Upstream / Downstream

The Watershed Explorer interactive map allows you to click anywhere in the world to view all of its upstream areas and the downstream flow.

When you click on this map a high-resolution digital elevation model is used to calculate the flow direction that water would take at every point on the surrounding land. The map then follows "these directions to calculate the region that contributes to a single outlet". You can view a more detailed explanation of how the map works on The Places Your Pee Will Go. 

 

The USGS's Streamer map allows you to trace rivers or streams upstream to their source or downstream to their final destinations in the USA. The interactive map can create very dramatic visualizations of river watersheds, particularly when you trace a river upstream to show all of its tributaries.

Streamer is incredibly easy to use. Just click on a river on the map and select either the 'upstream' or 'downstream' buttons (for the best results click on the Mississippi and then the upstream button). You can also get a detailed trace report for your selected river. This report includes information on the river's origin, length and the number of states it flows through. It also provides details about the streamflow gauging (measuring) stations found along the visualized river route.

FernLeaf Interactive has also created an interactive map which allows you to view over 100,000 watershed regions. This map shows the topological relationships between the USGS level 12 hydrologic units for the entire United States.

The Watersheds Map allows you to visualize watershed regions throughout the USA. As you mouse-over the map it automatically updates to show upstream areas in red and downstream areas in blue. You can click on the map at anytime to freeze the map view (click on the map again to unfreeze & re-enable the dynamic loading of the watershed data).