Streamer

http://nationalatlas.gov/streamer/Streamer/welcome.html

Streamer is a new website from the National Atlas of the United States. This government site allows you to map the water flow of rivers across America. Begin by going to the map. Locate the river you are looking for. Hold the shift key and drag a box around your river area of interest. The map provides the names of rivers in the area. Click on the river and you can see how it goes upstream or downstream. Clicking on the “Trace Report” button shows a summary or detailed report with the latitude, longitude, and elevation of the river. It also includes the total length of the river and what cities it passes by.

Two different maps can be chosen. The base Terrain map, on a white background or the Imagery map, which is on a green background. The Imagery map is more topographical, while the Terrain map is more of a basic map.