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 June 1995, although the report focuses on hydrologic events from April through June 1995. Cumulative rainfall for April through June 1995 was about 14 inches which is 70 percent of the mean cumulative rainfall of about 20 inches for the same 3 months in a year. April through June is within the annual dry season. Rainfall for each month was below average from the respective mean monthly rainfall. All mean rainfall values are calculated for the fixed base period 1951-90. Ground-water withdrawal during April through June 1995 averaged 833,700 gallons per day. Withdrawal for the same 3 months in 1994 averaged 950,000 gallons per day. At the end of June 1995, the chloride concentration of the composite water supply was 57 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 April through June 1995 ranged between 26 and 62 milligrams per liter. Chloride concentration of ground water in monitoring wells at Cantonment and Air Operations increased since April 1995, with water from the deepest monitoring wells increasing in chloride concentra- tion by about 1000 milligrams per liter. 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 contain and divert fuel migration away from water-supply wells by recirculating about 150,000 gallons of water each day.
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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 June 1995
U.S. Geological Survey ;
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