The difference between the potentiometric surfaces of the upper Patapsco aquifer, September 1990 and September 1999 in southern Maryland

This report presents a map showing the change in the potentiometric surface of the Upper Patapsco aquifer in the Upper Patapsco Formation of Cretaceous age in Southern Maryland for September 1990 and September 1999. The map, based on water-level measurements in 37 wells, shows that the potentiometric surface during the 9- year period ranged from a decline of 1 foot in the northernmost part of the study area, which is near the outcrop of the aquifer, to a decline of 22 feet at LaPlata, which is near the southwesternmost part of the study area.