Groundwater Availability
 

Alluvium (Qa)
Topography
The alluvium forms narrow floodplains and small terraces along Beech Fork and larger tributaries.

Hydrology
The alluvium is too thin and fine grained to yield much water along Beech Fork and the large tributaries. Water is hard and may have a high iron content.

New Albany Shale (MDnb)
Topography
The New Albany underlies broad, flat valleys with steep hillsides; steep, dissected bluffs are along streams.

Hydrology
The New Albany yields 100 to 500 gallons per day to drilled wells in broad valleys and on uplands. It yields water to dug wells almost any place in the black shale. It also yields water to small springs, which often go dry during late summer and fall. Water is in fractures that extend less than 50 feet below the land surface. Water is hard and may contain salt or hydrogen sulfide.

Laurel Dolomite (Slb)
Topography
The Laurel forms ledges on steep hillsides and in bluffs along streams.

Hydrology
The Laurel yields 100 to 500 gallons per day to drilled wells in valley bottoms, on broad ridges, and along streams on uplands. It yields water to many springs. Water is hard.

Osgood Formation (Slb)
Topography
The Osgood forms steep, dissected hillsides. It erodes easily, undermining the Laurel.

Hydrology
The Osgood yields almost no water, impedes recharge to the Drakes Formation, and holds up water in the Laurel. Limestone yields water to small springs. Water is hard.

Brassfield Formation (Slb)
Topography
The Brassfield forms ledges on slopes and on the tops of small cliffs.

Hydrology
The Brassfield yields almost no water to wells, but does yield water to seeps and small springs. Water is hard.

Drakes Formation (Saluda Dolomite, Bardstown, Rowland Members) (Od) and Bull Fork Formation (Ob)
Topography
These formations lie in somewhat-dissected upland areas, with moderately steep slopes where shale predominates, and moderately undulating to gently rolling surfaces where limestone predominates. Slopes are steep to cliffy and dissected along large streams; many are littered with limestone slabs left after shale erodes and washes away. Small sinkholes with some underground drainage are present where thick limestone beds occur along broad upland stream valleys.

Hydrology
These formations yield 100 to 500 gallons per day to drilled wells in broad valleys and along streams on uplands, but almost no water to drilled wells on hillsides or ridgetops. They do yield water to small springs. Water is hard and in valley bottoms may contain salt or hydrogen sulfide. Shale prevents circulation of water in thicker limestone beds except where limestone is exposed on flat ridges or valley bottoms.

Grant Lake Limestone, Calloway Creek Limestone (Oaf)
Topography
These limestones underlie gently to moderately rolling uplands away from major streams. They are more highly dissected where shale content increases, and dissected and steep along large streams. Thick limestone beds stand out as ledges along steep hillsides and bluffs along streams, and where present on uplands, they underlie broad, flat valleys that may have small sinkholes and some underground drainage. The lower part of the Calloway Creek caps broad, flat ridges between steep-sided valleys cut into underlying shale of the Clays Ferry Formation.

Hydrology
These limestones yield 100 to 500 gallons per day to drilled wells in broad valleys and along streams in uplands. They may yield more than 500 gallons per day from thick limestone beds in the broad valley bottoms, but almost no water to drilled wells on hillsides or ridgetops. They do yield water to small springs and seeps. A limestone bed 15 feet thick in the lower part of the Grant Lake Limestone yields as much as 30 gallons per minute to springs. The sandy zone near the base yields little water. Water is hard, and in valley bottoms may contain salt or hydrogen sulfide.

Clays Ferry Formation (Okc)
Topography
The Clays Ferry forms rugged, dissected topography of long, narrow, winding, steep-sided ridges with narrow, winding, V-shaped valleys of dendritic drainage pattern. Shale on steep slopes erodes easily and is covered with thin limestone slabs in many places. The contrast with rolling upland outcrop areas of the overlying Drakes, Grant Lake, and Calloway Creek formations is striking, except along large streams, where change is masked by dissection.

Hydrology
The Clays Ferry yields 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. It may yield some water to dug wells on ridgetops. It yields water to small springs and seeps. Water is hard, and in valley bottoms may contain salt or hydrogen sulfide. Shale has small, poorly connected openings, and groundwater circulation is slow. On ridgetops the shale impedes downward percolation of water and holds up water in the soil and weathered-rock zone. Dug wells, having large wall areas, are best suited for obtaining this water. On broad ridges capped by the Grant Lake or Calloway Creek formations, the underlying Clays Ferry holds up a semiperched water body in the Grant Lake and Calloway Creek, and dug wells produce some water; however, wells often go dry in late summer and fall.

Lexington Limestone (Ol)
Topography
The Lexington has very limited surface exposure in this county.

Hydrology
The Lexington may yield more than 500 gallons per day to wells in valley bottoms and 100 to 500 gallons per day to wells in small valleys. Water is hard and may contain salt or hydrogen sulfide in some places.

High Bridge Group (Ohb)
Topography
The High Bridge has no surface exposure in this county, but underlies the entire area.

Hydrology
The High Bridge is not likely to yield usable amounts for any purpose. It is not considered an aquifer in this area.

Knox Group (Okx)
Topography
The Knox has no surface exposure in Kentucky, but underlies the entire state at varying depths.

Hydrology
In the Inner Bluegrass Region of Kentucky, fresh water has been found in the upper 100 to 250 feet of this largely untested dolomite-rich aquifer. Wells often exceed 750 feet in total depth, and have high concentrations of dissolved solids in many areas. Average reported yields range in the 10 to 20 gallons per minute range but can be as high as 75 gallons per minute.

You can find out more about the Knox aquifer.

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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