7780

• UCREFRP Catalog Number: 7780
• Author: Brooks, J. E., et al.
• Title: San Juan River Seven Year Research Program Summary Report 1992.
• USFW Year: 1992.
• USFW - Doc Type: \
• Copyright Material: NO

videography to quantify potential endangered fish habitat versus
flow on the San Juan River. This methodology provided macrohabitat
morphology information for the San Juan River from the Hogback
Diversion (RM 158) to Mexican Hat (RM 52). Video from 1991 has
been analyzed and 1992 data analysis is in progress.
In the reach between Hogback Diversion (RM 158) and Four Corners
(RM 119), the data thus far indicate that maximum side channel
habitat area occurred at the highest flows. At the lowest flows
examined, side channel area reached its minimum. On the other
hand, backwater area was maximized at low flow. Backwater area at
midrange flows was fairly constant at a level 46 percent less than
the maximum (1991 data). This reach had the most side channel,
backwater, and main channel habitat per mile.
Between Four Corners (RM 118) and Bluff (RM 68) side channel area
was also maximized at the peak flows and minimum at lowest flows
(less than 1200 cubic feet per second). With the exception of peak
flow, backwater area was maximized at the lowest flows and
decreased with increased flow. As observed on the video of the
peak flows in 1991 and 1992, the water encroached ephemeral
tributary stream channels and arroyos creating a group of
backwaters found only at higher flows. Also observed were side
channels becoming active that normally are above the water level.
As the flow dropped from peak to base flow, there was a steady
increase in backwater area. The formation of this backwater habitat
appeared to stem from the flow. reaching a threshold where side
channels became cut off and formed backwaters. In addition, the
decreasing flow exposed and deposited sediment features that caused
the formation of a group of low flow backwaters.
The reach from Bluff to Mexican Hat (RM 67 to 52) had a distinctly
different channel morphology compared to the upper portions of the
river. Backwater and side channel habitat in this reach was
markedly lower and controlled by the geomorphology of the San Juan
canyon. Only at flows of 1,200 cubic feet per second and lower did
low velocity habitat appear in the data, other than backwaters
formed by tributary channel encroachment.
The Remote Sensing and Geographic Information Section is continuing
videography collection of the San Juan River during 1993 to
validate and refine preliminary findings and further detail flow
to habitat relationships.
Hydrology and Geomorphic Characterization - Studies were conducted
in the areas of: (1) geomorphic characterization; (2) river
dynamics; (3) habitat mapping; (4) hydraulic modeling; and (5)
hydrology of the San Juan River in 1992.
Base Map Preparation - A geographically based digital base map was
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