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[Water
Quality and Quantity Monitoring | Physical
Habitat Assessment |
Minimum Flow
Requirements | How
the Indices are Calculated | Back
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Physical Habitat Assessment
Fish need places in a stream to collect food,
breed, take refuge from predators, and retreat from uncomfortably
warm water temperatures; i.e. fish need good physical habitat.
Habitat measures usually include: the availability of cover
for fish such as woody debris, overhanging vegetation, and
undercut banks; the composition of the stream bed; the variety
of current velocities; the mixture of riffles, runs, and pools
in the stream; and alterations to the bank and near-stream
land areas.
Most of these parameters change with the change
in streamflow, thus estimating the amount of the streambed
covered with water can provide an estimate of the changes
in habitat availability. As flows decrease the water pulls
away from the river banks and their protective overhanging
vegetation, banks, and debris. ("Channel Flow Status"
-- the amount of streambed exposed--is estimated at a riffle
near the staff gage by the volunteer gage reader.)
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Channel Flow Status
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Streambed completely covered
(Channel Flow Status = 20)
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Same riffle largely dry
(Channel Flow Status = 1)
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Stream habitats:
riffles, runs and pools
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Riffle along Elizabeth
Brook, Stow
Riffles are generally the fast,
shallow sections of a stream where the water flows over
partially submerged rocks and gravel and the surface
is broken into small standing waves. Runs have a variety
of streambed substrates - sand and gravel.
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A run or glide along
Elizabeth Brook
Runs or glides are deeper sections
with moderate flow velocities where the flow is still
visible, but the water's surface is smooth and unbroken.
Glides tend to have slower flow velocities and fine-grained
substrates - sand, silt, organic debris.
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Pool in Elizabeth
Brook
Pools are deep and slow-moving. The
surface is smooth
and the current is generally not visible. Substrates
are fine-grained - sand, silt, and organic debris.
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