Map showing change in potentiometric surface of the Magothy Aquifer in southern Maryland between September 1975 and September 1981

A map has been prepared that shows the net differences between two sets of water-level measurements made in 67 observations wells over a six-year period. One set of measurements was made in 1975, a relatively wet year, and the other set of measurements was made in 1981, a relatively dry year. The map shows that, except for a small area near the Annapolis well field where Magothy production wells were temporarily shut down, the potentiometric surface of 1981, compared with the potentiometric surface 1975, was: lower throughout the entire area; lower by at least 10 feet in the southwestern third of the area; lower by 30 to 40 feet in parts of northern Charles County , where pumping rates increased from an average of one million gallons per day (Mgal/d) in 1975 to 2.5 Mgal/d in 1981. (USGS)