Summary of Sediment Data from the 

Yampa River and Upper Green River Basins, 

Colorado and Utah, 1993–2002

By John G. Elliott and Steven P. Anders

Prepared in cooperation with the

Colorado Division of Wildlife and the

U.S. Fish and Wildlife Service

Scientific Investigations Report 2004–5242

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: 2005

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

Box 25286, Denver Federal Center

Denver, CO 80225

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Elliott, John G., and Anders, Steven P., 2005, Summary of sediment data from the Yampa River and upper Green River 

Basins, Colorado and Utah, 1993–2002: U.S. Geological Survey Scientific Investigations Report 2004–5242, 35 p.
iii

Contents

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

Introduction ................................................................................................ 1

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

Previous Investigations ........................................................................... 3

Acknowledgments ................................................................................. 4

Study Area ................................................................................................ 4

Geographic Setting ................................................................................. 4

Streamflow .......................................................................................... 5

Fluvial Sediment Transport and Deposition ............................................................ 6

Sediment Storage Areas ........................................................................... 7

Sampling Sites ....................................................................................... 8

Sediment Sampling ................................................................................. 8

Sediment-Transport Curves .............................................................................. 10

Yampa River above Little Snake River, near Maybell, Colorado .................................... 11

Site Description .................................................................................... 11

Streamflow and Sediment Data .................................................................. 11

Analysis ............................................................................................. 11

Little Snake River near Lily, Colorado .................................................................. 14

Site Description .................................................................................... 14

Streamflow and Sediment Data .................................................................. 14

Analysis ............................................................................................. 14

Yampa River at Deerlodge Park, Colorado ............................................................ 15

Site Description .................................................................................... 15

Streamflow and Sediment Data .................................................................. 15

Analysis ............................................................................................. 15

Green River above Gates of Lodore, Colorado ......................................................... 25

Site Description .................................................................................... 25

Streamflow and Sediment Data .................................................................. 25

Analysis ............................................................................................. 25

Green River near Jensen, Utah ........................................................................ 28

Site Description .................................................................................... 28

Streamflow and Sediment Data .................................................................. 28

Analysis ............................................................................................. 28

Summary and Conclusions .............................................................................. 32

Yampa River above Little Snake River, near Maybell, Colorado .............................. 33

Little Snake River near Lily, Colorado ............................................................ 33

Yampa River at Deerlodge Park, Colorado ...................................................... 33

Green River above Gates of Lodore, Colorado ................................................... 33

Green River near Jensen, Utah .................................................................. 34

References Cited .......................................................................................... 34
iv

Figures

1. Map of the Yampa River and upper Green River Basins showing streamflowgaging stations and sediment-sampling locations ....................................... 2

2. Aerial photograph (1988) showing a bedrock-dominated reach and an alluvial 

reach of the Green River between Split Mountain and the Jensen, Utah, 

streamflow gage .............................................................................. 5

 3–10. Graphs showing:

3. Annual peak-flow series for station 09261000, Green River near Jensen, 

Utah, 1947–2002 .................................................................................................................. 6

4. Flow-duration curves for station 09261000, Green River near Jensen, 

Utah, for the periods before and after closure of Flaming Gorge Dam .................... 7

5. Relative abundance of alluvial deposits: A, Little Snake River from 3 miles 

above the Lily streamflow gage to the confluence with the Yampa River; 

B, Yampa River from Cross Mountain to the confluence with the Green 

River; and C, Green River from the Lodore Ranger Station to Jensen, Utah ........... 9

6. Relation of sediment load at 09251100 Yampa River above Little Snake 

River near Maybell, Colorado, 1998–2002, A, to water discharge; B, by 

particle size to water discharge; and C, by season to water discharge ................ 13

7. Relation of suspended load at 09260000 Little Snake River near Lily, 

Colorado, 1994–2002, A, to water discharge; B, by particle size to water 

discharge; and C, by season to water discharge ....................................................... 19

8. Relation of sediment load at 09260050 Yampa River at Deerlodge Park, 

Colorado, 1982–2001, A, to water discharge; B, by particle size to water 

discharge; and C, by season to water discharge ....................................................... 24

9. Relation of sediment load at 404417108524900 Green River above Gates 

of Lodore, Colorado, 1999–2002, A, to water discharge; B, by particle size 

to water discharge; and C, by season to water discharge ....................................... 27

10. Relation of sediment load at 09261000 Green River near Jensen, Utah, 

1996–2002, A, to water discharge; B, by particle size to water discharge; 

and C, by season to water discharge ........................................................................... 31

Tables

1. Streamflow characteristics at streamflow-gaging station 09251100 Yampa 

River above Little Snake River, near Maybell, Colorado, 1997–2002 ..................... 11

2. Summary of discharge and sediment loads by transport mode, particle-size 

range, and season, 09251100 Yampa River above Little Snake River near 

Maybell, Colorado, 1998–2002 ............................................................... 12

3. Sediment-transport equations derived from sediment discharges measured 

at station 09251100 Yampa River above Little Snake River near Maybell, 

Colorado, 1998–2002 ........................................................................... 14

4. Streamflow characteristics at streamflow-gaging station 09260000 Little 

Snake River near Lily, Colorado, 1922–2002 ................................................ 15

5. Summary of discharge and sediment loads by transport mode, particlesize range, and season, 09260000 Little Snake River near Lily, Colorado, 

1994–2002 ....................................................................................... 16
v

6. Sediment-transport equations derived from sediment discharges measured 

at station 09260000 Little Snake River near Lily, Colorado, 1994–2002 .................. 20

7. Streamflow characteristics at streamflow-gaging station 09260050 Yampa 

River at Deerlodge Park, Colorado, 1982–94 and 1997–2002 .............................. 20

8. Summary of discharge and sediment loads by transport mode, particle-size 

range, and season, 09260050 Yampa River at Deerlodge Park, Colorado, 

1982–2001 ....................................................................................... 21

9. Sediment-transport equations derived from sediment discharges measured 

at station 09260050 Yampa River at Deerlodge Park, Colorado, 1982–2001. ............ 25

10. Streamflow characteristics at streamflow-gaging station 09234500 Green 

River near Greendale, Utah, 1963–2002 ................................................... 25

11. Summary of discharge and sediment loads by transport mode, particle-size 

range, and season, 404417108524900 Green River above Gates of Lodore, 

Colorado, 1999–2002 ........................................................................... 26

12. Sediment-transport equations derived from sediment discharges measured 

at station 404417108524900 Green River above Gates of Lodore, Colorado, 

1999–2002 ....................................................................................... 28

13. Streamflow characteristics at streamflow-gaging station 09261000 Green 

River near Jensen, Utah, 1947–62 and 1963–2002 ....................................... 29

14. Summary of discharge and sediment loads by transport mode, particle-size 

range, and season, 09261000 Green River near Jensen, Utah, 1996–2002 ............ 30

15. Sediment-transport equations derived from sediment discharges measured 

at station 09261000 Green River near Jensen, Utah, 1996–2002 ........................ 32

