2009-05-22_PERMIT FILE - C1981044A (7)

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presented in Figure 33, Yampa River Average Annual Flow and On-Stream Water Rights. Curve No. 1 relates the average annual flow of the Yampa River to watershed area. As discussed previously, the high elevations of [he Yampa River drainages contribute [he largest proportion of the annual flow from the deeper snow pack. Curve No. 2 represents the summation of potential diversion by absolute on-stream direct flow rights as reported by the Office of the State Engineer (1978) to watershed azeas. The potential diversion to direct flow rights were converted from decreed amounts in cubic feet per second (CFS) to acre-feet per year on the basis of an average 120-day irrigation season. A comparison of curve 1 and curve 2 reveals that the present potential diversions from the Yampa River are small compared to the annual historical stream flow. Curve Number 3 represents the estimate of the water that will be diverted and consumed from the Yampa River under existing conditional rights when they become absolute. Consumptive use as it relates to water availability at the mine site was assumed to be 50 percent of the irrigation rights upstream of the mine, 5 percent of the upstream rights with other uses, 2.5 percent of the upstream storage rights and 100 percent of all the rights downstream of the mine. Curve Number 3 also includes the conditional rights of a large power project that is not on the main stem Yampa River but could affect the operation of a 1980 right. Comparing curve No. 3 with curves No. 1 and No. 2 indicated the Yampa River would be over-appropriated if all conditional rights became absolute. If and when this occurs, a 1980 water right near Craig, Colorado could be called out frequently and would not produce a dependable supply. The exact location within the Yampa River )3asin where the river becomes over-appropriated cannot be determined from this graph because of three (3) assumptions used for its preparation. These assumptions were 1) all rights in each district were considered together, 2) mostly on-stream Yampa rights were considered, and 3) no attempt was made [o order [he rights by basin rank. Current water rights for the Yampa and Williams Fork River are presented in Exhibit 11, Water Rights. The largest conditional water rights on the downstream Yampa River belong to the Juniper Reservoir Project. In addition to [he 1,000 CFS conditionally decreed in 1954, two (2) enlargements for a total of 6,000 CFS were filed in November and December of 1979 (cases 79CS195 and 79CW205). If these rights are approved, the Yampa River will be further over-appropriated. The conditional rights upstream of EC on the Yampa River are listed on Table 2, of Exhibit 11, Water Rights, and the conditional rights on the Williams Fork River mainstream are listed on Table 3, of Exhibit 11, Water Rights. The largest conditional rights on the upstream Yampa River are related [o the Oak Creek Power Project, which will draw water from Oak, Green, Service, Morrison, Middle, and Trout Creeks, as well as the main stem of the Yampa River. The consumptive use of these large conditional rights not on the main stem of the Yampa River are included in the analysis of the conditional rights in Curve 3 of Figure 33, Yampa River Average Annual Flow and On-Stream Water Rights. There are currently no conditional rights in the main stem of the Williams Fork River. During mining, [he mine discharge water will increase the flow of The Williams Fork River. After mining, when the pumps are shut off, the worst-case estimate of stream depletion is 182 gpm (0.41 cfs). This calculation is shown on Table 77, Calculated Inflow To Mine From Rivers. As can be seen from Exhibit 11, Water Rights, EC has more than sufficient water rights to augment this depletion. Surface Water Ouality EC has instituted an ongoing surface water-monitoring program to characterize water quality in the Yampa and Williams Fork Rivers. EC has sampled the Yampa and Williams Fork Rivers at four (4) different locations since 1981. Data from the sampling program include analyses of major ions, minor ions, and trace elements on a quarterly basis and pH, specific conductance, and temperature on a monthly basis. Sampling of the Yampa River stations was discontinued in 1985. The YAW wells and proposed YAW wells, along with surface sites Y-1 Y-2, and Y-3 will be monitoring in conjunction with the development of the North Mains. It is anticipated these sites will be monitored sometime in the future, depending on North Mains development. The No. 5 and No. 6 Mines will have no direct affect on the Yampa River. Sampling sites have been located upstream and downstream of the mine site on both the Yampa and Williams Fork Permit Revision 04-34 2.04-22 Revised 7/2/04