Evaluation of Streaniflow Losses Along the 
 

Gunnison River from Whitewater Downstream 
 

to the Redlands Canal Diversion Dam, 
Front Cover: 

Left photograph: Gunnison River about 2 miles downstream from Whitewater station (photograph by 

Paul Diaz, U.S. Geological Survey). 

Right photograph: Gunnison River near midpoint of study reach photograph by Paul Diaz, U.S. 

Geological Survey). 

Back Cover: 

Gunnison River at Redlands Canal diversion dam: Redlands Canal is to the right of the dam, 

and the fish ladder is to the left and immediately downstream from dam (photograph by Cory Williams, 

U.S. Geological Survey). 
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 

Prepared 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 the 


BUREAU OF RECLAMATION


Scientific Investigations Report 2004–5095 

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior 

Gale A. Norton, Secretary 

U.S. Geological Survey

Charles G. Groat, Director 

U.S. Geological Survey, Reston, Virginia: 2004 

For sale by U.S. Geological Survey, Information Services


Box 25286, Denver Federal Center


Denver, CO 80225


For more information about the USGS and its products:


Telephone: 1-888-ASK-USGS


World Wide Web: http://www.usgs.gov/


Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 


endorsement by the U.S. Government.

Contents
 iii 

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1


Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2


Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3


Description of Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Analysis of Historical Discharge Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Overview of Discharge-Records Computation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5


Analysis of Shift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7


Results for Water Years 1995–2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8


Results for Water Year 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11


Streamflow Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16


Measurement Set 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16


Measurement Set 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16


Discussion of Streamflow Losses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19


Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20


References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21


Figures 

1. Map showing location of streamflow-gaging stations and miscellaneous discharge-measurement 

sites along the Gunnison River study reach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2


2–12. Graphs showing:


2. Selected statistics of daily mean discharge for the Whitewater station before (1916–65) 


and after (1967–2003) major completion of the Aspinall Storage Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6


3. Discharge, shift, and percentage difference between discharge and discharge rating 


for measurements made at the Whitewater station, water years 1995–2002. . . . . . . . . . . . . . . . . . . . . .8


4. Discharge, shift, and percentage difference between discharge and discharge rating 


for measurements made at the below-Redlands-dam station, water years 1995–2002 . . . . . . . . . . . .9


5. Discharge, shift, and percentage difference between discharge and discharge rating 


for measurements made at the Redlands-Canal station, water years 1995–2002. . . . . . . . . . . . . . . . .10


6. Distribution of percentage differences for applied shifts for measurements made at 


stations along the Gunnison River study reach, water years 1995–2002. . . . . . . . . . . . . . . . . . . . . . . . . .11


7. Moving 3-day daily mean discharge for stations at the upstream and downstream 


ends of the Gunnison River study reach and differences between the discharges, 


water year 1996. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13


8. Distribution of differences between moving 3-day daily mean discharge at the upstream 


and downstream ends of the Gunnison River study reach, water years 1995–2003. . . . . . . . . . . . . . .14


9. Distribution of differences between moving 3-day daily mean discharge at the upstream 


and downstream ends of the Gunnison River study reach when discharge at the 


below-Redlands-dam station is less than 2,000 cubic feet per second, water years 


1995–2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15


10. Moving 3-day daily mean discharge for stations at the upstream and downstream ends 


of the Gunnison River study reach and differences between the discharges, 


water year 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17


11. Distribution of unit discharges for stations at the upstream and downstream ends 


of the Gunnison River study reach and distribution of discharge measurements made


at miscellaneous discharge-measurement sites along the reach during measurement 


set 1, February 5–6, 2003.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18


12. Unit discharges for stations at the upstream and downstream ends of the Gunnison 


River study reach and discharge measurements made at site M2 during measurement 


set 2, May 14–15, 2003.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

iv 

Tables 

1. Streamflow-gaging stations and miscellaneous discharge-measurement sites along the 

Gunnison River study reach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 

2. Cumulative annual and annual mean discharges for streamflow-gaging stations at the 

upstream and downstream ends of the Gunnison River study reach and difference 

between these discharges, water years 1995–2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 

CONVERSION FACTORS, DATUMS, ABBREVIATIONS, AND ACRONYMS 

Multiply By To obtain 

acre-foot (acre-ft) 1,233 cubic meter 

cubic foot per second (ft3

/s) 0.02832 cubic meter per second 

foot (ft) 0.3048 meter 

inch 25.4 millimeters 

Vertical coordinate information is referenced to the North American Vertical Datum of 

1988 (NAVD 88). 

Horizontal coordinate information is referenced to the North American Datum of 1927 

(NAD 27). 

BOR Bureau of Reclamation 

CDWR Colorado Division of Water Resources 

IQR Interquartile range (between the 25th and 75th percentiles) 

RPWA: Redlands Power and Water Authority 

WY	 Water year—A continuous 12-month period representing an annual hydrologic cycle 

selected to present data relative to hydrologic or meteorological phenomena. The 

water year used by the U.S. Geological Survey runs from October 1 through 

September 30, and is designated by the year in which it ends. 
 v
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 

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 report 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 –28,700 to 

–69,800 acre-feet (about –1.1 to –5.8 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) (about –10 to 1 percent) 

during one-half of each year, but the differences had 

absolute values as large as about 500 to 1,000 ft3

/s (about 

–60 to +50 percent) during the other one-half of the year. 

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 belowRedlands-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. 
2 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 

Introduction


The Gunnison River is a major tributary of the Colorado 

River and provides about 42 percent of the streamflow of the 

Colorado River at the Colorado–Utah State line (Kuhn and 

Parker, 1992). Administration and management of water 

resources in the Gunnison River basin are shared by many 

water-resource agencies, including the Colorado Division of 

Water Resources (CDWR) and the Bureau of Reclamation 

(BOR). A responsibility of the CDWR is administration of 

water-use rights for agricultural, industrial, and municipal 

108o35' 

users. A responsibility of the BOR is management of the 

Aspinall Storage Unit, which consists of Blue Mesa, Morrow 

Point, and Crystal Reservoirs. 

Since the mid-1990s, the use of web-based, real-time discharge data has become increasingly important for the administration of water-use rights and management of water resources 

in the Gunnison River basin. One particular reach along the 

Gunnison River where these data are used is from the town of 

Whitewater downstream to the Redlands Canal diversion dam 

(fig. 1). Three streamflow-gaging stations (fig. 1) (hereinafter 

referred to as station or gaging station) that provide real-time 

108o25' 

39o

05' 

39o

00' 

0 2 4 MILES

50 

6 

M1 

M2 

M4 

M3 

70 

Below-Redlands-dam 

Redlands Canal diversion dam 

Whitewater Creek 

Colorado River Sink Creek 

Gunnison River 

GRAND JUNCTION 

Streams base: 

U.S. Geological Survey, Digital Line Graph, 1:100,000, 1974, 1985,

 Albers Equal Area Conic projection NAD83, Standard parallels

 37o

30'N and 47o30'N, central meridian 105o00'W, NAD83. 

Redlands-Canal 

Redlands 

Ca nal 

70 

WHITEWATER 

Study 

reach 

Whitewater station 

station station 

Roads base: 0 2 4 KILOMETERS 

ESRI, 1:1,000,000, 1999, Albers Equal Area Conic projection, 


Standard parallels 37o

30'N and 47o00'N, central meridian 105o00'W, NAD83.


Elevation base: 

U.S. Geological Survey, National Elevation Dataset, 1:100,000, 1990,

 Universal Transverse Mercator, Zone 13N, NAD83.


EXPLANATION 

Whitewater 

station Streamflow-gaging station and name as used in this report

M1 Miscellaneous discharge-measurement site and name as used in this report 

(See table 1 for additional station and site details) 

DENVER 

Study area 

COLORADO 

South Pl atte River Yampa R 

Colora do R 

Figure 1. Location of streamflow-gaging stations and miscellaneous discharge-measurement sites along the Gunnison 

River study reach. 
 3 

discharge data are in operation (as of 2003) in the reach. During 

1995–2002, use of real-time discharge data for these three stations seemed to indicate that the sum of the discharges at the 

two downstream stations (a main channel and a canal 

station) usually was less than the discharge at the upstream station (only a main-channel station), indicating a general loss of 

streamflow in the reach (Coll Stanton, Bureau of Reclamation, 

and Jerry Thrush, Colorado Division of Water Resources, oral 

commun., 2002). 

