4247

• UCREFRP Catalog Number: 4247
• Author: Pucherelli, M. J. and R. C. Clark.
• Title: Comprehensive Report ‎(1986-1988)‎ on the Effects of Green River Flows on Backwater Habitat Availability as Determined by Remote Sensing Techniques ‎(Remote Sensing)‎.
• USFW Year: 1989.
• USFW - Doc Type: Denver, Colorado.
• Copyright Material: NO

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endangered species. These studies indicated that proper operation of
Flaming Gorge Dam was critical to the survival of various life stages of
endangered species. Therefore, an environmental study involving Reclamation
and FWS was initiated in 1986 in response to a FWS request and the pending
Section 7 Consultation for the Biological Opinion concerning the operation
of Flaming Gorge Dam and the proposed upgrade of Flaming Gorge Dam
generators increased hydropower production. The Endangered Species Act of
1973 (Public Law 93-205) charges Federal agencies to consider the needs of
listed species and produce biological opinions relative to the impacts of
planned and operating projects.

Studies conducted by the FWS and others have concluded that backwaters in
the Green River serve as important nursery habitat for young-of-the-year
Colorado squawfish (Tyus et al. 1987, Tyus and McAda 1984). Colorado
squawfish spawn during mid to late summer, and their larvae become
distributed in shallow backwater habitat that reduces predation and adverse
flow events (Tyus et al. 1987). Therefore, it is assumed that maximizing
backwater habitat during summer will increase the survival rate of young
Colorado squawfish.

In response to a request from Mr. Reed Harris and Mr. Bob Williams of the
Upper Colorado Regional Office (Reclamation), the feasibility of using
remote sensing techniques to study backwater habitat availability in the
Green River below Flaming Gorge Dam was examined. A pilot study was
developed in 1986 using color infrared (CIR) photography and Geographic
Information Systems (GIS) techniques to examine backwater availability in
response to different Green River flows. The pilot study proved successful,
and in 1987 an expanded study was initiated which examined the relationships
between seven different flows and backwater area and number at five sites on
the Green River in Utah. The objective of the 1987 study was to establish a
data base that would allow optimization of Green River flows for backwater
availability during late summer when young-of-the-year Colorado squawfish
would be present. During 1988 the Green River backwater study was
continued. The 1988 study was originally designed to test fluctuating flow
conditions and their effect on backwater habitat development. However,
extremely low-flow conditions produced by the drought preempted the
scheduled study. These stable low flows presented a unique situation to
establish a relative baseline condition for riverine habitat. Approximately
320 miles of the Green River from about Island Park to the Colorado River
confluence were photographed during the low flows that occurred during the
summer. The objective of the 1988 study was to establish baseline
conditions for backwater availability at extremely low flows, or a "normal"
summer hydrograph, for this portion of the river.

Aerial photography is currently thought to be the optimum method for mapping
and determining various riverine habitat availability. Future monitoring of
the Colorado River and its tributaries will be necessary to observe long-
term habitat trends vital for the survival and enhancement of endangered
fish populations. However, monitoring several hundred river-miles (rm) for
many years may prove prohibitively expensive. Therefore, in a related
project, a more cost-effective alternative for mapping backwater
availability using videography was investigated during 1988. This study