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Keywords:

  • benthic invertebrates;
  • flow disturbance;
  • habitat modelling;
  • productivity;
  • WUA;
  • IFIM;
  • resilience;
  • resistance

ABSTRACT

We describe and demonstrate a model (Benthic Invertebrate Time Series Habitat Simulation) for calculating the effect of changes to flow regimes on benthic invertebrate habitat and population dynamics. The following inputs are required: a hydrograph (discharge time series), habitat–discharge relationship, disturbance–discharge relationship, wetted width–discharge relationship and a recolonization time series. Habitat–discharge, disturbance–discharge and wetted width–discharge relationships are common outputs from instream hydraulic habitat models (e.g. Physical Habitat Simulation, River Hydraulic Habitat Simulation and River2D). Hydraulic habitat models calculate a combined habitat suitability index from physical habitat suitability curves for water depth, velocity and substrate composition and weight this by area to give a weighted usable area (WUA). Because conventional invertebrate habitat suitability curves are based on density estimates, the combined habitat suitability index can be treated as an index of density and WUA treated as an index of potential relative abundance (at the reach scale) in the absence of disturbance due to flow variation (flooding and drying) and biotic processes. Our approach begins with WUA and calculates realizable suitable habitat (i.e. relative abundance) by taking into account the resetting of benthic invertebrate densities by floods and drying and recovery (or accrual) rates and times. The approach is intended mainly to compare the relative amounts of productive invertebrate habitat sustained by natural and modified flow regimes, but it also has the potential for investigating the influence of flow variation on invertebrate population dynamics. We anticipate that the model will be particularly useful for assessing effects of changes in flow regimes caused by diversions, abstractions or water storage on annual benthic invertebrate productivity. Copyright © 2013 John Wiley & Sons, Ltd.