The Gunnison River also is important in the Upper 

Colorado River Endangered Fish Recovery Program (Recovery 

Program) (U.S. Fish and Wildlife Service, 2002a). The 

Recovery Program, established in 1988, was implemented to 

conduct a long-term recovery program for four endangered 

upper Colorado River basin fish species—the Colorado pikeminnow, razorback sucker, bonytail, and humpback chub—that 

are protected under the Federal Endangered Species Act of 

1973. These endangered fish species once thrived in the 

Colorado River system, but water-resource development, 

including the building of numerous diversion dams and several 

large reservoirs, and the introduction of nonnative fish resulted 

in large reductions in the numbers and range of the four species 

(U.S. Fish and Wildlife Service, 2002b). 

In March 1994, the Department of the Interior designated 

1,980 miles of the Colorado River as “critical habitat” for the 

Colorado pikeminnow, razorback sucker, bonytail, and humpback chub (U.S. Fish and Wildlife Service, 2002c). In the vicinity of Grand Junction, the designated critical habitat includes (1) 

the Gunnison River from Delta downstream to the confluence 

with the Colorado River at Grand Junction, (2) the Colorado 

River from the Gunnison River confluence upstream to the 

Grand Valley Canal diversion dam (the “15-mile reach”), and 

(3) the Colorado River from the Gunnison River confluence 

downstream to about Salt Creek (the “18-mile reach”). [Note: 

Delta, Grand Valley Canal, and Salt Creek are outside of the 

study area and are not shown in figure 1]. 

Movement of endangered fish from the 15- and 18-mile 

reaches on the Colorado River into the Gunnison River reach 

has not been possible since about 1917, when the existing 

Redlands Canal diversion dam (fig. 1) was completed. In 1996, 

a 350-foot fish ladder was built by the Recovery Program at the 

Redlands Canal diversion dam; the ladder provides upstream 

access to 57 miles of historical habitat that had been inaccessible for nearly a century (U.S. Fish and Wildlife Service, 2002d). 

However, during low-flow conditions [about 1,000 cubic feet 

per second (ft3

/s), or less] in the Gunnison River, diversion by 

the Redlands Canal, which has a decreed capacity of 850 ft3

/s, 

might decrease discharge flowing through the fish ladder to the 

point that fish cannot move upstream. The ladder requires 

100 ft3/s to operate and an additional 200 ft3/s are needed to 

help the fish navigate through shallow areas downstream from 

the dam (U.S. Fish and Wildlife Service, 2004). 

The Recovery Program has identified recommended flows 

for the Gunnison River. The BOR intends to prepare a draft 

Environmental Impact Statement to describe potential effects of 

operational changes to the Aspinall Unit and its authorized 

Introduction

purposes that are related to compliance with the Endangered 

Species Act (Coll Stanton, Bureau of Reclamation, written 

commun., May 3, 2004). An important aspect of any operational change is the resulting change to the Gunnison River; 

therefore, it is necessary to understand the streamflow-loss 

characteristics of the Gunnison River, particularly along the 

reach from Whitewater downstream to the Redlands Canal 

diversion dam, which is thought to be a losing reach. To better 

understand the streamflow-loss characteristics of this reach, the 

U.S. Geological Survey (USGS) began a study in 2003, in 

cooperation with the Colorado Water Conservation Board, the 

Recovery Program, the Colorado River Water Conservation 

District, the CDWR, and the BOR, to characterize streamflow 

losses in the reach of the Gunnison River from Whitewater 

downstream to the Redlands Canal diversion dam. Results of 

the study could help in refining operational release rates from 

the Aspinall Storage Unit to support the Recovery Program, as 

well as release rates for other purposes. 

Purpose and Scope

 The purpose of this report is to describe the methods and 

results of a study of the streamflow-loss characteristics of the 

Gunnison River from Whitewater downstream to the Redlands 

Canal diversion dam. Specifically, this report describes the 

methods and results of the two principal components of the 

study that include (1) a detailed mass-balance analysis of 

historical discharge records that were available for the three 

gaging stations along the study reach, and (2) two sets of discharge measurements that were made at the three stations and at 

four additional sites. 

For the mass-balance analysis of historical discharge 

records, data for these current (2003) gaging stations (fig. 1, 

table 1) were compiled and analyzed: (1) Station 09152500 

Gunnison River near Grand Junction (hereinafter the “Whitewater” station), operated by the USGS; (2) Station GUNREDCO Gunnison River below Redlands Canal diversion dam 

(hereinafter the “below-Redlands-dam” station), operated by 

the CDWR; and (3) station RLCGRJCO Redlands Canal near 

Grand Junction (hereinafter the “Redlands-Canal” station), also 

operated by the CDWR. Data for water years (WY) 1995–2003 

were used for the mass-balance analysis, because data for the 

below-Redlands-dam station were available only for this period 

(table 1). For WY 1995, data for the below-Redlands-dam 

station only are available for March 1–September 30, but in this 

report, the period is referred to as “WY 1995.” 

Although the below-Redlands-dam and Redlands-Canal 

stations are about 0.7 mile downstream from the Redlands 

Canal diversion dam (fig. 1, table 1), streamflow losses were 

investigated only for the reach from the Whitewater station 

downstream to the Redlands Canal diversion dam (fig. 1). It was 

assumed that the sum of the discharges at the below-Redlandsdam and Redlands-Canal stations, whether recorded or measured, was the same as the discharge in the Gunnison River just 

upstream from the diversion dam; hence, for purposes of the 
--

--

-- -- --

-- -- --

-- -- --

-- -- --

-- -- --

4 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 

Table 1. Streamflow-gaging stations and miscellaneous discharge-measurement sites along the Gunnison River study reach. 

[--, not applicable; USGS, U.S. Geological Survey; ND, not determined; CDWR, Colorado Division of Water Resources; RPWA, Redlands Power and 


Water Authority]


Station or site 

name as used 

in this report 

(figure 1) 

Complete station name 

Distance 

downstream 

from Whitewater station 

(river miles) 

Drainage 

area 

(square 

miles) 

Operating 

agency 

Period of 

discharge 

record 

(water year) 

Streamflow-gaging stations 

Whitewater station Station 09152500 Gunnison River near Grand 7,928 USGS 1897–98; 

Junction 1902–06; 

1916–2003 

Below-Redlands-dam station Station GUNREDCO Gunnison River below 12.64 ND CDWR 1995–20031 

Redlands Canal diversion dam 

Redlands-Canal station Station RLCGRJCO Redlands Canal near 12.52 CDWR 1975–2003 

Grand Junction 

Miscellaneous discharge-measurement sites 

M1 3.10 ND 

M2 5.68 ND 

M3 7.89 ND 

M4 9.92 ND 

Other site 

Redlands Canal diversion dam 11.83 RPWA 

1Station is operated only as a real-time station for purposes of water-rights administration and water-resources management— 

No historical daily mean discharge records are available. 

study described in this report, it also was assumed that there 

were no streamflow losses from the diversion dam downstream 

to the two stations. Streamflow losses were investigated directly 

(by making discharge measurements) for discharges of about 

600 and 2,000 ft3

/s, and indirectly (by analysis of historical discharge records) for the complete range of discharges recorded 

along the study reach. 

Prior to making the discharge measurements along the 

study reach, two reconnaissance trips were made during 

January 2003 to evaluate the geologic, hydrologic, and physical 

characteristics of the study reach and to select intermediate 

measuring sites between the upstream and downstream gaging 

stations. Four intermediate sites (M1, M2, M3, and M4; fig. 1, 

table 1) were selected for discharge measurements in addition 

to the current stations. Originally, five sets of discharge measurements were proposed to be made, but because of the results 

of the first two sets (described later in this report), it was determined that the additional measurement sets were not needed. 

Although streamflow transit losses along the Gunnison 

River for Recovery Program releases from the Aspinall Storage 

Unit eventually might require investigation from the release 

point downstream to the Redlands Canal diversion dam, the 

scope of the current study was limited to the reach from the 

Whitewater station downstream to the Redlands Canal diversion dam. Estimation of streamflow transit losses upstream 

from Whitewater will be more difficult because of extensive 

modification of streamflow by irrigated agriculture and the 

much longer distances involved. 

Description of Study Area 

The study area 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 (fig. 1). The 

Redlands Canal (properly named “Redlands Power Canal,” but 

commonly, and in this report, referred to as “Redlands Canal”) 

has operated since about 1906, but the existing dam was built in 

1917. The primary purpose of the canal is for power generation, 

but some of the diverted water also is used for agricultural irrigation. 

