Instream Flow Incremental Method (IFIM)
Instream habitat suitability studies are required for a wide variety of planning applications where aquatic organisms are an important consideration in the decision-making process. At certain flows, for example, the water may be too fast for juvenile fish or velocities may be too high for fish to spawn. At other flows, the water may be too shallow for spawning or suitable spawning gravel may not be covered by water. Identification of instream flow targets that allow fish to flourish are necessary for hydroelectric dam and water supply operators. These targets must be balanced with water management issues such as reservoir level targets, power generation, and recreational boating and fishing. These kinds of habitat studies typically require the Instream Flow Incremental Method (IFIM), one of the most widely used instruments in the world for assessing the effect of flow manipulation on river habitats.
A major component of IFIM is a collection of computer models called the Physical Habitat Simulation Model (PHABSIM). According to the US EPA, these “models incorporate hydrology, stream morphology, and microhabitat preferences to determine relations between streamflow and habitat availability”. EEMS has been enhanced to perform the IFIM analysis, thereby serving as a full capability and highly advanced 3D PHABSIM, incorporating water quality, sediment, toxics and many other highly relevant sub-models. Currently, other PHABSIM models do not simulate water quality. Instead, PHABSIM concentrates on simulation of physical habitat based on depth, velocity, and a channel index. Furthermore, PHABSIM, River2D, and similar IFIM models are restricted to 2D simulation. With full its 3D capability, EEMS has one of the most powerful habitat suitability criteria options currently available.
DSI developed a 2D hydrodynamic, sediment transport, toxics and water quality model for the Lower Athabasca River in Alberta, Canada. Part of this study included habitat analysis for various fish species native to this river.
DSI supported a multi-phase evaluation of the Jacksonville Harbor Navigation Project for USACE. The study uses EFDC+ with Sigma-ZED for hydrodynamic and salinity modeling to evaluate changes to the salinity in the Lower St Johns River. The first phase of this work required detailed habitat analysis related to the salinity impacts on fish in the river.
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Download an example model and run with the free EEMS Demo Version.
This model is used to simulate hydrodynamics of a river and then use Habitat Analysis post-processing features of EE to analyze critical limits and the habitat suitability index of model parameters of water depth, and velocity for two species of fish, muskellunge and burbot. The steps to do this are provided in the How-to-guides in the EE Knowledge Base. The final model is provided for comparison.