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<br />",~ <br />" ,.~ <br />-.,jJ <br /> <br />'-,1 <br />.:~..~ <br />'.:;.'.: <br />....~. <br /> <br />'1 <br />, , <br />" <br /> <br />, ~) <br /> <br />j <br /> <br />'.,' <br /> <br />:., ~::. <br /> <br />c'., <br />~ <br />l'- <br />,-4 <br />CJ <br />o <br /> <br />3. <br />4. <br />5. <br />6. <br /> <br />Riffle/chute habitat <br />Shallow, sand bottomed habitat (sand shoals and sand bars) <br />Cobble bottomed habitat (cobble shoals and cobble bars) <br />Island area (indirect measure of channel braidedness) <br /> <br />Summaries of these parameters indicated that, in many cases, significant differences existed between <br />geomorphologic reaches, particularly at high and low flows (Table .1). <br /> <br />Bliesner and Lamarra (1995, 1996) also presented results of habitat mapping from airborne <br />videography on the San Juan River by geomorphic reach. Data collected on macrohabitat <br />availability in 1996, as did that collected during previous years, indicated that run habitat is <br />predominant in all geomorphic reaches and is relatively constant, asa percent of total wetted <br />perimeter, between reaches (Table 2). However, some habitat types appeared to vary between <br />reaches. For example, in 1995, shoal habitat decreased from 20 percent of total to 2 percent of total <br />from Reach 2 to Reach 1, while low velocity habitats, which were relatively constant at 1-2 percent <br />of total in the lower four reaches, varied widely between the upper four reaches (Bliesner and <br />Lamarra 1996). <br /> <br />Additional information on habitat characteristics of geomorphic reaches was presented by Bliesner <br />and Lamarra (1996) from work conducted in 1995 and 1996. This included information on physical <br />"and biological characteristics of run, :riffle, and backwater habitats. Physical characteristics <br />measured included depth, velocity, substrate, and depth to embeddedness. Biological characteristics <br />measured included plant biomass, detritus biomass, and macro invertebrate biomass. A study on <br />backwater habitat quality was also initiated during 1995 which was analyzed using the geomorphic <br />reach designations. Physical and biological measurements of backwaters included: <br /> <br />Physical <br />dimensions <br />pebble counts <br />interstitial substrate composition <br />sediment depth <br />light transparency <br />dissolved oxygen <br />temperature <br />pH <br /> <br />Biological <br />nitrates <br />nitrites <br />orthophosphorus <br />ammoma <br />periphyton biomass <br />phytoplankton biomass <br />zooplankton biomass <br />benthic invertebrate density <br />fish biomass <br /> <br />Results of ongoing backwater habitat quality surveys are summarized by Bliesner and Lamarra <br />(1996) and suggest some trends in backwater quality across geomorphic reaches. For example, <br />backwater temperatures were highest in Reach 5 and dropped off in downstream reaches, particularly <br />in canyon-bound reaches like Reach 1 and 2, where shading may be a factor. Backwater volume also <br />exhibited trends that appear to be correlated with channel gradient. Backwater volume was generally <br />highest in the lowermost reaches and Reach 8 (the uppermost reach) where gradient was generally <br />lower. <br /> <br />San Juan River Recovery Implementation Program <br />Summary Report <br /> <br />9 <br /> <br />17 January 1997 <br />PR-576-2 <br />