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001511 information is available for most local areas. An example of the effect of vegetation on infiltration rates is shown by Croft (1953) who reports that surface runoff from aspen-herbaceous area amounts to only 0.01 inch per year from summer rains. The runoff from a herbaceous cover was about double this, and from a bare ar ea it was 60 times as much. ',' - /\~.;.; .:{ ;~;.. '.-..;. ';', '.'",'.- '., Changes in the vegetation brought about by man and his animals 'may have marked effects on the runoff. For example, Dunford (1954) found on small plots that grazing of a bunchgrass cover increased the surface runoff from 1 inch under no grazing to 2 1/2 inches under moder- ate grazing, and to 3.2 inches under heavy grazing. Erosion increased only slightly with the change from no grazing to moderate grazing,but doubled under heavy grazing. In the Badger Wash study in Colorado (USGS, USFS, 1960), the runoff rat iofrom grazed compared to ungrazed areas varied from 1. 1 to 2.0 with an average' of about L 2. In a pine forest removal of the litter under the pine stand increased the surface runoff by about 13 times (from O. 12 to 2.2 inches) the first year after removal, but the effect decreased with time, vanishing to zero the eighth or ninth year after removal,of the'litter.. Several investigators have found an increase in runoff when brushlands are converted to gras s (Patrie, 1959, and Pillsbury, et aI, 1961). In appraising the supply of water for a stock pond, the possibility of vegetative modification should be considered. -.~u" .,. .';, ".' ~.". .', :~~:.~~;.:':....:~ .. r'O,: ~i:i:';;f;; :-:~ -~~~~~"- ':~; .. . . '~-"': prainage channels ~i0~'}' ~~r!ii}\(j. il."",., .t{~~fL1t2~~ t,:0~~J;' :~: ~:~. '.......,..".,. ,:,.::>"., .'..'" ::;~:>t~~E;; Drainage dens ity may be a direct clue to expected amount of, runoff in local areas. Hadley and Schumm (1961) found a relation between the annual runoff and the drainage density in the upper Cheyenne River Basin. For example, a 5-acre watershed with 270 feet of drainage channel, had about 3 times the runoff of a watershed of similar size, with only half as much channel. Thus, in a local area the relative length of vis ible chan- nels may be a helpful index to the expected J:unoff in areas of si'milar watershed conditions. Size of watershed The effects of watershed size on the runoff can be quite important in estimating the total yield of ephemeral streams. The ru noff in small local storms tends to be absorbed in the channel and can cause a market reduction in the unit runoff as larger areas are considered. In the upper Cheyenne River Basin the average annual runoff from a 50-acre watershed was approximately 3 acre-feet; however, runoff was only double this from a 200-acre watershed (Hadley and Schumm, 1961). Kepple (1961) reports losses of 25 acre-feet per mile of dry channel in Arizona and estimates the maximum to be much higher. Merely increasing the drainage area is therefore probably not the most efficient way of increasing the supply; ;~i<)<~.J .~, "" " -"..." ..... .: '. ,..~' '::{~..>::~::~~: 20 '.-'- .... p,' . .... .'.