Concerns about the effects of hydropower operations on downstream environmental resources continue to prompt searches for ways to minimize adverse impacts while maintaining high levels of energy production. As part of the Water Use Optimization Toolset (WUOT) Project, funded by DOE’s Office of Energy Efficiency and Renewable Energy, EVS researchers — in collaboration with researchers from Argonne’s Energy Systems and Infrastructure Analysis Division and from Sandia National Laboratories and Pacific Northwest National Laboratory — have developed an analytical approach and software tool to evaluate how well discharge regimes meet ecosystem management goals downstream of hydropower facilities and assist in the planning and optimization of hydropower operations. The tool, referred to as the Index of River Functionality (IRF), was one of several hydropower planning tools developed for the project.

The IRF tool calculates an overall environmental score based on user-identified environmental objectives and is intended to assist facility operators, natural resource managers, and other stakeholders with the management of water resources. It provides an interface that assists users with input parameters based on the environmental objectives of interest. The tool identifies site-specific environmental objectives, along with metrics for characterizing the degree to which those objectives are met.

The environmental objectives are defined using:

• Relationships between the metrics and hydropower-influenced flow characteristics (e.g., discharge, velocity, depth, water temperature), and
• Consideration of seasonal timing, duration, and return frequency requirements for the environmental aspect associated with the metric.

The IRF tool is capable of integrating information for disparate environmental objectives in multiple downstream locations when users provide appropriate time-series for flow conditions for the various locations. There is also the potential for developing basin-wide environmental performance scores using objectives and time-series of flow conditions for different subbasins.

The IRF tool can be used as a standalone evaluation method or can be integrated with other software tools developed for operational planning, allowing stakeholders to prioritize and optimize environmental performance, hydropower generation, and power revenue goals. It can also be used to support adaptive management by using the results of research and monitoring to refine the way environmental objectives are defined.

Tests of the WUOT for the Bureau of Reclamation’s Aspinall Unit (a cascade system of three dams: Blue Mesa, Morrow Point, and Crystal on the Gunnison River in Colorado) and the California Department of Water Resources’ Oroville-Thermalito Complex (a combination of pump-storage and conventional hydropower generating units on the Feather River) demonstrated that the toolset could identify realistic operational scenarios to increase the value of generated hydropower compared with historic operation while maintaining or improving stakeholders’ ability to meet environmental objectives.