Conversion Factors, Vertical Datum, and Abbreviations

Multiply By To obtain

millimeter (mm) 0.03937 inch

meter (m) 3.281 foot (ft)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

acre 4,047 square meter (mi2)

square mile (mi2) 2.590 square kilometer (km2)

acre-foot (acre-ft) 1,233 cubic meter (m3)

ton, short 0.9072 megagram (Mg)

foot per day (ft/d) 0.3048 meter per day (m/d)

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD29).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD83).
Abstract

The water resources of the Upper Colorado River Basin 

have been extensively developed for water supply, irrigation, and power generation through water storage in upstream 

reservoirs during spring runoff and subsequent releases during 

the remainder of the year. The net effect of water-resource 

development has been to substantially modify the predevelopment annual hydrograph as well as the timing and amount of 

sediment delivery from the upper Green River and the Yampa 

River Basins tributaries to the main-stem reaches where 

endangered native fish populations have been observed. The 

U.S. Geological Survey, in cooperation with the Colorado 

Division of Wildlife and the U.S. Fish and Wildlife Service, 

began a study to identify sediment source reaches in the Green 

River main stem and the lower Yampa and Little Snake Rivers

and to identify sediment-transport relations that would be 

useful in assessing the potential effects of hydrograph modification by reservoir operation on sedimentation at identified 

razorback spawning bars in the Green River. The need for 

additional data collection is evaluated at each sampling site.

Sediment loads were calculated at five key areas within 

the watershed by using instantaneous measurements of 

streamflow, suspended-sediment concentration, and bedload. 

Sediment loads were computed at each site for two modes 

of transport (suspended load and bedload), as well as for the 

total-sediment load (suspended load plus bedload) where both 

modes were sampled. Sediment loads also were calculated 

for sediment particle-size range (silt-and-clay, and sand-andgravel sizes) if laboratory size analysis had been performed 

on the sample, and by hydrograph season. Sediment-transport 

curves were developed for each type of sediment load by a 

least-squares regression of logarithmic-transformed data.

Transport equations for suspended load and total load 

had coefficients of determination of at least 0.72 at all of the 

sampling sites except Little Snake River near Lily, Colorado. 

Bedload transport equations at the five sites had coefficients 

of determination that ranged from 0.40 (Yampa River at 

Deerlodge Park, Colorado) to 0.80 (Yampa River above Little 

Snake River near Maybell, Colorado). Transport equations for 

silt and clay-size material had coefficients of determination 

that ranged from 0.46 to 0.82.

Where particle-size data were available (Yampa River 

at Deerlodge Park, Colorado, and Green River near Jensen, 

Utah), transport equations for the smaller particle sizes (fine 

sand) tended to have higher coefficients of determination 

than the equations for coarser sizes (medium and coarse sand, 

and very coarse sand and gravel). Because the data had to be 

subdivided into at least two subsets (rising-limb, falling-limb 

and, occasionally, base-flow periods), the seasonal transport 

equations generally were based on relatively few samples. All 

transport equations probably could be improved by additional 

data collected at strategically timed periods.

Introduction

The water resources of the Upper Colorado River Basin 

have been extensively developed for water supply, irrigation, and power generation. The net effect of the development 

has been to substantially modify the predevelopment annual 

hydrograph by water storage in upstream reservoirs during 

spring runoff and subsequent releases during the remainder of 

the year. Another effect has been a change in the amount of 

sediment delivery from the basin to the main-stem reaches of 

the watershed. Hydrograph modification and sediment trapping by Flaming Gorge Dam on the Green River and land-use 

changes and water development in the Yampa and Little Snake 

River Basins have affected, and are likely to continue to affect, 

the habitat characteristics of the Yampa and Green Rivers 

(fig. 1). Changes in the hydrograph and in sediment delivery 

may have an effect on the suitability of spawning and other 

life-stage habitat for endangered fish.

The Yampa River is the only large river in the Upper 

Colorado River Basin in which the annual hydrograph has not 

been substantially altered by water-development projects and, 

therefore, is probably the best river to use as an example of 

the specific habitat requirements of endangered fish species. 

Closure of Flaming Gorge Dam on the Green River in 1962 

has not appreciably affected the mean annual discharge of the 

Green River but has decreased the magnitude of peak flows 

and increased the magnitude of streamflow in the historical 

low-flow and base-flow seasons (this report). Regulation of 

Summary of Sediment Data from the Yampa River 

and Upper Green River Basins, Colorado and Utah, 

1993–2002

By John G. Elliott and Steven P. Anders
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Figure 1. The Yampa River and upper Green River Basins showing streamflow-gaging stations and sediment-sampling locations.
the river also has altered the amount and timing of sediment 

delivery to an important spawning area (bar) of the endangered 

razorback sucker located downstream from the Yampa River 

confluence. Additional sediment-transport data are needed to 

augment existing data to evaluate the timing and magnitude of 

sediment movement in the vicinity of the spawning bar.

To address this need, the U.S. Geological Survey 

(USGS), in cooperation with the Colorado Division of Wildlife 

and the U.S. Fish and Wildlife Service, began a study in 1998 

to collect and evaluate sediment data in the Yampa River and 

upper Green River Basins. The objectives of the study were to 

(1) identify sediment source reaches of the Green River main 

stem upstream from Jensen, Utah, and its major tributaries, the 

Yampa and Little Snake Rivers; (2) develop sediment-transport 

curves that account for the magnitude and timing of sediment 

delivery at five sites on the major tributaries and main stem; 

and (3) evaluate the need for additional or long-term data collection to improve the utility of sediment-transport curves at 

the five major tributary and main-stem sites.

Purpose and Scope

The purpose of this report is to present sediment data 

collected and compiled from five sites on the Yampa River 

and in the upper Green River Basin and to describe sedimenttransport relations derived with these data that will be useful 

in assessing the potential effects of hydrograph modification 

by reservoir operation on sedimentation at identified razorback 

sucker spawning bars in the Green River. Such an assessment 

will be based on information included in this report that identifies the sources and size characteristics of the transported sediment, as well as an understanding of the timing and magnitude 

of suspended- and bedload-sediment transport in the major 

tributaries and main stem of the river system. This information 

supports site-specific studies of the hydraulic and depositional 

processes at specific spawning bars, such as the razorback 

spawning bar in the Green River downstream from Jensen, 

Utah. An assessment of site-specific conditions is beyond the 

scope of this report.

The five sediment-sampling sites were located at existing USGS streamflow-gaging stations: the Yampa River above 

Little Snake River near Maybell, Colorado, 09251100; the 

Little Snake River near Lily, Colorado, 09260000; the Yampa 

River at Deerlodge Park, Colorado, 09260050; the Green 

River above Gates of Lodore, Colorado, 404417108524900; 

and the Green River near Jensen, Utah, 09261000.

Sediment source reaches were identified from recent 

aerial photographs of the Green River main stem and 

the lower reaches of the Yampa and Little Snake Rivers. 

