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
by Gerhard Kuhn and Cory A. Williams
Available from the U.S. Geological Survey, Branch of Information
Services, Box 25286, Denver Federal Center, Denver, CO 80225, USGS
Scientific Investigations Report 2004-5095, 22 p., 12 figs.
This document also is available in pdf format:
SIR2004-5095 (2.9MB)
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The citation for this report, in USGS format, is as follows:
Kuhn, Gerhard, and Williams, C.A., 2004, 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: U.S. Geological Survey Scientific Investigations
Report 2004-5095, 22 p.
Abstract
In 2003, the U.S. Geological Survey, in cooperation with
the Colorado Water Conservation Board, Upper Colorado River Endangered
Fish Recovery Program, Colorado River Water Conservation District, Colorado
Division of Water Resources, and Bureau of Reclamation, initiated a study
to characterize streamflow losses along a reach of the Gunnison River
from the town of Whitewater downstream to the Redlands Canal diversion
dam. This describes the methods and results of the study that include:
(1) a detailed mass-balance analysis of historical discharge records that
were available for the three streamflow-gaging stations along the study
reach; and (2) two sets of discharge measurements that were made at the
three stations and at four additional locations.
Data for these existing streamflow-gaging stations were
compiled and analyzed: (1) Gunnison River near Grand Junction (Whitewater
station); (2) Gunnison River below Redlands Canal diversion dam (below-Redlands-dam
station); and (3) Redlands Canal near Grand Junction (Redlands-Canal station).
Data for water years 1995-2003 were used for the mass-balance analysis.
Four intermediate sites (M1, M2, M3, and M4) were selected for discharge
measurements 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 diversion dam, which is about
3 miles upstream from the confluence with the Colorado River.
For the mass-balance analysis, differences between the sum
of the annual cumulative daily mean discharge at the two downstream stations
and the annual cumulative daily mean discharges at the upstream station
ranged from about -8,700 to -69,800 acre-feet (about -.8 to -1.1 percent),
indicating that the downstream discharges generally were less than the
upstream discharges. Moving 3-day daily mean discharge averages also were
computed for each of the three stations to smooth out some of the abrupt
differences between the downstream and upstream daily mean discharges.
During water years 1995-2002, differences between the downstream and upstream
moving 3-day daily mean discharges ranged from about -200 to +100 cubic
feet per second (ft3/s) during one-half of each year, but the differences
had absolute values as large as about 500 to 1,000 ft3/s during the other
one-half of the year. The differences as a percentage of the upstream
discharge ranged from 0 to -10 percent within the interquartile range
and were as small or large as about -60 to +50.
Two sets of discharge measurements were obtained during
water year 2003. For measurement set 1 (February 5-6), discharge was measured
5-8 times over a 24-hour period at sites M1-M4, where measured discharges
ranged from 527 to 608 ft3/s. Discharge was measured once each day at
the Whitewater and below-Redlands-dam stations to verify discharge rating
shifts; the Redlands Canal was not in operation at this time, so measurements
were not needed at the Redlands-Canal station. Recorded 15-minute (unit)
discharges ranged from about 575 to 615 ft3/s at the Whitewater station
and from about 560 to 600 ft3/s at the below-Redlands-dam station during
the February 5-6 period. Because of the inherent error in discharge measurements
(5 percent for measurements rated good), and because the mean discharge
at the below-Redlands-dam station, about 580 ft3/s, was only about 2.5
percent smaller than the mean discharge at the Whitewater station, about
595 ft3/s, it is concluded that there was no measurable streamflow loss
along the study reach during measurement set 1.
For measurement set 2 (May 14-15), discharge in the Gunnison
River was about 2,000 ft3/s and increasing because of high-elevation snowmelt.
Five discharge measurements were made at site M2 and discharge ranged
from 1,668 to 2,117 ft3/s. Measured discharges at the gaging stations
were 2,730 ft3/s at the Whitewater station, 1,268 ft3/s at the below-Redlands-dam
station, and 819 ft3/s at the Redlands-Canal station. In a hydrographic
analysis of unit discharges during May 14-15, and using an estimated traveltime
of about 1.5 hours, the discharge measurements made at site M2 correlated
closely with the unit discharges recorded about 1.5 hours earlier at the
Whitewater station. Also, by using an estimated traveltime of about 3.5
hours, the sum of the unit discharges at the below-Redlands-dam and Redlands-Canal
stations also correlated closely to the unit discharges recorded about
3.5 hours earlier at the Whitewater station. Based on these results, it
is concluded that there also was no measurable streamflow loss in the
study reach during measurement set 2.
Table of Contents
Abstract
Introduction
Purpose and Scope
Description of Study Area
Acknowledgments
Analysis of Historical Discharge Records
Overview of Discharge-Records Computation
Analysis of Shifts
Results for Water Years 1995–2002
Results for Water Year 2003
Streamflow Measurements
Measurement Set 1
Measurement Set 2
Discussion of Streamflow Losses
Summary
References Cited
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