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<br />( <br />, <br /> <br />.) <br /> <br />. <br /> <br />. <br /> <br />l <br /> <br />0751 <br /> <br />Canon City, the river erosses alluvial deposits and is more tranquil in <br />nature. Truck farming predominates on irrigated land just east of <br />Canon City, Wheat, eorn, hay, alfalfa, and sugar beets are also grown <br />in this reaeh. <br /> <br />The natural streamflow of the upper Arkansas River results from <br />snowmelt from the high mountain peaks bordering the basin, rainfall, <br />and return flow from irrigated land, This flow, however, is supple- <br />mented by eight transmountain diversions ineluding the new Charles H, <br />Boustead Tunnel. Average flow in 1962-71 for the other seven diversions <br />was 71,370 acre-feet per year. The Boustead Tunnel, which began divert- <br />ing in 1972, is expected to bring an average of 69,200 acre-feet per <br />year to the Arkansas River basin as part of the Fryingpan-Arkansas <br />Projeet. Average flow at 13 current streamflow gaging stations on the <br />mainstem Arkansas River is given in table 1. <br /> <br />Three reservoirs on tributaries of the upper Arkansas River-- <br />Turquoise Lake, Twin Lakes Reservoir, and Clear Creek Reservoir--store <br />water for release during times of critical irrigation and industrial <br />r <br />demand. The current combined usable storage of these reservoirs is <br />186,400 acre-feet. The Fryingpan-Arkansas Project will increase this <br />storage by 363,700 acre-feet (including 234,000 acre-feet of storage <br />in Pueblo Reservoir on the Arkansas River mainstem west of Pueblo). <br />River hydrographs during a reservoir release are shown in figure 2. <br /> <br />As table 1 indicates, the upper Arkansas River basin has an area <br />of over 5,000 square miles. It includes all of Lake, Chaffee, Fremont, <br />and Custer Counties, and parts of Saguache, Park, Teller, El Paso, and <br />Pueblo Counties, Precipitation in the basin ranges from less than 10 <br />to more than 40 inches per year, generally increasing with elevation. <br />On an annual basis, and assuming no change in storage, about 86 percent <br />(4 million acre-feet) of the water entering the basin is consumed by <br />evapotranspiration and about 14 percent leaves the basin as surface- <br />and ground-water outflow (P. A, Emery, written commun, , 1972). <br /> <br />TRAVEL TIME OF RESERVOIR RELEASES <br /> <br />Records of 51 reservoir releases made during the period 1939-71 <br />were analyzed to show the relation of release travel time to river flow. <br />Figure 3 shows this relationship. It indicates that time of travel of <br />reservoir releases varies from 30 to 70 hours depending on the ante- <br />cedent river flow, the travel time being longer for lower river flows. <br /> <br />The time scale shows the number of hours elapsed between the re- <br />lease from Twin Lakes Reservoir and the arrival at the Colorado Canal <br />headgates. The time of release was determined either directly from <br />chart records for the outlet of Twin Lakes, or by subtracting about l~ <br />hours from the time the release arrived at the Granite gaging station <br />(07086000). The time of arrival at the Colorado Canal headgates was <br /> <br />5 <br />