Powder/Tongue River Basin Water Plan
Technical Memoranda

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

KEY STORAGE FACILITIES

Reservoir:	WILLOW PARK
Date:	27 Feb. 2001
Location:	SENE 24,T52N,R85W
Owner:	WILLOW PARK RES. CO.(BILL DOOLEY-SEC.)
	Willow Park Reservoir's upstream dam face and outlet structure
Year of Construction:	1959
Total Storage:	6,469 acre-feet
Active Storage:	4,457 acre-feet
Area/Capacity Data:	(Source: Undated table on file in the State Engineer's Office, Water Div. II)
	Feet Elevation Area Average Area Volume Released Volume Remaining 0.0 8616.5 0000.0 4457.0 0.5 8616.0 104.5 4352.5 1.0 8615.5 208.9 4248.1 1.5 8615.0 313.3 4143.7 2.0 8614.5 409.2 4047.8 2.5 8614.0 505.1 3851.9 3.0 8613.5 601.0 3856.0 3.5 8613.0 696.0 3760.1 4.0 8612.5 792.8 3664.2 4.5 8612.0 888.6 3568.4 5.0 8611.5 984.4 3472.6 5.5 8611.0 1080.2 3376.8 6.0 8610.5 1176.0 3281.0 6.5 8610.0 1271.8 3185.2 7.0 8609.5 1354.3 3102.7 7.5 8609.0 1436.7 3020.3 8.0 8608.5 1519.1 2937.9 8.5 8608.0 1601.5 2855.5 9.0 860?.5 1683.9 2773.1 9.5 8607.0 1766.3 2690.7 10.0 8606.5 1848.7 2608.3 10.5 8606.0 1931.1 2525.9 11.0 8605.5 2013.5 2443.5 11.5 8605.0 2095.9 2361.1 12.0 8604.5 2165.0 2292.0 12.5 8604.0 2234.1 2222.9 13.0 8603.5 2303.2 2153.8 13.5 8603.0 2372.3 2084.7 14.0 8602.5 2441.3 2015.7 14.5 8602.0 2510.3 1946.7 15.0 8601.5 2579.3 1877.7 15.5 8601.0 2648.3 1808.7 16.0 8600.5 2717.3 1739.7 16.5 8600.0 2186.3 1670.7 17.0 8599.5 2842.4 1614.6 17.5 8599.0 2898.5 1558.5 18.0 8598.5 2954.6 1502.4 18.5 8598.0 3010.7 1446.3 19.0 8597.5 3066.7 1390.3 19.5 8597.0 3122.7 1334.3 20.0 8596.5 3178.7 1278.3 20.5 8596.0 3234.7 1222.3 21.0 8595.5 3290.7 1166.3 21.5 8595.0 3346.7 1110.3 22.0 8594.5 3389.9 1067.1 22.5 8594.0 3433.1 1023.9 23.0 8593.5 3476.2 980.8 23.5 8593.0 3519.3 937.7 24.0 8592.5 3562.4 894.6 24.5 8592.0 3605.5 851.5 25.0 8591.5 3648.6 808.4 25.5 8591.0 3691.7 765.3 26.0 8590.5 3734.8 722.2 26.5 8590.0 3777.9 679.1 27.0 8589.5 3810.6 646.4 27.5 8589.0 3843.2 613.8 28.0 8588.5 3875.8 581.2 28.5 8588.0 3908.4 548.6 29.0 8587.5 3941.0 516.0 29.5 8587.0 3973.6 483.3 30.0 8586.5 4006.2 450.8 30.5 8586.0 4038.8 418.2 31.0 8585.5 4071.4 385.6 31.5 8585.0 4104.0 353.0 32.0 8584.5 4132.0 325.0
	Note: Area information is not provided in the State Engineer's Office table.
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) Willow Park Res 6408R D,I,S 08-26-1939 4457 24-52-085
Designated Use:	Irrigation, Stock, Recreation
Recreational Use:	Fishing, boating
Associated Irrigation Diversions:	(Source: Carmine LoGuidice, Div. II water commissioner/hydrographer)
	Diversion Tributary Jim Crow Rock Creek Sonnesberger Rock Creek Fenton Rock Creek Hallie Rock Creek Fox Rock Creek Lilly Rock Creek Lake DeSmet Rock Creek Johnny Come Early Rock Creek Last Chance Rock Creek Rounder Rock Creek Steady Run Rock Creek Tay Rock Creek Dee Rock Creek Ono Rock Creek Rock Crk. & Piney Ditch Co. Canal Piney Creek Mead & Coffeen (Crossover & 1°) Piney Creek Upper Harvey Piney Creek Lower Harvey Piney Creek Piney & Cruse (Crossover & 1°) Piney Creek Mueller Piney Creek Piney Divide Piney Creek Cleo Piney Creek Mueller & Leitner Piney Creek Prairie Dog (Crossover & 1°) Piney Creek Hilyer & Onslow Clear Creek Frank G. Hopkins Clear Creek Des Moines Clear Creek Watt Clear Creek City of Buffalo (exchange)1 Clear Creek
	1 The City of Buffalo's exchange right out of Willow Park Reservoir is limited to 150 acre-feet at a rate not to exceed 2 cfs.
Associated Industrial Diversions:	None
Operational Discussion:	Cloud Peak Reservoir has been considered a unit with Willow Park Reservoir downstream. 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.
	First release timing, Willow Park 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).
References:	Carmine Loguidice, State Engineer's Office Water Div. 2 water commissioner, interview, 20 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 Evaporative Loss from Willow Park Reservoir:

Lewis Annual Evaporation (in.)	46
Total Storage (acre-feet)	6,469

	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)	3669	3723	3744	3933	4603	4703	4410	4142	3727	3689	3803	3936
Corresponding area (acres)
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)	1.75	1.75	2.25	3.25	3.75	2.75	1.75	1.25	2.25	1.75	1.75	1.75
Net Evaporation (inches)	0	0	0	0.43	1.54	3.276	6.116	5.926	3.04	1.746	0.044	0	TOTAL
Total Net Evaporation (acre-feet)													N.A.

Note: Because an area-capacity table for Willow Park Reservoir was not available, evaporative loss could not be calculated.