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Gunnison River had higher invertebrate and detritus drift rates when compared to the Colorado River. Temporal Variations (River-Wide by Habitat Type) As noted earlier, for a number of physical, chemical and biological parameters significant differences were found on a river-wide basis between sample periods (one-way ANOVA results can be found in Appendix I). In this section of the report a similar analysis was undertaken; however, an ANOVA by sample trip was done on a habitat specific basis. Habitats considered in this analysis were riffles and runs. COLORADO AND GUNNISON RIVERS Drift 10.00 E E 100 - - ? v _ D I-0.10 r Z W z 0.0, 0 0.00 SPRING 94 FALL 95 SPRING 95 FALL 95 PERIOD - Cala ada DOldhm -4b- Cokwad0 rwarta .. Gu0YS00 DWdlua .:xh Gum- Imam, Figure 15. Invertebrate and detrital drift in the Colorado and Gunnison rivers during for the study period. Physical Parameters-Between the spring and fall of 1994 an increase in the quantity of the size fractions between 0.1 mm and 0.5 mm occurred in the run habitats in the Colorado River. This trend continued through the winter of 1994 and was reflected in the spring 1995 data (Figure 161 The spring runoff of 1995 W W I 2 ., a 0.1 - - - - - 0.00, J?- ad, a1 1 10 IOU 1000 BEER SUBSTRATE SIZE (mm) -SPRM 0 94-x- FALL 94 ? SPRING 95, -- FALL 95 COLORADO RIVER-RIFFLES RIVERBED SUBSTRATE SIZE W ,a 777-11 7&01 - - - - - AM a, 1 10 100 ,000 BED SUBSTRATE &M (mm( , -- ----SPRING 94-x- FALL 94 -- SPRING 96-A-- FALL 95 j Figure 16. The size distributions of substrates in run (above) and riffle (below) habitats in the Colorado River. removed some of these finer sediments, placing the cumulative size distributions intermediate between the spring 1994 and fall 1994/spring 1995 data. Riffle habitats did not demonstrate the same temporal patterns as runs. Within the riffle habitats, the spring 1994 and spring 1995 cumulative distributions were identical. In a similar manner, the fall 1994 and fall 1995 distributions were similar (Figure 16). In both years, the size distribution of the spring samples was greater in the substrate less than 1 mm when compared to the fall distributions. This difference was greatest in 1995. A comparison of the D50 and D16 values for runs and riffles (Figures 17 and 18) indicates that for each sample period, riffles had larger substrates than runs. Significant differences between these habitats were found between the fall 1994, spring 1995 and fall 1995 data. 17