Environmental Science Resources: Hydrogeology

This interactive site from the University of Illinois describes the Hydrology cycle in detail.

The AWWA is a resource for knowledge, information, and advocacy to improve the quality and supply of water in North America.

This site from the Environmental Protection Agency contains a list of contaminants and their Maximum Contaminant Level (MCLs). It also gives information about the standards for safe drinking water and explains the EPA's standard-setting process.