Geological Survey Water-Supply Paper 1475-Q Present and Future Water Supply for Mammoth Cave National Park, Kentucky

The purpose of this report is to evaluate the hydrology of alternative sources of water supply for the National Park Service. To evaluate the several potential sources of water, it is necessary to have a figure of water demand as a yardstick. A maximum daily demand of 250,000 gallons during the period June-September is probably a reasonable yardstick to use if the projected growth to 1980 is considered. The sources are discussed in approximate order of value as potential sources of water supply for Mammoth Cave.

GREEN RIVER

The Green River is the largest source of water available. The supply is more than enough for any future needs of Mammoth Cave National Park. The chemical quality is now suitable with normal treatment of surface-water supplies. Construction of Green River Reservoir will increase the quantity and improve the chemical quality of low flows.

Use of this source will necessitate an intake structure, treatment plant, and high pump lift (350-450 ft). The principal disadvantage of the use of Green River water is the possibility of renewed pollution by oil-field brine. As an insurance against this possibility, Green River water could be used to augment the present supply. In this event, the intake structure should probably be constructed near Great Onyx Cave and a pipeline (6,000-8,000 ft) run from this point to the reservoir at Bransford Spring or to the existing storage tanks on Flint Ridge. As added insurance, a remote-recording specific-conductance meter might be installed at the gaging station at Munfordville. This would provide operating personnel with advance warning of a change of chemical quality of Green River water that might be attributed to brine pollution.

NOLIN RIVER

The Nolin River is the second largest source of water available. Its water is moderately hard to very hard but well within the limits of drinking-water standards. Use of this source would necessitate a long pipeline, an intake structure, treatment plant, and high pump lift (350-450 ft). The chief disadvantage of this source is the length of the pipeline (about 8 miles).

PERCHED WATER IN HANEY LIMESTONE MEMBER OF THE GOLCONDA FORMATION

The existing water supply for Mammoth Cave is obtained from springs draining a perched aquifer in the Haney Limestone Member on Flint Ridge and a deep well at Bransford Spring. There are several additional springs draining this aquifer that could be incorporated into the present water-supply system.

The Haney is the best source of good quality water supply for Mammoth Cave now and in the near future. The chemical quality, except for Bransford well, is excellent, and the fact that the recharge area for the perched aquifer lies mostly within park boundaries facilitates pollution control.

The main disadvantage of this source as the ultimate supply for the park is the quantity available. The minimum total flow of all the known springs and Bransford well during the critical period in July-August 1962 was 102 gpm, or 147,000 gpd, and occurred on August 22, 1962. However, the absolute minimum total flow observed was 84.5 gpm, or 122,000 gpd, on November 8, 1962, and occurred after the end of the critical period. The average weekly measurement of flow of the springs plus Bransford well for the period May 29-September 6, 1962, was 137 gpm, or 197,000 gpd.

The deficiency in quantity can be overcome by storage. Table 8 shows observed or estimated flows for known springs on Flint Ridge and Bransford well and the surplus or deficiency for several demands. The observations were made every 7 or 8 days during the 100-day period, May 29-September 6, 1962. This represents a good study period for three reasons, namely: (1) The weekly observations give a good estimate of the available flow, (2) the period includes a drought that has a recurrence interval of about 12 years, and (3) the greatest use of water at Mammoth Cave is during the period from Memorial Day to Labor Day.

The data in table 8 were used to compile the storage requirements given in table 9 for indicated demands ranging from 50,000 gpd to 250,000 gpd. Part of these computations are illustrated graphically in figures 79, 80, and 81.

TABLE 8.—Observed weekly flows of Flint Ridge springs and Bransford well and surplus or deficiency for several demands during June-September 1962
[Data in gallons per minute]

(click on image for an enlargement in a new window)

TABLE 9.—Storage needed for selected supplies based on 100-day period, May 29-Sept. 6, 1962

FIGURE 79.—Comparison of present water supply (Three Springs), Bransford Spring, and Bransford well) for 100-day period, May 29-Sept. 6, 1962, with indicated demands. (click on image for an enlargement in a new window)

FIGURE 80.—Comparsion of present water supply plus Blair and Adwell Springs for 100-day period, May 29-Sept. 6, 1962, with indicated demands. (click on image for an enlargement in a new window)

FIGURE 81.—Comparision of total known water supply on Flint Ridge for 100-day period, May 29-Sept. 6, 1962, with indicated demands. (click on image for an enlargement in a new window)

The computed figures do not provide a factor of safety for equipment breakdown, losses by evaporation, leakage, or a bailer-water line, or an unusual demand such as might be required for a fire.

SMALL STREAMS

Wet Prong Buffalo Creek is the best of the several small-stream supplies in the vicinity of Mammoth Cave. The advantages of this source are good chemical quality, adequate supply (minimum probably about 300,000 gpd), and location of most of the watershed in the park for control of pollution. Disadvantages of this source are distance from park headquarters (about 5 miles) and the necessity for normal treatment of surface water.

BASAL GROUND WATER

Not enough is known about the recharge, movement, and discharge of the basal ground water to evaluate it properly as a potential supply. Development of the source by means of deep drilled wells appears to have low potential because of the low yields to existing wells and the difficulty of predicting the location of trunk conduits in advance of drilling. Development by pumping from known trunk conduits, such as the underground parts of Echo River in Mammoth Cave or Pike Spring in Great Onyx Cave, has a greater potential, however. If the withdrawal is made relatively close to the Green River the greatest yields during the low-flow period, with no depletion of ground-water storage, would probably be equal to the observed low flows of Echo River (162,000 gpd) and Pike Spring (1,250,000 gpd). Larger withdrawals during the low-flow period would decrease the storage, and thus cause a decline in water levels in the underground streams and an inflow of water from the Green River. The quality of the basal ground water is suitable with the normal treatment of surface-water supplies.

The chief disadvantages of the basal ground water as a potential source, in addition to the uncertainty of its yield, are the possibility of pollution by oil-field brine from the Green River, the high pump lift, and the difficulty of introducing the water into the present water system. Use of this source would require a treatment plant and probably a long pipeline to the reservoirs on Flint Ridge. Basal ground water might be developed as an auxiliary supply for periods of peak demand or low flow, however.

WATER IN ALLUVIUM ADJACENT TO THE GREEN RIVER

Based on available data, the alluvium adjacent to the Green River at Mammoth Cave has little potential as a water supply owing to low yield. Possibilities of better yields exist upstream from the Styx River, but the yields have not been tested. However, the water would be similar in quality to Green River water, and thus offers no advantage over the use of Green River water.

PERCHED WATER IN BIG CLIFTY SANDSTONE MEMBER OF THE GOLCONDA FORMATION AND GIRKIN FORMATION

Based on available data, perched water in the Big Clifty Sandstone Member of the Golconda Formation and the Girkin Formation has little potential as a water supply owing to its low yield.