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

Shiprock.
Habitat Mapping - During autumn 1992, semi-detailed mapping was
completed from RM 158 to RM 80. Thirty-one habitat types were
mapped on color prints from airborne videography. The habitat
mapping was geo-referenced and digitized, and is awaiting GIS
analysis. Three additional mapping trips are planned for 1993.
Aerial photography and digital contour mapping of one detailed test
reach (RM 133.5 to RM 129.5) has been completed for more detailed
habitat mapping. Baseline habitat mapping was completed in this
reach prior to spring runoff in 1993, but the data have not been
reduced.
Hydraulic Modeling - Survey data were collected for 21
representative secondary channels between RM 158 and RM 80 to allow
hydraulic modeling to predict secondary channel flow as a function
of main channel flow. In addition, the detailed maps for the test
reach (RM 133.5 to RM 129.5) will be used to model this test reach.
The U.S. Army Corps of Engineers HEC-2 computer model is being
used. To date, only limited test runs have been completed to
define data needs and determine accuracy of model predictions.
Ultimately, the model will be used to identify critical flows that
cause major habitat change as predicted from the habitat mapping.
Temperature Monitoring - Nine water temperature monitoring
stations were installed on the San Juan and Animas rivers. Data
collection began in August 1992 and will continue for the duration
of the research period. The data will be used in conjunction with
the habitat mapping data to further characterize habitat.
Biological Response to Hydrograph - Documented reproduction of
Colorado Squawfish (one element of a biological response to the
hydrograph) was limited in 1992 when compared to 1987, although the
hydrograph was typical of a normal natural hydrograph for the San
Juan River. Analyses of the hydrographs, computed spawning dates,
and water temperature data from 1987, 1988, and 1992 indicate that
the documented spawning success was the same in 1992 as in 1988 (1
y-o-y), a very low flow year, and much reduced from 1987 (18
y-o-y), a very high. flow year. Analysis of the longer term
hydrograph indicated that 1987 ended the 5 years with the highest
cumulative flow on record; 1992 ended the 5 years with the lowest
cumulative flow on record.
While a statistical analysis indicated that a significant
difference between the 18 y-o-y captures in 1987 and 1 y-o-y
capture in 1988 and 1992 was calculated, the biological
significance was not determined. Numerous other responses, such as
fish community structure and habitat availability need to be
assessed. Any interpretation of the lack or existence of a
biological response should consider the other variables involved.
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