Sediment-transport, or rating, curves were derived from measurement of suspended sediment and bedload at streamflowgaging sites. The sediment samples were collected several 

times per year during 1998–2002 for the study described 

in this report and combined with discharge readings at the 

gages. These data were combined with historical data from 

the sites that resulted in different periods of record, ranging 

from 1982–2001 to 1998–2002 for the derivation of sedimenttransport curves. Linear regression of the sediment-load and 

discharge data was performed to derive the sediment-transport 

curves. Measurements were scheduled to cover a range of 

discharge from base flow to the annual instantaneous peak 

and to include both early season, or rising limb, and late 

season, or falling limb, hydrograph periods. Needs for additional or long-term data at each site were based on regression 

coefficient of determination (R2) and mean square error (MSE) 

statistics, the sample size, and the distribution of measurements throughout hydrograph seasons and over the range of 

historical discharges.

Previous Investigations

Several previous studies have investigated the magnitude 

and effects of sediment transport and deposition in the upper 

Green River Basin. Andrews (1978) estimated existing and 

potential sediment yields in the Yampa and Little Snake River 

Basins in Colorado and Wyoming and found that the relative 

contributions of water and sediment from smaller subbasins 

were quite variable. Elliott and others (1984) estimated the 

annual sediment load supplied to the Yampa Canyon downstream from Deerlodge Park in Dinosaur National Monument 

based on regression analyses of measured sediment discharges 

and on sediment discharges estimated with the ModifiedEinstein equation. Their estimates showed the average annual 

supply to the Yampa Canyon to be in the range of 2,040,000 to 

2,420,000 tons per year.

Martin and others (Utah State University, written commun., 1998) studied sediment transport, channel geometry, and 

streambank topography of the Green River in the Canyon of 

Lodore during 1995–97, a period that included an 8,560-ft3/s 

release from Flaming Gorge Reservoir, the largest release 

in the previous 13 years. They observed channel scour of as 

much as 6.5 ft and the redistribution of sand into eddies and 

along the channel margins, as well as channel widening due 

to erosion of some previously vegetated, post-dam-deposited, 

flood-plain sediment.

O’Brien (1984a) made suspended- and bedloadsediment measurements at Mathers Hole on the Yampa River 

in Dinosaur National Monument (figs. 1, 5B) and derived 

sediment-transport curves. He determined that the mean 

annual sediment load at Mathers Hole was highly correlated 

with the annual sediment load calculated for the Yampa River 

at Deerlodge Park, 30 mi upstream (Elliott and others, 1984). 

O’Brien (1984b) also monitored the evolution of riffle-pool 

morphology and composition at two Colorado pike-minnow 

spawning bars in Yampa Canyon in 1982 and 1983. His 

identification of the hydraulic conditions responsible for 

Introduction 3
4 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

transporting the supplied sand load over the undisturbed 

cobble substrate, as well as the conditions under which the 

cobble material itself was entrained, led to a recommended 

hydrograph for habitat maintenance in Yampa Canyon.

Harvey and others (1993) developed a one-dimensional, 

physical- and biological-process response model for pikeminnow spawning habitat at another known spawning bar in 

Yampa Canyon. Their study identified the hydraulic conditions 

and discharge ranges associated with sediment deposition and 

bar formation, as well as those associated with scour and bar 

dissection at that spawning site. Later efforts by Mussetter and 

others (2001) resulted in a two-dimensional, finite elementbased model that predicted the optimum hydrodynamic conditions for spawning at the bar studied by Harvey and others 

(1993). Pitlick and others (2001) noted a decrease over the last 

30 years in the area of side channel and backwater zones, critical habitat for many endangered fish in the Upper Colorado

River Basin. Their study found an association between this 

geomorphic change on the main stem and the decrease in 

annual peak discharges and mean annual sediment loads in 

the Upper Colorado River Basin.

The channel responses typical of rivers downstream 

from reservoirs were addressed by Williams and Wolman 

(1984). Some of the effects noted by Williams and Wolman 

were observed on the Green River downstream from Flaming 

Gorge Reservoir by Fischer and others (1983). The Fischer 

study quantified changes in riparian vegetation as well as 

streambank stability and steepness at several locations in the 

Canyon of Lodore. Lyons and others (1992) used repeated 

aerial photographs to estimated changes in channel width on 

the Green River downstream from the mouth of the Yampa 

River since construction of Flaming Gorge Dam. Andrews 

(1986) evaluated changes in the Green River channel width 

in response to the reduced peak discharges that resulted from 

reservoir operation. He determined that the bankfull channel 

width decreased by about 10 percent between 1962 and 1986. 

Merritt and Cooper (2000) observed a complex sequence of 

changes in channel geometry, island formation, sedimenttransport mode, and vegetation community in the Browns Park 

area following the construction of Flaming Gorge Reservoir in 

1962.

Elliott and others (1984) derived a sediment budget 

for the Yampa River at Deerlodge Park under streamflow 

conditions that existed until the early 1980s and under various reduced-flow scenarios. Under one scenario, Yampa 

River streamflows were altered in the same way that Green 

River streamflows were altered by Flaming Gorge Dam (for 

example, with the same annual streamflow volume but with a 

decreased duration of high-range discharges and an increased 

duration of low-range discharges). Under this scenario, the 

estimated annual total-sediment load of the Yampa River 

decreased by 150,000 tons per year, or 7 percent, from the 

load transported by the prevailing streamflow regime.

Acknowledgments

The authors wish to acknowledge J.E. (Ed) Vaill who 

initiated and directed this project in its early years. Rich 

Carver’s experience was indispensable in measurements made 

by boat, from bridges, and by wading. Joe Dungan, Cam Adibi, 

Cory Williams, Patricia Solberg, and Michael Whiteman of 

the USGS Colorado District and J.R. (Rod) Tibbetts and Terry 

Kenney of the Utah District assisted with data collection. 

Sediment samples were processed by the USGS Sediment

Laboratory in Iowa City, Iowa. The authors also wish to thank 

Steven Petersburg of Dinosaur National Monument and other 

staff of the National Park Service for their cooperation and permission to collect sediment samples within Dinosaur National 

Monument. Technical reviews of the manuscript were performed by John W. Roberts and David L. Butler of the USGS.

Study Area

Geographic Setting

The Green River is the largest tributary and most important source of runoff in the Upper Colorado River Basin. At the 

Jensen, Utah, streamflow gage, the Green River transports runoff and sediment from over 25,400 mi2

 in Wyoming, Colorado, 

and Utah. The upper tributaries of the watershed generally 

drain snowmelt from the igneous and metamorphic lithologies of several mountain ranges, whereas the lower tributaries 

generally drain more arid regions of sedimentary lithologies. 

Sediment sources tend to correlate with lithology and precipitation patterns, and a large amount of the annual sediment load 

is supplied to the Green River from the Little Snake River, by 

way of the Yampa River (Andrews, 1978, 1986).

The major tributaries in the study area—the Little Snake, 

the Yampa, and the upper Green Rivers—flow through a succession of wide, parklike reaches and narrow, steep canyons 

(figs. 1 and 2). The geomorphology of the park and canyon 

reaches may have an effect on the transport and temporary 

storage of sediment carried by the rivers. Steep, confined canyon reaches may function as sediment-conveying zones during 

floods, whereas broad, parklike reaches with low gradients 

may be associated with depositional environments during the 

same floods.

