrosive properties.
Waters with much more than 1,000 parts per million of dissolved
solids are likely to contain enough of certain constituents to impart a,
noticeable taste to the water. However, some waters that, contain
more than 1,000 parts per million are satisfactory for domestic use and
for some industrial purposes. .
The ground waters from most springs and wells of shallow or mod­
erate depth in north-central Tennessee range in concentration from
about 50 to 500 parts per million and are satisfactory for all ordinary
uses if not polluted by organic waste (pp. 108-109). The waters from
most of the deep wells and from some shallow sources, however, are
highly concentrated, and some contain as much as 25,000 parts per
million of dissolved solids. ;
Ground water that percolates slowly through permeable rocks is
likely to be relatively invariable in concentration throughout the year.
However, much of the ground water of north-central Tennessee circu­
lates in solution conduits in limestone and is likely to be subject to
seasonal variations in concentration that are comparable to seasonal
variations in the discharge of the system of conduits. ; Mos,t of the
representative samples were collected during the season of minimum
ground-water discharge. Hence, their concentration probably, approx­
imates the seasonal maximum. The magnitude of the average
seasonal variations in concentration of the ground water is unknown
M Oollins, W. D., Notes on practical water analysis: U. S. Geol. Survey Water-Supply Paper 596, pp. 236-
261, 1928. ., ,. , .
u Adapted from Collins, W. D., Chemical character of waters of Florida: TJ. S. Geol. Survey Water
Supply Paper 596, pp. 181-186,1928.