Dinosaur National Monument is a land of rivers. Here, the Green and the Yampa, two of the west's premiere whitewater rivers, flow through deep canyons with swelling rapids, and open parks where the rivers widen and the water runs smooth.
In 1938, President Franklin D. Roosevelt enlarged Dinosaur NM from its original 80 acres to more than 210,000 acres to protect the river corridors and adjacent viewsheds for the major canyons of the Green and Yampa rivers.
Today, Dinosaur National Monument protects 105 miles of river and more than 200,000 acres of ruggedly beautiful river canyons. Every year, 15,000 people experience the beauty, adventure, and solitude of Dinosaur's rivers and river canyons on multi-day and single-day raft trips.
The Green River
The Green River extends 730 miles from its headwaters in Wyoming to its confluence with the Colorado River in southern Utah. The river enters Dinosaur at the monument's northern boundary and flows out of the monument 58.5 miles later, just south of Split Mountain.
Within Dinosaur NM, the Green's journey takes it through the Canyon of Lodore, Echo Park, Whirlpool Canyon, Island Park, and Split Mountain Gorge. The Green and its largest tributary, the Yampa River, meet at Steamboat Rock in Echo Park.
Flaming Gorge Dam, 47 miles upstream from Dinosaur's boundary, has regulated the Green since November 1962. Impoundment has severely altered the river's natural regime below the dam. Before Flaming Gorge Dam, the Green River was often clouded by dirt, silt, and other sediments; was subject to high spring flows fed by snow melt; and the water temperature could range from near freezing in winter to almost 70F (21C) in summer.
In 1962, with the opening of the dam, these conditions largely disappeared from the Green River. Spring flows, temperature fluctuation, and turbidity (the cloudiness of the water) were all reduced. The Green River downstream from the dam became a much clearer, cooler, and calmer river.
The Yampa River extends for nearly 250 miles from its source in the mountains of Colorado to its confluence with the Green River. For the last 47 of those miles, the Yampa River is within Dinosaur National Monument. The river enters Dinosaur on the monument's eastern boundary and joins the Green River at Echo Park.
The Yampa is the only remaining free-flowing tributary in the Colorado River system and the major drainage of northwestern Colorado.
High flow, resulting from spring run-off, generally lasts only a few weeks in late May and June. During the remainder of the year, the river is essentially unnavigable.
The Yampa River harbors outstanding examples of remnant native cottonwood willow and box elder riparian communities, and it provides critical habitat for several endangered fish.
Prior to November 1962, the Yampa and Green rivers were very similar in their discharge, water chemistry, sediment load, and fish communities.
Today, Dinosaur NM represents a unique opportunity for research because it contains three distinct river reaches: 1) the regulated Green, 2) the unregulated Yampa, and 3) the hybrid Green below the Yampa confluence.
Pre-dam similarity between the Yampa and the upper Green creates an unparalleled opportunity for comparison studies that will help guide restoration efforts in riparian systems far beyond the monument's boundaries. These three river stretches offer a rare opportunity for scientific study related to impacts, preservation and restoration - what we have lost and our opportunities for conservation and restoration.
Last updated: March 16, 2018