8251

• UCREFRP Catalog Number: 8251
• Author: Rakowski, C. L. and J. C. Schmidt.
• Title: The Geomorphic Basis of Colorado Squawfish Nursery Habitat in the Green River Near Ouray, Utah.
• USFW Year: 1996.
• USFW - Doc Type: #93-1070,
• Copyright Material: NO

Draft Fmal Completion Repon to UDWR for Contract #93-1070, Amendment 3

3

typically occurs in April, May, and June. The water for this flood originates as snow melt in the headwaters of the

Yampa and upper Green River basins. The US Geological Survey (USGS) gage near Jensen (station number

09261000) provides the best measure of flow conditions for the Green River as it flows through the Ouray NWR

because no large tributaries enter the river downstream from the gage (Andrews and Nelson. 1989).

Floods

The magnitude of the spring flood near Jensen. Utah. has been reduced since the closure of Flaming Gorge

Dam (Fig. 4) (Schmidt, 1994). The 2-, 5-, and lO-yr recurrence floods have been reduced by 26, 19 and 13 percent,

respectively, from the period prior to dam closure (1923 to 1962) compared to after dam closure (1963 to 1993) ( Table

1) (Schmidt, 1994). Schmidt (1994) synthesized the Jensen USGS gage record, extending the record to include the

period 1923 to 1947 using correlations to other USGS gages.

Table 1. Recurrence inte1Val (R.I.), in years, of peak discharges for the Green
River near Jensen. Utah. Discharge in cubic meters per second with fi'/s in
parentheses for the periods before (1923 to 1962) and after (1963 to 1993)
closure of Flaming Gorge Dam (from Schmidt, 1994).

Recurrence Interval (years)
Years 1.25 2 5 10
1923 - 1962 446.4 622.1 791.6 869.6
(15764) (21967) (27952) (30707)
1963 - 1993 326.3 463.0 640.5 753.3
(11521) (16347) (22617) (26598)

Prior to this study, 6 years of drought occurred in the Green River basin (Fig. 5). The annual peak flows of

1993 and 1994, the period of this study, were each less than the pre-dam 2-yr recurrence flood (622 m3/s). The

magnitude of the 1993 flood (570 m3/s), with an estimated recurrence of4.5 yrs for the post-dam period, caused flooding
through much of the central Uinta Basin. The flood of 1994(331 m3/s) was similar in magnitude to those of the drought

years 1987 to 1992.

US Geological Survey gage records show that, prior to dam closure, the Yampa River provided less than half

of the volume of water for 'the annual peak discharge. Since the closure of Flaming Gorge Dam, the Yampa provides,

on average, 3/4 of the volume of water for the annual peak discharge (Fig. 3).