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16 I I I I I I I I I I I I I I I I I I I rimes and rapids are general habitat categories and are referred to as meso-habitats. Pools have low velocity, runs have moderate velocity, rimes are swift areas and rapids are areas with fastest current. Habitat availability is a function of channel morphology and flow. Channel morphology is relatively stable during the base flow period and at this time habitat availability varies mostly with flow. To quantify fish habitat availability, it is necessary to define habitat in terms that distinguish between good, poor and unsuitable conditions for each species and age groups. A value can be assigned to each combination of depths and velocity to indicate the relative value of that condition for a fish species. Habitat types, defined by depth and velocity criteria are mapped at each flow for statistical analysis of surface area and distribution. As a starting point, sixteen habitat types were defined for analysis of habitat availability (Table 1). Pools had a velocity of zero to 0.15 m/sec and had five differing depths from very shallow (< 0.2m) to deep (>2m). The velocity of runs ranged from 0.15 to 0.6 m/sec and depths were the same as for pools. Riffles had velocity ranging from 0.6 to 1.5 m/sec and rapids had velocities over 1.5 m/sec. Table 3. Depth and velocity criteria used to define meso-habitat types. Habitat Types Depth Velocity (m) (m/s) 1 Wetted-pool 0.01 - 0.2 < 0.15 2 Shoal-pool 0.2 - 0.5 <0.15 3 Shallow-pool 0.5 - 1.0 < 0.15 4 Medi-pool 1.0 - 2.0 <0.15 5 Deep-pool > 2.0 <0.15 6 Wetted-run .01 - 0.2 0.15-.6 7 Shoal-run 0.2 - 0.5 0.15 -.6 8 Shallow-run 0.5 to 1.0 0.15-.6 9 Medi-run 1.0 to 2.0 0.15 -.6 10 Deep-run > 2.0 0.15 - .6 11 Shallow-rime < 0.2 0.6 - 1.5 12 Riffle 0.2 to 0.5 0.6 - 1.5 13 Deep-rime 0.5 to 1.0 0.6 - 1.5 14 Very-deep-rime > 1.0 0.6 - 1.5 15 Shallow-rapid <0.5 > 1.5 16 Deep-rapid > 0.5 > 1.5