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<br />ABSTRACT <br /> <br /> <br />Four general categories of instream flow methods were evaluated to determine <br /> <br />thei r biases relative to each other. <br /> <br />The categories included (1) the Tennant <br /> <br />method, (2) wetted perimeter curves, (3) habitat retention models, and (4) phy- <br /> <br />sica1 habitat simulation (PHABSIM) models. <br /> <br />The Tennant method (30% of average ,flow) was one of the lea&~~>iased <br /> <br />methods, but it does not include biological data and is incapable of identifying <br /> <br />trade-offs. <br /> <br />No wetted perimeter methods were significantly unbiased, and <br /> <br />me thods relying on subj ec tive identification of inflec tion 'points were biased <br /> <br />upwards. <br /> <br />Two habitat retention methods were significantly unbiased. <br /> <br />These <br /> <br />methods included (1) the mean recommendation of all riffles in a st~~~ reach <br /> <br />where all three criteria are met, 'and (2) the recommendation for the single most <br /> <br />. <br />"critical" riffle in a study reach where two of the three criteria are met. No <br /> <br />PHABS 1M models were unbiased. <br /> <br />The IFG-4 model was biased upwards for small <br /> <br />streams and low for large streams. <br /> <br /> <br />,.' <br /> <br />1 <br />