Omega Engineering
Technical Dissolved Oxygen: The Fundamentals
This site is useful to find information about dissolved oxygen and the types of tests that are administered to determine the dissolved oxygen level.
US Geological Survey
Usgs: Common Water Measurements
This site from the U.S. Geological Survey provides great definitions of seven measurements that can be taken on water. Includes pH, dissolved oxygen, and turbidity. Click Home to access the site in Spanish.
Other
Idaho Department of Environmental Quality: Common Water Quality Measures
An organized resource highlighting properties of freshwater and water quality concerns.