by D.A. Webster and J.K. Carmichael
This report is available as a pdf below
An investigation of the ground-water-flow system that supplies Carson Spring and the surrounding lower Wolftever Creek basin northeast of Chattanooga, Tennessee, was conducted from September 1986 through December 1989. About two-thirds of the lower basin is underlain by the Chepultepec Dolomite of Ordovician age. Test drilling within a few miles of the spring showed that numerous solution cavities have developed in this formation; many are partly or completely plugged with cherty gravels and mud. In the recharge area to the spring, the formation can provide yields of 100 to perhaps 600 gallons of water per minute to bedrock wells. A well that penetrated a well-integrated cavity system underlying Carson Spring was tested at 2,000 gallons per minute.
From May 1987 through December 1989, mean daily withdrawals from four wells at Carson Spring ranged from 4.78 to 5.83 cubic feet per second; mean daily spring discharge, which includes withdrawals, ranged from 5.53 to 5.79 cubic feet per second. For a 16-month drought period during 1987 and 1988, withdrawals from these wells exceeded natural spring discharge, and demonstrates that for a period of many consecutive months, the aquifer supplying the spring is capable of yielding more water than the spring would have discharged under natural conditions.
Although the lower basin encompasses 17 square miles, the Carson Spring recharge area probably is not greater than 9 square miles. Most water not captured by cavities supplying the spring is discharged to Wolftever Creek. In the lower basin, the rate of ground-water discharge to the creek is about twice the average rate of discharge (0.25 cubic foot per second per square mile of drainage area) to area streams.
Principal constituents in ground water in the lower basin are calcium and bicarbonate, or calcium, magnesium, and bicarbonate. Specific conductance commonly ranges from 100 to 700 microsiemens per centimeter, and pH usually ranges from about 7 to 8. Overall, the ground water is of good quality and suitable for most uses. Several potential sources of degradation are present and arise from industrial, municipal, and domestic activities.
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