7072

• UCREFRP Catalog Number: 7072
• Author: Brewer, M. and J. Renne.
• Title: Crystal Reservoir Temperature Study.
• USFW Year: 1988.
• USFW - Doc Type: Lakewood, CO.
• Copyright Material: NO

' y Crystal Reservoir Temperature Study
. Page 6
September 23, 1988
At the Gunnison Gage Near Delta, water temperatures were under-
predicted for all time periods (Table 5). Several irrigation
return flows in this area may be heating up the water. The annual
mean difference and probable difference were 1.17°C and 1.48°C,
respectively.
Statistics at the Gunnison Gage Near Grand Junction are similar to
those at Delta (Table 5). The annual mean difference was 1.65°C
with a probable difference of 1.21°C. Again, unaccounted irrigation
returns may be warming the Gunnison river through- this area.
Model predictions at the stateline gage were underpredicted for all
time periods execpt those in June, August, and September (Table 5).
The mean difference on an annual basis was 0.49°C; the probable
difference was 0.82°C. A plot of regressed versus model water
temperatures is in Figure 2.
For all validation nodes, the annual mean difference was -0.57°C
with a probable difference of 2.03°C. The 50~ confidence interval
of 0.57 ± 2.03 is within the diel fluctuation of water temperatures
throughout this network.
Gunnison River Influences-
A cursory analysis of predicted water temperatures at the confluence
of the Colorado and Gunnison Rivers indicates that the Gunnison
river is a thermal source for the Colorado River during the summer
months. Colorado River temperatures above and below the Gunnison
river are plotted in Figure 3.
CONCLUSIONS
The USGS gages within the study area had useful instream temperature
data. However, all of the gages had missing data, and several gages
had two or more years in a row with no water temperature data. In
addition, none of the gage data were developed from accurate 24-hour
averages; it can only be assumed that instream temperatures acquired
from the USGS represent temperatures somewhere between the minimum
and maximum for the day recorded. Furthermore, accurate bi-weekly
means were unattainable whenever the period included missing data.
Regression aids in the model were used to smooth the instream
temperature data and estimate water temperatures at required nodes.
The regressions were used at headwater nodes to determine initial
water temperatures and at validation nodes for measuring the
performance of the transport model. When there is a difference
between regressed and predicted water temperatures, it must be
assumed that both temperatures are incorrect, because errors exist