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Grand Canyon and Colorado Plateau conservation advocates : Grand Canyon Trust

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Protecting the Colorado River in Grand Canyon

Before Glen Canyon Dam’s existence, Grand Canyon was characterized by huge sweeping beaches built up with raging snowmelt floods in the spring. The wind picked up the beach sediment and carried it inland, burying a multitude of archaeological sites. Water temperature varied from freezing in the winter to a balmy 85 degrees in the summer. Eight native fish, supremely adapted to these harsh conditions, thrived in the mainstem and tributaries. River runners during the twentieth century began taking advantage of these huge beaches for camping.

Glen Canyon Dam blocked the Colorado River in 1963 and initiated a cascade of ecosystem changes. The dam traps about 90 percent of the annual sediment supply for Grand Canyon — the other 10 percent coming from tributaries within the canyon. In addition, water releases from the dam were altered to generate the maximum amount of peaking hydropower. The loss of sediment supply and the greatly increased rate of erosion from flows designed to maximize hydropower set in motion the continual loss of sediment from Grand Canyon.

The Grand Canyon has suffered dramatically from downstream flows from Glen Canyon Dam. The fluctuating flows that have been a regular part of dam operations since blocking the river in 1963 have eroded beaches, reduced native fish populations and habitat, and undermined sediment support for cultural sites. Grand Canyon’s declining state has been well documented. The 2005 USGS Colorado River report concluded that every resource of concern in Grand Canyon has declined over the past decade. Scientists recently reported that fluctuating flows immediately following the 2008 high-flow release quickly destroyed the beach-building benefits originally conferred by the high flow.

Severe drought combined with burgeoning growth has also put intense pressure on the Colorado River and its canyons, species, habitats, and communities. As reservoir levels have fallen to historic lows, it has become imperative to not only change the way we manage the river but also to reconsider how we operate dams.

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