Auxiliary attraction flow
From BAWiki
Definition
The water injected into the fishway in addition to the operating flow. Auxiliary water is supplied for the purpose of maintaining the appropriate attraction flow in the tailwater and thus the fish’s ability to find the entrances to the fishway and/or ensuring passability (and/or velocity threshold for rheotactic behaviour) in the lower pools with increasing downstream water level.
Synonyms
auxiliary water; auxiliary water flow; auxiliary water supply
Abbreviations
Source
Guideline Upstream Fishways on German Federal Waterways (AH FAA), Bundesanstalt für Wasserbau (BAW) und Bundesanstalt für Gewässerkunde (BfG), Version 2.0, 26/06/2015 (retrieved 10.05.2017)