Table 12. Estimated recharge temperatures from dissolved gases and range in age from chlorofluorocarbon analyses of water sampled from Cave Springs, a permanent pool in Lehman Caves, and two nearby springs, Great Basin National Park, Nevada.

[Site locations are shown in figure 2. Analyses were done by U.S. Geological Survey Chlorofluorocarbon Laboratory Reston, Virginia. Abbreviation: CFC, chlorofluorocarbon. Symbol: <, less than]

Dissolved gas or chlorofluorocarbon	Site 1 Cave Springs	Site 2 Pool in Lehman Caves	Site 3 Spring near upper Lehman Creek campground	Site 4 Marmot Spring
Estimated recharge temperature and excess air from dissolved gases
Number of samples analyzed	2	2	2	2
Assumed recharge altitude, in feet above mean sea level1	9,000	6,800	9,500	9,000
Recharge temperature, in degrees Celsius2	8.4	10.8	3.2	6.2
Excess air, in cubic centimeters at standard temperature and pressure per liter of water2	0.2	0.0	0.3	0.0
Estimated range in age of water
Estimated mean age in years3
CFC-11	31-33	Contaminated	24	27
CFC-12	27-30	<15	19	21–22
CFC-113	24-27	<19	19	21
Estimated year of recharge4	1977-83	After 1990	1988	1985-86

¹ Assumed recharge altitude for sites 1 and 4 are based on average land-surface elevation in drainage and site 3 estimated from average land-surface elevation of glacial deposits. A change in the estimate of recharge altitude of 1,000 feet resulted in an uncertainty in the average age of water of 0.5 year for sites 1 and 4, 1 year for site 3, and several years for site 2.

² Estimated temperature and excess air estimated from dissolved gas concentrations of nitrogen and argon, and assumed recharge altitude. Recharge temperature estimated by iteration until excess air computed from nitrogen and argon concentrations are the same. Increasing the recharge altitude 1,000 feet decreased the recharge temperature by about 1 degree Celsius and increased the excess air by about 0.05 cubic centimeter per liter at standard temperature and pressure. Decreasing the recharge altitude 1,000 feet increased the recharge temperature and decreased the excess air by a corresponding value.

³ Estimated mean age of water was computed using estimates of recharge altitude, temperature, and excess air and assuming piston flow.

⁴ Estimated year of recharge is based on mean age of water using CFC-12 and CFC-113. Water at Cave Springs (site 1) may be less than listed because of potential degradation caused by low dissolved oxygen concentrations; however, the mean age estimated from CFC-12 is older than that from CFC-113 and if degradation was a problem, the mean age of CFC-113 would be older because it degrades more rapidly than CFC-12.