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I'l !'l'll':~ ~ ~J ~..' _.:.. '.J L ',J 19 Stre~mflows. Figure 2-2 shows the monthly di stribution of average stream diischarge for the South Platte River at the gaging station at South Pl atte, Colorado. Typically, about 70 percent of the annual discharge occurs during spring runoff. The three hydrographs shown are representative of the yearly variations in annual di scharge. The lower hydrograph is a drought condition while the upper one is a year of high runoff. i,' Figure 2-3 shows how the river flow changes with distance from the South Platte Gaging Station to Julesburg. During spring runoff in June the tributaries between Denver and Kersey, e.g. Clear Creek, St. Vrain Creek, etc., contribute flow while diversions occur from Kersey to Julesburg. reducing the streamflow. The high flows at Kersey reflect the contrfbution of the Cache La Poudre River. Summer flow conditions prevail in August with diversions from the tributaries and main stem, while the reaches below the tribu- taries are replenished by return flows. In February, the return flows dominate the flow pattern, but diversions from Kersey to Juleshurg cause predipitous decl ines in flow. Flows then steadily increase along the reaches by return flows from the adjacent aquifer. The average monthly runoff is highly variable, as indicated in Figure 2-2. The average annual native runoff is about 1,440,000 acre- feet. Hol'i!!ver, in 1970, which was a wet year, the runoff was 1,900,000 ~., acre-feet and during the 1953-56 drought, it averaged 842,000 acre-feet per year. Imported Water. Some twenty ditches and tunnel scarry 370,000 acre-feet of imported water from the North Platte, the Colorado, and the , ,<-1 1. . ."..",,.;,,,,, . ~ ~ 1Lb'~~ > ,i,.~_",a~