On February 27, 1996, synoptic water-level and barometric pressure data were collected in the General Separations Area, Savannah River Site, South Carolina. These data were collected during a 9-hour period. Water levels were measured at 231 observation wells, 19 piezometers, and 16 surface-water sites. An automated data-collection system was used to continuously measure water levels and barometric pressure at the SRS P27 well cluster in Area H. During the measurement period, barometric pressure varied 0.06 pound per square inch and water levels fluctuated 0.06 and 0.09 feet. Water levels did not fluctuate significantly due to barometric pressure changes during the measurement period.
Ground-water recharge to the upper and lower aquifer zones of the Upper Three Runs aquifer occurs in the topographically high interfluve areas of the General Separations Area on the Savannah River Site. The upper aquifer zone is unconfined and the lower aquifer zone is unconfined, semi-confined, and confined. Water levels in the upper aquifer zone are higher than water levels in the lower aquifer zone across the crest of the General Separations Area interfluve, suggesting that the unconfined and semi-confined parts of the lower aquifer zone receive recharge by leakage from the upper aquifer zone. The water- level surfaces of the upper and lower aquifer zones of the Upper Three Runs aquifer resembles the local topography. Two ground-water divides trending approximately east-west and north-south are prominent features in the upper and lower aquifer zones of the Upper Three Runs aquifer. The ground-water divides roughly coincide with the topographically high areas of the interfluve. Both aquifer zones discharge to McQueen Branch, Crouch Branch, and the other tributaries of the Upper Three Runs and Fourmile Branch on the flanks of the General Separations Area interfluve.
Ground-water recharge to the Gordon aquifer is by lateral flow from areas to the east and northeast of the General Separations Area and by leakage from the lower aquifer zone of the Upper Three Runs aquifer. The Gordon aquifer is confined beneath all of the General Separations Area interfluve, except where the Gordon confining unit is breached by the incision of Upper Three Runs to the north and west of Area F. The potentiometric surface of the Gordon aquifer does not resemble the local topography.
--- 1998By Harrelson, L.G., Conlon, K.J., and Harris, M.K.