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<br />~ <br /> <br />. <br /> <br />. <br /> <br />, <br /> <br />Permission by NPS to place staff gage at 3-m~le bar. <br /> <br />Reconnaissance trip pr~or to constant flow dates. <br /> <br />Personnel in place for survey testing during constant <br />flow. <br /> <br />Bathumetric Maooine <br /> <br />Objectives: <br />Generate a preliminary bathymetric map of the upper 16 <br />miles of the lower Colorado R~ver (Lee's ferry to Glen <br />Canyon Dam). <br /> <br />Qualitatively identify and categorize through ground <br />truthing the substrate types established on the Lee' <br />ferry 198~ 5000 cfs map . <br /> <br />Justification: <br />The upper 16 miles of the lower Colorado River is <br />considered a blue ribbon trout fishery. The topography <br />and substrates of this reach greatly influence the <br />ability of trout to spawn, trout food resources to <br />develop and anglers and boats to have access. Based on <br />198~ constant flow photographs, substrates in and along <br />the river have been mapped. 1989 constant flows will <br />allow ground truthing of these mapped units. Tied to <br />this is the need to have a more accurate bathymetric <br />map of the river channel. On site bathymetric <br />measurements to be compared with topographic maps and <br />the 1989 aerial photos will permit develooment of a <br />relatively accurate bathymetric map of this reach. <br />This can then be used by researchers dealing with trout <br />habitat and fishing access. <br /> <br />Methods: <br />Beat down stream from Glen Canyon Dam following the <br />thalweg using sonar to determine bottom topography. <br /> <br />Preliminary identification of transects for future <br />channel x-section measurements. <br /> <br />Ground truth substrates from 198~ map including <br />preliminary analyses of Cladophora substrate and <br />qualitative estimates of Cladophora biomass above and <br />below the 5000 cfs flow level. <br /> <br />ReqUirements: <br />Boats for upstream research. <br /> <br />Personnel and equipment (e.g., sonar) for topographic <br />and substrate analysis. <br /> <br />8 <br />