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""""3 ~ \. .. .... _" ".i ~.... . Ditch and the Michigan Ditch, diverting from the Michigan River; the Skyline Ditch, the Iaramie-Poudre Tunnel and the Bob Creek Ditch diverting from the Laramie River. Two transbasin diversions--the Columbine Ditch and the Wilson Supply Ditch--import an average of 3,000 acre-feet a year to the North Fork from the Laramie River. Twenty-ttlo reservoirs with a combined decreed capacity of 50, 5ll acre-feet are located in the mountains of the Cache la Poudre Basin above Fort Collins. These range in size (water right capacity) from 69 acre-feet (Bellaires Lake) to 10,128 acre-feet (Halligan Reservoir). The historic operation of these reservoirs is reflected in the stream gaging station records. The dif:ficulties and expense of operation and maintenance has reduced the over-all effectiveness and has led to near a~andonment of some of these reservoirs, particu- larly the sma.11er ones, Due to time limitation and the relatively slllS.ll effect on the future basin water supply, any change in the reg1l.1a1lory effect of the mountain reservoirs was not evaluated for this reconnaissance report. . Below the confluence of the North Fork and the Cache la Poudre the river flows thr.ough a short, na=ow canyon before flowing into the plains area near the town of Belleview. Three diversions are made from this reach of the river immediately above the "mouth of canyon near Fort Collins'" gaging station. These are the North Poudre Supply Canal, the City of Fort Collins pipe line, and the Poudre Valley Canal, ,1hich divert a combined average of 58,500 acre- feet per year. An additional diversion above the gage, the North Poudre Canal, diverts 33,300 acre-feet yearly from the North Fork near Livermore, Colorado. During the period of study, 1947-1960, the average annual flow at the "mouth of canyon" gage was 233,300 acre-feet which includes the imports and effects of reservoir regulation above. The proposed Grey Mountain Damsi te is located about a mile upstream from this gaging station. The total water supply above the damsite is the recorded flow at the "mouth of canyon" gage adjusted for the four diversions above the gage (91,800 acre-feet per year) or an an~ua1 average of 325,100 acre-feet. This total supply is termed Mountain SUPP1! and represents the historic water supply available at Grey Mountain De.msite for use in the plains below. A yearly SUllllll8.ry of stream flow in the mountain area is presented in Teble 1 with a description of columns in the Explanatory Notes, . 14