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maintained some flow despite much reduced discharge. Main- <br />channel width was highly variable due to extensive braiding but <br />was generally 40-60 m. The gradient in this stretch of the river <br />was 1.44 m/km, and current velocity was reduced. Water <br />temperatures were warmer than upstream reaches by several <br />degrees, but they exhibited a similar diel range. The warmest <br />main-channel water temperature recorded during any of the surveys <br />was 250 C. Backwater temperatures had greater ranges, and a high <br />temperature of 290 C was recorded. The large number of channels <br />and lower velocity of the San Juan River below Shiprock promoted <br />development of more and larger backwater habitats. Backwaters <br />were commonly associated with, and connected to, the mainstream <br />during August flows. During the October survey, backwaters were <br />r - <br />commonly derived from isolated high-flow stream channels. Large, <br />deep backwaters contiguous with the main channel were rare. <br />Cobble bars and riffles were present throughout the study area, <br />but they were especially common above Shiprock. Only in the <br />lowermost 5 river miles of the study area was current velocity <br />low enough to allow deposition of large amounts of sand, the <br />dominant substrate in that reach. Where the current scoured <br />against large rock faces in the lower reach, a few large, deep <br />pools were present. <br />13