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Stratum Z began at the confluence with the Green River and extended to Mountain Fuel Bridge at RM 21.3 (34.3 km). The river in this stratum is dominated by a wide alluvial plain, where depths averaged 2.2 ft (0.68 m) during runoff and 1.7 ft (0.52 m) during postrunoff. The average wetted stream width during the entire y?ar was 94.2 ft (28.7 m). An average conductivity of 550 micromhos per cm (umho) was found during prerunoff and increased to an average conductivity of 710 umho during postrunoff. The substrate was sand/silt with occasional areas of exposed bedrock and riffles of rubble and cobble. Average turbidities fluctuated from 105 to 1,451 FTU, the greatest fluctuation recorded for any stratum. Stratum Z had six habitat types represented, but did not contain rapids or deep pools (Figure 6). Also, the lower portion of Z contained no riffles. Stratum Y started at Mountain Fuel Bridge at RM 21.3 (34 km) and ended at the Ignacio Bridge located at RM 59.3 (95.4 km). The river flowed through low canyons of shale where the average depth was 2.2 ft (0.68 m) during runoff and 1.4 ft (0.43 m) during postrunoff sampling periods. Average conductivities were 495 umho during postrunoff samples. The substrate is a mixture of sand/silt in the low velocity habitats to cobble/rubble in the faster areas and rubble/ boulder in the highest gradient areas (near Bitter Creek, RM 31; 49.60 km). Seven of the eight habitat types recorded were present in stratum Y (Figure 6). Stratum X began at the Ignacio Bridge, RM 59.3 (95.4 km) and ended at the highway 64 bridge in Rangely, Colorado, RM 94.2 (151.2 km). This stratum was dominated by a deep canyon intersected with numerous side drainages. The gradient was higher than adjacent strata, as evidenced by the maintenance of cobble/boulder and rubble/cobble riffles. Depths averaged 3.5 ft (1.07 m) during runoff and 1.6 ft (0.5 m) during post- runoff. Conductivities were high (265-459 FTU) and the water was turbid throughout the sampling period. Stratum X was the most diverse stratum relative to habitat types and all eight were recorded (Figure 6). Stratum W started at the Ignacio Bridge, RM 94.2 (151.2 km) and ended at RM 132.5 (213.2 km), 1 mi (1.6 km) above Yellow Creek confluence. The river in this stratum meandered through a relatively broad valley bordered by agricultural lands on one or both sides. Bottom types ranged from sand/silt to rubble/gravel with the majority of the stream bottom composed of the latter. Depths averaged 2.4 ft (0.7 m) during runoff to 2.1 ft (0.6 m) during postrunoff. This stratum had no rapids, few deep pools and few side channels (Figure 6) and was the lowest in gradient. Stratum V began at RM 132.5 (213.2 km) and ended at RM 150 (241.4 km), 2 mi (3.2 km) above the Piceance Greek confluence. The river in this stratum is bordered by pinyon-juniper. Average turbidities were the lowest recorded (18-80 FTU) for any stratum. Conductivities averaged 285 to 729. Stratum V was generally characterized by clear water and the substrate was predominately rubble/cobble and gravel. Conductivities and temperatures were lower for this stratum than for any other during the study. Stratum V contained no rapids or pools (Figure 6). 20.