Colorado River

In the Upper Colorado River Basin, smallmouth bass ( Micropterus dolomieu) are considered the greatest threat to native fishes and have been linked to declines in federally protected humpback chub ( Gila cypha), including one population that was rapidly extirpated in the past. Long-term management efforts have been underway to remove smallmouth bass from rivers in the Upper Basin, but smallmouth...

Threatened humpback chub are a native fish found only in the Colorado River Basin. Once found in warm-water canyons in the Basin, the largest population now persists in the Colorado River in Grand Canyon National Park, downstream of Glen Canyon Dam and Lake Powell, the reservoir upstream, created by the dam.

River channels and their adjacent floodplains are ever evolving in form and composition in response to changing patterns of streamflow, the quantity and size of supplied sediment, and feedbacks with the riparian and aquatic ecosystems. Changes in channel form affect aquatic and riparian habitats, which are important for plants, animals, and insects. Erosion and deposition of river channels and...

Partners in Science is a collaborative effort between Grand Canyon Monitoring and Research Center, Grand Canyon Youth, and the National Park Service to provide opportunities for youth to engage in scientific field research in Grand Canyon. This partnership connects youth from diverse backgrounds with the Nation’s natural and cultural resources on 2-3 river-based expeditions on the Colorado River...

The Southwest Biological Science Center (SBSC) conducts and provides scientific information as part of our mission and Federal Trust Responsibility to strengthen relationships and build partnerships with sovereign tribal nations. Here, we highlight a few examples of projects with tribal partners.

Rainbow trout are a desirable sport fish that have been introduced in many locations around the world, including the Colorado River. Although introductions of rainbow trout and other nonnative fishes provide recreational fishing opportunities, they can also pose threats to native fish populations. The Glen Canyon Dam Adaptive Management Program has tasked scientists and managers with identifying...

The Grand Canyon Monitoring and Research Center, a branch of the Southwest Biological Science Center, conducts scientific assessments of the Colorado River in Grand Canyon, focused primarily on Lake Powell and the river ecosystem downstream of Glen Canyon Dam. On this page, we'd like to share related interactive tools and projects by other USGS Centers that cover science across the upper and lower...

USGS Southwest Biological Science Center's Grand Canyon Monitoring and Research Center provided scientific expertise to evaluate potential effects of reservoir management on various resources in Lake Powell and Grand Canyon. This information, published in a cooperator report, was requested and used by the Bureau of Reclamation for decision-making on water flows from Glen Canyon Dam.

Sediment controls the physical habitat of river ecosystems. Changes in the amount and areal distribution of different sediment types cause changes in river-channel form and river habitat. The amount and type of sediment suspended in the water column determines water clarity. Understanding sediment transport and the conditions under which sediment is deposited or eroded from the various...

Grand Canyon National Park is a hotspot for bat diversity. Twenty-two bat species have been documented in the Park, more than any other national park unit.

Aquatic insects are important components of riverine foodwebs as they are prey for fish, birds, bats, lizards, and spiders. The closure of Glen Canyon Dam in 1963 fundamentally altered the hydrology, water temperature, and turbidity of the Colorado River through Grand Canyon. These changes, along with competition with invasive species and limited food availability have led to the decline and...

Glen Canyon Dam has altered flow and sediment dynamics of the Colorado River in Grand Canyon. Before the dam was completed in 1963, the Colorado River carried a large amount of sand, silt, and clay through Grand Canyon, some of which was deposited during spring floods to create large and abundant sandbars. Sandbars in Grand Canyon are valued as camping areas, create aquatic and riparian habitat...