Powder/Tongue River Basin Water Plan
Technical Memoranda

SUBJECT:	Appendix J Storage Operation and Description CLOUD PEAK
PREPARED BY:	HKM Engineering Inc.
DATE:	March 2002

KEY STORAGE FACILITIES

Reservoir:	CLOUD PEAK
Date:	20 Feb. 2001
Note:	This reservoir began as a natural lake on the main stem of South Piney Creek. It was expanded with dams and Cloud Peak has been considered and operated as part of Willow Park reservoir.
Location:	SESE 9,T51N,R85W
Owner:	ROCK CREEK AND PINEY RES. & DITCH CO.
Year of Construction:	1896
Enlargement History:	1933 (with a re-survey and subsequent filing in 1961), 1968
Total Storage:	4620 acre-feet
Active Storage:	3570 acre-feet
Dead Storage:	Information not available. The dead storage is considerable because Cloud Peak was originally a natural mountain lake.
Area/Capacity Data:	(Source: undated table on file with State Engineer's Office, Water Div. II)
	Feet Elevation Area Average Area Volume Released Volume Remaining 0.0 9725.0 171.11 165.86 000.00 3385.13 1.0 9724.0 171.11 165.86 165.86 3219.27 2.0 9723.0 171.11 165.86 331.72 3053.41 3.0 9722.0 171.11 165.86 497.58 2887.55 4.0 9721.0 171.11 165.86 663.44 2721.69 5.0 9720.0 160.62 165.86 829.30 2555.83 6.0 9719.0 160.62 157.14 986.44 2398.69 7.0 9718.0 160.62 157.14 1143.58 2241.55 8.0 9717.0 153.66 157.14 1300.72 2085.11 9.0 9716.0 153.66 150.17 1450.89 1934.24 10.0 9715.0 146.69 150.17 1601.06 1784.07 11.0 9714.0 146.69 150.17 1740.80 1644.33 12.0 9713.0 146.69 139.74 1880.54 1504.59 13.0 9712.0 146.69 139.74 2020.28 1364.85 14.0 9711.0 146.69 139.74 2160.02 1225.11 15.0 9710.0 132.79 139.74 2299.76 1085.37 16.0 9709.0 132.79 125.88 2425,64 959.49 17.0 9708.0 132.79 125.88 2551.52 833.61 18.0 9707.0 132.79 125.88 2677.40 707.73 19.0 9706.0 132.79 125.88 2803.28 581.85 20.0 9705.0 118.98 125.88 2929.16 455.97 21.0 9704.0 118.98 113.99 3043.15 341.98 22.0 9703.0 118.98 113.99 3157.14 227.99 23.0 9702.0 118.98 113.99 3271.13 114.00 24.0 9701.0 0 113.99 3385.13 0
Dam Construction Type:	Earth Fill
End-of-Month Storage Records:	No
Water Rights:	((Source: Tabulation of Adjudicated Surface Water Rights of the State of Wyoming, Water Division Number Two, Oct. 1999.)
	Reservoir Permit Number Permitted Use Priority Date Volume (af) Headgate Location (S-T-R) Cloud Peak Res. 65R I 07-13-1896 2720 9-51-085 Enl. Cloud Peak Res. 6223R I 09-28-1933 677.68 9-51-085 Enl. Cloud Peak Res. 6906R I 09-22-1961 172.72 9-51-085
Designated Use:	Irrigation
Recreational Use:	Fishing
Associated Irrigation Diversions:	Because of its high elevation and connection to Piney Creek irrigators through the South Fork of Piney Creek and connection with Rock and South Piney Ditch, Cloud Peak Reservoir provides water to a number of irrigators.
	(Source: Carmine LoGuidice, Div. II water commissioner/hydrographer) Diversion Tributary Mowry Basin (exchange water) Rock Creek Jim Crow Rock Creek Sonnesberger Rock Creek Fenton Rock Creek Hallie Rock Creek Fox Rock Creek Lilly Rock Creek Johnny Come Early Rock Creek Lake DeSmet Rock Creek Last Chance Rock Creek Rounder Rock Creek Tay Rock Creek Ono Rock Creek Rock Crk. & Piney Ditch Canal Co. Piney Creek Piney Divide Piney Creek Mueller & Leitner Piney Creek Six Mile (exchange water) Clear Creek
Operational Discussion:	Cloud Peak Reservoir has been considered a unit with Willow Park Reservoir downstream. In the past, operators have been able to store water higher than the top of the dam, thanks to snow drifting across the spillway and ice buildup on the dam. As a result, operators tend to empty the reservoir's active capacity into Willow Park toward the end of the season to avoid carrying water into the next year. Water commissioners point out that operators prefer to drain the reservoir for winter as much as possible (to avoid buildup and possible overtopping) or not drain it at all (to store more water than is apparently possible).
	First release timing, Cloud Peak Reservoir Wet Year Average Year Dry Year 2nd week of July 4th week of June 2nd week of June
	Operators end irrigation releases from the dam on Oct. 1 (the end of the water year). Through an agreement with the U.S. Forest Service, operators release approx. 5 cfs for winter flows.
References:	Carmine LoGuidice, water commissioner, interview, State Engineer's Office, Sheridan, Wyoming, 13 Feb. 2001
	Active Dams, State Engineer's Office Safety of Dams Engineering Div. Database, transmitted by Larry Stockdale, Safety of Dams engineering consultant, 16 Feb. 2001.
	Tabulation of Adjudicated Surface Water Rights of the State of Wyoming, Water Division Number Two, Oct. 1999, database transmitted by Rebecca Mathisen, SEO Technical Services Division administrator, 8 Sept. 2000.

Net Evaporation from Cloud Peak Reservoir:

Lewis Annual Evaporation (in.)	46
Total Storage (acre-feet)	4,620

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Average percent of total storage	56.72	57.55	57.87	60.80	71.16	72.71	68.17	64.03	57.62	57.03	58.79	60.84
Generated storage (acre-feet)	2621	2659	2674	2809	3288	3359	3149	2958	2662	2635	2716	2811
Corresponding area (acres)	165.86	165.86	165.86	165.86	165.86	165.86	165.86	165.86	165.86	165.86	165.86	165.86
Calculations:
Monthly Lewis Evap. (inches)	1.242	1.15	1.794	3.68	5.29	6.026	7.866	7.176	5.29	3.496	1.794	1.196
Monthly Precipitation (inches)	2.25	2.25	3.25	3.75	4.25	3.25	1.75	1.25	2.25	2.25	2.25	1.75
Net Evaporation (inches)	0	0	0	0	1.04	2.776	6.116	5.926	3.04	1.246	0	0	TOTAL
Net Evaporation (acre-feet)	0	0	0	0	14	38	85	82	42	17	0	0	278