Yampa River Basin Water Resources Planning Model Final Report

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4.5 Operating Criteria File The operating criteria file (yampaTH.opr) describes unique reservoir operations required to simulate the Yampa River basin. Entries for explicitly modeled reservoirs were based on the special water rights operations developed by W.W.Wheeler, Appendix C, Section 10. To simplify review, they are arranged by water supply into the following: 4.5.1 Stillwater Reservoir 4.5.2 Yamcolo Reservoir 4.5.3 Allen Basin Reservoir 4.5.4 Stagecoach Reservoir 4.5.5 Lake Catamount 4.5.6 Fish Creek Reservoir 4.5.7 Steamboat Lake Reservoir 4.5.8 Elkhead Reservoir 4.5.9 Lester Creek Reservoir 4.5. 10 Aggregated Operational Reservoirs Phase IIIa enhancements that impacted the operating criteria file include adding three aggregated reservoirs. Appendix D.11 describes these Phase IIIa enhancements. 4.5.1 Stillwater Reservoir Stillwater Reservoir No. 1 (WDID 583540) is the most upstream of the major reservoirs in the Yampa River (Bear River) drainage. It is owned by the Bear River Reservoir Company and is used to provide supplemental irrigation water supplies to a number of individuals served by several of the major direct flow structures in the upper Bear River. The reservoir has a decreed capacity of 6,392 acre -feet and carries an appropriation date of January 9, 1935 (State Administration Number 33782.31054), making it one of the most senior storage decrees the Yampa River basin. Although it is reported that the outlet for the reservoir is at the bottom of the reservoir, the reservoir company and the water commissioner consider the active storage to be approximately 5,175 acre -feet. This is further evidenced by the reservoir shareholder list, which allocates 5,175 acre -feet among 22 shareholders. Using reservoir and ditch ownership data provided by the division engineer, the individually owned storage accounts in Stillwater Reservoir No. 1 were grouped according to the ditch structures that serve the irrigated land owned by those individuals. Because of the relatively small size of some of these sub - accounts, the smaller ownerships were aggregated into a single account (agg- pool). Stillwater is operated with eight accounts and one water right as shown in Tables 4.5.1 a -c: TABLE 4.5.1A Stillwater Reservoir Accounts Reservoir Account Owner Capacity acre -feet Stillwater 1 BIGMESA 444 Stillwater 2 COALCR 435 Stillwater 3 LINDSEY 394 Stillwater 4 MANDALL 386 Stillwater L 5 STILLWTRCO 979 Operating Criteria File 4 -17