Locations on the Little Snake, the Yampa, and the 

upper Green Rivers are referred to in this report in terms 

of river miles upstream from some reference point. River 

miles on the Little Snake River are measured upstream from 

its confluence with the Yampa River in Lily Park (fig. 1). 

River miles on the Yampa are measured upstream from its 

confluence with the Green River at Echo Park. River miles on 

the Green River between Flaming Gorge Dam and the Jensen 
Figure 2. Aerial photograph (1988) showing a bedrock-dominated reach and an alluvial reach of the Green River between 

Split Mountain and the Jensen, Utah, streamflow gage.

streamflow gage are the same as those published in the widely 

used Dinosaur River Guide (Evans and Belknap, 1973). Evans 

and Belknap measured river miles upstream from the town of 

Green River, Utah, which is about 117 river miles upstream 

from the confluence of the Green River with the Colorado 

River.

Streamflow

Long-term streamflow records have been collected 

at the Little Snake River near Lily gage (1921–present), 

the Green River near Greendale gage (USGS station number 

09234500; 1951–present), and the Green River near Jensen 

gage (1947–present). The Yampa River at Deerlodge 

Park gage was installed in 1982 and has operated almost 

continuously since then. A new streamflow-gaging station 

was installed on the Yampa River upstream from Little 

Snake River in 1996. All gages are active at this time 

(2004).

Flow in the Green River upstream from the two 

Green River streamflow-gaging stations has been regulated 

by Flaming Gorge Reservoir since November 1962. Regulation by the reservoir has altered the magnitude and timing 

of the instantaneous peak discharge in the Green River 

downstream from the reservoir, but not the annual volume 

of runoff (Andrews, 1986).

Study Area 5

Split

Mountain

boat ramp

Split

Mountain

Sampling

site

Gage

Spawning

bar

BEDROCK

DOMINANT

ALLUVIAL

DOMINANT
6 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

Streamflow characteristics were derived for each sampling site based on the recorded discharge data. The frequency 

of annual, instantaneous peak discharges and the duration of 

daily mean discharges were calculated by standard USGS 

procedures (U.S. Interagency Advisory Committee on Water 

Data, 1982) using records from gaging stations in the study 

area. Peak-flow frequency for the Yampa River above Little 

Snake River gage was calculated from only 6 years of record 

(1997–2002). Peak-flow frequency was not calculated for 

the Green River near Greendale gage because the magnitude 

of streamflow at that site is entirely controlled by the operation of Flaming Gorge Reservoir. Flow-duration statistics 

and peak-flow frequency for the Green River near Jensen are 

presented only for the years after completion of the Flaming 

Gorge Dam (1963–2002). Streamflow characteristics for each 

sampling site are summarized later in this report in tables 1, 4, 

7, 10, and 13, which are in the respective sections for individual sampling-site summaries.

Streamflow and sediment transport in the Little Snake 

and Yampa Rivers have been affected only slightly by 

water storage and transbasin diversions within the respective watersheds, and no major dams have been constructed 

on the main stems of these rivers. However, Flaming Gorge 

Reservoir, completed in 1962, has had a significant effect 

on streamflow, sediment transport, and the geomorphology of 

the Green River downstream from the dam (Andrews, 1986). 

The Green River near Jensen gage has operated since 1947, 

and discharge characteristics from that gage reflect alterations in streamflow as a result of reservoir operation. Andrews 

(1986) used discharge data recorded at this site from 1962 

through 1981 in his analyses of downstream reservoir effects 

on the Green River. Annual peak discharges and flow-duration 

curves for the Green River near Jensen gage, updated through 

water year 2002, reveal the changes in streamflow caused by 

Flaming Gorge Reservoir (figs. 3 and 4).

Fluvial Sediment Transport and 

Deposition

Sediment transported by the Green River downstream 

from Flaming Gorge Reservoir has been affected by impoundment of upstream-supplied sediment and by changes in the 

streamflow regime. Andrews (1986) determined that, at 

the time of his study, the sediment supply to the river was 

exceeded by the sediment transport for a relatively short 

distance downstream from the reservoir. This reach included 

Figure 3. Annual peak-flow series for station 09261000, Green River near Jensen, Utah, 1947–2002.

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most of the river from Flaming Gorge Dam at river mile 290 to 

the confluence of the Yampa River at river mile 225. Andrews 

(1986) noted the channel of the Green River appeared to be 

in equilibrium from the mouth of the Yampa River (river 

mile 225) to the mouth of the Duchesne River (river mile 46). 

Downstream from the Duchesne River, the combined sediment 

supply from upstream, from within the channel, and from 

tributaries joining the river downstream from the reservoir 

exceeded the transport by about 5,400,000 tons per year on 

average. In response to reduced peak discharges and a net 

surplus of sediment, the bankfull channel width had decreased 

by about 10 percent by 1986; but according to Andrews, these 

adjustments were not complete and would continue for perhaps another century.

Andrews (1986) noted that the sediment transported by 

the Green River downstream from Flaming Gorge Reservoir 

was contributed primarily by the downstream part of tributary 

drainage basins. These tributary basins range from small, 

ephemeral watersheds to the large, perennial Yampa River 

Basin (fig. 1). Elliott and others (1984) estimated that the 

mean annual sediment load of the Yampa River at Deerlodge 

Park ranged from 2,040,000 to 2,420,000 tons per year. Of 

this annual load, 78 to 95 percent was sand, silt, and clay 

transported in suspension. Andrews (1978) estimated that 

approximately 60 percent of the Yampa River sediment load 

at Deerlodge Park was contributed by tributaries draining the 

lower Little Snake River Basin (fig. 1).

Sediment Storage Areas

Onsite observations and an examination of aerial photographs of the lower Little Snake, lower Yampa, and lower 

Green Rivers taken during the autumn of 1988 reveal that a 

large amount of sediment is stored in the river channel and 

flood plain in the form of alluvial banks, bars, and islands. 

Best observed as subaerial alluvial deposits during low-stage 

periods, these near-channel areas may be important secondary sources of sediment that periodically is entrained by 

the Green River and its larger tributaries. Base-flow season 

aerial photographs of the channels of the Little Snake River 

downstream from the Lily streamflow gage, the Yampa River 

downstream from Cross Mountain, and the Green River from 

the Lodore Ranger Station to Jensen were assessed to determine the relative abundance of alluvial materials in the banks 

and bars. It was assumed that this material has a potential for 

remobilization. Neither the condition of the streambed, the 

thickness of alluvial deposits, nor the particle-size characteristics of the alluvial materials could be determined from the 

aerial photographs.

Subaerial alluvial banks and bars visible in the aerial 

photographs were mapped by 1-mile subreaches on 7.5-minute 

topographic maps. The total length of alluvial channel 

boundaries was then expressed as a percentage of twice the 

1-mile subreach length. For example, if both banks of a 1-mile 

subreach were alluvial, then the alluvial-boundary percentage would be [(1+1) / (2×1)] × 100 = 100. If one bank of the 

Figure 4. Flow-duration curves for station 09261000, Green River near Jensen, Utah, for the periods before and after closure of 

Flaming Gorge Dam.

