Further validation of PHABSIM for the habitat requirements of salmonid fish

PHABSIM (the Physical Habitat Simulation system) is a set of hydraulic and hydro-ecological models that define changes in physical habitat availability for target species given a change in river flow or channel geometry. The PHABSIM methodology was conceived and developed by the US Fish and Wildlife Service and has been further developed for use in the UK by the Institute of Hydrology (now CEH Wallingford). It has been used at more than 76 sites on 44 rivers in the UK. About half of these have been applied studies to determine the potential impacts of abstraction and channel restoration, and half have been research studies. In particular it has been its use by the Environment Agency for assessing the effect of groundwater and river abstraction on salmonid habitat availability. To support the application of PHABSIM to these issues, the Environment Agency established a programme of research and development entitled "Ecologically Acceptable Flows” (EAF). Phase I of the programme included a wide ranging review of how the PHABSIM models works and confirmed its general applicability to rivers of England and Wales, where management objectives relate particularly to salmonid fish or coarse fish with particular depth and velocity requirements.