Laserfiche WebLink
22 <br />regular intervals along the cable. Where wading was possible, the depth was measured <br />with a top-setting wading rod. Otherwise, depths were sounded using a calibrated <br />sounding reel and weight from a boat that was attached to the cable (Buchanan and <br />Somers 1969). The water surface elevation was measured at each cross-section using <br />GPS or differential leveling. Submerged streambed elevations were calculated by <br />subtracting the depth at each interval from the water surface elevation for the transect. <br />Additional sets of transect data were collected during April and May using a boat- <br />mounted GPS receiver in conjunction with a high-precision echo sounder and acoustic <br />doppler current profiler (ADCP). The Green River survey was conducted during April <br />25-27 at flows of 200-207 m3/s, May 16-18 at about 204-238 m%, and during May 27- <br />28 at 405-441 m%. The Yampa River was re-surveyed May 24-25. During this period, <br />the Yampa River was experiencing a secondary peak runoff (the first occurring about two <br />weeks earlier). Discharge increased steadily from 194 m3/s on May 24 to 248 m3/s on <br />May 25. Positions, antenna elevations, depths, and velocities were logged for each cross- <br />section, and streambed elevations calculated by subtracting the measured depth and the <br />distance from the transducer face to the base of the GPS receiver from the measured <br />elevation of the receiver. This procedure eliminated the need to correct for the <br />submersion depth of the transducer, which varied depending on the weight and loading of <br />the boat. <br />The post-runoff transect surveys were conducted between July 25-26 on the <br />Yampa River and August 8-10 on the Green River. Discharge was 7 m3/s and 38 m3/s in <br />the Yampa and Green Rivers, respectively, during these surveys. Transect data in the <br />Yampa were collected primarily with GPS and conventional total station survey