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• Because evapotranspiration exceeds precipitation in the lowlands surrounding the lease area, perennial <br />water sources in the general area are limited to a few small springs in the headwaters of the Red Wash <br />Basin about six or more miles north of the permit area. However, a number of stock-watering ponds have <br />been constructed at lower elevations within the two watersheds (see Map 1 for the purpose of catching <br />storm runoff for animal use until it is lost to seepage or evapotranspiration. The contribution of snowmelt <br />runoff to these ponds is probably low since snowpack accumulation at the lower elevations is generally not <br />sufficient to overcome local soil moisture deficits during the melt season. <br />The disposal site area was included in the inventory of water sources conducted as part of the hydrologic <br />study. Vegetative changes in and immediately upstream from Darwin Reservoir and Red Wash Reservoir <br />No. 2 provide some indication that seeps exist at these two locations during spring runoff. These potential <br />seep areas have been totally dry when examined and are probably the result of localized perched water <br />seeping to the surface. Vegetative changes on the east side of Red Wash also imply that wet springs have <br />been located on or adjacent to the permit area. Water courses on and adjacent of the disposal site are <br />normally dry, and flow only in response to heavy rainfall or snowmelt. <br />DoRignac (1960) reports that infiltration rates measured on the Mesaverde Formation in an ungrazed area <br />in southwestern Colorado averaged 3.75 inches per hour in the pinyon-juniper stands and 2.37 inches per <br />hour in the intervening open areas. A nearby grazed site had an infiltration capacity of 1.71 inches per hour <br />in the pinyon-juniper stand and 1.07 inches per hour in the open areas. These latter values are presumably <br />• more representative of the sandy soils of the lease and adjacent area, where grazing is extensive. <br />II.C.2.b.1 Flow Characteristics The potential average annual water yield from the lease area streams has <br />been estimated using Grunsky's Formula (Grunsky, 1908; Sellars, 1965). According to this method <br />Q = aP' (for P <_1/(2a)) (1) <br />and <br />Q = P - 1/(4a) (for P>_ 2 1/2a)) (2) <br />where Q is the long-term average annual runoff, in inches; P is the long-term average annual precipitation, <br />in inches; and a is a runoff coefficient, in inches''. A value of 0.004 was assumed for a based on hydrologic <br />judgement and guidelines set forth by Hawkins (1976). Using this assumed value, 1/(2a) equals 125.0. <br />Because this is greater than P (9.5 inches), equation 1 is used for determining the average annual runoff <br />from the ephemeral streams of the area, with a resulting value of 0.36 inches. This compares favorably <br />with estimates made by Dortignac (1960). Thus, Scullion Gulch and Red Wash potentially contribute an <br />average of 228 acre-feet and 2358 acre-feet, respectively, to the White River. The amount of water actually <br />yielded by these streams to the White River, however, is likely lower because of the presence of <br />stock-watering ponds at the lower elevations. <br />. Permit Renewal #3 (Rev. 8/99) II.C-9 <br />