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Fluvial Sediment Transport and Deposition 7
8 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

1-mile subreach was alluvial and the other bank was bedrock 

or coarse talus (that is, nonalluvial), the percentage would 

be [(1+0) / (2×1)] × 100 = 50. Midchannel alluvial islands 

were treated as an alluvial bank if one or both banks were 

nonalluvial. Lengths of these islands were not factored in 

when both riverbanks adjacent to the island were alluvial; this 

constrained the alluvial boundary percentage to a maximum of 

100 percent.

The relative abundance of subaerial alluvial deposits in 

the 1988 photographs varied from river to river in the watershed and from subreach to subreach along a river. Although 

the flood-plain width was relatively narrow and the surface 

area of subaerially exposed alluvial deposits was small, the 

Little Snake River, a few miles downstream from streamflowgaging station 09260000, had a consistently high percentage 

of its banks consisting of alluvial deposits (fig. 5A).

The large sediment yield of the Little Snake River, noted 

by Andrews (1978), is reflected in the increase in relative 

abundance of alluvial deposits in the Yampa River immediately downstream from the Little Snake River confluence at 

river mile 50.5 (fig. 5B). The relative abundance of alluvial 

deposits drops abruptly from greater than 80 percent to less 

than 20 percent as the Yampa River flows into the steep and 

narrow Yampa Canyon (fig. 1). Alluvial deposits are relatively 

scarce in Yampa Canyon between river miles 45 and 21. The 

canyon geomorphology in this reach is dominated by the massive limestone of the Morgan Formation, and the river is steep 

and the canyon floor is narrow, providing little area suitable 

for significant alluvial sediment storage. The Yampa River 

flows through the massive Weber Sandstone downstream from 

river mile 21 and, from here to the mouth, the canyon floor is 

wider and more conducive to sediment deposition.

The abundance of subaerial alluvial sediment in the 

Green River downstream from the Lodore Ranger Station is 

less uniform than in the Little Snake or Yampa Rivers. The 

relative abundance of alluvial deposits ranges from less than 

10 to more than 80 percent of the visible channel boundary between the Lodore Ranger Station and the downstream 

end of the study reach at river mile 194 (figs. 1 and 5C). The 

regional structural geology and lithology at river level may 

be significant in determining variations in canyon-floor width 

and gradient that influence the relative abundance of alluvial 

deposits in the Green River.

The sediment-transport equations presented in the 

“Sediment-Transport Curves” section of this report indicate 

that the transport of gravel, sand, silt, and clay in these rivers 

is strongly dependent on the streamflow magnitude and, to 

a lesser degree, on the season. The timing of annual runoff, 

and consequently the timing of sediment entrainment, transport, and deposition, affects aquatic habitat and is dependent 

on long-term climate, seasonal weather patterns, and on the 

operation of upstream reservoirs. Reach-specific estimates of 

the timing, volume, and particle size of sediment deposited at 

critical aquatic-habitat sites other than at the gaged sampling 

sites require streamflow routing simulations through the drainage network and are beyond the scope of this report.

Sampling Sites

Understanding the timing and mechanics of sediment 

delivery at a specific location, such as the spawning bar on 

the Green River, requires an understanding of the timing and 

mechanics of sediment delivery from the entire watershed. 

A first step in determining sediment delivery to a specific 

location or in creating a sediment budget for the watershed 

is to derive sediment-transport equations (sediment-transport 

curves) on the principal streams. These transport curves should 

reflect the transport of sediment by both suspended and bedload modes, the transport of sediment particles in various size 

ranges, and the seasonal variability of supply and transport in 

order to be useful in modeling and budget computations.

Sediment-transport curves were derived using instantaneous measurements of streamflow, suspended-sediment 

concentration, and bedload. Sediment samples were collected 

at five sites within the watershed where streamflow data also 

were collected (fig. 1):

1. Yampa River above Little Snake River near Maybell, 

Colorado, 09251100;

2. Little Snake River near Lily, Colorado, 09260000;

3. Yampa River at Deerlodge Park, Colorado, 09260050;

4. Green River above Gates of Lodore, Colorado; 

404417108524900 (the nearest streamflow gage is Green 

River near Greendale, Utah, 09234500); and

5. Green River near Jensen, Utah, 09261000.

Sampling-site locations, descriptions, and periods of streamflow and sediment records are given in later sections of the 

report that pertain to the five specific sites.

Sediment Sampling

Suspended-sediment and bedload samples were collected 

using conventional methods described in Guy and Norman 

(1970) and Edwards and Glysson (1999). Bedload-sediment 

samples were collected with a 3-inch Helley-Smith bedload 

sampler (Helley and Smith, 1971). Suspended-sediment and 

bedload samples were collected at two sites on the Yampa 

River to bracket the inflow from the Little Snake River, a major 

sediment source in the Yampa River Basin (Andrews, 1978). 

Suspended- and bedload-sediment sampling at the Yampa 

River above Little Snake River site began in 1998. Suspendedand bedload-sediment measurements at the Yampa River at 

Deerlodge Park site were made in 1982 and 1983 (Elliott 

and others, 1984), in 1994, and from 1997 through 2001.

Suspended-sediment samples were collected at the Little Snake 

River near Lily in 1983, from 1994 through 1998, and from 

2000 through 2002. Bedload samples were collected only in 

2001 and 2002. Data collected before the beginning of this 

study (1998) were incorporated into the present analyses.

No sediment data before 1999 were available from the 

Green River immediately downstream from Flaming Gorge 

Reservoir. Suspended-sediment and bedload measurements 
Figure 5. Relative abundance of alluvial deposits: A, Little Snake River from 3 miles above the Lily 

streamflow gage to the confluence with the Yampa River; B, Yampa River from Cross Mountain to the 

confluence with the Green River; and C, Green River from the Lodore Ranger Station to Jensen, Utah.

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Fluvial Sediment Transport and Deposition 9
10 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

were made on the Green River above the Gates of Lodore 

Canyon from 1999 through 2002. Although little sediment 

passes through the reservoir, the variability of streamflow is 

regulated by operation of the reservoir and has an effect on 

tributary-supplied sediment downstream. Downstream effects 

on discharge fluctuations, streambed scour, and sediment 

entrainment can be significant for many miles downstream 

from large reservoirs (Williams and Wolman, 1984).

The longest period of sediment record in the study area 

is from the Green River near Jensen. Suspended sediment was 

measured at this site from 1948 through 1979, but no bedload 

measurements were made. Suspended-sediment and bedload 

samples were collected at the Jensen site in 1996. After a 

1-year hiatus, suspended-sediment and bedload samples were 

collected from 1998 through 2002.

Seasonal, or hysteretic, variability in sediment supply 

and transport is common on many rivers. The daily sediment load for a specific discharge may be greater during 

the spring than for the same discharge in the summer or fall. 

