7752

• UCREFRP Catalog Number: 7752
• Author: Stanford, J. A.
• Title: Instream Flows to Assist the Recovery of Endangered Fishes of the Upper Colorado River Basin
• USFW Year: 1993.
• USFW - Doc Type: Review and Synthesis of Ecological Information, Issues, Methods and Rationale.
• Copyright Material: NO

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preliminary conclusions. Written reviews of fIrst and second drafts of this report were provided by
the expert panel and members of the Instream Flow Subcommittee. Many other scientists and
. experts working in the Upper Colorado River Basin also kindly provided written comments on the
second draft.. All the comments I received were insightful, and I attempted to address all concerns
that I felt would improve the report. I was especially cognizant of comments by the expert panel,
and their input is evident throughout the document. However, I take full responsibility for the

accuracy and completeness of information and conclusions contained herein.

Ecolo~cal Context for Instream Flow Analysis
I approached this analysis from an ecosystem perspective, recognizing that ecological
processes or management actions in one subbasin or river reach may influence processes in others

(Le., system components are ecologically interconnected). For example, migrations by fIshes
ecologically interconnect the entire river system, except as influenced by dams which usually block

upstream movements. Dams and reservoirs rarely prevent fIshes from moving downstream,

although monality may be high in passage and conditions downstream from the dams mayor may
not favor colonization by fishes living upstream from the impoundment. My point is that reaches
in the river system where the endangered fishes live (Le., downstream from the larger dams) are
hydrologically and ecologically connected to upstream reaches, where the endangered fishes may
have never existed. Interactions between flow dynamics and channel and floodplain features vital to
the existence of the endangered fishes also occur from river reach to catchment scales and represent
another example of ecosystem connectivity. Hence, the ecosystem in this analysis included the
entire Upper Colorado River Basin (Figure 1).

Uncertainty exists as to whether ecological and/or water regulation processes in Lake
Powell have significant influences on the ecology of the Upper Colorado River Basin. Certainly
regulation of Lake Powell is influenced by delivery of water from the Upper Colorado River Basin
and it is likely that the reselVoir is a source of nonnative fishes that may migrate upstream, thereby

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