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 Final Completion Report to UDWR for Contract #93-1070. Amendment 3

2

OVERVIEW OF GREEN RIVER PHYSIOGRAPHY, HYDROLOGY.
AND RESPONSE TO RAMING GORGE DAM

Physiography

The Green River is a major tributary of the Colorado River. draining approximately 115.800 Jan2 (Fig. 1). The

mainstem of the Green River has its headwaters in the Wind River Range of Wyoming. The Yampa River. the Green

River's major tributary. has its headwaters in the Park Range of Colorado and supplies almost half of the Green River's

water. Flaming Gorge Dam, located 662 river kilometers from the Green River's confluence with the Colorado River.

has regulated the flow of the main stem of the Green River since October 1962. The Yampa River remains largely

unregulated.

The longitudinal profile of most large rivers is generally concave up (Leopold and others, 1964). and has larger

bed material and steeper gradients in the headwaters and lower gradients and smaller grain size downstream. The Green

River below Flaming Gorge Dam passes through formations of differing erosional resistance (Schmidt and Rubin.

1995). such as the harder, resistant Uinta Mountain group in Dinosaur National Monument (Hansen, 1986). the less

resistant Duchesne and Uinta Formations of the central Uinta Basin. and the more resistant Mesa Verde sandstone of

Gray Canyon. The channel shape and gradient are partly adjusted to these varying resistances (Grams and Schmidt, in

press). Downstream from Flaming Gorge Dam. the Green River has steep-gradient, eddy-dominated canyon reaches

with large bed material interspersed with low-gradient, sand-bedded alluvial reaches forming a complex longitudinal

profile (Fig. 2) (Schmidt, 1994; Schmidt and Rubin. 1995). The Green River in the central Uinta Basin is the area of

interest for this study. In this area. the Green River has the lowest gradient of any reach of the Green River in Utah, and

is sand-bedded. The study reach is located within the Ouray National Wildlife Refuge (Ouray NWR).

Hydrology

Dams are used to store peak flows for later release during low flow periods for irrigation and other "beneficial"
uses. The total annual stream. flow (3.9xI09 m3) of the Green River is essentially unchanged by Flaming Gorge Dam
(Andrews. 1986). although the magnitude and duration of peak and base flow have changed dramatically.
The annual hydrograph (Fig. 3) of the Green River near Jensen, Utah, is characterized by a spring flood which