Environmental Flows: Habitat Modeling

Aquatic habitat modelling is commonly used in riverine wetlands for environmen.tal flow assessments as a means of defining the empirical relationship between environmental variables, and usable habitat for selected target species, life stages or aquatic communities. Aquatic habitat modelling is used to determine environmental flow strategies by estimating the effects of historic, current or future flow scenarios on habitat availability. The origins of aquatic habitat modelling for determining environmental flows can be traced to the development of the Instream Flow Incremental Methodology (IFIM) and the set of computer programs required to implement an IFIM study, i.e. the Physical Habitat Simulation (PHABSIM) system. More recently, other models have used alternative approaches, such as CASiMiR (Computer Aided Simulation Model for Instream Flow and Riparia) that utilises a mix of expert opinion and fuzzy logic based rules to describe the habitat use of target species or the application of multidimensional, i.e., two-dimensional and to a lesser extent three-dimensional hydraulic-habitat models. These enable an enhanced representation of the hydraulic environment and allow the calculation and modelling of turbulent flow properties. However, a knowledge of how biota respond to and are influenced by these properties remains an ongoing challenge to incorporate them into environmental flow setting.