1986-06-13_GENERAL DOCUMENTS - C1981018

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-24- 2. Scullion Gulch Geomorphic Characteristics Scullion Gulch is an ephemeral stream which crosses the lower southwest portion of the permit area, draining to the White River. the confluence of Scullion Gulch and the White River is also within the permit area. Scullion Gulch receives drainage from the southwestern and southcentral portions of the permit area, as well as from adjacent lands to the west. Scullion Gulch is approximately one-tenth the size of Red Wash, draining an area of 11 .7 square miles. Approximately half of the drainage area exists within the permit area. Map 102 identifies the alluvial deposits mapped by the permittee along Scullion Gulch. The deposits typically range between 50 and 200 feet in width, with a depth of about 15 feet. ' The deposits were mapped by the permittee to a point approximately 1/4 mile upstream from the permit area, where they become discontinuous. At this location, the deposits do not appear to extend any further up the drainage. The permittee again did not quantify the amount of',land area occupied by the deposits; however, based on Map 102 it appears the alluvial deposits occupy a few hundred acres. Scullion Gulch is incised into both the upper sandstone facies and a portion of the middle sandstone facies, both of which are waterbearing rock units. 0 Five stock-watering ponds exist along Scullion Gulch. As in Red Wash, the ponds serve to retain water for stock purposes until it is lost to seepage or evaporation. They do not hold water year round. Based on the width and areal extent of alluvial deposits along Scullion Gulch, the drainage generally meets the geomorphic criteria and therefore qualifies for further consideration as an alluvial valley floor. Water Availability Criteria - Artificial Flood Irrigation As with Red Wash, flow events along Scullion Gulch were monitored using a crest stage gage. During the two year inventory period conducted by the permittee, only three runoff events were recorded, the highest event measuring 185 cfs. Again,- however, crest-gage data has only limited application for AVF purposes. The mean annual yield estimations provided by the permittee are more applicable for identifying the amount of water which may be expected for Scullion Gulch. The permittees' estimations, derived using Grunsky's formula, indicate that the potential average annual water yield from the Scullion Gulch watershed is 202 acre feet. This corresponds to approximately 0.34 inches of runoff. The amount of water available annually, as estimated through this method, indicates that Scullion Gulch warrants further consideration as a potential alluvial valley floor. Subi rri gati on As with Red Wash, the presence of subirrigation along Scullion Gulch was investigated by the permittee based on the type of vegetation present along the drainage. The permittee has identified a big sage brush - greasewood community along the entire length of unconsolidated alluvial deposits identified on Map 102, and concludes that water is available to the vegetation "on a limited and sporadic basis". The big sage brush-greasewood community, however, is more sparse compared to that community found along Red Wash,