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? T <br />o Develop, test, and validate predictive habitat models for the rare Colorado <br />River fish. <br />Rationale - Modeling is a valuable tool that can be used for <br />simu ating and predicting responses of organisms to <br />environmental changes. The Instream Flow Methodology <br />developed by the Instream Flow Group at the Western Energy <br />and Land Use Team in Fort Collins, Colorado includes a <br />PRABSIM model (species utilization curves, channel structure, <br />usable habitat, and hydraulic components) that describes <br />relationships between fish and selected habitat parameters <br />(i.e., microhabitat), a macrohabitat model (including <br />temperature, water quality, species suitability criteria, and <br />usable macrohabitat), habitat network model (including <br />representative reaches, critical reaches, total usable <br />habitat based upon time series, effective habitat over time, <br />and population data), and an institutional model that <br />combines water law, policies, etc.. This methodology is a <br />comprehensive modeling effort that will allow comparison, <br />simulation, and prediction of effects due to changes in any <br />component of the model. This tool can be used to predict <br />discharge conditions of different water development <br />scenarios, to predict water terperature from reservoir <br />releases and trace the changes in temperature downstream, and <br />to estimate the availability of usable habitat by life stage <br />and species under different flow regimes. <br />Considerations - The predictive ability of a model is based <br />upon the detail of information used in the models, accuracy <br />in obtaining the information, relation between parts of the <br />model and how the models interface. <br />Therefore, input is needed from all potential users in the <br />model design and linkages. Since the primary use of the <br />models will be for predicting available habitat for rare fish <br />by life stage, it is imperative that the field biologists <br />review the data on habitat utilization carefully, determine <br />if significant differences occur by sampling gear and rivers, <br />and evaluate existing data to be certain that the habitat <br />utilization curves are representative and accurate based on <br />their expert opinion. They should also have adequate input <br />on the design of surveys for measuring the channel cross- <br />sections of representative or critical reaches to be certain <br />that the "cells" or "windows" adequately describe the habitat <br />conditions for these reaches. It is extremely important to <br />identify/describe habitat conditions in the utilization <br />curves that are not being used by the various life stages or <br />species so that habitat preferences can be established. <br />Habitat conditions that are routinely used in the models <br />include water temperature, depth, water velocity, and <br />10