7346

• UCREFRP Catalog Number: 7346
• Author: Wick, E. J. and J. A. Hawkins.
• Title: Colorado Squawfish Winter Habitat Study, Yampa River, Colorado 1986-1988.
• USFW Year: 1989.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

periodic ice jamuig and release, act to raise or lower water surface
elevations at the gage. 'T'hese elevation changes caused by ice effect can

' translate into either higher or lower discharges than are actually occurring.
Ice-affected flaw readings were adjusted by USGS hydrologists by compering
various data sources. Actual flow measurements were made near gaging stations
at least twice each winter, usually at initial ice formation in Decembex and
again in February. These known discharges were compared with weather data
(air temperature and precipitation) and flaw data collected at other gaging
stations to correct discharge data for the winter period. Adjusted discharge
data for the winter were as accurate as possible given the extremely variable
ice conditions present when it was collected. Accuracy could be improved by
more frequent actual field discharge measurements. However, at the present
time neither the funds nor demand exists for more accurate winter discharge
' data. Because the total water discharged in the winter is small compared to
the rest of the year, any flow calculation error during winter is relatively
small. We worked closely with USGS during the second year of the study to
insure that our discharge measurements were made correctly. Our data was
incorporated into the USGS data base in 1988 to aid in correcting final winter
discharge records. If additional winter flow impacts are expected in the
future as a result of dam construction, funding should be made available to
increase field flow measurements during the winter to improve the accuracy of
winter discharge records. For greater accuracy, gaging stations should be
checked at least twice monthly to correct for ice effect. The only way to be
certain of discharge and water surface elevations relationships at a particular
time is to make actual discharge and water surface elevation measurements..
This relationship will change as the winter progresses and ice thickr ss
r
Ecological considerations of winter stream flaw
' In planning strategy to determine winter flaws, consideration should be
given to all the primary factors that influence the structure and function of
the stream ecosystem (Orth 1987). Karr and Dudley (1981) outlined the
' following primary factors: (1) energy source (sediment inputs, particulate
organic matter, and nutrients); (2) water quality; (3) temperature; (4)
physical habitat structure (channel form, substrate distribution, and riparian
vegetation); (5) flow regime; and (6) biotic interactions.
Obviously, detailed analysis of all these factors could not be undertaken
in this study. However, consideration of these factors is helpful in
determining which habitats may be important to maintain. Micro-habitat use
patterns of squawfish should be examined in light of these factors to
determine additional beneficial aspects to the system of a particular habitat
type. other logical criteria that could be used to prioritize habitats that
1 should be examined for effects of altered flow include: (1) vulnerability to
low flows, (2) natural availability in the ecosystem, and (3) stability of
habitat.

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