7199

• UCREFRP Catalog Number: 7199
• Author: O'Brien, J. S. and W. J. Miller.
• Title: Yampa and Green Rivers Water Temperature Simulation, Dinosaur National Monument.
• USFW Year: 1984.
• USFW - Doc Type: Fort Collins, Co.
• Copyright Material: NO

11
Monument boundary. The results of the calibration are shown in Table 1
and Figures 8-13. The mean error for all six years of study for the 24
weekly time increments was 0.141C with the single maximum error for a
given time increment of 2.33°C. Some years were more accurately
calibrated than others because of the sporadic availability of water
temperature records for Maybell and Lily gaging stations on the Yampa
and Little Snake Rivers respectively. Whereas the water temperature
records on the Green River at Flaming Gorge and Jensen were nearly
complete, the Maybell was only about 60 percent and the Lily gage about
80 percent complete. Those missing water temperature data were
simulated using the regression models in the water temperature computer
model rackage. The accuracy of the calibration underscores the
reliabiiity in regressing the water temperature simulation at these two
gaging stations.
The historical water temperatures for the six years of study were
predicted at Mathers Hole (river mile 17.5) representing the cobble
reach of the Yampa River from river mile 20.5 to river mile 16.5
upstream of the Green River confluence. This is the river reach
where Colorado squawfish spawn during the months of July and August
(U.S. Fish and Wildlife Service (USFWS), 1984). Migration of the
Colorado squawfish to the spawning reach was observed to-begin at water
temperatures approximately 161C. Spawning behavior was observed when
water temperatures exceeded 19-20°C. The water temperature at Mathers
Hole for the historical discharges and the predicted composite
discharges (simulated) are shown in Figures 14-19.
The greatest deviation from the historical water temperatures at
Mathers Hole for the simulated composite water discharges occurred for
those water years with greatest water volumes and surpluses (see Table 2
and Figures 2-7). Those years displaying the greatest deviation
include 1975, 1982, and 1983. The water temperature deviation from the
historical is greatest for 1983 (Figure 19), the year of highest
discharge and volume of the years studied. A reduction in water
discharge from that historically measured, results in an increase in
water temperature during the months of July and August for the same
meteorological conditions. The NPS minimum streamflow hydrograph has no
effect on the date when the water temperature of 16°C is exceeded except
for 1983, when it is reached approximately one week earlier in the year.
The 20°C departure water temperature for spawning of the Colorado
squawfish would be reached about two weeks earlier in the summer of
1983. It would also reach earlier in 1975 and 1982 by 1.5 and 0.5 weeks
respectively. In four of the six study years (with the exclusion of
1976 and 1977) the annual peak water temperature for the composite flows
are higher than the historical flows.
CONCLUSIONS AND RECOMMENDATIONS
The NPS minimum streamflow hydrograph resembles, in shape and
magnitude, the mean annual hydrograph (Figure 22). This hydrograph has
little effect on the flows and water temperatures for low volume years.
On wetter than average years, the reduced simulated discharge causes
the water temperature to rise faster and peak higher than would have