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<br />002406 <br /> <br />13, 1966, all discharge measurements are made at a third location that is 15 m upstream <br />from the recording gage. We refer to this location as the Lees Ferry cableway. Because <br />of the distance between the Upper Cableway and the recording gage, a staff gage was <br />installed at the Upper Cableway in April 1924 to help constrain stage change during <br />discharge measurements. This gage is known as the "cable gage." For most of the <br />discharge measurements made at the Upper Cableway, stage was measured at both the <br />cable gage and the recording gage, <br />In his analysis of bed change at Lees Ferry, Burkham (1986) argued that the <br />behavior of the bed at the three cableway locations was similar, and he included <br />measurements made at all ofthese locations in a single time series. He calculated <br />minimum bed elevation by subtracting the maximum depth, recorded on the discharge <br />measurement notes, from the recording gage height. Thus, bed elevations for <br />measurements made at the Upper Cableway were determined based on the gage height <br />measured 1.5 km downstream. We recalculated the time series of minimum bed <br />elevation separately for measurements made at the Upper Cableway and measurements <br />made at the Lower Cableway, and calculated water surface elevations independently for <br />those locations. <br />The minimum bed elevations that we report for all Upper and Lower Cableway <br />measurements were calculated as the difference between water surface elevation and <br />maximum depth. Maximum depth was determined by inspection of each USGS <br />discharge measurement note for all 4353 measurements made at both cableway locations <br />from August 3, 1921, to December 1, 1966. Three thousand nine hundred ninety-six <br />measurements were made at the Upper Cableway, 350 were made at the Lower <br />Cableway, and seven were made from a boat before a cableway was constructed. The <br />maximum depths were tabulated with the data analyzed by Topping et al. (2003), which <br />include the date, channel width, cross-sectional area, and recording gage height for each <br />measurement, and the cable gage height when measured. We calculated the water <br />surface elevation for each measurement. The calculation varied depending on whether <br />the measurement was made at the Upper Cableway or the Lower Cableway and whether <br /> <br />16 <br />