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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· Channel and floodplain morphology in time anc;l space is not a simple flow-area
relationship and complex interactions not yet fully understood may emerge that will compromise
recovery of the fish.
· What is the tradeoff between propensity of endangered fish larvae to drift downstream and
the need for high flows to maintain connectivity between the channel and backwaters and wetlands?
· Can food webs re-establish in key low velocity habitats (backwaters) to the extent needed
to recover the fishes, given the windows permitted or needed for hydropower operations?
· Can the endangered fishes expand their range and productivity gIven the downstream
extension of cold water environments caused by regulation, and is the locality of the transition zone
between cold and warm reaches likely to stay constant as reregulated flow regimes are
implemented?
· Interactions with nonnative fishes may limit recovery of endangered fishes regardless of
flow provisions.
The report concludes with recommendations that couple management action
(implementation of interim flow regimes) with additional study to resolve the uncertainties
presented above. The suite of recommendations constitute an ecosystem approach to resolution of
flows needed to protect and enhance the endangered fishes of the Upper Colorado River Basin. In
essence, these recommendations constitute a new, holistic instream flow methodology.
· Implement interim flows that re-establish seasonality with spring peaks that approach the
amplitude and frequency of preregulation events and summer and winter baseflows with daily
changes (not daily volume) limited to near preregulation conditions Oikely no more than about 5%
per day).
· Provide common understanding of water availability so that interim flows can be provided
in relation to precipitation and legal flow abstraction in each subbasin.
· Improve the standardized monitoring program as a mechanism to evaluate effectiveness of
interim flows by adding a community ecology perspective.

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