There are lots of ways to explore water quality, and many resources to help you do so.
Groups working on water quality issues:
Mystic River Open Water
Along with IOBY.org, the Mystic River Open Water project aims to build an open-source, DIY water quality monitoring network. Support the IOBY campaign here.
The project will use environmental sensors connected via mobile networks to generate indicators of water quality in cities in the Brazilian Amazon. Read more.
Leif Percifield's water quality sensor system. Developed during the Water Hackathon on March 23-25 in New York City, the water quality sensor is a multipurpose tool for collecting data remotely. This tool is rapidly changing and is being used as part of the on going research initiative called DontFlush.Me