Elevations along the river range from about 4,560 feet at 

the below-Redlands-dam station to about 4,630 feet at the 

Whitewater station, but elevations are about 400–600 feet 

higher on top of the canyon walls that are along some parts of 

the study reach. Precipitation rates are typical of the arid to 

semiarid climate and average about 9 inches annually 

(Western Regional Climate Center, 2004). Rangeland (mixed, 

herbaceous, and shrub and brush) and forest (evergreen, mixed, 

and deciduous) predominate the high-desert landscape, 
5 

accompanied by minor amounts of residential area and a few 

gravel pits (U.S. Geological Survey, 1992). 

Snowmelt during late spring and early summer in the 

mountainous headwaters of the Gunnison River basin provides 

most of the streamflow to the study reach. With the exception 

of occasional monsoonal-thunderstorm events and minor, infrequent snowmelt, the surrounding highlands adjacent to the 

study reach contribute little streamflow to the main stem of the 

Gunnison River (Butler and Leib, 2002). Since major completion of the Aspinall Storage Unit (1967), the timing and quantity 

of streamflow have changed at the Whitewater station. Snowmelt peak flows during April–July are attenuated, and low flows 

during August–March are larger after completion of the 

Aspinall Storage Unit in comparison to the more natural flow 

conditions prior to completion of the unit (fig. 2). Nevertheless, 

mean annual discharge decreased only slightly from about 

2,577 ft3/s (1,867,000 acre-ft) during 1916–65 to about 

2,538 ft3/s (1,838,000 acre-ft) during 1967–2003. Discharge 

during the study period (WY 2003) generally was less than the 

10th percentile discharge (for WYs 1967–2003) during the first 

half of the water year and generally was between the 10th and 

25th percentiles, except for a few days of higher flow, during 

the second half of the water year (fig. 2). 

The geology within and adjacent to the study reach predominantly consists of Mesozoic sedimentary rock formations 

and Quaternary alluvium (Bankey, 2004). The oldest formation 

in the area is the Brushy Basin Member of the Jurassic Morrison 

Formation, which is composed primarily of multicolored claystone and mudstone (bentonitic). The Brushy Basin Member 

outcrops along the western flanks of the area and often is overlain by Quaternary landslide deposits. The Cretaceous Burro 

Canyon Formation and the Cretaceous Dakota Sandstone Formation overlie the Brushy Basin Member throughout the area 

and form sandstone-topped cliffs along the banks of the river, 

especially between sites M3 and M4. Jointing in these sandstones seen during reconnaissance of measuring sites is consistent with the northwest trend of faults mapped by Scott and others (2002). Overlying the Dakota Sandstone, the Cretaceous 

Mancos Shale Formation outcrops along the riverbanks 

between the Whitewater station and site M1. Various gravels, 

alluvium, and colluvium of Quaternary age cover the valley 

floor, some of which are mined in gravel pits along the river 

between the Whitewater station and site M1, and between site 

M3 and the Redlands Canal diversion dam (Scott and others, 

2002). 

Acknowledgments 

The authors extend a special thank you to Jerry Thrush of 

the CDWR in Montrose; his knowledge of the operation of the 

below-Redlands-dam and Redlands-Canal stations was very 

useful in completing the analysis of the historical discharge 

records, and this analysis could not have been completed without his assistance in providing the needed records for the analysis. In addition, his assistance during measurement set 2, 

Analysis of Historical Discharge Records 

especially in measuring discharge at the Redlands-Canal station 

is greatly appreciated. The assistance of Coll Stanton, BOR in 

Grand Junction also is appreciated, especially for providing a 

discharge database for water year 2003 to be included in the 

analysis of historical discharge. Technical reviews of the report 

made by George Smith (U.S. Fish and Wildlife Service), and 

Coll Stanton also are greatly appreciated. 

Thanks also are extended to these USGS personnel who 

assisted in completion of the study and preparation of this 

report: Assistance during measurement sets 1 and 2, especially 

those who spent a cold night out along the river during February 

5–6, 2003—Eric Adams, Rich Carver, Dan Chafin, Paul Diaz, 

Ben Glass, Dave Hartle, Ken Leib, Paul von Guerard, and Kirby 

Wynn; additional technical reviews—William H. Asquith and 

Jack Veenhuis; editorial review—Carol Anderson; preparation 

of figure 1—Jean Dupree; and preparation of final manuscript—Margo VanAlstine and Alene Brogan. 

Analysis of Historical Discharge Records 

As previously discussed, a cursory use of real-time discharge data for the three stations along the study reach (fig. 1, 

table 1) by water-resource managers indicates that the study 

reach generally is a losing reach. Therefore, a component of the 

study was a detailed mass-balance analysis of the historical discharge records available for the three stations along the study 

reach. 

Overview of Discharge-Records Computation 

Two types of discharge data usually are available for a 

gaging station. First, unit discharge data, which typically are 

data recorded at 15-minute intervals, and second, daily mean 

discharge data, which are computed from 24 hours (midnight to 

midnight) of unit-discharge data. A streamflow-gaging station 

is equipped to directly measure water-surface (stream) elevation (stage) relative to an arbitrary datum, and a recording 

device records the stage every 15 minutes. Discharge is indirectly measured using stage and a stage-discharge relation. 

When a station is first established, a number of discharge 

measurements are made at the station at various stages, which 

are used to develop the stage-discharge relation (discharge rating) that relates a given stage to a specific discharge. The discharge rating then is used to determine a unit-discharge value 

for each of the unit-stage values that are recorded; the daily 

mean discharge is computed by applying the daily mean stage 

to the discharge rating or by computing the mean of the unit 

discharges. After a station has been established and the stagedischarge relation defined, periodic discharge measurements 

are needed because changes in the channel conditions, such as 

bed scour or fill during changes in the flow regime, commonly 

modify the original stage-discharge relation; this is especially 

relevant to natural stream channels. These additional measurements might define corrections, called shifts, that are applied to 
6 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 

30,000 

DISCHARGE, IN CUBIC FEET PER SECOND DISCHARGE, IN CUBIC FEET PER SECOND

20,000 

10,000


7,000


5,000


3,000 

2,000 

1,000


700


500


300 

200 

100


30,000


20,000 

10,000


7,000


5,000


3,000 

2,000 

1,000


700


500


300 

200 

100 

90th percentile 

75th percentile 

Mean 

Median 

25th percentile 

10th percentile 

Water years 1916-1965 

Water years 1967-2003 

Daily mean discharge 

for water year 2003 

Measurement set 1 Measurement set 2 

OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT 

Figure 2. Selected statistics of daily mean discharge for the Whitewater station before (1916–65) and after 

(1967–2003) major completion of the Aspinall Storage Unit. 
7 

the discharge rating to ensure the accuracy of the discharge 

values. It is common practice in the USGS not to apply shifts if 

the percentage difference between the measured discharge and 

the discharge rating is within 5 percent. These methods are 

described in detail in Rantz and others (1982a, 1982b). 

A large proportion of gaging stations currently (2003) 

operated, including the three stations along the study reach, are 

equipped with satellite telemetry devices, enabling access of 

real-time data using the internet. These real-time data are considered provisional (subject to revision) because (1) the 

recorded stage data might be in error due to equipment malfunctions or other factors; (2) the application of shifts may require 

modification as more information of gage operation is determined during the year; (3) or other reasons. In most cases, realtime discharge data are reasonably accurate because the technology, operation, and maintenance of real-time discharge stations are well established. During the course of, and at the end 

of a water year, the recorded unit-stage data undergo extensive 

quality assurance to ensure that the computed unit-discharge 

data and the computed daily mean discharges, have the best 

possible accuracy. During the quality assurance, the shifts that 

were applied previously to the real-time data may be modified. 

When all of the quality assurance is completed after the end of 

the water year, the daily mean discharges are finalized and published. Unit data are not published, but for USGS stations, the 

unit data are permanently stored in the National Water Information System. 

Data computation for the Whitewater and Redlands-Canal 

stations follows the procedures just described, resulting in published daily mean discharges that are quality assured. The 

below-Redlands-dam station, however, is operated only for purposes of real-time water-rights administration and waterresource management, and no quality-assured daily mean discharges are available. The only available discharge data are the 

unit data. These data are subject to a larger degree of error than 

the quality-assured data for the Whitewater and Redlands-Canal 

stations. The CDWR makes discharge measurements at regular 

intervals at the below-Redlands-dam station to identify any discharge rating shifts; however, once applied to the real-time data, 

no retrospective shift adjustments (quality assurance) to the 

data are made. 

