Abiotic & Biotic Responses of the Colorado River to Controlled Floods at Glen Canyon Dam, Arizona, USA

Controlled floods from Glen Canyon Dam can rebuild and maintain sandbars in Grand Canyon National Park, but only if timed with tributary sand deliveries. Monitoring data reveal that sandbar erosion after flooding is influenced by discharge levels and tributary sand production. The 2008 flood significantly increased early survival rates of non-native rainbow trout, more than fourfold compared to prior years, due to improved food availability from midges and black flies. While this boosted the tailwater fishery, it also posed a risk to endangered humpback chub through competitive interactions and predation. The study suggests that repeated, strategically timed floods could sustainably restore sandbars while balancing ecological trade-offs for both native and non-native species.

Melis, T. S., Korman, J., & Kennedy, T. A. (2011). ABIOTIC & BIOTIC RESPONSES OF THE COLORADO RIVER TO CONTROLLED FLOODS AT GLEN CANYON DAM, ARIZONA, USA. River Research and Applications, 28(6), 764–776. Portico. https://doi.org/10.1002/rra.1503