Hydrology - Water Resources Report 38

Water Resources of Lexington County, South Carolina

by
Karen W. Agerton and Samuel E. Baker
2006

ABSTRACT

Lexington County encompasses an area of 700 square miles in west-central South Carolina. The Fall Line traverses the county, placing the northern third in the Piedmont and the rest in the Coastal Plain. This has produced two vastly different aquifer systems; hard crystalline rocks and unconsolidated sand.

Water use in Lexington County is about equally divided between surface water and ground water. In 2003, 12 mgd (million gallons per day) were obtained from Lake Murray and the Saluda River, and about 11 mgd were obtained from wells, much of the latter for rural domestic use. The largest public-supply water system in the county is the city of West Columbia, which obtains its water from Lake Murray and the Saluda River.

Wells in the Piedmont rocks rarely produce more than 10 gpm (gallons per minute), and dry holes are common, forcing larger water users to rely on surface water. Sand aquifers have not been heavily tapped and are capable of yielding up to 2000 gpm to wells in the southern part of the county. Pumping tests indicate transmissivities ranging from 1,500 to 55,000 gpd/ft (gallons per day per foot), and specific capacities of sand wells can be more than 25 gpm.

Ground-water quality for rock wells in the Piedmont and sand wells in the Coastal Plain is generally good and the latter often resembles that of rainwater. Excessive levels of radionuclides (226Ra and 228Ra), however, have been reported in some wells in the county since the mid-1970’s. Several sand and rock wells have produced water containing excessive iron and manganese; no other constituents exceed the maximum contaminant levels established by the U.S. Environmental Protection Agency’s National Drinking Water Standards. The sand wells typically have low (acidic) pH values.

Of the three major rivers that drain the county, the Congaree River has the largest annual mean flow, 8,946 cfs (cubic feet per second); it is formed by the confluence of the Saluda and Broad Rivers. The lower Saluda is regulated, according to power demand, by releases from Lake Murray at the Saluda Dam and has the second-highest annual mean flow (2,794 cfs). Draining the western section of the county, the North Fork Edisto River has an annual mean flow of 766 cfs. Lake Murray, the fifth-largest lake in the State, is located in the northern part of the county and contains more than 2 million acre-feet of water.

Surface-water quality is fair, with over 65 percent of the State-monitored water-quality stations meeting the guidelines for several types of uses; however, when water quality standards are not met, it has been predominately due to pH and fecal coliform bacteria infractions.


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