Environmental mitigation at hydroelectric projects: Volume 1. Current practices for instream flow needs, dissolved oxygen, and fish passage

Abstract

The first report of the Environmental Study examines current mitigation practices for water quality [specifically, dissolved oxygen (DO)], instream flows, and upstream and downstream fish passage. This review describes information on the types and frequency of mitigations methods in use, their environmental benefits and effectiveness, and their environmental benefits and effectiveness, and their costs. Information on mitigation practices was obtained directly from three sources: (a) existing records from the Federal Energy Regulatory Commission (FERC), (b) new information provided by nonfederal hydropower developers, and (c) new information obtained from the state and federal natural resource agencies involved in hydropower regulation. Information on specific mitigation practices was obtained from 280 projects, more than 40% of all the projects licensed during the 1980s that were identified a priori as having the mitigation requirements of interest. Of all projects receiving FERC licenses or license exemptions since 1980, instream flow requirements are the most common mitigation requirement, followed by requirements for downstream fish passage, DO protection, and upstream fish passage facilities. The proportion of projects with environmental mitigation requirements has increased significantly during the past decade.