8182 - Laserfiche WebLink

Home Browse Search

1 STUDY AREA The Green River basin drains mountainous and high desert portions of southern Wyoming, eastern Utah, and northwestern Colorado (Fig. 1) and is the largest tributary of the Colorado River. The study area encompassed the Green and Yampa rivers in and above Dinosaur National Monument and included highly regulated, partially modified, and relatively unregulated river reaches. The Green River below Flaming Gorge Dam downstream to near Jensen, Utah, was the primary focus of the study. The river below Flaming Gorge Dam flows for 22 km through Red Canyon, enters the 48 km-long low gradient Browns Park valley, and then flows for 32 km through high-gradient Lodore Canyon before entering Echo Park at the confluence with the Yampa River. From Echo Park, the Green River flows 18 km mostly through Whirlpool Canyon, another 11 km through Island and Rainbow parks, and another 13 km through Split Mountain Canyon before emerging into an alluvial valley reach near Jensen. Extent of river meandering (river plan form) and habitat types in the major reaches of river are controlled by local geology. In Lodore, Whirlpool, and Split Mountain canyons the Green River is generally confined to a single, relatively narrow channel. Canyon river reaches constricted by debris fans form riffles and rapids with cobble and boulder substrate. These river reaches generally have higher current velocities and deeper runs and pools than lower gradient areas without debris fans. In lower gradient alluvial reaches such as Browns, and Island and Rainbow parks, river plan form is characterized by restricted meanders (Grams 1997), and the channel is relatively wide, shallow, and interspersed with islands. Lower velocity runs with sand and cobble substrate predominates. Flaming Gorge Reservoir in northeastern Utah impounds the mainstem Green River at the upstream end of the study area. With a storage capacity of 3.74 million acre-ft (4,624 million m3), it is the largest reservoir in the Green River basin. Upstream Fontenelle Reservoir, the only other mainstem Green River reservoir, does not appreciably affect releases from Flaming Gorge Dam. Flaming Gorge Dam was closed in 1962 as part of the Colorado River Storage Project 4