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� '" <br />�y� mou t to 2E2 cfs. ihis quantity flowina for <br />" one manth would amount to over 17,000 acre-feet, or about <br />ha1* the average anr.uu'_ supply at the reservoir site. It is <br />apparent that stream additions and return flows between Coal <br />Creek and Chimney Rock Creek provide an appreciable portion <br />of diversian reguirements, pa:: in the lo�aer ditches. <br />In orster to determine the releases which would be required <br />from Yamcolo Reservoir to satisfy prior rights, a review was <br />made af the water commissioner's records for the years of 1967. <br />through 1966. For clarification, the ditches have been d,ivi- <br />ded into three groups -- the lower nine, the upper thirteen <br />and the Still�oater. As the Still�oater Ditch is a transbasin <br />diversion, and will divert from the outlet works of the <br />reservoir, 100� of its diversion will be a depletion. The <br />upper thirteen will have abou*_ 25� return flow and additions <br />to augment releases at Yamcolo and the lower nine will derive <br />about half of their requirements therefrom. In normal years <br />the lower ditches have enongh c��ater to meet their requirements, <br />but the upper ditches and the Stillwater Ditch are frequently <br />in short supply. Diversion records for the various ditches <br />show a wide variation from year to year for the same months, <br />the variation being due to several factors such as amount of <br />runoff available, weather conditions during the growing <br />season, and the pattern of snow melt runoff. In some years <br />excess water is diverted simply because it is available; in <br />others, summer rainfall reduces the normal diversion require- <br />ment. On the average the ideal diversion requirement is about <br />3.1 acre-feeti per acre ner year. <br />Tables 12 and 13 show the historic irrigation diversions <br />for the unper thirteen and lo;aer nine ditches during a six year <br />period, as �ompared with the ideal requirements. Averaging <br />the historic diversions for the same months, the normal irri- <br />gation pattern can easily be seen. During :�Say, the average <br />historic diversion exceeds the= ideal. During the main portion <br />of the irrigating season, June and July, the average diversion <br />is far less than the ideal. Toward the end of the growing <br />season, the ideal required flows are d�creased and can nor.mall.y <br />IV •- 4 <br />1 <br />i <br />f� <br />�' I <br />�t <br />r <br />1 <br />� , <br />, <br />' <br />' <br />� , <br />' , <br />' <br />I <br />' <br />� <br />�' , <br />� ' <br />{ <br />{ ' <br />' <br />' <br />�' I <br />�' <br />