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

Economic, political, and sociological factors are also important and must be
considered concurrently with the biological, chemical, and physical factors
(Table 5). Nearly all large rivers in the northern third of the Earth have
been dammed and regulated to provide water for irrigated agriculture, flood
control, hydro-electric power, industry, and domestic use (Dynesius and
Nilsson 1994). Humans settled in the corridors of these large rivers largely
because the rivers provided transportation and floodplains provided productive
agricultural areas and prime areas for industrial development. Humans have
and will continue to have a dominating influence on watersheds and river
ecosystems that dramatically influences environmental integrity, productivity,
biodiversity, and heterogeneity (Frissell et al. 1993). Cairns (1995)
emphasized that, to be successful, ecological integrity of aquatic systems
must include the sustainable use of water resources by humans. Restoration of
large river-floodplain ecosystems to a pristine or virgin state is probably
not possible for highly altered systems that are used by humans (Welcome 1989,
1995). Instead, Gore and Shields (1995) suggest that the logical approach is
to recover some of the ecological functions and values.

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Habitat enhancement or restoration involving river margins (Large and petts
1994) must consider biological, economic, political, and sociological factors
(Wydoski 1977) and decisions should be made through negotiated adaptive
management (Brown 1993; Ludwig et al. 1993; Walters 1986; Walters and Hillborn
1978). Because of strong economic, political, and social pressures from
humans for multiple-use of large river-floodplain systems for hydro-electric
power, agriculture, industry, and municipal uses, it is doubtful that
restoration or returning rivers to an original state is possible (Bradshaw
1996). However, it is entirely possible to mitigate (i.e., to moderate), to
remediate (i.e., to rectify), or to enhance (i.e., to improve) environmental
conditions in a river ecosystem (Stanford et al. 1996).

The restoration of large floodplain rivers will require at least partial
recovery of the natural hydrograph based on the current knowledge of such
systems (Bayley 1991; Hesse 1995; Poff et al. 1997; Stanford et al. 1996; Ward
and Stanford 1995). However, Dolan et al. (1974) .stated that the historic
natural hydrograph of Colorado River System can no longer be restored because
of human alterations and the river system is rapidly approaching a new state
such that the future of river bars and floodplain terraces is unclear. Yet
restoration of large river ecosystem integrity requires full consideration of
the river continuum and flood pulse concepts of energy transfer (Walker et al.
1995). Walker et al. emphasized that the greatest conflict occurs between the
supply and demand of water from dryland river systems and believe that the
integrity of large dryland rivers will be maintained only if users use water
that is surplus to maintenance requirements of the riverine ecosystem. Site-
specific efforts will not restore the ecological integrity of large rivers.

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Many of the floodplain habitats flooded ephemerally under historic riverine
conditions. For example, Cooper and Severn (1994d) estimated that
streamflows between 481 and 566 m3/s (17,000 and 20,000 cfs) were required to
inundate the floodplain along the middle Green River on the Ouray National
Wildlife Refuge. A streamflow of 566 m3/s (20,000 cfs) occurred 17 times
during the 47-year period of record (1946-1993) but only 7 times since the
completion of Flaming Gorge Dam in 1964 (29 years). This floodplain was
inundated only 6 times during the 47-year period for over 20 days. More
recently, FLO Engineering, Inc. (1995) estimated that a streamflow of 575 m3/s
(20,300 cfs) was required for extensive inundation of the middle Green River
floodplain on the Ouray National Wildlife Refuge. To reconnect the river with
the floodplain will either require breaching the levees to produce inundation
under present streamflows or excavation of the floodplain terraces to lower
the elevation so that floodplain inundation can occur without overbank
flooding of private lands.

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