7401 - Laserfiche WebLink

Home Browse Search

3.12 depth of the reservoir is 276 feet with yearly fluctuations in water levels ranging between 20 and 60 feet. Maximum surface water temperatures of 649F to 68'F usually occur in late July or August, while bottom temperatures during this same period range from 40'F to 50'F (Finnell, 1977; Nesler, 1979). The reservoir usually becomes stratified between May and July with a thermal gradient formed at depths of 12 to 30 feet (Nesler, 1979). Due to an abundance of gypsum in the reservoir basin, the water chemistry is characterized by relatively high alkalinity, hardness, pH, and conductivity (Finnell, 1977; Yahnke, 1982). Measured nutrient levels are relatively low in the reservoir, maximum concentrations usually occur in the spring or fall near the bottom; minimum values usually occur in July (Nesler, 1979). The configuration of the reservoir is influenced by the steep shoreline and the location of tributaries. The north shore of the reservoir is moderately steep and has four large bays (Ruedi/Pond Creeks, Hanson Gulch, Smith Creek, and Freeman Creek). These bays provide important habitat for aquatic organisms as a result of more diverse bottom substrates and extensive macrophyte growth. In contrast, the south shore of the reservoir is steep with few perennial tributaries. The section of the Fryingpan River in the project study area is a 14-mile segment extending from Ruedi Dam at an elevation of about 7,510 feet downstream to its confluence with the Roaring Fork River near Basalt at an elevation of approximately 6,600 feet (Figure 3.2). Generally, the physical and chemical characteristics of this section of the Fryingpan River represent good quality habitat for trout. Based on a system that rates important habitat features in Rocky Mountain trout streams (Binns, 1982), the Fryingpan River ranks as a good quality stream for most attributes (Table 3.6). A brief description of the more important physical/chemical characteristics is provided below. Of the physical and chemical parameters measured in the Fryingpan River (Appendix B, Table B.1), temperature appears to be the only potential limiting factor to the fisheries. Due to the deep release of water from the reservoir, mean monthly summer temperatures in the river have decreased about 150F at the dam site and 9'F near Basalt compared to predam records (Nehring and Anderson, 1981). Low-water temperatures in the spring (37'F to 410F) reduces the survival of rainbow trout eggs in the upper two to three mile section of the river (Nehring and Anderson, 1982).