These benthic macroinvertebrate data and associated site characteristics were compiled for the purpose of exploring any relationships between large dams in the Colorado River Basin, their flow management and geographical context, and their associated downstream benthic macroinvertebrate communities. The goal of the analyses based upon these data was to understand how dam conditions, specifically hydropower fluctuations for hydropower generation ("hydropeaking") might influence the structure of benthic macroinvertebrate communities, and how this community structure may change with distance downstream from each dam. These benthic macroinvertebrate samples were collected in spring 2015 by scientists from the U.S. Geological Survey's Grand Canyon Monitoring and Research Center and collaborators at Oregon State University, and samples were subsequently processed in the research laboratories of these entities. Samples were collected from the tailwaters downstream of seven large dams in the Colorado River Basin: Fontenelle and Flaming Gorge Dams on the Green River, Navajo Dam on the San Juan River, and Glen Canyon, Hoover, Davis, and Parker Dams on the Colorado River. Samples were collected using a variety of methods depending on the available habitat, including Surber net, ponar dredge, rock scrubbing, Hess sampler, and vacuum suction device methods.