The Colorado River carves its route from high in the Rocky Mountains through a vast landscape of canyons and deserts transporting millions of tons of sand and silt downstream every year. This water borne sediment creates a unique riverine ecosystem that is constantly shifting as beaches and sandbars accumulate and erode with the seasons. The beaches along the Colorado River through Grand Canyon are crucial components of the ever changing riparian ecology along the river and have played a central role in human use of the river corridor for millennia.

Prior to the construction of large dams and reservoirs in the 20th century, the Colorado River’s flow fluctuated dramatically with high water during spring snowmelt in the Rockies and low water during late summer and fall. Glen Canyon Dam changed everything. Starting in 1963 when the reservoir behind the dam began to fill, the US Bureau of Reclamation managed the flow of water through the dam to optimize hydropower production. It reduced the seasonal fluctuations and introduced new daily fluctuations as electric demand rose in the afternoons and ebbed overnight. The river remained cold all year and 90 percent of its sand and silt became trapped in Lake Powell behind the dam. As a consequence, the beaches along the river through Grand Canyon lost the great majority of their sediment supply. The clear river steadily scoured the beaches sending sand downstream to Lake Mead.

River runners first noticed and protested these changes in the late 1960s and 1970s because beaches were the only places for rest and camping in most parts of the narrow, boulder and cobble strewn canyon. River runners had particular trouble with the daily fluctuating flows from the dam. The large pulses of water during times of high electricity demand changed the character of the rapids and caused flooding and stranding at beaches and campsites.

River guides alerted the conservation community to these alarming changes and encouraged their clients to write letters to politicians and the media to raise public awareness and advocate for modifications to how Reclamation released water from the dam.

Archeologists and biologists joined the chorus of protest because the steady loss of beaches uncovered and eroded ancient indigenous sites and altered species compositions along the river. Shrubs and other vegetation invaded the remaining beaches, non-native species gained a foothold, and native fish rearing habitat declined.
By the 1980s, public pressure from citizens and river running organizations along with litigation from environmental groups resulted in a series of studies led by the US Bureau of Reclamation to clarify and quantify the impacts of Glen Canyon Dam on downstream resources in the Grand Canyon. Dubbed the “Glen Canyon Environmental Studies” (conducted in two phases), this research led to passage of the 1992 Grand Canyon Protection Act and the subsequent establishment of the Glen Canyon Dam Adaptive Management Program (GCDAMP).

In 1996, on the eve of the creation of GCDAMP and just months before the first “beach building” high flow experiment, Grand Canyon River Guides launched its Adopt-a-Beach (AAB) program to begin documenting changes in beaches and shorelines in the Grand Canyon. This successful volunteer citizen science program continues to the present day.