This report contains hydrologic and climatic data that describe the status of ground-water resources at U.S. Navy Support Facility, Diego Garcia. Data presented are from January 1993 through December 1995, although the report focuses on hydrologic events from October through December 1995 (fourth quarter of 1995). Cumulative rainfall for October through December 1995 was about 41 inches, which is 32 percent more than the mean cumulative rainfall of about 31 inches for October through December. The period October through December is within the annual wet season. Mean cumulative rainfall is calculated for the fixed base period 1951-90. Ground-water withdrawal during October through December 1995 averaged 931,000 gallons per day. Withdrawal for the same 3 months in 1994 averaged 902,900 gallons per day. Patterns of withdrawal during the fourth quarter of 1995 did not change significantly since 1993 at all five ground-water production areas. At the end of December 1995, the chloride concentration of the composite water supply was 60 milligrams per liter, well below the 250 milligrams per liter secondary drinking-water standard established by the U.S. Environmental Protection Agency. Chloride concentrations of the composite water supply from October through December 1995 ranged between 28 and 67 milligrams per liter. Chloride concentration of ground water in monitoring wells at Cantonment and Air Operations continued to decrease during the fourth quarter of 1995, with water from the deepest monitoring wells decreasing in chloride concentration by as much as 2,000 milligrams per liter. This trend follows increases in chloride concentration during the first half of 1995. A fuel leak at Air Operations caused the shutdown of ten wells in May 1991. Four of the wells resumed pumping for water-supply purposes in April 1992. The remaining six wells are being used to hydraulically divert fuel migration away from water-supply wells by recirculating about 150,000 gallons of water each day.
Additional publication details
USGS Numbered Series
Status of ground-water resources at U.S. Navy Support Facility, Diego Garcia; summary of hydrologic and climatic data, January 1993 through December 1995
U.S. Geological Survey ;
Earth Science Information Center, Open-File Reports Section [distributor],