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<br />Figure 2. Typical Weighted Usable Area - Discharge relationship. <br /> <br />. Weighted Usable Area <br />25 <br /> <br />5 <br /> <br /> <br />20 <br /> <br />15 <br /> <br />10 <br /> <br />0 <br />0 2 4 6 8 10 12 14 16 18 20 <br />. Discharge (cfs) <br />relationship. <br /> <br />The positive aspects ofIFIM/PHABSIM's flexibility rnay be partially offset by the relatively <br />high cost associated with running this rather data intensive rnodel. A reliable hydraulic sirnulation <br />typically requires one complete set of discharge/water surface elevation data at a mid-range flow for <br />each transect in the IFIM study. In addition, water surface elevation datasets are also required at <br />high and low flows at each transect in order to properly calibrate the IFIM stage-discharge <br />relationship. Development of site-specific habitat suitability curves can also elevate the cost of an <br />IFIM study. Stalnaker et al. (1995) estimate the costofIFIM studies on single river segments to be <br />around $45,000. <br /> <br />IFIMlPHABSIM studies are commonly used to evaluate impacts from hydroelectric power <br />projects and to develop permit conditions on federal permits and licenses (Sta1naker 1995). Because <br />of the relatively high cost of performing IFIMlPHABSIM studies, their utility may be limited to the <br />development of instream flow recommendations on controversial stream segments with high water <br />development potential (Nehring 1979). The CWCB and CDOW have utilized combinations of <br /> <br />. <br /> <br />8 <br />