9410

• UCREFRP Catalog Number: 9410
• Author: Wydoski, R. S. and E. J. Wick.
• Title: Ecological Value of Floodplain Habitats to Razorback Suckers in the Upper Colorado River Basin.
• USFW Year: 1998.
• USFW - Doc Type: Denver.
• Copyright Material: NO

streamflows that were greater than 283 m3/s (10,000 cfs) on the Gunnison River
were about 3 weeks in duration but the post-dam (1966-1993) streamflows were
less than 1 week at flows greater than 283 m3/s (10,000 cfs). Cooper and
Severn (1994a) estimated that streamflows of 1,133 m3/s (40,000 cfs) were
required for overbank flooding at Moab Slough along the Colorado River. This
flow occurred 26 times during the 70-year period of record (1924-1993) but
only 6 times between 1963 and 1993. The duration of inundation at Moab Slough
over 25 days occurred only 5 times.

Even floodplain habitats that become inundated for a short time can produce
relatively high densities of zooplankton as in the flooded willow habitat of
Moab Slough along the Colorado River described by Cooper and Severn (1994bi
Appendix 2) that benefit fish in backwaters and main river channels. However,
a short duration of inundation on floodplain terraces is probably not
sufficient for survival of larval razorback suckers and subsequent population
recruitment today because the larvae will not have adequate time to grow large
enough to escape predation by nonnative fishes when they enter backwaters of
the rivers as streamflows subside.

VII. INTEGRATION OF RECOVERY PROGRAM ELEMENTS

It is imperative to integrate all Recovery Program elements, especially
streamflow management, habitat enhancement/restoration, control of nonnative
fishes, and captive propagation and stocking of razorback suckers.

A. Streamflow Manaqement. Streamflow management must consider the magnitude
of discharge, frequency of occurrence, duration of specific flow
conditions, timing of flows, predictability of flows of a defined
magnitude, and rate of flow change (Poff et al. 1997). If possible, it
would be ideal to mimic the natural hydrographwith streamflows high
enough to flood existing terraces (Stanford 1994). Although ecologically
sound, this strategy will have to take into account private lands that
are occupied by humans or used for agriculture would be flooded and could
result in loss of human lives or economic losses to agricultural crops.
Streamflows and habitat requirements for endangered Colorado River fishes
were described for the Green River (Tyus and Karp 1991), Yampa River
(Tyus and Karp 1989), and "15-mile reach" of the upper Colorado River
(Osmundson et al. 1995).

If increasing streamflows is not feasible in the Upper Basin because of
economic, political, or sociological constraints, then excavation of
existing terraces may be necessary so that the floodplain can be
inundated within the present streamflow regime. Field experiments to
evaluate increasing streamflows would probably preclude extremely high
releases and may have to be made incrementally to minimize flood hazards
to private agricultural areas or to ensure the safety of humans living on
floodplains.

Gore (1985) pointed out that substrate composition, critical to
macroinvertebrate abundance and diversity, can be easily manipulated
through streamflow management. He emphasized that "benthic
macroinvertebrates comprise a large and diverse faunal community in most
undisturbed running water ecosystems" and that benthic organisms provide
a critical pathway for energy transport and utilization within stream
ecosystems. An example of enhancement in a benthic invertebrate
community through establishment of a minimum flow from a hydroelectric
plant was described by Weisberg et al. (1990).

B.

Habitat Enhancement/Restoration. All enhancement or restoration
endeavors must be made through well designed experiments that will allow
a thorough evaluation using an adaptive management approach. Evaluation
of habitat enhancement includes the Recovery Program element of

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