The Chesapeake Bay watershed dominates the lower left portion of the image, while snow and ice can be seen in parts of New England and Canada. The watershed or 165,000 square kilometer drainage basin encompasses parts of New York, Pennsylvania, Delaware, Maryland, Virginia, and West Virginia
The Chesapeake Bay (located at the bottom center of the image) is the largest estuary in North America and is an important fishery and recreation area. There are important linkages between the land surface upstream and the aquatic environment downstream. Also any activity that takes place with the Bay watershed impacts its water quality.
Rainfall carries materials from the surface into the stream network of the watershed and ultimately into the Bay itself. Some of these materials, such as nitrogen and phosphorus, stimulate the growth of algae. When the algae die, they are decomposed by a type of bacteria. Therefore depletes the oxygen that is dissolved in the water. Therefore without this dissolved oxygen, fish and other aquatic organisms cannot survive.