Geohydrology of Indian River County, Florida

The surficial aquifer system and the Floridan aquifer system are the sources of groundwater used in Indian River County, Florida. About 65% of the groundwater is used for irrigation and is from the Floridan aquifer system. Saline water ranging from slightly saline to brine underlies the fresh groundwater throughout the county and is the chief water quality problem. Transmissivities of the surficial aquifer system in eastern Indian River County range from 1,500 to 11,000 sq ft/d. Yields of wells are as much as 1,200 gal/min. Reported transmissivities for the Floridan aquifer system range from 65,000 to 200,000 sq ft/d. Most wells that tap the Floridan aquifer system flow; flow rates range from 30 to 2,000 gal/min. Chloride concentrations of water in the surficial aquifer system generally are below 100 mg/L, but concentrations often exceed 250 mg/L in water from the Floridan aquifer system. Between 1976 and 1983, average chloride concentrations in water from six wells that tap the surficial aquifer system in the Vero Beach well field increased about 36 mg/L, but were unchanged in four other wells. The increase in chloride concentration probably is related to a well-field pumpage increase from 5.44 million gal/d in 1976 to 8.00 million gal/d in 1983. In most of the County, chloride concentrations of wells that tap the Floridan aquifer system have not changed significantly in the 15-year period, 1968-83. Water levels in the surficial aquifer system declined 15 to 19 ft between 1971 and 1984 in the Vero Beach well field where the larger groundwater withdrawals occur, but have not declined significantly outside heavily pumped areas. Water levels in the Floridan aquifer system have declined 16 to 24 ft in eastern Indian River County in the 50-year period, 1934-84, but declines outside the heavily pumped areas generally have been less than 10 ft during this period. (USGS)