FLOOD00235

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Title: Stream, Riparian, and Wetland Ecology - Class material, Volume 1 of 2
• Date: 9/1/1987
• Prepared For: Students
• Prepared By: Professor Windell
• Floodplain - Doc Type: Educational/Technical/Reference Information

66

CIlAPTER 4

STREAM ECOSYSTEMS

Introduct1cm

Historically, aquatic research has been concentrated on small streams
(first to fourth order) because of greater ease of sampling and a lesser
degree of man-caused perturbation. Although monitoring types of studies on
large streams have increased as a result of federal rE'quJ.rements for
environmental impact statements, basic research continues to be
concentrated on smaller streams.

As discussed in Chapter 3, stream ecosystems may be divided :lnto the
channeled aquatic zone and the riparian streambank zone. The two zones may
be studied individually or as a combined ecosystem. ,/hen studied as a
combined ecosystem it is viewed as containing one aquatic zone and two
adjacent riparian zones that are bordered by two upland terrestrial zones.
When studied separately, the aquatic zone may be restricted horizontally
between the opposite high water marks and lClngitudinally between the
headwaters and mouth or estuary. The upper and lower boundaries and length
of the linear segment of a stream ecosystem are usually arbitraril,y defined
by the investigators and the nature of the question bE,ing asked. Therefore
stream ecosystems may range from a short segment or re!Bch of one stream
order to the entire coalescing network of streams in a, drainage z)'stem that
forms a complex gradient of environmental variables and conditions
dominated by width, depth, velocity, flow volume, temperature and entropy
gain (Vannote et al. 1980).

BiOlogically, temperate zone streams are the result of hundreds of
1Ili11ions of years of evolution and at leas t 10 to 20 thousand years of
acclimatization and adaptation of resident populations (Cummins 1979). It
is already clear that with only minor exceptions, all streams fourth order
and larger within the 21 maj or drainage basins of the United States
(excluding Hawaii and Alaska) have been significantly impounded with dams
and reservoirs, channelized, polluted, overgrazed, de"atered, etc. The
tragic result of man-caused perturbations on the limited remaining milage
of large streams is that we may never know how streams function
biologically (Cummins 1979).

The whole subject of streams as ecosystems has been reviewed and
discussed in recent years in a number of excellent volumes including: The
Ecology of Running Waters by H.B.N. Hynes (1970), River Ecology and Man by
Oglesby, Carlson and McCann (Eds.) (1972), Fiver Ecolo~ by B.A. Whitton
(Ed.) (1975), Fundamentals of Aquatic Systems by R.S.K. Barnes and K.H.
Mann (Ed.) (1978), Perspectives in Running Water Ecolo~ by M.A. Lock and
D. Williams (Eds.) (1981), and Dynamics of ~otic Ecosystems by T.D.
Fontaine and S.M. Bartell (Eds.) (1983). They are recommended for a more
comprehensive treatment than is possible here. The following represents a