Peter G. Griffiths Theodre S. Melis Daniel R. Hartley Robert H. Webb 2000 <p><span>Sediment input to the Colorado River in Grand Canyon, Arizona, is a valuable resource required to sustain both terrestrial and aquatic ecosystems.&nbsp; A total of 768 ungaged tributaries deliver sediment to the river between Glen Canyon Dan and the Grand Wash Cliffs (river miles - 15 to 276).&nbsp; The 32 tributaries between the dam and Lee's Ferry produce only streamflow floods, whereas 736 tributaries in Grand Canyon produce streamflow floods and debris flows.&nbsp; We used three techniques to estimate annual streamflow sediment yield from ungaged tributaries to the Colorado River.&nbsp; For the Glen Canyon and Marble Canyon reaches (river miles -15 to 61.5), respectively, these techniques indicate that 0.065^.10⁶ and&nbsp;0.610^.10^6&nbsp;Mg/yr (0.68^.10^6&nbsp;Mg/yr of total sediment) enters the river.&nbsp; This amount is 20 percent of the sediment yield of the Paria River, the only gaged tributary in this reach and a major sediment contributor to the Colorado River.&nbsp; The amout of sand delivered ranges from&nbsp;0.10^.10^6&nbsp;to&nbsp;0.51^.10^6&nbsp;Mg/yr, depending on the sand content of streamflow sediment.&nbsp; Sand delivered in Glen Canyon is notably coarser (D₅₀ = 0.24 mm) than sand in other reaches (D₅₀ = 0.15 mm).&nbsp; A relation is given for possible variation of this sediment delivery with climate.</span></p> application/pdf 10.3133/wri004055 en U.S. Geological Survey Sediment delivery by ungaged tributaries of the Colorado River in Grand Canyon, Arizona reports