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Subject: Re: stream order and flow velocity
From: Jim Gilliam <[log in to unmask]>
Reply-To:Academic forum on fisheries ecology and related topics <[log in to unmask]>
Date:Fri, 9 May 1997 19:15:54 -0400
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I did just pull some info from an appendix in a 1993 paper regarding
tropical streams in Trinidad, West Indies (Gilliam, J. F., D. F. Fraser,
and M. Alkins-Koo. 1993. Structure of a tropical stream fish community: A
role for biotic interactions. Ecology 74:1856-1870).

Mean velocities (cm/sec) measured in the center of pools were:

First order: 4.5 cm/sec,  N=13 pools, range = 1-12 cm/sec
Second order: 4.6 cm/sec, N=25 pools, range = 1-15 cm/sec
Third order: 9.6 cm/sec, N=33 pools, range = 0=40 cm/sec
Fourth order: 13.0 cm/sec, N=15 pools, range = 0-50 cm/sec

I include the ranges to emphasize the variability.  The measurements were
taken between 7 January and 15 March, 1990, during the early-to-mid dry
season.  The gradient was steeper for lower-order streams, but even the
4th-order 'stream' (the Guanapo River) had pool-riffle development at the
sites we sampled.  The higher orders were also larger in cross section, so
both velocity and discharge increased with order.  We did not do
statistical tests on these descriptive data, but I am pretty sure a
Friedman or whatever would yield 1=2<3<4.

The table also includes info on 14 other measurements across the 4 stream
orders: e.g., area, depth, %boulders, %bedrock, %overhead cover, etc.  I
can, of course, send a reprint if you wish.

Jim Gilliam

-------------------------------------------------------------------------
Eric Schultz wrote:
Date:    Thu, 8 May 1997 14:54:41 +0000
From:    Eric Schultz <[log in to unmask]>
Subject: flow velocity and stream order

Dear fish netters:

A question arose while I was giving a lecture.  This is one of those
'interesting' moments when an undergraduate tells you in class that...
[deleted]
----------------------------------------------------------------------------
===============================================
Jim Gilliam
[log in to unmask] (preferred) or [log in to unmask]
http://www4.ncsu.edu/~jfgzo/jfgzo.html

Department of Zoology
North Carolina State University
Raleigh, NC 27695-7617
USA

You can see our NCSU Ornithology home page at
http://www2.ncsu.edu/ncsu/cals/course/zo501/

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