Analysis of Shifts 

Use of discharge rating shifts in computation of discharge 

records is a common and necessary practice and increases the 

accuracy of the record. In computation of a discharge record, 

use of percentage differences in discharge (difference between 

the measured discharge and the discharge rating) requires critical evaluation. Use of percentage differences that have either 

negative or positive tendencies can introduce some bias into a 

computed record. Discharge rating shift and percentage difference in discharge data were compiled for the three stations 

along the study reach and graphically analyzed in order to gain 

some understanding of the shift history. 

Analysis of Historical Discharge Records 

Discharge measurements made at the Whitewater 

station during WYs 1995–2002 usually ranged from 1,000 to 

5,000 ft3/s, with some measurements outside of that range 

(fig. 3). Zero shifts, with a few exceptions, were used most of 

the time, and percentage differences in discharge for the shifts 

generally ranged from –4 to +4 percent (fig. 3). The USGS 

hydrologic technicians responsible for the station consider the 

use of mostly zero shifts with some percentage difference 

between the discharge and the discharge rating as a better 

approach to records computation than variable shifts with zero 

percentage difference because the stage-discharge relation at 

the station is quite stable and has not changed substantially 

during the past several years (J.R. Sullivan, U.S. Geological 

Survey, oral commun., 2004). 

Discharge measurements made at the below-Redlandsdam station during WYs 1995–2002 usually ranged from 200 to 

1,800 ft3/s, with a few measurements made at discharges less 

than 200 ft3

/s (fig. 4). Shifts were variable throughout the 

period and always were negative; reasons for the large decrease 

in shifts during 1999–2000 are not known, but could be attributable to channel changes resulting from construction of the fish 

ladder at the Redlands Canal diversion dam or changes in operation of the sand trap at the Redlands Canal diversion dam. Percentage differences in discharge, when applying the indicated 

shifts, were zero, with a few exceptions (fig. 4). 

Discharge measurements made at the Redlands-Canal 

station during WYs 1995–2002 usually ranged from 700 to 

900 ft3/s, with a few measurements made at discharges less than 

700 ft3/s (fig. 5). Shifts were variable throughout the period and 

ranged from –0.18 to +0.11 feet. Percentage differences, when 

applying the indicated shifts, frequently were zero, but about 

one-third of the measurements had a percentage difference 

other than zero (fig. 5). 

Although the percentage differences for the three stations 

(figs. 3–5) generally do not appear to be particularly one-sided, 

box plots were prepared to further evaluate the percentage differences (fig. 6). Based on the results shown in figures 3–6, it 

was concluded that application of percentage differences in discharge did not result in any discernible bias in the computation 

of the discharge records for the three stations along the study 

reach. 

Characteristics of the box plots (fig. 6, and others to follow) are as follows (paraphrased from Helsel and Hirsch, 2002, 

p. 25): The median (50th percentile) is the midpoint of the data 

values. The end points of the box, the 25th and 75th percentiles, 

define the interquartile range (IQR). The whiskers extend to the 

furthest data point that is within one step beyond either end of 

the box (adjacent values); one step is equal to 1.5 times the IQR. 

Data points that are between one and two steps from the box in 

either direction are plotted with an “x” (outliers). Data points 

that are farther than two steps beyond the box are plotted with 

an “o” (far outliers). 
8 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 

20,000 

DISCHARGE, IN CUBIC

FEET PER SECOND

PERCENTAGE DIFFERENCE SHIFT, IN FEET

10,000


7,000


5,000


3,000 

2,000 

1,000


700


500


0.4 

0.3 

0.2 

0.1 

0.0 

-0.1


8


4 

0 

-4 

-8 

1995 1996 1997 1998 1999 2000 2001 2002 

WATER YEAR 

Figure 3. Discharge, shift, and percentage difference between discharge and discharge rating for measurements made 

at the Whitewater station, water years 1995–2002. 

Results for Water Years 1995–2002 Some of the unit-discharge values were missing because the 

unit-stage values were not recorded for a variety of reasons. For 

When the discharge mass-balance analysis was made, data days with missing unit data, the mean of the available data was 

for WY 2003 were not completed, so the analysis was made used provided that no more than about 25 percent of the unit 

only for WYs 1995–2002. Because final, published daily mean values were missing. For days that the number of missing data 

discharge data were not available for the below-Redlands-dam exceeded 25-percent, the daily mean discharge was estimated 

station, the archived, real-time unit (15-minute) data were (sometimes for more than 1 day) by linear interpolation 

obtained (Jerry Thrush, Colorado Division of Water Resources, between the daily mean discharges on the adjacent days that had 

written commun., 2003) and daily mean discharges for the a computed daily mean discharge. The interpolated values also 

below-Redlands-dam station were computed from these data. were compared to the difference between daily mean discharge 
Analysis of Historical Discharge Records 9 

DISCHARGE, IN CUBIC

FEET PER SECOND SHIFT, IN FEET

5,000 

3,000 

2,000 

1,000 

700 

500 

300 

200 

100 

0.1 

0.0 

-0.1 

-0.2 

-0.3 

-0.4 

-0.5 

2 

PERCENTAGE DIFFERENCE

0 

-2 

-4 

1995 1996 1997 1998 1999 2000 2001 2002 

WATER YEAR 

Figure 4. Discharge, shift, and percentage difference between discharge and discharge rating for measurements 

made at the below-Redlands-dam station, water years 1995–2002. 

for the Whitewater and Redlands-Canal stations. For WYs 

1995–2002, daily mean discharge was estimated for 85 days 

(out of 2,771) for the below-Redlands-dam station. 

Daily mean discharges at the two downstream stations 

(below-Redlands-dam and Redlands-Canal) were summed to 

produce an estimate of the downstream streamflow; this sum 

was subtracted from the daily mean discharge at the Whitewater 

station (the upstream streamflow). This difference provides an 

estimate of the difference between downstream and upstream 

streamflow along the study reach. These data were compiled for 

each day of WYs 1995–2002, and the values were summed by 

water year (table 2). Excluding the partial data for WY 1995, 

the differences between the annual sums of daily mean discharge at the two downstream stations and the annual sums of 

daily mean discharges at the upstream station ranged from 

about –28,700 to –69,800 acre-ft. The difference, as a percentage of the upstream discharge, ranged from about –1.1 to 

–5.8 percent (table 2). These results indicate 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 and the differences between the 
10 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 

1,000

DISCHARGE, IN CUBIC

FEET PER SECOND

PERCENTAGE DIFFERENCE SHIFT, IN FEET

900 

800 

700 

600 

500 

0.2 

0.1 

0.0 

-0.1 

-0.2 

4 

2 

0 

-2 

-4 

1995 1996 1997 1998 1999 2000 2001 2002 

WATER YEAR 

Figure 5. Discharge, shift, and percentage difference between discharge and discharge rating for measurements 

made at the Redlands-Canal station, water years 1995–2002. 

sum of the 3-day daily mean discharges at the two downstream An example of the moving 3-day daily mean discharges at 

stations and the 3-day daily mean discharge at the upstream sta- the three stations along the study reach, the sum of the 3-day 

tion, for additional analyses. The moving 3-day daily mean was daily mean discharges at the two downstream stations, and the 

used because the sum of the daily mean discharge at the down- differences between the downstream and upstream discharges 

stream stations almost never is the same as the daily mean dis- for WY 1996 are shown in figure 7. The characteristics of 

charge at the upstream station because of traveltime effects, the data for the other WYs (excluding WY 2003) were similar. 

even with no loss or gain in the reach; a moving 3-day daily Most of the discharge differences are between –200 and 

mean could smooth out some of the abrupt differences between +100 ft3/s and most of the percentage differences are between 

the daily mean discharges attributed to traveltime. More com- –10 and 0 percent (fig. 7). The differences between the 3-day 

plex analytical methods, such as those involving computerized daily mean discharge sum at the two downstream stations and 

streamflow routing programs, were beyond the scope of this the 3-day daily mean discharge at the upstream station seem to 

study. be smaller in figure 7A in comparison to figure 7B; this prima 
Analysis of Historical Discharge Records 11 

6 

x 

o

o 

o 

o 

o 

o 

o

o 

o

o

o 

ooo

o 

o 

o

o

o

EXPLANATION 

o Upper far outlier 

4 x	 Upper outlier 

Upper adjacent 

2 

75th percentile 

0 Median 

25th percentile 

-2 

Lower adjacent 

x	 Lower outlier 

o Lower far outlier 

-4 

(See text for additional 

explanation of boxplot values.) 

