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, , . 0061 .!~ 3.16 reduces the survival of rainbow trout eggs in the upper two to three mil~ SeC- tion of the river (Nehring and Anderson, 1982). Habitat characterization surveys conducted in October 1982 revealed that the ratio of pools and runs to riffles is about 0.7 (Appendix B, Table B.2 and Figures B.l to B.8). Based on observations at eight study reaches, the per- centage of total area comprised of riffles and pool/runs is 57 percent and 43 percent, respectively. In most instances, water depth provides adequate cover in pool/runs, exceeding 30 percent of the total reach area at five of eight study reaches. A section of the river about 0.8 miles in length near the confluence with Seven Castles Creek is unique due to the abundance of deep runs and pools. Cover for adult and juvenile trout is excellent in this sec- tion of river due to extensive macrophyte beds, undercut banks, and depth. Bottom substrates at most sections of the river are dominated by cobble and boulder. Spawning gravels seem to be limited to a few sections located below the dam, near the Taylor Creek and Seven Castles Creek confluences. The study segment for the Roaring Fork River extends from the confluence with the Fryingpan River near Basalt to the confluence with the Colorado River at Glenwood Springs (Figure 3.1). Generally, the physical and chemical characteristics in this section of the Roaring Fork River represent fair to 990d quality habitat for trout (Table 3.8 and Appendix B, Table B.3). A brief description of the more important habitat characteristics is provided below. Habitat characteristics in the Roaring Fork River are quite different in the upper (between Basalt and Carbondale) and lower sections (just below Carbondale to confluence with Colorado River) (Appendix B, Figures B.9 to B.14). In general, the lower section of the Roaring Fork River is much wider and deeper and. contains more pools and runs and more cover for trout than the upper section. Based on six study reaches in the Roaring Fork River (Figure 3.1), the average percentage of area comprised of riffles and pools/runs in the upper section (Reaches 1 through 4) are 30 percent and 70 percent, while values in the lower section are 57 percent and 43 percent, respectively. Similarly, the percentage of area providing cover for juvenile and adult trout is higher in the lower section with a mean value of 49 percent compared to 22 percent in the upper section. Substrate is similar throughout most of the river with boulder and cobble representing the dominant size groups. Limited spawning gravels appear to be available in the mainstem of the river with only