7822

• UCREFRP Catalog Number: 7822
• Author: Miller, W. H., et al.
• Title: Colorado River Fishery Project, Part I, Summary Report.
• USFW Year: 1982.
• USFW - Doc Type: ‎(contract no. 9-07-40-L-1016 with the Bureau of Reclamation)‎,
• Copyright Material: NO

HABITAT AND GEOPHYSCIAL CHARACTER, UPPER COLORADO RIVER BASIN
The width, depth, and physical characteristics of streams of
the Upper Colorado River Basin vary greatly by geographic area and
with flow volume. Some of the deeper areas in the Upper Colorado
River were Cataract Canyon with maximum depths of 92 feet, and Black
Rocks and Westwater Canyons with maximum depths of about 60 feet. In the
Green River a maximum depth of about 60 feet was recorded for Gray Canyon
and up to 28-foot depths were recorded for the Lower Green River in
Labyrinth Canyon. Average depths for cross sections of the different
' river strata varied from about 2 feet to over 60 feet.
Various habitats in the Upper Colorado River were quantified at key
locations using computer modeling methodology developed by the FWS
IFG (Part 3, Report No. 1). Three hydraulic simulation stations were
established on the Green River: Mineral Bottom (RM 56), Gray Canyon
(RM 141), and Ouray (RM 248); and three stations on the Colorado River
at Potash (RM 53), Moab (RM 73), and Black Rocks (RM 136). Analyses
were made to evaluate potential habitats available for young squawfish
and adult humpback chub at these sites.
Flow changes in the Upper Colorado River were compared by hydrologic
time series at the six hydraulic stations. U.S. Geological Survey
(USGS) gaging station flow records for 1960-1980 were compared to
simulated flows depicting: (1) flow conditions without any development
and (2) flow conditions with 1980 development projected from historic
conditions. Temparature modeling was also done to determine the effect
of flow changes on river temperatures at the key hydraulic stations.
The IFG analysis shows significant peak flow reductions on both
the Green and Colorado Rivers. Average monthly peak flows in the Colo-
rado River have been reduced by about 35 percent and the Green River
has experienced similiar reductions of 25-40 percent. Instantaneous
peaks (daily maximum flows) have changed as indicated by an analysis of
the 10 percent exceedance flows for the period before major impoundments
and the period after. As shown in Table 1 the peak flow depletions in
May, June, and July have all been greater than 20 percent with maximum
depletions near 37 percent. Manipulation of flow regimens by reservoir
regulation has resulted in higher low flows (fall, and winter) and lower
peak flows (spring and early summer).
Table 1
Changes in peak flow in the Green and
Colorado Rivers as a result of major _impoundments.!/
Colorado River Green River
+ Month Percentage depletion?/ Month Percentage depletion
May 20.4 May 28.7
June 34.6 June 36.9
` July 36.7 July 36.5
August 15.3 August 7.0
1 Pre-impoundment period - Colorado River 1914-1965, Green River
1947-1962. Post-impoundment period - Colorado River 1969-1981, Green
River 1964-1981. A 2- to 4-year reservoir filling period was eliminated
from the analysis.
2/ Depletion percentages based on the changes in the 10 percent
exceedance flow parameter, i.e., an analysis of those peak flows occur-
ring 10 percent of the time before and after development.
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