GROUND WATER IN NORTH-CENTRAL TENNESSEE

GEOGRAPHY O
exist at several localities in the western part of the Highland Rim
plateau, although none produce commercially at present. A full
discussion of these mineral resources is not pertinent in this paper.
Hydroelectric power is developed at several points along the High­
land Rim ;and Cumberland Plateau escarpments immediately east of
the area under consideration and is transmitted to the central basin.
Potential power sites both within and near the region constitute an
ample reserve for future development and for any likely industrial
expansion,
CLIMATE ;
GENERAL FEATURES »
Climatic data are first recorded in Tennessee in 1834, although a
well-coordinated system of observations did not exist for nearly half
a century thereafter. In 1883 a State weather service was established
under the direction of the United States Signal Service. In July,
1891, this work was transferred to the United States Weather Bureau
and has since been continued in a more comprehensive manner under
the uniform procedure of that organization.
North-central Tennessee, having a mean latitude of 36°, has a
relatively mild climate, although its inland position and diverse
physiography lend some rigor to its winters. However, it is not
traversed by any of the principal transcontinental storm tracks, so
that the climatic changes are neither highly frequent nor sudden.
In general, the climate ranges from mild to temperate. The rainfall
is abundant for the needs of agriculture but not excessive. Tfye
humidity is moderate, and the distribution of sunshine and cloudi­
ness is desirable. The ground is rarely covered with snow for more
than a few days at a time, and the period that is free from killing
frosts is relatively long.
TEMPERATURE
The average mean annual temperature is fairly uniform throughout
the region i covered by this investigation and ranges from 58° F. at
Clarksville to 59.7° F. at Johnsonville. In the valley of the Tennes­
see River, :to the south and west, however, the mean annual tempera­
ture is higher, being 60.6° F. at Savannah, in Hardin County. To
the east of the region, on the Cumberland Plateau, it is markedly
lower, as at Crossville, Cumberland County, which has an average
mean annual temperature of 55.4° F. The approximate geographic
variation in average mean annual temperature is also shown by the
isothermal map forming Figure 1.
" Adapted from Nnnn, Bcscoe, The climate of Tennessee: Resources of Tennessee, vol. 8, No. 1, pp.
7-45, Tennessee Geol. Survey, 1918.