Geologist Dr. Bob Raynolds and space scientist Dr. Ka Chun Yu explain the planetary processes that affect water supplies around the world and in the American West. Aired May 24, 2011. [1:14:41]

[Free Registration/Login Required] Students test water from multiple locations on the Potomac River for dissolved oxygen, nitrates, phosphates, pH levels, salinity, and turbidity. What do these tests tell us about the health of the...