The population served by public water systems in the three counties of Mississippi 's Gulf Coast increased from about 227 ,000 to nearly 253,000 between 1975 and 1980. Water use by public systems increased from about 27.6 million gallons per day to more than 31.3 million gallons per day. Self-supplied industrial use of ground water decreased from about 18.4 to 17.7 million per day, and that for fresh surface water increased from about 42.3 to 56.1 million gallons per day. Total freshwater was including that for rural domestic supplies, increased from about 92.0 to 109 million gallons per day. Industrial use of brackish surface water decreased from about 790 to 660 million gallons per day. (USGS)