Another excellent resource to teach about watersheds from a spatial perspective is the EPA’s Surf Your Watershed site (http://cfpub.epa.gov/surf/locate/index.cfm). For each watershed, environmental threats, streamflow, citizen-based action groups, and water quality data can be analyzed. Navigate upstream and downstream to foster understanding of the interconnectivity between adjacent watersheds, and to watersheds far away. Water Science for Schools (http://ga.water.usgs.gov/edu/) helps cement the basics as well as calculating the astounding amount of rain that falls on user-specified area and covers it at a certain depth.

On the National Atlas web-GIS site (http://nationalatlas.gov), explorable water-related layers include aquifers, arsenic in groundwater, dams, streams and waterbodies, and watersheds. Use the National Atlas’ MapMaker function to create a map of watersheds and rivers, overlaid with the USGS realtime streamflow stations. Compare the streamflow and water quality on a gaging station at the headwaters of the Arkansas River in Colorado to the gaging station where the Arkansas flows into the Mississippi River. Why do such vast differences exist?

Perhaps the best way to teach about and understand watersheds is in 3-D. ArcGIS Explorer is ESRI’s free, easy-to-use 3-D virtual globe that can model spatial data such as that on National Atlas. Download the watershed boundaries and rivers, access ArcGIS Explorer, and add the watersheds and rivers. First, you may need to define the data’s projection as geographic inside ArcMap. Below, the watersheds looking west from the Great Plains to the Front Range of Colorado are shown in ArcGIS Explorer. A short time spent with this tool easily conveys the relationship between the nested rivers and the watershed boundaries.

To the south (left) of our ESRI office lies a ridge that does not seem significant on the ground, but because it divides the St. Vrain from the Clear Creek watershed, it appears as a red line. What are the closest watershed boundaries to your campus? Do any divide major drainage basins? Add cities, land use, and gaging stations. What urban and non-urban land use affects water quality in each watershed?

-Joseph Kerski, ESRI Education Manager