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San Jnan Ziver <br />River Milea 16.2-5.0 <br />Physical and Cheaical Description <br />?his section of the river, although shoving some seasonal effects <br />of crater backing up from Lake Powell, ^aintains cost of its riverine <br />characteristics. The section is contained within a steep walled, <br />meandering canyon, which, under most flow conditions, provides little <br />shallow, low water-velocity habitat. Although river profiles indicate <br />the river is not exceptionally deep (the deepest point measured at <br />3,800 cfs was only 8 ft. at river mile 16.2) it maintains a relatively <br />swift current throughout. The bottoms substrate comprised primarily of <br />sand and a few large slabs of sandstone, which have fallen from high <br />cliffs, overall provides little diversity in aquatic habitat. 8iparian <br />veSetation was extremely sparse. <br />The only permanent backwaters present are associated with side <br />canryon_4 cut through the sandstone by intermittent streass. The back- <br />waters created from this association vary considerably in size and are <br />connected to the main channel only daring periods of relatively high <br />floe. Sediment deposition at the south of each one of these canyons, <br />however, isolate these backwaters as Spring rua-off recedes, trapping <br />the fish that have sought refuge from the swift river. Some of the <br />shallower backwaters dry np during the suer, while the deeper ones, <br />althoagh maintaining water, may no[ provide sufficient water quality to <br />keep the trapped fish alive. The long-term value of these backwaters <br />to the fishery is questionable. <br />7 <br />