The U.S. EPA defines
a watershed as "a geographic area in which water, sediments, and dissolved
materials drain into a common outlet" - a stream, lake, estuary, aquifer,
or ocean. This area is also called the drainage basin, drainage area, or
catchment of the receiving water body. Sometimes the word watershed is
used to refer to a watershed boundary, or dividing line. In this sense,
for example, the North American Continental Divide - the boundary between
all waters flowing to the Atlantic Ocean and the Pacific Ocean - can be
called a watershed.
How many major river drainage systems can you find? |
| How does
elevation affect river drainage?
In this view, the lower elevations are represented by blue and yellow (coastlines and valleys);the middle elevations (plains and foothills) are orange, green and brown; and the higher elevations (mountains and alpine peaks) are shown in lavender and white.  |
Find the largest white region on this map. Count the number of rivers which start in this high mountain region. How many are there? Each of these rivers flows downhill and joins with other rivers on the way to the ocean. Look at the yellow region in the southeast U.S. and find the major river in this area. This is the Mississippi River, which drains many mountainous creeks and lowland rivers. |
 |
Find the Mississippi River drainage
and count the number of tributary rivers which flow toward the ocean.
Now we will zoom in on our local watershed regions to discover the location and extent of our own watersheds. Choose your state to continue.
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How does
the number of rivers in this view compare with the number of rivers you
saw on the U.S. map?  |
The watershed of a large river, lake, or estuary can be divided
into numerous subwatersheds (or subbasins). The watershed of the Mississippi
River covers the entire central United States and is made up of hundreds
of smaller subwatersheds, down to the individual watersheds of the smallest
creeks. The drainage areas of estuaries can also be enormous.
Choose one of these areas to get an even closer
look at watersheds
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| Can
you identify the watershed of the Calaveras River?
First try to identify the Calaveras River and mark on the map where this stream ends (at the San Joaquin River) - this is your "watershed exit". Visually follow the river upstream, locating all the tributaries if possible, and draw a line that divides the slopes that feed your stream from the slopes that drain into other watersheds. You should be able to draw one line which surrounds all the streams that flow into the Calaveras River. You now have your watershed boundary! Click here
to check your results. |
Interested in learning about the health of this watershed? Surf Your Watershed |
| Can
you identify the watersheds of these local rivers?
How many watersheds are there in
this area?
|
| Can you
identify the watershed of the San Lorenzo River?
First try to identify the San Lorenzo River and mark on the map where this river ends (at the Pacific Ocean) - this is your "watershed exit". Visually follow the river upstream, locating all the tributaries if possible, and draw a line that divides the slopes that feed your stream from the slopes that drain into other watersheds. You should be able to draw one line which surrounds all the streams that flow into the San Lorenzo River. You now have your watershed boundary.  |
How did you do?
Now try identifying the watershed of
Soquel Creek using the same technique. |
How did
you do? Check your results against this map.
Interested in learning about the health of this watershed? Surf Your Watershed Would you like to try another watershed? Choose one below: |
Can you identify the watersheds of
the North Canadian River? How
many watersheds are there in this area?  |
| Can you identify the watershed
of "tributary 1" of the North Canadian River?
First try to identify "tributary 1" and mark on the map where this river ends (at the North Canadian River) - this is your "watershed exit". Visually follow the river upstream, locating all the tributaries if possible, and draw a line that divides the slopes that feed your stream from the slopes that drain into other watersheds. You should be able to draw one line which surrounds all the streams that flow into "tributary 1". You now have your watershed boundary! Click here
to check your results. |
 |
Julie Stoughton julestar@inreach.com
|
Larry Johnson
