National Parks of the Colorado River Basin

National parks are special places that have been set aside for their abundant, ecologically or historically significant, and often unique resources. These resources are valuable not only for these reasons; in fact, it has been demonstrated that national parks have recreational value, they have value simply due to their existence and mission, they are attractive amenities to residents and investors, and they contribute dollars to local communities through visitor spending.

Dams within the Colorado River Basin have changed ecological and environmental processes—in many cases quite fundamentally—within Dinosaur National Monument, Black Canyon of the Gunnison National Park, Canyonlands National Park, Glen Canyon National Recreation Area, and Grand Canyon National Park by inundating and destroying natural habitats in some areas, creating highly unnatural flow regimes, trapping sediments that are critical for building and maintaining aquatic and riparian habitats, and altering natural water temperatures that fostered native fish communities. As a result of dam operations, spring floods no longer occur as they once did, peak river flows have decreased while flows during non-peak periods have increased, sediments no longer replenish riverbeds, and water temperatures are generally colder and no longer follow seasonal variations. Cultural resources have also suffered due to dams, with some resources being inundated as reservoirs filled, while others are affected by the same changes in flows and sediment supplies that harm natural resources. Analysis has indicated that changes to dam operations could be made to provide conditions more favorable for resource protection while having relatively small impacts on aspects of hydropower generation. Such changes could begin to repair the detrimental effects documented in this report that will eventually detract from the parks’ economic value and their inherent value as symbols of America’s unique heritage.

As populations served by the waters of the Colorado River Basin grow and their water demands increase, ways will be sought to satisfy these demands. Water diversions, new dams, and changes in current water management through alterations in operations of existing dams are all likely to be considered. Uncertainty about changes in precipitation due to climate change will further complicate matters. This report has identified and examined how current water management strategies, primarily the operation of large dams, have affected and continue to affect national park resources in the Colorado River Basin. This baseline information should be strongly considered in decision-making pertaining to water allocation, supply, flow management, and hydropower generation in the Colorado River Basin.