The opposite relation can exist on some rivers as well. If the 

hysteresis effect is strong on a particular river reach, use of a 

single sediment-transport curve for all seasons may result in 

less precise estimates of annual sediment load than if curves 

for each season are used. Separate transport curves for the 

early, or rising-limb hydrograph, and later, or falling-limb 

hydrograph, periods are desirable if there are data to indicate 

a strong hysteresis and if enough measurements are available 

to derive representative and statistically significant sedimenttransport curves.

The sampling strategy of this project was to collect 

enough samples to cover the full range of expected discharges 

at a site and to account for seasonality or hysteresis effects. 

Base-flow periods usually were not sampled because only 

a small portion of the annual sediment load is transported 

during that time. Normally, such a strategy would require 

several dozen measurements for each sediment-transport curve 

(Elliott and others, 1984); however, the design of this study 

was to collect a few samples at each site over a period of several years rather than to sample all sites intensively for a 1- or 

2-year period. This strategy allowed year-to-year adjustments 

in the sampling schedule so appropriate discharge ranges 

could be sampled.

Sediment-Transport Curves

Sediment loads, or sediment discharges, were calculated 

for the five sampling sites by using instantaneous measurements of streamflow, suspended-sediment concentration, and 

bedload. Sediment loads, in tons per day, were computed for 

two modes of transport (suspended load and bedload) as well 

as for the total sediment load (suspended load plus bedload) 

if both modes had been sampled. Suspended-sediment load 

(tons per day) was calculated as the product of water discharge 

(cubic feet per second), suspended-sediment concentration 

(milligrams per liter), and a coefficient of 0.0027 (Porterfield, 

1972, p. 43). Bedload (tons per day) was calculated as the 

product of the channel width (feet), the mass of the bedload 

sample (grams), and a units conversion factor of 0.381 (for a 

3-inch sampler orifice), divided by the time the Helley-Smith 

sampler was in contact with the streambed (seconds) (Edwards 

and Glysson, 1999, p. 80).

Sediment loads also were calculated for sediment 

particle-size range (silt-and-clay, and sand-and-gravel sizes) 

if laboratory size analysis had been done on the sample. 

Silt-and-clay load included all sediment finer than 0.062 mm 

in diameter, mostly transported as suspended load; sand-andgravel load included any sediment with a diameter greater 

than or equal to 0.062 mm, including both suspended load 

and bedload. The size-range designation was independent of 

transport mode.

Each sediment measurement was given a seasonal 

classification based on when the sample was collected relative 

to the date of the annual peak discharge (rising-limb season 

or falling-limb season). In the case of sediment collected at 

the Green River above Gates of Lodore site, where streamflow peaks are regulated by Flaming Gorge Dam, seasons 

were classified as “early” or “late” with respect to the timing 

of the annual peak discharge on the Yampa River at Deerlodge 

Park.

Sediment-transport curves were derived for each transportation mode, particle-size range, and season by fitting a line 

to the sediment-discharge and water-discharge data so that the 

deviation of all points from the line was minimized. Sedimenttransport curves commonly are approximated by a leastsquares regression of logarithmic-transformed data (Walling, 

1977) and, as presented in this analysis, are expressed in the 

form of a power equation:

Qs = aQb (1)

where

Qs is sediment discharge, in tons per day;

a is regression constant, or intercept;

Q is water discharge, in cubic feet per second;

and

b is regression exponent, or slope.

Linear regression may not always be appropriate 

because it assumes that the linear relation is continuous from 

low streamflows to high streamflows. Other curve-fitting 

techniques may be appropriate in certain circumstances, but 

Troutman and Williams (1987) indicate that ordinary leastsquares regression is an appropriate technique when the prediction of the dependent variable is the objective and when the 

assumption of linearity can be met. When the transport curve is 

used as a predictive tool, it usually is used to estimate the mean 

response of the dependent variable (sediment load) given a 

value of the independent variable (measured water discharge).

The use of the transport curves presented in this report to 

estimate sediment loads could result in biased estimates of the 

loads because logarithmic transformation of data can result in 

biased estimates of the dependent variable in regression analysis. Transformation bias occurs when regression estimates 
(expressed in log values) are detransformed (to nonlog values, 

for example, tons per day) and usually results in underestimation of the mean response of the dependent variable (estimated 

sediment load). Transformation bias is greatest when the sediment and water discharge data are characterized by a relatively 

large number of measurements at low discharges and when 

the scatter of data points around the regression curve is great 

(Jansson, 1985).

Miller (1984) discussed transformation bias when fitting 

curves to natural logarithm-transformed data and shows that, 

for estimates of the dependent variable, transformation bias is 

multiplicative and increases exponentially with the variance. 

Therefore, it is possible to eliminate most transformation bias 

by multiplying the sediment-discharge estimate by a correction factor:

Cb = e0.5(MSE) (2)

where

Cb is transformation-bias correction factor;

e is base of the natural logarithm;

and

MSE is mean square error, an unbiased estimator 

of the error variance.

The relative accuracy and representativeness of the 

transport relations derived in this study can be assessed on 

the values of the coefficients of determination (R2) of regression equations, the MSE (or variance), the range of discharges 

sampled relative to typically observed discharges, the seasonality of the relations, and the number of samples. The transport 

equations in this report are considered to be reasonably representative if the R2

 value is greater than about 0.70, if sediment 

samples are evenly distributed over the likely range of water 

discharges in a year, if the samples are distributed between the 

rising-limb and falling-limb hydrograph seasons, and if the 

number of samples is large enough to reflect the variance in 

the sediment load to water-discharge relation.

Yampa River above Little Snake River, 

near Maybell, Colorado

Site Description

Streamflow and sediment measurements were made at 

streamflow-gaging station 09251100 Yampa River above Little 

Snake River, near Maybell, Colorado. The gage is located at 

latitude 40o27'39", longitude 108o25'30", in NW1/4 NE1/4 

sec. 20, T. 6 N., R. 98 W., Moffat County, on the Moffat

County Road 25 bridge, 1 mile upstream from the mouth of 

the Little Snake River. Drainage area at the gaging station is 

3,837 mi2.

The sampling site is in an area known as Lily Park, 

a broad alluvial valley, approximately 2.5 miles downstream from the mouth of Cross Mountain Canyon, a steep, 

bedrock-dominated reach of the Yampa River (fig. 1). Discharge and sediment measurements were made from the 

bridge at most streamflows. Measurements at low streamflows 

were made approximately 150 ft upstream from the bridge by 

wading.

Streamflow and Sediment Data

Streamflow characteristics from streamflow data collected at the streamflow-gaging station are presented in table 1 

and sediment-load data are presented in table 2. Plots of the 

sediment-load data are presented in figure 6.

Analysis

Streamflow data have been collected at gaging station

09251100 Yampa River above Little Snake River, near 

Maybell, Colorado, since May 1996. Streamflow-duration

and peak-flow statistics based on 6 years of record are presented in table 1. During this period, annual instantaneous 

discharge peaks ranged from 7,920 ft3/s in 2001 to 16,400 ft3/s 

in 1997 (Crowfoot and others, 2002). Base-flow conditions 

occur at discharges of less than about 500 to 600 ft3/s and 

are equaled or exceeded about 45 to 55 percent of the time 

(table 1).

