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<br />.; <br /> <br />range in infiltration rates for this ares of 0.2-0.6 inch per hour <br /> <br /> <br />which sverages about 50 percent of the infiltrometer studies dis- <br /> <br /> <br />cussed above. On this basis, a model infiltration rate of 0.5 <br /> <br /> <br />inch per hour was selected for use in ana1ysing high plains tribu- <br /> <br /> <br />taries. <br /> <br />. Mountain Losses. Infi1trometer studies on forest land, mixed <br /> <br /> <br />forest and grassland, and grassland in the mountain areas of the <br /> <br /> <br />South Platte River basin have been conducted over a period of years <br /> <br /> <br />by the U.S. Forest Service and were summarized in a report by <br /> <br /> <br />Dortignoc and Love. Their results showed average rates of 2.37 <br /> <br /> <br />inches per hour for pine forest, 1.94 inches per hour for pine <br /> <br /> <br />forest and grassland mixed, and 1.5 inches per hour for grass- <br /> <br /> <br />land. Using the same factor of 50 percent applied to the infi1tro- <br /> <br /> <br />meter studies for the plains area resulted in a model infiltration <br /> <br /> <br />rate of 1.00 inch per hour in mountain areas. <br /> <br />. Urbanized Losses. The change in loss rates in urbanized areas <br /> <br /> <br />were accounted for by assuming that the area covered by roads, <br /> <br /> <br />driveways, buildings, and parking lots were impervious and would <br /> <br /> <br />not infiltrate rainfall application. The amount of impervious <br /> <br /> <br />area allocated for each type of land use were taken from an Urban <br /> <br /> <br />Storm Drainage Manual prepared for the Denver Regional Council of <br /> <br /> <br />Government by Wright-McLaughlin in 1969. The values used are <br /> <br />shown in table 11. <br /> <br />58 <br /> <br />. <br />