Glossary Category:
April 11, 2022

303(d) List

The term is short for a state’s list of impaired and threatened waters (e.g. stream/river segments, lakes). States are required to submit their list for EPA approval […]
April 11, 2022

4(d) Rule

Section 4(d) of the federal Endangered Species Act (ESA) directs the US Fish and Wildlife Service to issue regulations deemed “necessary and advisable to provide for […]
April 11, 2022

Abutment

The part of the valley edge against which a dam is constructed. An artificial abutment is sometimes constructed where there is no suitable natural abutment. Right […]
April 11, 2022

Adaptive Management Plan

A system of management practices based on clearly identified timeframes and outcomes with monitoring to determine if management actions are meeting outcomes, and, if they are […]
April 11, 2022

Aerator

Forced air systems used to re-aerate water released downstream of a powerhouse.
April 11, 2022

Ambursen

A buttress dam in which the upstream part is a relatively thin flat slab usually made of reinforced concrete.
April 11, 2022

Anadromous Fish

Fish that begin their life cycle in freshwater, then migrate as juveniles to the ocean, where they grow into adults before migrating back into freshwater to […]
April 11, 2022

Angled Bar Racks

Angled bar racks and louvers are used to direct downstream migrating fish toward bypasses and sluiceways rather than through a hydropower plant. These structural guidance systems […]
April 11, 2022

Appurtenant Facilities

Refers to the non-integral aspects of a hydropower facility such as substations and transmission lines.