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<br />evaluations, we used the Roeske (1978) flood-
<br />frequency relations and Moenkopi Wash # I
<br />sediment-discharge relations to calculate
<br />streamflow sediment yield from all 768 the
<br />ungaged tributaries and extra areas in Grand
<br />Canyon.
<br />
<br /> 10'
<br />I 10'
<br />~ 10'
<br />..
<br />"
<br />i
<br />E
<br />i 10'
<br />'"
<br /> 1 0.2
<br /> 1 0
<br /> 1 0 ' 1 0.' 1 o'
<br />
<br />
<br />Blight Angel Creek
<br />Moenkopi Wash"
<br />-0,-193 A'C4
<br />- - . Renard (1972) Equabon
<br />
<br />10'
<br />
<br />10'
<br />
<br />10'
<br />
<br />Drainage Atea (krrr)
<br />
<br />Figure 9. Streamflow sediment-yield estimates for 768
<br />Grand Canyon tributaries calculated using the regional
<br />flood-frequency estimates of Roeske (1978) and
<br />sediment-rating data from Bright Angel Creek and
<br />Moenkopi Wash #1 compared to the data regression
<br />equation and the Renard (1972) equation.
<br />
<br />The results of the flood-frequency, rating-curve
<br />method are smaller than the results from the data
<br />regression equation and the Renard (1972) equation
<br />(tables 5 and 10). For Reach B, the Marble Canyon
<br />reach, the flood-frequency, rating-curve method
<br />estimates 0.457'106 Mg/yr of sediment, compared
<br />with 0.610'106 Mg/yr estimated from the data
<br />regression equation and 0.593'106 Mg/yr estimated
<br />
<br />from the Renard (1972) equation. The total
<br />streamflow sediment yield from all ungaged
<br />drainage areas was 1.75'106,2.65'106, and 2.65'106
<br />Mg/yr from the flood-frequency, data regression,
<br />and Renard (1972) equations, respectively. Because
<br />all three methods produce reasonably similar
<br />numbers, we chose to use only the simplest relation,
<br />the regional data regression equation, for estimating
<br />total streamflow sediment yield and sand delivery
<br />rates from ungaged drainage areas. These results
<br />appear in table 5.
<br />
<br />Particle-Size Distribution of Streamflow
<br />Sediment
<br />
<br />1C
<br />
<br />Effective management of sediment resources
<br />of the Colorado River requires an estimate not only
<br />of total sediment yield but also of the par1icle-size
<br />distribution of that sediment. The size of the sand
<br />component is of particular interest for the
<br />management and restoration of sand bars in Grand
<br />Canyon (Schmidt and Rubin, 1995; U.S.
<br />Department of the Interior, 1995). Randle and
<br />Pemberton (1987), in constructing a sediment
<br />budget of the Colorado River, estimated that on
<br />average 15 percent of the total sediment yield is
<br />sand-sized particles, based on data from Kanab
<br />Creek and the Little Colorado River. Measurements
<br />of par1icle-size distributions at various other
<br />tributaries provide sand contents ranging from I -
<br />99 percent of total yield with no discernible pattern
<br />(table II). These data were collected from a large
<br />discharge range and thus highly variable sand
<br />contents would be expected.
<br />
<br />Table 10. Annual streamflow sediment yield from ungaged tributaries of the Colorado River in Grand Canyon,
<br />Arizona, calculated using the flood-frequency rating-curve method,
<br />
<br />Sediment Tributary Extra-area Total
<br />-yield sediment yield sediment yield sediment yield
<br />reach River miles (Mgiyr) (Mg/yr) (Mg/yr)
<br />A -15.5 to 0.9 40,700 4,530 45,200
<br />B 0.9 to 61.5 431,000 25,600 457,000
<br />C 61.5 to 87.8 74.200 8,100 82.300
<br />D 87.8 to 143.5 218,000 21,500 240,000
<br />E 143.5 to 156.8 33,100 7,500 40,500
<br />F 156.8 to 225.8 460,000 27,800 488,000
<br />G 225.8 to 276.0 384,000 13,200 397,000
<br /> TOTAL , ,642,000 I 08.000 1,750,000
<br />
<br />STREAMFLOW SEDIMENT YIELD 19
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