Streams
and Watersheds - Stream Classification
Method
1 = In relation to other streams
One way to classify
streams is by looking at where they lie in relation to other streams
in the watershed (Figure 1-3).
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First
order streams
("1" in Figure 1-3) can be thought of as "starter"
streams. Most often they are located in the upper parts of a
watershed, and water enters them from over land, seeping groundwater,
or springs rather than by flowing in from another stream.
-
Second
order streams ("2" in Figure 1-3) are fed
by two or more first order streams.
-
Third
order streams ("3" in Figure 1-3)
are formed by the joining of two or more second order streams.
Stream orders above 7 are considered large rivers. The highest
order stream in North America, the Mississippi River, is a 12th
order stream.
Figure
1-3
Streams higher up
in a watershed tend to be smaller and of lower order because
they are the recipients primarily of seeps and springs and
only limited over land flow. |
The higher the
stream order--the more streams that feed into it--the larger the
size of the stream. In general, the higher the order (for example,
3rd order versus 1st order), the more likely the stream is to be
influenced by events occurring higher up in the watershed. This
also means the more of the watershed you control, the greater the
impact--positive or negative--your management decisions have.
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