Alluvium (Qa) and Glacial Sediments (Qg)
These sediments form floodplains and terraces, as much as 6 miles wide,
in the Ohio River Valley, and broad flat areas in the valleys of the
Kentucky River and large tributaries. Some Ohio River terraces are as
much as 80 feet above normal pool stage. Flats are dissected by short,
steep-sided gullies near tributaries.
These unconsolidated materials yield 200 to 500 gallons per minute to
most wells that penetrate the full thickness of alluvium in the Ohio
Valley, and more than 1,000 gallons per minute to large-diameter wells.
Wells in tributary-stream valleys yield 100 to 500 gallons per day,
and may yield more than 500 gallons per day where gravel is present.
Water is hard, and the iron content may be high near the Ohio River
Valley walls and along the Kentucky River.
Drakes Formation (Saluda Dolomite, Bardstown, Rowland Members) (Od)
and Bull Fork Formation (Ob)
These rock bodies form moderately dissected upland areas, with moderately
steep slopes where shale predominates and less steep slopes where limestone
predominates. Slopes along large streams are steep; many slopes are
dotted with weathered limestone slabs. Solutional features are evident
where thick limestone beds underlie streams.
The Drakes and Bull Fork yield 100 to 500 gallons per day to wells in
large stream valleys, and more where thick limestone is present. They
yield almost no water to wells on hillsides and ridges, except in broad
ridges in the upper part of the formation, but do yield water to small
springs. Water is hard and may contain salt in valley bottoms, but generally
is of good quality.
Grant Lake Limestone, Fairview Formation, Calloway Creek Limestone
These rock bodies form gently to moderately rolling uplands away from
major streams, more highly dissected where shale content increases.
Small sinkholes, minor underground drainage, and broad, flat valleys
occur where limestone predominates. The lower part forms broad, flat
ridges between steep-sided valleys cut into the underlying shale of
the Kope or Clays Ferry formations.
These rocks yield 100 to 500 gallons per day to drilled wells in broad
valleys and along streams in uplands. Yields of more than 500 gallons
per day occur from thick limestone beds in the broad valley bottoms.
These formations yield almost no water to drilled wells on hillsides
or ridgetops, but some water to small springs and seeps. A limestone
bed 15 feet thick in the lower part of the Grant Lake yields as much
as 30 gallons per minute to springs. The sandy zone near its base yields
little water. Water is hard and in valley bottoms may contain salt or
Clays Ferry Formation and Kope Formation (Okc)
These formations create rugged topography of narrow, steep-sided ridges
with narrow V-shaped valleys of dendritic drainage. Shales on steep
slopes erode easily and are covered with thin limestone slabs in many
places. The contrast with the less-rugged surface of the adjacent areas
is marked except near major streams. In the lower part of the formation,
topography becomes more gently to moderately rolling uplands with small
sinkholes and some underground drainage where limestone predominates.
These formations yield 100 to 500 gallons per day to drilled wells in
large valley bottoms along streams, but almost no water to drilled wells
on hillsides or ridgetops. They do yield water to small springs and
seeps. Water is hard in valley bottoms, and may contain salt or hydrogen
The U.S. Geological Survey's Hydrologic Atlas Series, published cooperatively
with the Kentucky Geological Survey, provides hydrologic information
for the entire state. Atlases covering the county are HA-23,
to "Groundwater Resources in Kentucky"