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Alluvium and Glacial Outwash Sediments (Qa)
Topography
These sediments form floodplains, valley bottoms, and terraces of the
Mississippi River and tributaries. Valley-train deposits lie beneath
terraces along the Mississippi River.
Hydrology
Yields from shallow driven wells in the Mississippi Valley are reported
adequate for domeestic use; however, near the river water levels fluctuate
greatly, and some shallow wells are dry or inadequate in the summer
and fall. Drilled wells in the Mississippian alluvium may supply large
amounts of water from the deeper gravelly unit for irrigation and for
public and industrial uses, except in areas where the saturated thickness
is less than 10 feet. Saturated thickness generally ranges from about
30 to 150 feet, and a well may yield 3,000 gallons per minute or more
in favorable areas. 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. Enough water for a modern domestic supply (more
than 500 gallons per day) is yielded to nearly all wells. Practically
no water is yielded 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.
Continental Deposits (QTcl)
Topography
Continental 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 a 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 solidds from 43 to 782 parts
per million. Iron content is generally low.
Jackson, Claiborne (Tjc), and Wilcox Formations (Tw)
Topography
These formations provide uplands and a high-level erosional surface
over most of the area. They extend beneath river terraces along the
Mississippi Valley.
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 solidds from 28 to 431 parts per million Iron
may be present in objectionable amounts.
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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