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Alluvium and Glacial Outwash Sediments (Qa)
Topography
These sediments form floodplains, valley bottoms, and terraces of large
streams.
Hydrology
Yields from shallow driven wells in the Mississippi Valley are adequate
for domestic use; however, near the river, water levels fluctuate greatly
and some shallow wells are dry or inadequate in the summer and fall.
Yields of 1,000 gallons per minute may be expected in most places. The
water is hard and contains objectionable amounts of iron and manganese.
The sediments yield enough water for a modern domestic supply (more
than 500 gallons per day) to nearly all wells, but practically no water
to wells in small valleys where the alluvium is thin and fine-grained.
Water ranges in hardness from 12 to 664 parts per million and in dissolved
solids from 53 to 1,220 parts per million. Iron may be present in objectionable
amounts.
Loess
Topography
Loess forms a thin mantle over most uplands and gently sloping sides
of stream valleys, thinning west to east. It forms steep bluffs where
thick. Many badlands or heavily eroded gullies occur in the uplands.
Hydrology
The loess is not an aquifer. It does yield small amounts of water to
a few wells. When saturated by rainfall, it transmits water to underlying
aquifers.
Terrace Gravel Deposits and Continental Deposits (QTcl)
Topography
These deposits occur on uplands and eroded edges of uplands above 370
feet.
Hydrology
These deposits yield small quantities of water suitable for household
use. One spring had measured discharge of 47 gallons per minute. Most
wells yield less than 10 gallons per minute. Water-bearing gravel usually
overlies clay or indurated layers. Water ranges in hardness from 8 to
724 parts per million and in dissolved solids from 43 to 782 parts per
million. Iron content is generally low.
Jackson, Claiborne (Tjc), and Wilcox Formations (Tw)
Topography
These formations occur in uplands and high-level erosional surfaces
over most of the area.
Hydrology
Sand yields enough water for domestic use near the outcrop area of the
Porters Creek Clay and in areas of perched water. Drilled wells penetrating
the main zone of saturation where beds are thick yield as much as 1,700
gallons per minute. Hardness of water ranges from 7 to 212 parts per
million, and dissolved solids from 28 to 431 parts per million. Iron
may be present in objectionable amounts.
Porters Creek Clay (Tp)
Topography
The Porters Creek crops out along the Clarks River Valley and in adjacent
uplands from the Tennessee state line to Paducah.
Hydrology
The Porters Creek probably will yield a little water from joints and
from sandstone dikes.Water is probably hard and high in iron. This formation
is important as a confining layer.
The U.S. Geological Survey's Hydrologic
Atlas Series, published cooperatively with the Kentucky Geological
Survey, provides hydrologic information for the entire state.
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