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zi <br />Habitat tvaes and discharge relationships.--While many phy- <br />_ sical, chemical and biological factors determine the quality of fishing <br />streams, the occurrence of shelter and food-producing areas are basic. <br />• Both the total amount and the interspersion of pools, riffles, and <br />deep fast areas are limiting with respect to fish production. It is <br />difficult to define and map these classes precisely; however, this is <br />a practical method for appraising the fishery and estimating relative <br />productivity at different rates of discharge, <br />Habitat types are influenced particularly by depth, volume, <br />and velocity of water, and by bottom characteristics. As the rate of <br />discharge of a stream is reduced, the several water factors are reduced <br />fn the following order of magnitude: surface area, least; depth, next; <br />_ volume,.next; and velocity, most. Typical reductions in stream surface <br />area with reduced discharge are shown in Figures 8 and 9; reductions <br />in depth are shown in Figures 10 and 11. Reductions in volumes of water <br />at typical stations, and in mean velocities at places of discharge meas- <br />urements are shown in Table 5. <br />Table S.--VOLUME AND VELOCITY IN RELATION Ta DISCHARGE <br />Discharge Volume- of ~ Velocity <br />Station c.f.s. Water Cu ft Ft./See <br />I 42 6,299 1.83 <br />22 4,401 1,48 <br />16 4,078 1.30 <br />_ 7 2,782 0,76 <br />VIII 59 15,877 1.79 <br />22 9,102 1,07 <br />_ 14 - 8,520 0,90 <br />8 5,795 0.63 <br />For streams of the size, type and discharge characteristics <br />