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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />marked and released into the same run of capture. This process was continued over the entire <br /> <br /> <br />reach. The entire study site was sampled for the second time on July 18 and 19. Block nets <br /> <br /> <br />were not used on the third and fourth samples made on July 20 and July 27. Summer flows <br /> <br /> <br />are regulated by releases from McPhee dam and flows generally vary between 65 and 80 cfs. <br /> <br />Habitat Mauuin!! <br /> <br />Global Positioning Systems and Sonar <br /> <br />In 2000, bathymetric surveys of the channel were taken at four sites using the Global <br /> <br /> <br />Positioning Systems (GPS) and sonar technology. This technique, described in detail in the <br /> <br /> <br />2000 progress report (Anderson and Stewart 2000), is performed from a moving boat and <br /> <br /> <br />gathers a large amount of bathymetry data in a short amount of time. <br /> <br /> <br />The GPS system used in this study was a Javad Oddessy Ll/L2 RTK GPS with <br /> <br /> <br />Glonass and Multi-path reduction options turned on. This system has a published vertical <br /> <br /> <br />accuracy of 15mm +/- 1.5 mm. The sonar unit used was an ODOM Hyrographic Systems, <br /> <br /> <br />Hydrotrac - Single Frequency, Portable Survey Sounder. This unit used a 200kHZ frequency <br /> <br /> <br />with a published accuracy of lcm +/- 1% of depth and an output resolution of lcm. The <br /> <br /> <br />sonar unit pings and logs 20 depth readings per second and the GPS logs one position per <br /> <br /> <br />second. The GPS system output a NMEA GGA string at a rate of 1HZ while the sonar output <br /> <br /> <br />text strings indicating depth at a rate of 10HZ. Data from these instruments was sent to a <br /> <br /> <br />laptop computer and recorded using the COMLOG software from ODOM Hydrographic. <br /> <br /> <br />Because the GPS and Sonar data were received at different rates, all data entries collected by <br /> <br /> <br />the COMLOG software were time-tagged to the millisecond using the computer's clock. The <br /> <br /> <br />depth readings immediately before and after the GPS reading were interpolated by the <br /> <br /> <br />computer clock time (nearest millisecond) to produce the XYZ coordinates used to map bed <br />topography of the river channel. <br /> <br />13 <br />