-6 

-8 

Whitewater Below-Redlands- Redlands-Canal

 station dam station station 

(See figure 1 and table 1 for station details) 

Figure 6. Distribution of percentage differences for applied shifts for measurements made at 

stations along the Gunnison River study reach, water years 1995–2002. PERCENTAGE DIFFERENCE 

rily is due to the different types of y-axes—Logarithmic in 

figure 7A and arithmetic in figure 7B. 

Distributions of daily differences between the moving 

3-day daily mean discharge sum at the two downstream stations 

and the moving 3-day daily mean discharge at the upstream 

station and the percentage differences during WYs 1995–2002 

are shown in figure 8. Excluding WY 2003, differences 

between the downstream and upstream 3-day daily mean discharges ranged from about –200 to +100 ft3

/s during one-half of 

each year (the values within the IQR), 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 values outside the IQR). Daily 

percentage differences each year (1995–2002) almost always 

ranged from 0 to –10 percent within the IQR and were as small 

or large as about –60 to +50 percent outside the IQR. 

The below-Redlands-dam station does not have a bridge or 

cableway nearby from which high-discharge measurements can 

be made, and the highest wading discharge measurement made 

at the station during WYs 1995–2002 was about 1,800 ft3/s 

(fig. 4). Consequently, discharge rating shifts might have considerable error when discharge is larger than about 1,800 ft3

/s. 

Therefore, a subset of the moving 3-day daily mean discharge 

data was analyzed that only included those data for which the 

3-day daily mean discharges at the below-Redlands-dam station 

were less than 2,000 ft3

/s. For the subsetted data, the height of 

the IQR box (between 25th and 75th percentiles) for both the 

discharge differences and the percentage differences (fig. 9) is 

somewhat smaller than for all the data (fig. 8). The range of the 

discharge and percentages differences outside the IQR is nearly 

as large for the subsetted data (fig. 8), as for all the data (fig. 9), 

although the number of values each year is smaller for the subsetted data. Overall, differences between the subsetted data and 

all the data are not large, indicating that the differences can be 

large even during times of smaller discharge. 

Results for Water Year 2003 

Near the end of WY 2003, water-resource managers that 

used the real-time data at the three stations noticed that the 

general trend of decreased downstream discharge observed during the previous years seemed to have changed to an increase in 

downstream discharge (Coll Stanton, Bureau of Reclamation, 

oral commun., 2003). The reasons for the apparent change in 

downstream discharge were not known, but perhaps the change 

might be attributed to some changes in the equipment at the 

below-Redlands-dam station made earlier during WY 2003. At 

the station, the nitrogen bubbling system, the nitrogen line 

feeder tubing, and the orifice end cap were replaced on 

February 21, 2003; the new bubbling system automatically 

purges the nitrogen line to the stream every 15 minutes, 

decreasing the possibility of a plugged orifice (Jerry Thrush, 

Colorado Division of Water Resources, written commun., 
12	 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 

Table 2. Cumulative annual and annual mean discharges for streamflow-gaging stations at the upstream and downstream ends of the 

Gunnison River study reach and difference between these discharges, water years 1995–2003. 

[acre-ft, acre-feet; ft3/s, cubic feet per second; see figure 1 and table 1 for station details] 

Discharge, for indicated water year, in indicated units 

Sum of 

Water year Units Whitewater 

station 

(upstream) 

BelowRedlands-dam 

station 

Redlands-Canal 

station 

Below-Redlandsdam and 

Redlands-Canal 

stations 

(downstream) 

Difference 

(downstream -

upstream) 

1

Percentage 

difference 

2

1995 acre-ft 

ft3

/s 

2,803,400 

4,977 

2,475,800 

4,395 

318,400 

565 

2,794,200 

4,960 

-9,200 

-16.3 -0.33 

1996 acre-ft 

ft3

/s 

2,007,600 

2,773 

1,400,000 

1,934 

546,300 

752 

1,946,300 

2,681 

-61,300 

-84.5 

-3.05 

1997 acre-ft 

ft3/s 

2,817,000 

3,891 

2,226,900 

3,076 

558,000 

771 

2,784,900 

3,847 

-32,100 

-44.3 -1.14 

1998 acre-ft 

ft3/s 

2,093,000 

2,891 

1,505,600 

2,080 

542,200 

749 

2,047,800 

2,829 

-45,200 

-62.4 -2.16 

1999 acre-ft 

ft3/s 

1,692,700 

2,338 

1,051,300 

1,452 

571,600 

790 

1,622,900 

2,242 

-69,800 

-96.3 -4.12 

2000 acre-ft 

ft3

/s 

1,466,400 

2,020 

863,000 

1,192 

542,000 

747 

1,405,000 

1,939 

-61,400 

-84.5 -4.19 

2001 acre-ft 

ft3/s 

1,170,700 

1,617 

547,300 

756 

555,700 

768 

1,103,000 

1,524 

-68,000 

-93.5 -5.81 

2002 acre-ft 

ft3/s 

805,100 

1,112 

296,900 

410 

479,500 

662 

776,400 

1,072 

-28,700 

-39.6 -3.56 

2003 acre-ft 

ft3

/s 

860,100 

1,188 

522,300 

721 

333,800 

461 

856,100 

1,182 

-4,000 

-5.43 -0.47 

1Percentage difference = [(downstream discharge - upstream discharge) / upstream discharge] x 100. 

2For the March 1–September 30, 1995, period. 

2004). In order to evaluate the apparent change in downstream 

discharge, it was decided to expand the previously completed 

mass-balance analysis to include WY 2003. In addition to using 

the published daily mean discharge data for the Whitewater and 

Redlands-Canal stations for the mass-balance analysis, daily 

mean discharges for WY 2003 that received some quality assurance also were computed for the below-Redlands-dam station 

(Jerry Thrush, Colorado Division of Water Resources, written 

commun., 2003). 

Methods for mass-balance analysis for WY 2003 were 

identical to those used for WYs 1995–2002, but the results were 

somewhat different. The difference between the sums of daily 

mean discharges at the two downstream stations and the daily 

mean discharge at the upstream station, about –4,000 acre-ft, 

and the percentage difference, about –0.5 percent, for WY 2003 

are substantially smaller than for any other water year, excluding the 1995 partial year (table 2). Differences between the sum 

of the moving 3-day daily mean discharges at the two downstream stations and the moving 3-day daily mean discharge at 

the upstream station, as well as the percentage differences, for 

WY 2003 (fig. 10) are substantially smaller than those for 

WY 1996 (fig. 7), which is representative of WYs 1995–2002. 

In addition to a smaller annual difference for WY 2003 (table 

2), the variability in the differences between downstream and 

upstream moving 3-day daily mean discharge also was much 

less during WY 2003 than during the previous years (figs. 8–9). 

Although the IQRs for discharge difference and percentage 

difference for WY 2003 are not the smallest, 2003 is the only 

water year for which the medians are near zero (figs. 8–9). 

