2008 High-flow experiment at Glen Canyon Dam: Morphologic response of eddy-deposited sandbars and associated aquatic backwater habitats along the Colorado River in Grand Canyon National Park

A 2008 high-flow experiment (HFE) at Glen Canyon Dam significantly increased the area and volume of backwater aquatic habitats in Grand Canyon National Park by reshaping eddy-deposited sandbars. The study found that habitat area surged by up to 300% and volume by up to 15 times one month post-HFE, due to elevated sandbar relief isolating backwaters from the main channel. However, subsequent diurnal flow fluctuations eroded sandbars, reducing habitat size but maintaining broader flow-range availability than pre-HFE conditions. Topographic analysis revealed that steady flows sustained more continuous backwater habitat than fluctuating flows, with lower-volume operations yielding greater habitat stability. Monitoring 20% of potential backwaters, the study also documented both native and nonnative fish species in these habitats.

Grams, P. E., Schmidt, J. C., & Andersen, M. E. (2010). 2008 High-flow experiment at Glen Canyon Dam: Morphologic response of eddy-deposited sandbars and associated aquatic backwater habitats along the Colorado River in Grand Canyon National Park. Open-File Report. https://doi.org/10.3133/ofr20101032