Continuous water-level records from 152 wells and water-level measurements from an additional 750 wells in Georgia during 1986 provide the basic data for this report. Hydrographs for selected wells illustrate the effects that changes in recharge and discharge have had on the groundwater reservoirs in the State. Daily mean water levels are shown in hydrographs for 1986. Monthly mean water levels are shown for the 10-year period 1977-86. During 1986, a prolonged drought resulted in water-level declines throughout the State. Annual mean water levels were from 2.7 feet higher to 17.3 feet lower than in 1985, and record lows were measured in 33 wells in the summer and fall. The 1986 lows were from 0.02 foot to 29.2 feet lower than the previous record lows. The largest declines were measured in the Clayton aquifer in the southwestern part of the State. The declines can be attributed to reduced recharge and increased pumping that resulted from below-normal precipitation during the first half of the year. Water-quality samples are collected periodically throughout Georgia and analyzed as part of area! and regional groundwater studies. Periodic monitoring of water quality in the Savannah and Brunswick areas indicates that the chloride concentration in the Upper Floridan aquifer there generally has remained stable. This report continues a series of publications that annually presents both groundwater level and groundwater quality data for Georgia. Hydrographs from 59 wells have been selected to illustrate the effects that changes in recharge and discharge have had on the various aquifers in the State. A new chapter on Miocene aquifers and expanded coverage of the crystalline rock, water-table, and Upper Floridan aquifers have been added to this year's report. Daily mean water levels are shown in hydrographs for 1986. Monthly mean water levels, as well as chloride concentrations for selected areas along the coast, are shown for the 10-year period 1977-86. Because the 1986 hydrographs are plotted from daily mean values, a record low or record high water level that occurred on a given day would have been lower or higher than that shown on the hydrograph. The report also includes maps that show the potentiometric surfaces of the Upper Floridan, Claiborne, Clayton, Providence, and Dublin-Midvil1e aquifers. The potentiometric surface of an aquifer is an imaginary surface that represents the altitude to which water would rise in tightly cased wells that penetrate the aquifer. The potentiometric surface is highest in areas of recharge and lowest in areas of discharge, indicating that ground water flows from recharge areas to discharge areas. Where discharge is concentrated and exceeds recharge, the potentiometric surface is lowered, forming a cone of depression. The cooperation and assistance of the following agencies in collecting water-level and water-quality data during 1986 are gratefully acknowledged:

Introduction 2 Purpose and scope 2 Well-numbering system 2 Precipitation 3 Groundwater resources 15 Groundwater levels 18 Surficial aquifers 21 Northern area 21 Southwestern area 21 Coastal area 26 Upper Brunswick aquifer 32 Floridan aquifer system 37 Upper Floridan aquifer 37 Southwestern area 39 South-central area 48 East-central area 53 Coastal area 57 Savannah subarea 59 Jesup-Doctortown subarea 67 Brunswick subarea 71 St Marys-Okefenokee Swamp subarea 76 Lower Floridan aquifer 79 Brunswick area 79 Claiborne aquifer 83 Clayton aquifer Cretaceous aquifers and aquifer systems 102 Providence aquifer 105 Dublin aquifer system 107 Midville aquifer system 109 Dublin-Midville aquifer system 112 Paleozoic rock aquifers 115 Crystalline-rock aquifers 118 Chloride concentration in water from the Floridan aquifer system 125 Savannah area 126 Brunswick area 129 Selected references 133 in ILLUSTRATIONS-Continued Hydrographs showing the water level in observation well:-Continued 78. 11K005, Dougherty County 100 79. 14P014, Crisp County 101 Map showing locations of observation wells completed in Cretaceous aquifers and aquifer systems 103 Hydrographs showing the water level in observation well: 81. 06S001,

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Owner: City of Sylvester. AQUIFER. Upper Floridan aquifer. WELL CHARACTERISTICS. Drilled unused municipal well, diameter 18 in., depth 450 ft, cased to 212 ft, open hole. DATUM. Elevation of land-surface datum is 420 ft. Measuring point: Floor of recorder shelter, 2.90 ft above land-surface datum. REMARKS.