8056

• UCREFRP Catalog Number: 8056
• Author: Hamill, J.
• Title: Restoring and Protecting Instream Flows for Endangered Fish in the Upper Colorado River Basin.
• USFW Year: 1992.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

Priority Area for Acquisition of Water Rights

In March 1988, priority areas were identified for investigating
acquisition of water rights in the Upper Colorado River Basin
based on two criteria: (1) the biological importance of a river
reach to the recovery of the endangered fish and (2) the timing
of water development that may alter the quantity or quality of
habitat. Three priority reaches were identified: (1) the lower
140 miles of the Yampa River; (2) a 15-mile reach of the Colorado
River immediately upstream of the confluence of the Gunnison
River; and (3) the lower 109 miles of the White River. This
prioritization contemplated that the instream flow requirements
of the endangered fish in other parts of the upper basin (i.e.,
the Green River, the Gunnison River, and the Colorado River below
the confluence of the Gunnison River) can be provided through
refinement in the operation of Flaming Gorge Dam and the Aspinall
Units (Figure 2).

Instream Flow Determinations

service efforts to define the flow needs of the endangered fish
date back to the early 1980's. Early efforts focused heavily on
the application of the Instream Flow Incremental Methodology
(IFIM) and the Physical Habitat simulation (PHABSIM) System in
the upper basin. However, the broad application of PHABSIM has
been judged inappropriate by most native fish biologists because
certain habitats used by the fish were not easily simulated,
microhabitat parameters used (depth, velocity, and substrate)
were not accepted as the only factors required by the fish, and
conflicting flows have been obtained for different species and
life stages in the same location (Tyus 1992).

Recent studies by the Service have focused on developing flow
recommendations based on current biological theory; statistical
analysis of the relationship between streamflows, habitat, and
fish populations; and the use of professional judgment to
integrate information into a flow recommendation that makes
biological sense. Results have indicated that the endangered
fish require flows that more closely mimic the natural flows that
existed historically in the basin. These flows, which are
characterized by high flow in the spring and low stable flow for
the summer, fall, and winter period, are closely associated with

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