The investigation explored all aspects of water quality associated with a reservoir development on Middle Snake, and advised the Bureau of Reclamation on those aspects needing consideration in formulating development plans. The report focused primarily on needs for downstream water quality control, principally temperature, for fishery enhancement purposes. In addition, project effects on water quality, both downstream and in the reservoirs, under alternative development and operation schemes, have been analyzed, and an appraisal of the need for water quality management facilities in the project structures has been made. The influence of altered quality on present and future uses and the net change to be expected in these uses have been determined, considering both beneficial and detrimental. Available data on water uses, waste sources, and water quality in the study area were examined, evaluated, and projected to provide a base for this water quality analysis.