Last updated: January 20, 2025
Article
Vegetation Study Shows Colorado and Green Rivers Face Ongoing Challenges
Environmental releases, combined with a large spring flood, have slowed but not reversed the effects of dams built in the 1960s.
By the editors of Park Science magazine
Image credit: NPS / Amy Washuta
Many communities in the western United States get their water from the Upper Colorado River Basin. The basin is also home to significant numbers of native plants and wildlife. The Green River is a tributary of the Colorado River and an important part of this freshwater system. Dams completed in the 1960s changed the Colorado and Green rivers’ natural flows. This led to increasing numbers of plants along the riverbanks and narrower river channels. Since 1992, water has been released from the dams to help bring back more natural flows and protect native fish.
A study published in the October 2024 issue of River Research and Applications tells how researchers used images obtained by aircraft and satellites to study vegetation along the rivers. They looked at images collected before and after the dams and during the environmental releases. They found that since 1940, plant growth has increased significantly along the rivers. But over the last 16 years, plant encroachment has slowed, suggesting channel narrowing has also slowed.
The study authors conclude that the environmental releases, combined with a large spring flood in 2011, have slowed but not reversed the effects of the dams. They think this is partly because less water is flowing into the rivers and more of it is being diverted. Large periodic peak flows combined with environmental releases are essential to minimize channel narrowing.
Perkins and others. 2024. Riparian Vegetated Area in Pre-Dam, Post-Dam, and Environmental Flow Periods in Canyonlands National Park From 1940 to 2022. River Research and Applications.