Water Resource Reports from the Pennsylvania Geological Survey
Technical reports on the groundwater resources of areas, commonly defined on a countywide basis. Most of these reports include a book and a large-scale, full-color geologic map
County comprehensive plans have a section on water resources. Each county's plan can be located by going to the website of the specific county you're interested in and searching for comprehensive county plans within the website.
Groundwater Data
Ground-water quality and data on wells and springs in Pennsylvania
This series presents ground-water quality and physical data on about 1,250 wells and springs.