US Geological Survey
Usgs: How Much Water Is There on (And In) the Earth?
The USGS gives an overview of the amount of water on Earth and where it is located. It gives a few interesting facts about the Earth's supply of water. Click Home to access the site in Spanish.
US Geological Survey
Usgs: Trends in Ground Water Use, 1950 2005
This site from USGS describes the importance of ground-water, provides a map of ground-water use (by state), a map of the percent of total withdrawals coming from ground water, and a map of the percent of public-supplied population...
US Geological Survey
Earth's Water: Rivers and Streams
The USGS explains the definition of a river and how a river is supplied with water. Included is a cross section of a river. Click Home to access the site in Spanish.