Table 1. Streamflow characteristics at streamflow-gaging 

station 09251100 Yampa River above Little Snake River, near 

Maybell, Colorado, 1997–2002.

[Streamflow duration in percentage of time specific discharge is equaled or 

exceeded, calculated with daily mean discharge; ft3/s, cubic foot per second; 

%, percentage; nc, not calculated]

Recurrence interval 

of peak discharge

Duration of daily 

mean discharge

Recurrence 

interval 

(years)

Discharge 

(ft3/s)

Duration 

(% time)

Discharge 

(ft3/s)

1.05 nc 95 92.9

1.11 nc 90 177.8

1.25 7,779 85 215.6

2 9,836 80 246.9

5 12,500 75 278.1

10 14,190 70 309.3

25 16,270 65 341.7

50 17,790 60 375.6

100 19,280 55 409.4

200 20,770 50 453.0

500 22,740 45 508.4

40 565.9

35 800.9

30 1,175.7

25 1,556.1

20 2,121.5

15 3,384.2

10 4,933.9

5 7,205.4

Yampa River above Little Snake River near Maybell, Colorado 11
12 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002 Table 2. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 09251100 Yampa River above Little Snake River near Maybell, Colorado, 1998–2002. [dd min yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; Susp Sed, suspended sediment; nd, no data] Sample date (dd mm yy) Instanta- neous discharge (ft3/s) Hydro- graph season Suspended- sediment load (tons/d) Bedload (tons/d) Total sediment load (tons/d) Bedload percentage of total load (%) Total load <0.062 mm (tons/d) Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks

06 May 98 9,590 Rising 22,400 69 22,469 0.3 16,800 5,669 16,800 5,600 nd nd nd No suspended size fractions19 May 98 7,580 Rising 9,930 174 10,104 1.7 7,944 2,160 7,944 1,986 nd nd nd Peak 22 May 199827 May 98 6,760 Falling 6,420 210 6,630 3.2 4,494 2,136 4,494 1,926 nd nd nd No suspended size fractions03 June 98 7,640 Falling 5,710 264 5,974 4.4 3,883 2,091 3,883 1,827 nd nd nd No suspended size fractions10 June 98 4,950 Falling 3,680 50 3,730 1.3 2,098 1,632 2,098 1,582 nd nd nd No suspended size fractions17 June 98 5,130 Falling 6,900 36 6,936 0.5 3,864 3,072 3,864 3,036 nd nd nd No suspended size fractions30 June 98 4,740 Falling 1,330 35 1,365 2.5 638 726 638 692 nd nd nd No suspended size fractions31 Mar 99 1,420 Rising 372 13 385 3.4 294 91 294 78 nd nd nd No suspended size fractions20 May 99 4,820 Rising 5,400 101 5,501 1.8 4,105 1,396 4,104 1,296 992 387 16 Peak 31 May 199905 Apr 00 908 Rising 81 0.22 81 0.3 74 7 74 7 nd nd nd19 Apr 00 3,930 Rising 4,150 43 4,193 1.0 2,432 1,761 2,432 1,718 981 780 102 May 00 5,670 Rising 7,010 72 7,082 1.0 4,900 2,182 4,900 2,110 1,432 745 426 May 00 7,620 Rising 10,700 221 10,921 2.0 6,720 4,202 6,720 3,980 1,930 2,196 75 Peak 31 May 200005 July 00 558 Falling 20 0.15 20 0.7 17 3 17 3 nd nd nd No suspended size fractions16 Mar 01 558 Base flow 21 nd nd nd nd nd 16 5 nd nd nd No bedload 16 Mar 200126 Mar 01 1,720 Rising 1,410 4.5 1,414 0.3 1,156 258 1,156 254 0 4 0 Susp Sed sand break only16 Apr 01 1,160 Rising 254 3.5 257 1.4 224 34 224 30 0 3 1 Peak 18 May 200112 June 01 3,070 Falling 796 35 831 4.2 390 441 390 406 287 145 914 June 01 2,390 Falling 542 21 563 3.8 314 249 314 228 211 30 819 June 01 1,410 Falling 278 2.7 281 1.0 125 156 125 153 92 63 020 June 01 1,330 Falling 104 1.7 106 1.6 81 25 81 23 0 1 0 Susp Sed sand break only02 Apr 02 1,150 Rising 357 5.1 362 1.4 325 37 325 32 32 5 023 Apr 02 1,320 Rising 2,190 2.3 2,192 0.1 1,467 725 1,467 723 0 2 0 Susp Sed sand break only14 May 02 1,590 Rising 219 23.9 243 9.8 186 57 186 33 33 23 121 May 02 2,730 Rising 1,800 39.6 1,840 2.2 1,206 634 1,206 594 558 72 304 June 02 2,810 Falling 1,690 191.6 1,882 10.2 862 1,020 862 828 597 411 11 Peak about 2 May 2002
Figure 6. Relation of sediment load at 09251100 Yampa River above Little Snake 

River near Maybell, Colorado, 1998–2002, A, to water discharge; B, by particle 

size to water discharge; and C, by season to water discharge.

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Yampa River above Little Snake River near Maybell, Colorado 13
14 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

Sediment-load measurements were made at gaging 

station 09251100 from 1998 through 2002 (table 2). Annual 

instantaneous discharge peaks for the years when sediment 

measurements were made ranged from 7,920 ft3/s in 2001 to 

9,980 ft3/s in 1998. The instantaneous discharge peak for 2000 

was not recorded due to equipment malfunction. Suspended 

sediment was measured 25 times at discharges ranging from 

558 to 9,590 ft3/s and included 14 measurements during the 

rising-limb hydrograph season and 11 measurements during 

the recessional- or falling-limb hydrograph season. Bedload 

as a percentage of total-sediment load ranged from 0.1 to 

10.2 percent and averaged 2.4 percent.

The sediment-transport equation for total-sediment load 

had a coefficient of determination (R2) of 0.85, the equation 

for suspended-sediment load had an R2 of 0.87, and bedload 

discharge had an R2 of 0.80 (table 3). The equations for siltand-clay load and sand-and-gravel load had an R2

 of 0.82 

and 0.86, respectively. The seasonality transport equations 

for total load during the rising-limb and falling-limb hydrograph seasons had R2

 values of 0.87 or greater, but were 

based on a relatively small number of samples. The relatively 

large R2 values (greater than or equal to 0.80) for all transport 

equations at station 09251100 indicate that the transport 

equations may be useful for annual load estimation or sediment budget calculations for discharges ranging from about 

500 to 10,000 ft3/s. These transport equations may not adequately reflect transport conditions of higher discharges that 

occurred in 1997 or in the mid-1980s before the streamflowgaging station was established. Additional measurements in 

the 500- to 10,000-ft3/s range from both the rising-limb 

and falling-limb hydrograph seasons, and any measurements 

during discharges greater than 10,000 ft3/s, would make 

these equations more representative of flow conditions at 

this site.

