During the 1997 water year, the water level in the Sparta and Memphis aquifers was measured in about 274 wells in Arkansas, and the water level in the Sparta aquifer was measured in about 55 wells in Louisiana. The potentiometric surface data reveal spatial trends across the study area. In Arkansas, the altitude of the potentiometric surfaced ranged from 199 feet below sea level in Union County to 307 feet above sea level in Saline County. In Louisiana, the altitude of the potentiometric surface ranged from 224 feet below sea level in Ouachita Parish to 230 feet above sea level in Bienville Parish.
The general direction of ground-water flow in the Sparta and Memphis aquifers is from the west to the Southeast. The regional direction of ground-water flow in Arkansas is from the north and west to the south and east, away from the recharge zone in the outcrop and subcrop area, except near areas affected by intense ground-water withdrawals; such areas are manifested by large cones of depression centered in Columbia, Jefferson, and Union Counties. The regional ground-water flow in the Sparta aquifer in north-central Louisiana generally is downdip in an easterly direction from the recharge zone in the outcrop and subcrop area in the west toward the Mississippi Alluvial Plain. The potentiometric surface of the Sparta aquifer in Arkansas and Louisiana exhibits cones of depression descending below sea level. Comparison of potentiometric surface maps through time shows that the cones of depression in Columbia and Union Counties are coalescing at or near the Columbia and Union County line. However, the general direction of ground-water movement indicates that heavy pumpage locally has altered or reversed the natural direction of flow in some areas. Flow in these areas is toward the cones of depression at the center of pumping. Hydrographs from wells in the Sparta and Memphis aquifers reveals that water levels have declined more than 2.0 feet per year in some wells. Long-term hydrographs of eight wells in Arkansas, during the period 1972-1997, reveal water-level declines ranging from less than 0.8 foot per year in Phillips County to more than 2.0 feet per year in Union County. Long-term hydrographs of two wells in Louisiana, during the period 1972-1997, reveal water-level declines were more than 2.0 feet per year in Lincoln and Ouachita Parishes.