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year. A bank along the large island was sampled for stratigraphy in a manner similar <br />to that described above. <br />D. Stream Gage Installation and Operation <br />A recording stage gage was installed along the middle channel of the Platte River at <br />the downstream end of the Output reach in May 2000, 06768035 Platte River Middle <br />Channel, Cottonwood Ranch, Near Elm Creek, NE. The real time stage and discharge <br />data for this gage can be accessed through the Internet (http://www-ne.cr.usgs.gov/rt- <br />cgi/gen_stn_pg?station=06768035). At the time of this writing 5 dischazge <br />measurements have been made. These discharge measurements define the rating <br />curve for this gage. All of the measurements up to this point have been made at low <br />flow, less than 1000 cubic feet per second (cfs), so additional measurements at higher <br />flows will be needed to apply the rating over a larger range of flows. <br />E. Optical Backscatter Sensor <br />We installed an optical backscatter (OBS) sensor in the Output reach adjacent to the <br />stage gage in May 2000. The OBS sensor can measure turbidity and suspended solids <br />concentration by detecting infrared radiation scattered from suspended matter. With <br />proper calibration OBS sensors can be used to measure suspended sediment <br />concentration. The OBS sensor was mounted to a steel pipe driven into the bed of the <br />river. The sensor was oriented orthogonal to the flow in the channel at a depth that <br />would ensure it was immersed at all but the lowest of discharges. The data output <br />from the OBS sensor is a voltage that is recorded at 30-minute intervals to the same <br />data logger that stores the stage data. This data is not currently available on a public <br />Internet site as calibration of the sensor remains a problem. Continued work in <br />calibrating this instrument is planned. <br />F. Serial Still Photography <br />In May 2000 a conventiona135mm camera was installed to routinely (one photograph <br />per day at a set time) photograph the river within the Output reach. Interval <br />photography is a useful technique to monitor geomorphic features in river channels <br />and identify flow patterns with changes in discharge and time. Sequences of <br />photographs can be built up over a period of time to create time-lapse movies. These <br />image sequences can assist in qualifying changes in sandbar size, vegetation patterns <br />and inundation extent as a function of time and water level. Additional cameras will <br />be installed from different vantage points in the Managed reach to document <br />management activities and monitor potential geomorphic responses.