The near-zero annual difference (table 2) and near-zero 

medians for WY 2003 (figs. 8–9) resulted from generally 

negative differences during the first one-half of the year and 
Analysis of Historical Discharge Records 13 

A

MOVING 3-DAY DAILY MEAN DISCHARGE,

IN CUBIC FEET PER SECOND

IN CUBIC FEET PER SECOND

DIFFERENCE (DOWNSTREAM - UPSTREAM),

Downstream discharge > upstream discharge 

Downstream discharge < upstream discharge 

Downstream discharge > upstream discharge 

Downstream discharge < upstream discharge

DIFFERENCE (DOWNSTREAM - UPSTREAM),

AS A PERCENTAGE OF

UPSTREAM DISCHARGE 

100 

1,000 

10,000 

200 

300 

500 

700 

2,000 

3,000 

5,000 

7,000 

20,000 

-200 

-100 

100 

200 

0 

-15 

-10 

-5 

10 

15 

0 

5 

Whitewater station (Upstream) 

Below-Redlands-dam station Sum of below-Redlands-dam and

 Redlands-Canal stations (Downstream) 

Redlands-Canal station 

(See figure 1 and table 1 for station details) 

B 

C 

OCT NOV DEC JAN FEB MAY APR MAY JUNE JULY AUG SEPT 

Figure 7. Moving 3-day daily mean discharge for stations at the upstream and downstream ends of the Gunnison 

River study reach and differences between the discharges, water year 1996. 
14 	 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 

1,500 

1,000 

500 

0 

x 

x 

x 

x 

x

x

o 

o	

o 

x 

x 

x x 

x 

x 

o 

oo

oo

o

o 

o

o

o

x x 

x 

o 

o 

o 

o 

x 

x x xx

x

x xx

x

x

x

x

x

x

x

x

x

xx

x

x 

xx

xxx

x

x

xx

x x

x

x x

x

x

x

x

xx

o 

oo

o 

o 

o 

oo 

o

o 

o 

o 

o 

o 

o 

x 

xx

xx

x

x 

o 

o 

o 

oooo

o 

oo

o

o

o

o 

oo

o 

o

o

o 

x

x 

o 

ooo

o

o 

x 

o 

o 

o 

o 

o 

oo

o 

o 

o 

x 

x 

x

xx

xx

xxxx x

x

o

o 

o

x 

x 

o 

o 

o 

o

o

o 

x 

o 

o 

o 

oo

o 

x 

xx

x 

o 

o

ooo

o 

o

o 

o 

o 

o 

o 

oooooo

o 

o o 

o 

o

Note: Water year 1995 data are 

for March 1-September 30 

Downstream discharge > upstream discharge 

Downstream discharge < upstream discharge 

EXPLANATION 

o Upper far outlier 

x Upper outlier 

-500 Upper adjacent 

x 

x 

x x 

xx

x

x

o 

o 

o 

x 

x 

x 

x

o 

oo

ooo

o 

o

o

o

o 

x 

x 

x 

x

o 

o 

o 

x 

o 

x

x 

xx

x 

o 

o 

o 

o 

o

ooo

o

o

o 

x

x

xx

x

xx

xx

o 

o 

ooo

o oo

o 

xxx

x

x

x

x 

o 

o 

oooo 

o o 

o 

o 

xx

x

x 

x 

x 

x 

o 

o 

o 

oo

o 

o 

xx

x 

x 

x 

x 

xx

x

xx

x

x

ooooooo 

x 

x

x

x

x

x 

o 

o 

o 

o

o 

o 

o 

o 

o 

o 

o 

o 

o 

x 

x

x 

x 

x 

x

o 

o 

o 

oo

o 

o 

o

o 

o 

x 

x 

o 

o 

o 

o 

ooo

o 

o 

o 

o

Downstream discharge > upstream discharge 

Downstream discharge < upstream discharge 

75th percentile 

-1,000 

Median 

60 

25th percentile 

Lower adjacent 

40 x Lower outlier 

o Lower far outlier 

(See text for additional 

explanation of box20 plot values.) 

0 

-20 

-40 

-60 

1995 1996 1997 1998 1999 2000 2001 2002 2003 

WATER YEAR 

Figure 8. Distribution of differences between moving 3-day daily mean discharge at the upstream and downstream ends 

of the Gunnison River study reach, water years 1995–2003. DIFFERENCE (DOWNSTREAM - UPSTREAM), DIFFERENCE (DOWNSTREAM - UPSTREAM), AS A PERCENTAGE OF IN CUBIC FEET PER SECOND UPSTREAM DISCHARGE 
Analysis of Historical Discharge Records 15 

DIFFERENCE (DOWNSTREAM - UPSTREAM), DIFFERENCE (DOWNSTREAM - UPSTREAM), AS A PERCENTAGE OF

IN CUBIC FEET PER SECOND UPSTREAM DISCHARGE 

1,000 

500 

0 

x 

x 

x 

x 

o 

o 

x 

x 

x 

o 

o 

o 

o	

xxx

x

x 

x

x

o 

o 

o 

o 

o 

oooo

o 

oo 

o 

x 

x 

x

o 

o 

o 

x x

xx

x

x

xx

x

x

x

x 

x 

o 

o 

o 

o

o

o 

x 

x 

o 

o 

o 

oo

o 

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o 

o 

o 

o

o

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x 

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o 

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o 

oo

o 

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oooooo

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o 

o

71 240 203 250 249 343 343 365 344 

Number of 

data points 

Downstream discharge > upstream discharge 

Downstream discharge < upstream discharge 

EXPLANATION 

o Upper far outlier 

-500 x	 Upper outlier 

Upper adjacent 

75th percentile 

-1,000 

Median 

60 

25th percentile 

o 

o 

oo Lower adjacent o
 40
 Downstream discharge > upstream discharge x	 Lower outlier o o o o o	 Lower far outlier o 

o	 o o o o o o o o x (See text for additional x 

x	 explanation of box- 20 o x oo o	 o plot values.) o o 

o o o

x x

o	 xx xx xx

x x

xx x

xx x o x x x xx 0 

x 

xxx oo


-20
 o x x 

o x x o x o o 

ooo o o x x	 o o o o o

-40 o	 o o 

Downstream discharge < upstream discharge o 

o o o o o ooo

o o o o o 

o -60


1995 1996 1997 1998 1999 2000 2001 2002 2003


WATER YEAR 

Figure 9. Distribution of differences between moving 3-day daily mean discharge at the upstream and downstream 

ends of the Gunnison River study reach when discharge at the below-Redlands-dam station is less than 2,000 cubic 

feet per second, water years 1995–2003. 
16 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 

generally positive differences during the second one-half of the 

year (fig.10B). The smaller overall difference (table 2) and the 

smaller 3-day daily mean differences (fig. 10) for WY 2003, 

however, partly could be the result of (1) the smaller than 

normal discharges during WY 2003 (fig. 2); (2) the period of no 

diversion by the Redlands Canal (fig. 10); and (3) the use of 

daily mean discharges for the below-Redlands-dam station that 

were partially quality assured. 

Streamflow Measurements 

A reconnaissance of the study reach was made during 

January 2003 to evaluate the geologic, hydrologic, and physical 

characteristics of the study reach. The location of geologic features, such as faults, or man-made features, such as gravel pits, 

that could affect streamflow loss along the study reach were 

noted for consideration in analysis of the study results; however, the effects of these on streamflow in the study reach were 

considered to be very minimal. Most of the study reach is inaccessible by vehicles, except in the vicinity of the upstream and 

downstream stations; therefore, the reconnaissance was made 

by canoes, traveling downstream from the Whitewater station. 

Four miscellaneous-measuring sites (M1–M4; fig.1, table 1) 

were selected during the reconnaissance for use in making the 

discharge measurement sets to aid in evaluating streamflow 

loss. Discharge measurements at the intermediate locations 

could help determine if the losses are uniformly distributed 

throughout the study reach or if the losses are just in a certain 

location or locations. 

Two discharge measurement sets were obtained, one during February 2003, and one during May 2003 (fig. 2). All discharge measurements for measurement set 1 were made by 

wading and using standard current meters (Rantz and others, 

1982a). Discharge measurements for measurement set 2 were 

made by wading (at the below-Redlands-dam station), long rod 

(at the Redlands-Canal station), and cableway (at the 

Whitewater station), all using standard current meters (Rantz 

and others, 1982a), and by using boat-mounted acoustic doppler 

current profiler equipment (Morlock, 1996; Simpson, 2001) at 

site M2. 

Measurement Set 1 

Discharge measurements for measurement set 1 were 

obtained during February 5–6, near the lowest discharge period 

during WY 2003 (fig. 2). Discharge was measured 5–8 times 

over a 24-hour period during the 2-day period at sites M1–M4, 

by teams who accessed the sites by canoe and remained onsite 

(from about mid-day on February 5 to about mid-day on 

February 6). Temporary staff gages also were installed at the 

four sites, and stage was observed about every hour and more 

frequently during each measurement. Maximum change in 

observed stage was small at the sites, ranging from 0.03 to 

0.05 foot. 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, 

so measurements were not needed at the Redlands-Canal station. 

Measured discharges at sites M1–M4 ranged from 527 to 

608 ft3

/s; measured discharges at the Whitewater station were 

628 and 588 ft3/s; and measured discharges at the belowRedlands-dam station were 579 and 565 ft3/s (fig. 11). All measurements were rated good (5-percent accuracy), except the 

measurement of 628 ft3

/s at the Whitewater station, which was 

rated fair (8-percent accuracy). Recorded unit discharges at the 

Whitewater station ranged from about 575 to 615 ft3/s, and 

recorded unit discharges at the below-Redlands-dam station 

ranged from about 560 to 600 ft3/s during the 2-day period 

(fig. 11). 

