U.S. Environmental Protection Agency (US EPA)
The mission of this federal agency is to protect human health and to safeguard the quality of the air, land and water of the U.S. At their home page, one can access information by topics, laws and regulations, information sources, a newsroom, educational resources, and programs.
http://www.epa.gov/epahome/index.html

Monitoring Water Quality. US EPA Office of Water
At this site, one can find information about watershed protection, water quality reporting, biological assessment, data systems, mapping tools, and monitoring programs and procedures.
http://www.epa.gov/OWOW/monitoring/

US EPA's STORET database for water quality data
You may obtain water quality data for streams and waterways throughout the United States through the Retrieval Request menu. Follow the on-line directions and be very specific in your request.
http://www.epa.gov/STORET/

Nonpoint Source News-Notes
This is an online version of the Nonpoint Source News-Notes, a publication sponsored by the US EPA.
http://www.epa.gov/owow/info/NewsNotes/

Groundwater and Drinking Water. U.S. EPA
Frequently asked questions covering issues like water safety, testing, home treatment units, bottled water, protection of sources, and fact sheets on contaminants.
http://www.epa.gov/safewater/faq/faq.html

Water Science for Schools
Sponsored by the USGS. This is a glossary of water-related terms.
http://ga.water.usgs.gov/edu/dictionary.html

Exxon Valdez Office of Oil Spill Damage Assessment and Restoration
This is an office of the National Marine Fisheries Service and provides access to information about programs, projects, reports, news, and educational resources related to the spill in Prince William Sound. The site also provides links to sites about marine life.
http://www.fakr.noaa.gov/oil/default.htm

Flush with Pride!
The story of the Arcata, California "constructed wetlands" that are used to treat the City's sewage as well as providing wildlife habitat and salmon aquaculture facilities.
http://www.humboldt.edu/~ere_dept/marsh/pride.html

Cryptosporidium
Centers for Disease Control and Prevention (CDC) fact sheet about Cryptosporidium.
http://www.cdc.gov/ncidod/diseases/crypto/cryptos.htm

Environmental Working Group, Dishonorable Discharge
List of the 50 most polluted rivers in the United States.
http://www.ewg.org/pub/home/reports/dishonorable/ddrivers.html

Clean Waters and Oceans
Sponsored by the Natural Resources Defense Council (NRDC). With a membership of more than 500,000, NRDC works to protect the environment for all living things. This site furnishes access to a huge amount of information in the form of brief summaries and full text of numerous reports dealing with water pollution, drinking water, conservation, and restoration.
http://www.nrdc.org/water/pollution/default.asp

U.S. Geological Survey Water Resources Division
Contains plentiful information on federal water resources programs, water use, water quality assessments for the U.S. and more.
http://water.usgs.gov/

Eutrophication (Nutrient Pollution)
This page, sponsored by the Experimental Lakes Area of the University of Manitoba explains research work involving whole lake manipulations of plant nutrient levels and their ecosystem and community level consequences.
http://www.umanitoba.ca/institutes/fisheries/eutro.html