US Geological Survey
U.s. Geological Survey: What Is Ground Water?
This report from the U.S. Geological Survey uses illustrations to show how water moves through an aquifier and also how water is obtained from the ground.
CK-12 Foundation
Ck 12: Earth Science: Groundwater Depletion
[Free Registration/Login may be required to access all resource tools.] Looks at how the overuse of groundwater can lead to problems.