7275

• UCREFRP Catalog Number: 7275
• 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 operations at Flaming
Gorge Dam can be critical for the survival of various life stages of
endangered species. Therefore, Reclamation and FWS initiated an
environmental study 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 it's generators. 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 ale 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). Reclamation and FWS assume that maximizing
backwater habitat during the summer will increase the survival rate of young
Colorado squawfish.

In response to a request from Reed Harris and 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 prevented 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 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, Reclamation
investigated a more cost-effective alternative for mapping backwater
availability using videography during 1988. This study compared backwater