Although the variation in mean or median discharge 

among the sites seems large (fig. 11), this partly results from the 

y-axis scale that has a large expansion of a relatively small discharge range. Generally, the range of the discharge measurements at each site is well within the 5-percent accuracy. For 

example, assuming a central discharge tendency of 580 ft3/s, at 

a 5-percent accuracy, a measured discharge could range from 

551 to 609 ft3/s. The variation in discharge from one site or station to another (fig. 11) partly might be the result of differences 

in measurement technique, but probably is more attributable to 

local variations in channel conditions. For example, site M1 

was just downstream from a pool and riffle sequence and site 

M4 was just downstream from a large bend where the channel 

began to broaden. At these sites, some discharge could have 

been flowing through the unconsolidated gravel adjacent to or 

under the streambed (underflow), only to be discharged back to 

the stream some distance downstream, indicated by the rises in 

discharge at site M2 and at the below-Redlands-dam station. 

Because of the inherent error in discharge measurements 

(5 percent for measurements rated good), and because the mean 

discharge (about 580 ft3

/s) at the below-Redlands-dam station 

was only about 2.5 percent smaller than the mean discharge 

(about 595 ft3/s) at the Whitewater station it was concluded that 

there was no measurable streamflow loss along the study reach 

during measurement set 1. 

Measurement Set 2 

Discharge in the Gunnison River during measurement 

set 2 (May 14–15, fig. 2) was about 2,000 ft3

/s and increasing 

because of high-elevation snowmelt. Because of the high 

discharge, wading measurements were not possible at any of the 

sites or stations, except at the below-Redlands-dam station, 

where discharge was lower due to the upstream diversion into 

the Redlands Canal. In addition, besides making discharge 

measurements at the three stations to verify discharge rating 

shifts, discharge was measured only at site M2 for the following 

reasons: (1) The changes in discharge observed from one site or 

station to another during measurement set 1 (fig. 11), likely 

would not be observed during measurement set 2 because of the 
Streamflow Measurements 17 

MOVING 3-DAY DAILY MEAN DISCHARGE,

IN CUBIC FEET PER SECOND

100 

1,000 

10,000 

200 

300 

500 

700 

2,000 

3,000 

5,000 

7,000 

A 

Whitewater station (Upstream) 

Below-Redlands-dam station 

Sum of below-Redlands-dam and 

Redlands-Canal stations (Downstream) 

Redlands-Canal station 

(See figure 1 and table 1 for station details) 

B 

IN CUBIC FEET PER SECOND

DIFFERENCE (DOWNSTREAM - UPSTREAM),

Downstream discharge > upstream discharge 

Downstream discharge < upstream discharge 

Downstream discharge > upstream discharge 

Downstream discharge < upstream discharge

DIFFERENCE (DOWNSTREAM - UPSTREAM),

AS A PERCENTAGE OF

UPSTREAM DISCHARGE 

-200 

-100 

100 

200 

0 

-15 

-10 

-5 

10 

15 

0 

5 

C 

OCT NOV DEC JAN FEB MAY APR MAY JUNE JULY AUG SEPT 

Figure 10. Moving 3-day daily mean discharge for stations at the upstream and downstream ends of the Gunnison River 

study reach and differences between the discharges, water year 2003. 
650 

18 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 

Discharge measurement at station 

Whitewater stationSite M1Site M2 Site M3Site M4Below-Redlands-dam station

(See figure 1 and table 1 for station and site details) 

25th percentile 

Median 

75th percentile 

Maximum 

Minimum 

Mean 

DISCHARGE, IN CUBIC FEET PER SECOND 

625 

600 

575 

550 

525 

500 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 

DISTANCE DOWNSTREAM FROM WHITEWATER STATION, IN RIVER MILES 

Figure 11. Distribution of unit discharges for stations at the upstream and downstream ends of the Gunnison River 

study reach and distribution of discharge measurements made at miscellaneous discharge-measurement sites along 

the reach during measurement set 1, February 5–6, 2003. 

much larger discharge; and (2) the changes likely would not be 

proportionally larger because the much smaller traveltime 

during the higher flow would minimize any localized changes 

in discharge. Therefore, site M2, being nearest to the midpoint 

of the study reach, was the only miscellaneous site at which discharge measurements were made. A temporary staff gage was 

not installed at site M2 for measurement set 2. 

Five discharge measurements made at site M2 ranged from 

1,668 to 2,117 ft3/s, and all but one were rated good; one measurement was made May 14 and four measurements were made 

May 15 (fig. 12). One measurement, 2,730 ft3/s (rated good), 

was made at the Whitewater station, but the measurement was 

not made until May 16 (not shown in fig. 12) because of equipment problems. One measurement, 1,268 ft3/s (rated good), was 

made at the below-Redlands-dam station; and one measurement, 819 ft3/s (rated good), was made at the Redlands-Canal 

station (not shown in fig. 12). 

Because of the change in discharge during measurement 

set 2 (fig. 12), consideration of traveltime is of critical importance in evaluating any streamflow losses. Traveltimes through 

the study reach were estimated by comparing the unit-discharge 

hydrographs at the Whitewater and below-Redlands-dam 

stations; the estimated traveltimes then were used to lag the 

recorded unit discharges at the Whitewater station through the 

study reach. Using an estimated traveltime of about 1.5 hours, 

the discharge measurements made at site M2 correlated closely 

with the discharges recorded about 1.5 hours earlier at the 

Whitewater station (fig. 12). Using an estimated traveltime of 

about 3.5 hours, the sum of the unit discharges at the belowRedlands-dam and Redlands-Canal stations, correlated closely 

to the unit discharges recorded about 3.5 hours earlier at the 

Whitewater station (fig. 12). The use of constant traveltimes 

likely resulted in some error in the lagging of the unit discharges 

because the traveltime most certainly varied with changes in 

discharge. Results of measurement set 2 also indicate no substantial streamflow loss along the study reach. Based on the 

results of the mass-balance analyses and the two measurement 

sets, and discussion of the results with the cooperators, the additional measurement sets that were planned were not made. 
Discussion of Streamflow Losses 19 

3,000 

2,700 

2,400 

2,100 

1,800 

1,500 

1,200 

900 

600 

1200 1600 2000 0000 0400 0800 1200 1600 2000 0000 

Actual-time unit discharge for the Whitewater station 

Unit discharge for the Whitewater station lagged 1.5 hours downstream to site M2 

Actual-time unit discharge for the below-Redlands-dam station 

Sum of actual-time unit discharges for the below-Redlands-dam and 

Redlands-Canal stations 

Unit discharge for the Whitewater station lagged 3.5 hours downstream 

to the below-Redlands-dam station 

Discharge measurements made at site M2 

Discharge measurement made at the below-Redlands-dam station 

(See figure 1 and table 1 for station and site details) 

MAY 14 MAY 15 

Figure 12. Unit discharges for stations at the upstream and downstream ends of the Gunnison River study reach 

and discharge measurements made at site M2 during measurement set 2, May 14–15, 2003. DISCHARGE, IN CUBIC FEET PER SECOND 

Discussion of Streamflow Losses 

Results of the mass-balance analyses shown in table 2 and 

figures 7–9 clearly show that, for WYs 1995–2002, the sum of 

recorded discharges at stations below-Redlands-dam and 

Redlands-Canal generally tend to be less than recorded discharges at the Whitewater station. Even on the basis of that time 

period alone, however, it cannot be concluded that the study 

reach is, in fact, a losing stream reach because 

1. 	 The lack of a final, quality-assured daily discharge record 

for the below-Redlands-dam station does not provide a 

quantitative estimate of the error in that discharge record, 

especially in light of the seemingly better discharge 

record during WY 2003 following the changes in equipment. 

2. 	 The water-year differences listed in table 1, even without 

any quantitative estimate of the error in the discharge 

record for the below-Redlands-dam station, mostly are 

less than 5 percent and within the stated 5-percent 

accuracy of the discharge measurements and the final, 

quality-assured daily discharge records for the 

Whitewater and Redlands-Canal stations. 

3. 	Although some differences between daily mean discharge 

at the downstream and upstream stations are large, some 

of the differences are attributable to traveltime of 

streamflow through the reach, which is not entirely 

accounted for in the discharge record, especially in the 

daily mean values. 

