1. Potentiometric surface of the Upper Patapsco Aquifer in southern Maryland, September 1990 [microform] Yale Public content 1992. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; Books and Open-File Reports [Section. English. Public. Maryland and Patapsco Aquifer.