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<br />C'J <br />CoO <br />r-.. Reach 7 (RM 181-213) Below confluence of Animas River to between Blanco and Archuleta. <br />''"'"4 <br />( -', <br />C This reach is characterized by a wide valley, with width similar in dimension to Reach 6. Channel <br />gradient is greater in this reach than all other reaches (0.00213 ft/ft) and sinuosity is similar to <br />Reaches 5 and 6 but significantly less than Reach 8. Reach 7 has less total water surface than Reach <br />6, indicating a narrower and deeper channel than in the downstream reach. Island area in this reach <br />is similar to the adjacent reaches, and the islands are generally stable relative to those in most other <br />reaches. Runs are the prevalent habitat in Reach 7. The municipalities of Bloomfield and Blanco,' <br />NM, are located within the reach. Irrigated land is adjacent to 100 percent of the river channel and <br />one major diversion is located within the reach. Water temperatures in this reach are transitional <br />between the cold temperatures of Reach 8 to warmer temperatures in Reach 6. Water clarity is also <br />relatively high in this reach compared to those downstream, except when Canyon Largo is active. <br /> <br />Reach 8 (RM 214-224) Between Blanco and Archuleta to Navajo Dam. <br /> <br />Valley width narrows significantly in this reach compared to Reach 7. Channel gradient is also <br />significantly less than Reach 7 at 0.0016 ft/ft. Sinuosity in this reach is greater than all other <br />reaches. Density and amount oflow velocity habitat is high in the reach, particularly near the dam, <br />and is probably related to substantial channel alterations in the area and to the low gradient. Cobble <br />substrate is prevalent and pool habitat is more abundant in Reach 8 than in any other reach. The <br />municipality of Archuleta, NM, is located within the reach and approximately 30 percent of land <br />adjacent to the river channel is irrigated. This is significantly less than in Reach 7. One diversion <br />dam is also located within the reach. <br /> <br />/'~. <br /> <br />':'"f. <br /> <br />Summary <br />Eight distinct geomorphic reaches were identified in 1995 following 3 years of investigation and <br />analysis of an array of physical factors in the San Juan River between Navajo Dam and Lake Powell <br />(Bliesner and Lamarra 1993, 1994). Identification of these reaches effectively addressed Objective <br />5.2.2.1 of the LRP and provides the basis t,o evaluate relationships between geomorphology and <br />biologic phenomena in the San Juan River below Navajo Dam. In addition, ongoing studies <br />described by Bliesner and Lamarra (1996) continue to evaluate differences in various physical and <br />biological factors such as substrate embeddedness, biomass, and backwater productivity between <br />the eight geomorphic reaches. <br /> <br />5.2.1.2. <br /> <br />Characterize Habitat for Each of the Reaches. <br /> <br />":F. <br /> <br />Eight distinct geomorphic reaches were identified by Bliesner and Lamarra (1995) for the San Juan <br />River between Navajo Dam and Lake Powell. A substantial amount of data on habitat <br />characteristics associated with these reaches were collected and presented by Bliesner and Lamarra <br />(1995) as part of the process used to delineate the reaches. Some of the parameters used to define <br />geomorphic reaches included aquatic habitat variables. These variables were measured ' <br />at each of three flow levels (high, medium, and low) and represented very generalized, physical <br />habitat attributes induding: <br /> <br />1. Total water surface <br />2. Low velocity habitat (backwater, embayment, eddy, and pools) <br /> <br />San Juan River Recovery Implementation Program <br />Summary Report <br /> <br />8 <br /> <br />17 January 1997 <br />PR-576-2 <br />