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I Findings <br />Results of videography conducted during 1991 showed a strong relationship between flow and <br />backwater habitat and secondary channel habitat. Maximum backwater habitat occurred with flows <br />in the range of 653 to 1,210 cubic feet per second (cfs). Maximum secondary channel habitat <br />occurred at higher flows, in the range of 2,350 to 4,530 cfs. An intermediate range of flows from <br />S 1,210 to 2,380 cfs maximized both habitat types (Pucherelli and Goettlicher 1992). <br />Videography recorded in 1991 revealed some morphologic differences among the various portions <br />of the study area. From RM 158 to RM 119, the area and number of secondary channels decreased <br />with decreased flow. However, between RM 118 and RM 68, secondary channel area decreased with <br />decreased flow while the number of secondary channels remained relatively constant until flows <br />dropped below 1,210 cfs. This suggested that morphology of the river channel between RM 118 and <br />RM 68 allowed secondary channels to exist over a wider range of flows than in the area from RM <br />158 to RM 119 (Pucherelli and Goettlicher 1992). <br />Backwater area generally increased with decreased flow from RM 158 to RM 68. However, <br />backwater area was highest during peak flow from RM 118 to RM 68. This was speculated to be <br />due to a "high flow habitat zone," where backwaters formed only at higher flows as water <br />encroached into ephemeral tributary stream channels. <br />Habitat to flow relationships indicated that the reach from RM 67 to RM 52 had a distinctly different <br />morphology than the area from RM 158 to RM 68. Both backwater and secondary channel habitats <br />were limited in this reach (RM 67 to RM 52) until flows dropped to 1,200 cfs. At higher flows, low <br />velocity habitats were generally confined to backwaters formed by tributary stream channel <br />encroachment. At flows below 1,200 cfs, area and size of backwater and secondary channel habitats <br />from RM 67 to RM 52 were substantially less than from RM 158 to RM 68. <br />Airborne videography habitat mapping was also conducted in 1992 (Goettlicher and Pucherelli <br />1994). During 1992, the San Juan River was mapped on four occasions at flows ranging from 585 <br />to 9,290 cfs. These flows were substantially higher than during 1991, a very dry year, and <br />represented a more normal flow year as well as test flows from Navajo Dam timed to coincide with <br />runoff in the Animas River. <br />Results of habitat mapping in 1992 showed similar patterns to those seen during 1991. Sidechannel <br />areas showed a positive response with flow (i.e., increased with increased flow), while backwater <br />areas responded negatively. The effects of the "high flow habitat zone" were apparent from RM 158 <br />to RM 68 as in 1991. <br />Bliesner and Lamarra (1994, 1995) presented a more detailed analysis of habitat composition relative <br />to flow in the San Juan River. Their analysis used six different periods representing 1992 base flow <br />(December), 1993 peak flow (June), 1993 suspected spawning period for Colorado squawfish (July), <br />1993 fall base flow (October), 1994 peak flow (June), and 1994 summer low flow (August). <br />In the 1993 analysis, runs were found to be the most common habitat type available between RM 2 <br />to RM 158, ranging from 72.4 percent of the total wetted area (TWA) in June at flows of 8,670 to <br />9,990 cfs, to 83.9 percent of the TWA in October at flows of 917 to 1,000 cfs. The distribution of <br />San Juan River Recovery Implementation Program December 1997 <br />Summary Report 14 PR -602 -1 <br />