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<br /> <br />2.5 - 3.5 <br />1.8 - 2.5 <br />0.5 - 1.8 <br /> <br /> <br />Table 3.3.--Generalized guidelines for estimating lag coefficients <br /> <br />Loss Rate <br />Study Subbasin (in/hr) <br />1951 1987 <br /> <br />Table 3.1 showed the selected loss rates for the upper and lower <br />basins. Loss rates developed in previous studies were used if they <br />were available for the subbasins. In the other subbasins, the loss <br />rates were determined by using the elevation-vegetation-loss rate <br />relationship. <br /> <br />The areas around Lake Mead and Lake Powell were generally those with <br />the lower loss rates. Those subbasins showed evidence of flash <br />flooding and also had extensive areas of "desert pavement" - a very <br />hard-packed, nearly impervious soil. Many of these subbasins had <br />extensive rock outcrops. The vegetation in these subbasins was very <br />sparse or non-existent. The higher plateaus and mountains generally <br />have higher loss rates. <br /> <br />Some subbasins in the upper basin, generally west and north of Lake <br />Powell, also are areas of low loss rates. These areas are more <br />desert-like and more prone to flash floods than had been anticipated <br />prior to the June, 1987 field trip. <br /> <br />Watershed condition <br />Forests <br />Sage, grass <br />Rocky, canyon areas <br /> <br />"C" value <br /> <br />Table 3.4.--Comparison of loss rates <br /> <br />Upper Grand Canyon <br />zuni and Upper Little Colorado Rivers <br />Puerco Wash <br />Jadito Wash, Pueblo Colorado Wash <br />Lower Little Colorado and Cedar Wash <br />Upper Grand Canyon <br />Kanab Creek <br />Havasu Creek and Lower Grand Canyon <br /> <br />.23 <br />.23 <br />.16 <br />.23 <br />.18 - .23 <br />.23 <br />.18 <br />.25 <br /> <br />38 <br /> <br />.20 - .25 <br />.20 <br />.20 <br />.20 - .25 <br />.20 - .25 <br />.20 <br />.20 <br />.25 <br />