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<br />the highest peak discharge from a drainage area of over 3,100
<br />square miles is 19,000 c.f.s. which occurred on 2 August 1921.
<br />Most of this flow originated from Grape Creek, a right bank tribu-
<br />tary immediately upstream of Canon City. The second highest
<br />peak of 12,300 c.f.s. occurred on 18 August 1909. At Pueblo,
<br />with a drainage area of 4,686 square miles, the peak discharge
<br />for 79 years of record is 103,000 c.f.s. which occurreu on
<br />J June 1921. The record further shows thst there was a peak
<br />discharge of 30,000 c.f.s. an S August 1902; 25,600 c.f.s. on
<br />12 July 1923; and 19 other discharges over 10,000 c.f.s. Table
<br />4-5 shows the monthly and annual flow in acre-feet for the inflow
<br />gsge at Pueblo Dam and Reservoir located on Arkansas River near
<br />Portland, Colorado. Table 4-6 shows the monthly and annual flow
<br />in ac~e-feet for the outflow gage located 0.4 mile downstream
<br />of the dam. Table 4-7 tabulates the inflow volume-frequency
<br />values at Pueblo Dam. Table 4-8 is the estimated monthly and
<br />annual flows in acre-feet at the Pueblo Dam for the period 1895
<br />to 1973 and includes transmountain diversions. Plates 4-3
<br />through 4-7 presents the inflow hydro graph to Pueblo Reservoir for
<br />the period 1913 to 1970. Plate 4-8 shows the flow duration curve
<br />for Pueblo Reservoir for the period 1941 to 1975.
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<br />4-05. Channel and Floodway Characteristics. Channel capaci-
<br />ties in the reach from Pueblo to John Martin Dam show the effects
<br />of depletion of flows. Downstream from the Pueblo Floodwsy, the
<br />channel capacities, as determined by backwater studies, sre:
<br />below Pueblo Floodway and Levee Extension 5,000 c.f.s.; at Avon-
<br />dale 6,600 c.f.s.; at Nepesta B,200 c.f.s.; at La Junta lO,200
<br />c.f.s.; and at Las Animas 6,500 c.f.s. In general, channel
<br />capacities increase from Pueblo to La Junta and decrease from
<br />La Junta to Las Animas. The decrease can be attributed to the
<br />numerous diversions and the absence of major uncontrolled tribu-
<br />taries entering the main stem to contribute the volume and
<br />moderatelY-high flows necessary to prevent aggradation. The
<br />uamages occurring on the Arkansas River in the reach between
<br />Pueblo and John Martin Dams are the results of inundation of
<br />agricultural land. However, losses are also encountered on
<br />low-lying unprotected urban areas. The travel time from Pueblo
<br />to John Hartin is between 3S and 62 hours. A simplified disgram
<br />showing travel time is presented on Plate 4-9. Discharge rating
<br />curves for stream-gaging stations near Portland, above Pueblo,
<br />and near Avondale, are presented on Plates 4-l0, 4-1l, and 4-l2,
<br />respectively. Other discharge rating curves can bs found in
<br />the Hoster Regulation Manual on Plates 35 through 56.
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<br />~-06. Upstream Structures.
<br />structures above Pueblo Dam.
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<br />There are no flood control
<br />However, there are structures for
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