Additionally, results of the mass-balance analysis for 

WY 2003, which seem to indicate a change in the observed 

trend of streamflow losses during WYs 1995–2002 (table 2), 

and results of the two measurement sets, indicate that these 

losses only might be “perceived” because of inaccuracies in the 

real-time data and the effects of traveltime. 

Those involved in administration of water-use rights and 

management of water resources in the Gunnison River basin 

frequently look at web-based real-time discharge data for the 

three stations along the study reach. Often, there is some difference between the sum of the discharges at the two downstream 

stations (below-Redlands-dam and Redlands-Canal) and the 

upstream station (Whitewater). Because the study of streamflow losses in the reach described in this report indicated that 

there likely are no measurable losses, the differences between 

real-time upstream and downstream discharge primarily can be 

attributed to (1) traveltime of streamflow through the reach, 
20 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 

(2) inaccuracies in the real-time discharges because the realtime discharge rating shift corrections are not completely accurate, 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 discharges. 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 lagging 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 differences between the daily mean discharge sum for the two downstream 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 stations 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 discharges 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 perceived difference is unacceptable for administration of wateruse rights and management of water resources, new technologies, such as acoustic doppler velocity measurement, are 

becoming available that might improve the accuracy of realtime 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 waterresource issues in the reach: (1) the use of web-based, real-time 

discharge data for three streamflowgaging 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 reservoir 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 stations 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 GUNREDCO 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 massbalance analysis, because data for the below-Redlands-dam station 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 analysis 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 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, 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 subtracted from 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 discharge 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 
between the moving 3-day daily mean discharges at the downstream and upstream stations during WYs 1995–2002 were 

between about –200 and +100 ft3/s during about one-half of the 

time [within the inter-quartile range (IQR)], but had absolute 

values as large as about 500 to 1,000 ft3/s during the other onehalf of the time (outside the IQR). Percentage differences 

almost always were between 0 and –10 percent within the IQR 

and were as small or large as about –60 to +50 percent outside 

the IQR. 

Recorded discharge data for WY 2003 also were analyzed 

after the end of the water year because use of the real-time 

discharge data for the year seemed to indicate a change in the 

previously observed trend of losing streamflow along the study 

reach. The annual difference between downstream and 

upstream discharge and the percentage difference for WY 2003 

were substantially smaller than for any of the previously analyzed years (WYs 1995–2002). WY 2003 was the only year for 

which the medians were near zero. In addition to a smaller 

annual difference for WY 2003, the variability in the differences between downstream and upstream discharge also was 

much less during WY 2003 than during the previous years. 

Two discharge measurement sets were obtained, one 

during February 2003, and one during May 2003. Discharge 

measurements for measurement set 1 were obtained during 

February 5–6, near the lowest discharge period during 

WY 2003. Discharge was measured 5–8 times over a 24-hour 

period during the 2-day period at sites M1–M4. Temporary staff 

gages also were installed at the four sites, and stage was 

observed about every hour and more frequently during each 

measurement. Maximum change in observed stage was small at 

the sites, ranging from 0.03 to 0.05 ft. 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, so measurements were not needed at the 

Redlands-Canal station. 

Measured discharges at sites M1–M4 ranged from 527 to 

608 ft3/s, measured discharges at the Whitewater station were 

628 and 588 ft3/s, and measured discharges at the belowRedlands-dam station were 579 and 565 ft3/s. Recorded unit 

discharges at the Whitewater station ranged from about 575 to 

615 ft3/s, and recorded unit discharges at the below-Redlandsdam station ranged from about 560 to 600 ft3/s during the 2-day 

period. Because of the expected 5-percent differences in discharge measurements, 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 was concluded that there was no measurable streamflow loss along the study reach during measurement set 1. 

Discharge in the Gunnison River during measurement 

set 2 (May 14–15) was about 2,000 ft3

/s and increasing because 

of high-elevation snowmelt. Discharge measurements were 

made at the three gaging stations to verify discharge rating 

shifts. Five discharge measurements also were made at site M2 

and ranged from 1,668 to 2,117 ft3/s. Discharges measured at 

the gaging stations were 2,730 ft3

/s (on May 16) at the 

References Cited 21 

Whitewater station, 1,268 ft3

/s at the below-Redlands-dam station, and 819 ft3/s at the Redlands-Canal station. 

Because of the change in discharge during measurement 

set 2, consideration of traveltime was of critical importance in 

evaluating any streamflow losses. 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 discharges recorded about 

1.5 hours earlier at the Whitewater station. 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. These results for 

measurement set 2 also indicate no measurable streamflow loss 

along the study reach. 

On the basis of the study results, it cannot be concluded 

that the study reach is, in fact, a losing stream reach because 

1. 	 The lack of a final, quality-assured discharge record for the 

below-Redlands-dam station does not provide a quantitative estimate of the error in that discharge record. 

2. 	 Even without any quantitative estimate of the error in the 

discharge record for the below-Redlands-dam station, the 

annual water-year differences between downstream and 

upstream discharge mostly are less than 5 percent and 

within the stated 5-percent accuracy of discharge 

measurements and the finalized discharge records for the 

Whitewater and Redlands-Canal stations. 

3. 	 Although some differences between the sum of the daily 

mean discharge at the downstream stations and the daily 

mean discharge at the upstream station are large, some of 

the differences are attributable to traveltime of 

streamflow through the reach, which is not entirely 

accounted for in the discharge record, especially in the 

daily mean values. 

References Cited 

Bankey, Viki, 2004, ed., Resource Potential and Geology 

of the Grand Mesa, Uncompahgre, and Gunnison (GMUG) 

National Forest and Vicinity, Colorado–Summary information of known mineral resources: U.S. Geological Survey 

Bulletin 2213, 276 p. [Available on-line at URL 

http://pubs.usgs.gov/bul/b2213] 

Butler, D.L., and Leib, K.J., 2002, Characterization of Selenium 

in the Lower Gunnison River Basin, Colorado, 1988–2000: 

U.S. Geological Survey Water-Resources Investigations 

Report 02–4151, 26 p. 

Helsel, D.R., and Hirsch, R.M., 2002, Statistical Methods in 

Water Resources—Hydrologic Analysis and Interpretation: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 4, chap. A3, 510 p. 
22	 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 

Kuhn, Gerhard, and Parker, R.S., 1992, Transfer of watershed- U.S. Fish and Wildlife Service, 2002a, Upper Colorado River 

model-parameter values to noncalibrated basins in the endangered fish recovery program—Home page: 

Gunnison River basin, Colorado, in Herrmann, Raymond, Upper Colorado River Endangered Fish Recovery Program, 

ed., Managing Water Resources During Global Change, accessed October 29 at URL http://www.r6.fws.gov/ 

Proceedings for American Water Resources Association 28th coloradoriver/index.htm. 

Annual Conference and Symposium, November 1–5, 1992, U.S. Fish and Wildlife Service, 2002b, Why some native fish in Reno, Nevada: p. 741–750. the upper Colorado River basin are endangered—Overview: Morlock, S.E., 1996, Evaluation of acoustic doppler profiler Upper Colorado River Endangered Fish Recovery Program, measurements of river discharge: U.S. Geological Survey accessed October 29 at URL http://www.r6.fws.gov/ Water-Resources Investigations Report 95–4218, 37 p. coloradoriver/Crwhyovu.htm. Rantz, S. E., and others, 1982a, Measurement and computation 

of streamflow—Volume 1, measurement of stage and dis- U.S. Fish and Wildlife Service, 2002c, Recovery of endangered 

charge: U.S. Geological Survey Water-Supply Paper 2175, fish in the upper Colorado River basin—Designated ‘critical 

p. 1–284.	 habitat’: Upper Colorado River Endangered Fish Recovery 

Rantz, S. E., and others, 1982b, Measurement and computation 	 Program, accessed October 29 at URL http:// 

of streamflow—Volume 2, computation of discharge: www.r6.fws.gov/coloradoriver/Crrpch.htm. 

U.S. Geological Survey Water-Supply Paper 2175, U.S. Fish and Wildlife Service, 2002d, Recovery of endangered 

p. 285–631. 

Scott, R.B., Carrara, P.E., Hood, W.C., and Murray, K.E., 

2002, Geologic map of the Grand Junction quadrangle, 

Mesa County, Colorado, Version 1.0: U.S. Geological 

Survey Miscellaneous Field Studies Map MF–2363, 

fish in the upper Colorado River basin—Improving river 

habitat: Upper Colorado River Endangered Fish Recovery 

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