9513

• UCREFRP Catalog Number: 9513
• Author: Kuhn, G. and C. A. Williams.
• Title: Evaluation of Streamflow Losses Along the Gunnison River from Whitewater Downstream to the Redlands Canal Diversion Dam, near Grand Junction Colorado, Water Years 1995-2003.
• USFW Year: 2004.
• USFW - Doc Type: Reston, VA.
• Copyright Material: NO

20 Evaluation of Streamflow Losses Along the Gunnison River from Whitewater Downstream to the Redlands Canal Diversion
Dam, near Grand Junction, Colorado, Water Years 199x2003
(2) inaccuracies in the real-time discharges because the real-
time discharge rating shift corrections are not completely accu-
rate, and (3) inaccuracies in the instantaneous measurement of
stage at one or more of the stations.
Use of traveltime (discharge lagging) can provide some
improvement in comparison of downstream and upstream dis-
charges. The mass-balance analysis for WY 2003 included an
additional analysis of a discharge data set of unit discharges for
the three stations along the study reach that included some lag-
ging for the discharge at the downstream stations (Coll Stanton,
Bureau of Reclamation, written commun., 2003). Analysis of
these data (similar to that in fig. 10) for the June 24-September
30, 2003, interval (the available period) indicated that differ-
ences between the daily mean discharge sum for the two down-
stream stations and the daily mean discharge for the upstream
station were noticeably smaller than in comparison to using
daily mean discharges that did not include an adjustment for
traveltime. Traveltime through the reach, however, can vary
substantially, from 12 hours or more during low discharge to
4 hours or less during high discharge. Variable traveltimes from
a traveltime/discharge relation could be used to make one-time
comparisons between real-time discharges at the stations, but
simple tabulation of unit discharges for an extended period of
time requires use of a single traveltime, which still results in
some inaccuracy in the comparisons.
When using the real-time unit discharges for the three sta-
tions along the study reach, it is important to remember that
there will always be some perceived differences between the
discharge at the Whitewater station and the sum of the dis-
charges at the below-Redlands-dam and Redlands-Canal
stations because of random discharge computation errors. Even
when using a lag time, the estimated difference between these
discharges often will be 5 to 10 percent, and much more some
of the time. Data for 1 or 2 additional years could be analyzed
in a fashion similar to that used for WY 2003 to determine if the
annual difference between upstream and downstream discharge
will remain small and if the annual trend in variability (negative
difference during low-discharge periods, positive difference
during high-discharge periods; fig. 10) will be the same in
future years. Lastly, if the likely 5 to 10 percent range of per-
ceived difference is unacceptable for administration of water-
use rights and management of water resources, new technolo-
gies, such as acoustic doppler velocity measurement, are
becoming available that might improve the accuracy of real-
time discharge data.
Summary
The U.S. Geological Survey began a study in 2003, in
cooperation with the Colorado Water Conservation Board, the
Upper Colorado River Endangered Fish Recovery Program, the
Colorado River Water Conservation District, the Colorado
Division of Water Resources, and the Bureau of Reclamation,
to characterize streamflow losses in the reach of the Gunnison
River from Whitewater downstream to the Redlands Canal
diversion dam. The need for the study was related to two water-
resourceissues in the reach: (1) the use of web-based, real-time
discharge data for three streamflow-
gaging stations operated in the reach seemed to indicate that the
sum of the discharges at the two downstream stations usually
was less than the discharge at the upstream station, indicating
the likelihood of a losing stream reach, and (2) the losses would
need to be quantified for the possible delivery of upstream res-
ervoir releases made in support of the Upper Colorado River
Endangered Fish Recovery Program, a recovery program for
four endangered upper Colorado River basin fish species. The
releases would be made to augment low-flow discharges at a
fish ladder that was completed in 1996 at the Redlands Canal
diversion dam.
The two principal components of the study were a detailed
mass-balance analysis of historical discharge records that were
available for the three stations along the study reach and two
sets of discharge measurements that were made at the three sta-
tions and at a number of additional locations along the study
reach.
Data for these existing streamflow-gaging stations were
compiled and analyzed: (1) Station 09152500 Gunnison River
near Grand Junction (Whitewater station); (2) Station GUN-
REDCO Gunnison River below Redlands Canal diversion dam
(below-Redlands-dam station); and (3) station RLCGRJCO
Redlands Canal near Grand Junction (Redlands-Canal station).
Data for water years (WY) 1995-2003 were used for the mass-
balance analysis, because data for the below-Redlands-dam sta-
tion were available only for this period. Streamflow losses were
investigated directly (by making discharge measurements) for
discharges of about 600 and 2,000 ft3/s, and indirectly (by anal-
ysis of historical discharge records) for the complete range of
discharges recorded along the study reach. Four intermediate
sites (M1, M2, M3, and M4) were selected for discharge mea-
surements in addition to the existing stations. The study reach is
the approximate 12-mile reach of the Gunnison River from the
Whitewater station downstream to the Redlands Canal diver-
sion dam, which is about 3 miles upstream from the confluence
with the Colorado River.
For the mass-balance analysis, daily mean discharges at
the two downstream stations (below-Redlands-dam and
Redlands-Canal) were summed to provide an estimate of the
total downstream daily mean discharge; this value was sub-
tractedfrom the daily mean discharge at the Whitewater station
(the upstream discharge). Excluding the partial data for
WY 1995, the annual differences between the daily mean dis-
charge sums at the downstream stations and the daily mean
discharges at the upstream station ranged from about -28,700 to
-69,800 acre-ft, or about -1.1 to -5.8 percent of the upstream
discharge, indicating that the downstream discharges generally
were less than the upstream discharges.
Moving 3-day daily mean discharges also were computed
for each of the three stations to smooth out some of the abrupt
differences between the daily mean discharges that are due to
traveltime. Discharge differences and percentage differences