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(Appendix A). Site C is the lower Rapid Creek intake; Site I is the middle Cottonwood Creek intake. The water at Site I meets l\ll Secondary Standards; the water at Site C exceeds limits for total dissolved solids, hardness and alkalinity. It should be noted that Site C is about 400 feet lower than Site I. Water tends to pick up more minerals at lower elevations. This is demonstrated by the data in Tables A2 and A3 (Appendix A). Only specific conductance was measured irt the samples; however, a rule of thumb conversion factor is .65 mg/l TDS for one unit of specific conductance. Rapid Creek has a lesser gradient Compared to Cottonwood basin. This allows more precipitation to infiltrate into the ground. This water later surfaces at springs, many of which are near the contact point with the Mesa Verde formation (which is relatively impermeable). The groundwater dissolves soluble minerals as it passes through the Green River and Wasatch formations. This is the primary reason for the higher mineral content in Rapid Creek. Kruzen Springs, which is located at a relatively high elevation, has the highest quality (lowest nrineral content) of any of the water sources. Palisade mixes water from its lowet Rapid Creek diversions with water from other sources; thus, the water which passes through the water treatment plant has always passed the requirements for Secondary Standards. During the wet years, Palisade uses Cottonwood Creek water as much as possible. F. AVERAGE AND FIRM YIELD OJ? WATERSHED 1. General. The tabulation of water rights is only one indication of the water which will be available to the TOWn of Palisade from their watershed. Equally important is the actual physical supply of water available in the basin from year to year. The two parameters normally used to assess physical supply are: average year flow and l:xtreme dry year flow. If there is adequate reservoir storage to carry thl: system over 2-3 dry years, then average year flow may be the most impoI1ant parameter. However, if reservoir storage is limited, then the dry year flow becomes more important. Both average year and dry year flows will be evaluated as part of the operations model discussed in this section. 2. Source of Information Two previous reports have been prepared for the Town which evaluate water resources on the PaliSllde watershed. The first report was prepared in 1979 by Leonard Rice & Associates of Denver. That report used stream gage data from 10 similar watersheds in Western Colorado to develop regression equations which related stream flow, basin area and elevation. These equations were then used, in turn, to calcu1ate the firm yield of the Rapid Creek/Cottonwood Creek watershed. IV-14 I I I I I I I I I I I I I I I I I I I