Groundwater Availability
 

New Albany Shale (MDnb)
Topography
The New Albany forms broad, flat valleys and flat upland surfaces. It forms steep, dissected hillsides and bluffs along streams.

Hydrology
The New Albany yields 100 to 500 gallons per day to drilled wells in valley bottoms and on uplands, usually at depths of less than 50 feet. Water from depths greater than 50 feet is highly mineralized. The New Albany yields water to small springs. Water may be soft or highly mineralized. Salt, hydrogen sulfide, and iron are the usual objectionable constituents.

Crab Orchard Formation and Brassfield Dolomite (Scb)
Topography
The shale forms steep, dissected hillsides and broad, flat valley bottoms. It erodes readily below more resistant overlying limestone, forming notches and recesses. Dolomite beds form discontinuous ledges along hillsides.

Hydrology
The shale yields almost no water to wells or springs, but may yield small amounts of water to wells in valley bottoms. Water is highly mineralized. Dolomite beds yield hard water to small springs.

Drakes Formation (Od)
Topography
The Drakes forms dissected upland areas, with slopes moderately steep where underlain by shale, and moderately undulating to gently rolling where underlain by limestone. It forms steep and cliffy slopes along large streams, littered with limestone slabs left as shale beds weather and wash away.

Hydrology
The Drakes yields 100 to 500 gallons per day to drilled wells in broad valleys and along streams in upland, but almost no water to drilled wells on hillsides or ridgetops. It does yield water to small springs. Water is hard and in valley bottoms may contain salt or hydrogen sulfide. Shale limits amount of water that has access to thick limestone beds, and therefore restricts number of openings in these beds enlarged by solution. As a result, the limestone beds yield little water.

Ashlock Formation and Calloway Creek Limestone (Oaf)
Topography
These formations create 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.

Hydrology
These rocks yield 100 to 500 gallons per day to drilled wells in broad valleys and along streams in 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. Where thick limestone beds with little shale occur below stream level in valley bottoms or on uplands, they may have undergone solutional enlargement of fractures and bedding-plane openings. Wells drilled into these limestone beds may produce more than 500 gallons per day. These thick beds also yield water to some large springs.

Garrard Siltstone (Okc)
Topography
The Garrard forms prominent ledges along hillsides.

Hydrology
The Garrard yields 100 to 500 gallons per day to drilled wells in valley bottoms, but almost no water to wells on hillsides or ridgetops. It yields little water to springs. The well-cemented siltstone and fine-grained sandstone and siltstone do not provide many openings for water and yields almost no water to wells. Water is hard.

Clays Ferry Formation and Kope Formation (Okc)
Topography
These rocks form a rugged topography of narrow, steep-sided ridges with narrow V-shaped valleys of dendritic drainage. Steep slopes erode easily and are covered with thin limestone slabs in many places. 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.

Hydrology
These formations yield 100 gallons per day to drilled wells in valley bottoms, but almost no water to drilled wells on hillsides or ridgetops. They do yield water to small springs and seeps. In the lower, limestone rich section, drilled wells can yield 100 to 500 gallons per day in valley bottoms along streams. Water is hard in valley bottoms may contain salt or hydrogen sulfide. Shale has small, poorly-connected openings, and ground-water circulation is slow; as a result, little water is available to wells and springs. On ridgetops the shale prevents downward percolation of water, and creates small semiperched water bodies in lower part of soil and upper part of weathered bedrock.

Upper Part of Lexington Limestone (Tanglewood Limestone, Millersburg, Strodes Creek,
Devils Hollow, Sulfur Well, Brannon and Perryville Members) (Ol)

Topography
The Upper Lexington forms broad flat valleys in uplands. Where dominantly limestone, the Upper Lexington has well-developed subsurface drainage and many sinkholes, with gently sloping hillsides adjacent to small streams in uplands. The resistant shale and soft bentonite-rich beds form a subdued benchlike topography along hillsides and streams.

Hydrology
The Upper Lexington yields more than 500 gallons per day to wells in valley bottoms and along streams in uplands. It yields 100 to 500 gallons per day to many perennial springs, and more than 100 gallons per minute to a few large springs. The amount of water available in rocks of the Lexington Limestone is dependent on the amount of shale. Generally, throughout the whole Lexington Limestone section, the more shale found within the zone of interest, the less water will be found. Yields water to springs from resistant Brannon Member. Water is hard and may contain salt or hydrogen sulfide in some places. Water from wells near fault zones may contain objectionable amounts of salt.

Lower Part of Lexington Limestone (Grier, Logana and Curdsville Members) (Ol)
Topography
These limestones form rolling to dissected uplands. Sinkholes are very common; the large ones occur in the Grier Limestone. Underground drainage is well developed. Natural outcrops are rare in the rolling upland, but the limestone beneath hill slopes is evident from the benchlike or terrace like appearance of the slopes. Limestone crops out in discontinuous bands in the valley sides in the dissected part near the Kentucky River.

Hydrology
The lower Lexington yields more than 500 gallons per day to wells in valley bottoms and along streams in uplands. In the Curdsville along large streams yields are up to 150 gallons per minute from thick limestone beds. The limestones yield water to many small and large springs. The amount of water available in rocks of the Lexington Limestone is dependent on the amount of shale. Generally, the upper part of the Lexington Limestone contains more shale and yields less water in contrast to the lower part which is mostly limestone in many places. Water is hard and may contain salt or hydrogen sulfide in some places. Water from wells near fault zones may contain objectionable amounts of salt.

High Bridge Group ( Tyrone Limestone, Oregon Formation, Camp Nelson Limestone) (Ohb)
Topography
The High Bridge forms steep slopes and high cliffs along the Kentucky River and lower parts of tributaries. The Camp Nelson limestone forms flat terraces with occasional sinkholes in the bottom of the Kentucky River gorge and steep cliffs along the lower sides. It also extends up the large tributaries, forming flat bottoms and steep walls. The Oregon crops out in a band in the walls of the gorge and up a few large tributaries. The Tyrone crops out in the upper walls of the Kentucky River gorge and extends up the large tributaries nearly to the upland, forming broad, flat valleys with sinkholes and underground drainage.

Hydrology
These limestones yield 100 to more than 500 gallons per day to drilled wells in valleys of the Kentucky River and large tributaries. Yields have been reported as much as 225 gallons per minute to wells drilled into the Camp Nelson limestone adjacent to the Kentucky River, from solution channels and fractures connected with the river. The limestones also yield water to springs on hillsides and in steep walls along large streams. Water is hard and may contain hydrogen sulfide but generally of good quality. Wells drilled into the Highbridge through overlying rocks produce almost no water because bentonite beds in the Tyrone prevent recharge to underlying rocks except where the bentonite has been breached or removed by erosion.

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 with high concentrations of dissolved solids found in many areas. Average reported yields range in the 10 to 20 gallons per minute range but 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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