Little Snake River near Lily, Colorado

Site Description

Streamflow and sediment measurements were made at 

streamflow-gaging station 09260000 Little Snake River near 

Lily, Colorado. The gage is located at latitude 40o32'50", longitude 108o

25'25", in NW1/4 NE1/4 sec. 20, T. 7 N., R. 98 W., 

Moffat County, Colorado, on the left bank 170 ft downstream 

from the highway bridge, approximately 10 mi upstream 

from the mouth (fig. 1). Drainage area at the gaging station 

is approximately 3,730 mi2.

The sampling site is at a bedrock-constricted river reach 

immediately downstream from a wide, sandy reach of the 

Little Snake River. Discharge and sediment measurements 

were made from the bridge at moderate and high streamflows 

and approximately 300 ft downstream from the bridge at low 

streamflows by wading.

Streamflow and Sediment Data

Streamflow characteristics from discharge data collected 

at the streamflow-gaging station are presented in table 4, 

and sediment-load data are presented in table 5. Plots of the 

sediment-load data are presented in figure 7.

Analysis

Streamflow data have been collected at gaging 

station 09260000 Little Snake River, near Lily, Colorado, 

since October 1921, and representative peak-flow and 

streamflow-duration statistics for the period are presented 

in table 4. During the period of streamflow data collection, 

annual instantaneous discharge peaks ranged from 996 ft3/s 

in 1934 to 16,700 ft3/s in 1984 (Crowfoot and others, 2002). 

Base-flow conditions occur at discharges of less than about 

100 to 200 ft3/s and are equaled or exceeded about 40 to 

60 percent of the time (table 4).

Suspended-sediment measurements were made at gaging 

station 09260000 from 1994 through 2002 (table 5). Bedload measurements were made in 2001 and 2002. Annual 

instantaneous discharge peaks for the years when sediment 

measurements were made ranged from 2,840 ft3/s in 1994 

to 6,480 ft3/s in 1999. Suspended sediment was measured 

96 times at discharges ranging from 1 to 5,840 ft3/s and 

included 40 measurements during the rising-limb hydrograph 

season and 28 measurements during the recessional- or fallinglimb hydrograph season. The 10 bedload measurements were 

made at discharges ranging from 346 to 1,280 ft3/s. Bedload 

as a percentage of total-sediment load ranged from 10.8 to 

52.1 percent and averaged 23.5 percent.

Table 3. Sediment-transport equations derived from sediment 

discharges measured at station 09251100 Yampa River above 

Little Snake River near Maybell, Colorado, 1998–2002.

[Qs, sediment discharge in tons per day; Q, water discharge in cubic feet per 

second; R2, coefficient of determination; MSE, mean square error; n, number 

of samples]

Type of 

sediment 

discharge

Regression 

equation R2 MSE n

Total Qs = 0.000106 Q2.33 0.85 0.479 25

Suspended Qs = 0.0000581 Q2.13 0.87 0.492 26

Bedload Qs = 0.000000188 Q2.33 0.80 0.885 25

Silt and clay Qs = 0.000151 Q1.96 0.82 0.564 25

Sand and gravel Qs = 0.00000223 Q2.39 0.86 0.640 25

Total, rising Qs = 0.000335 Q1.96 0.87 0.427 14

Total, falling Qs = 0.0000137 Q2.26 0.94 0.246 11
The sediment-transport equations for total-sediment 

load (R2 = 0.22) and bedload (R2 = 0.60) are based on only 

10 measurements and probably are inadequate for annual load 

or sediment budget calculations. The sediment-transport equation for suspended-sediment load had an R2

 of 0.74 (table 6). 

Regression of subsets of suspended-sediment data on the basis 

of particle size and seasonality produced generally poorer 

results with individual transport equation R2 values ranging 

between 0.46 and 0.54. An exception was the transport equation for suspended load during the falling-limb hydrograph 

season with an R2 of 0.76.

The suspended-sediment measurements at station 

09260000 are relatively evenly distributed over streamflows 

from about 40 to 6,000 ft3/s; however, streamflows at conditions approaching the 1984 historical instantaneous peak discharge have not occurred in recent years. The transport equation for suspended-sediment load is adequate for estimating 

annual suspended loads for discharges ranging from about 40 

to 6,000 ft3/s and may have some applicability for discharges 

ranging from about 1 to 40 ft3/s. The suspended-sediment 

load transport equation must be recomputed with data from 

discharges greater than 6,000 ft3/s for it to be applicable at 

extremely high discharges. Transport equations by suspendedparticle size show greater variance (mean square error, MSE, 

greater than 2), but are applicable for discharges ranging from 

about 50 to 6,000 ft3/s. Although the distribution of data indicates a seasonal sediment-load hysteresis may exist (fig. 7C), 

the relatively low R2 value for the rising-hydrograph season 

could be improved with additional data collected in the appropriate season. Also, because bedload data have been collected 

for only 2 years at this site, neither the total-annual sediment 

load nor the relative portion of total-sediment load transported 

as bedload are well documented. Bedload is an important component of the annual sediment budget in the Little Snake River 

at Lily and could be quantified with future measurements.

Yampa River at Deerlodge Park, 

Colorado

Site Description

Streamflow and sediment measurements were made 

at streamflow-gaging station 09260050 Yampa River at 

Deerlodge Park, Colorado. The gage is located at latitude 

40o27'06", longitude 108o31'28", in SE1/4 SW1/4 sec. 21, 

T. 6 N., R. 99 W., Moffat County, at the eastern entrance to 

Dinosaur National Monument, 5 river miles downstream from 

the mouth of the Little Snake River. Drainage area at the gage 

is approximately 7,660 mi2.

The sampling site is in an area known as Deerlodge Park, 

a broad alluvial valley, approximately 0.5 mi upstream from 

the entrance to Yampa Canyon, a steep, bedrock-dominated 

reach of the Yampa River (fig. 1). Discharge and sediment 

measurements were made from a boat at most streamflows. 

One low-streamflow measurement was made approximately 

100 ft downstream from the gage by wading.

Streamflow and Sediment Data

Streamflow characteristics from discharge data collected 

at the streamflow-gaging station are presented in table 7, 

and sediment-load data are presented in table 8. Plots of the 

sediment-load data are presented in figure 8.

Analysis

Streamflow data have been collected at gaging station 

09260050 Yampa River, at Deerlodge Park, Colorado, since 

April 1982. The station was inactive in 1995 and 1996 but was 

reactivated in 1997. Peak-flow and streamflow-duration statistics for the period of record are presented in table 7. During 

the period of streamflow-data collection, annual instantaneous 

discharge peaks ranged from 3,810 ft3/s in 2002 to 33,200 ft3/s 

in 1984 (Crowfoot and others, 2002). Base-flow conditions 

occur at discharges of less than about 600 to 700 ft3/s and are 

equaled or exceeded about 50 percent of the time (table 7).

Table 4. Streamflow characteristics at streamflow-gaging 

station 09260000 Little Snake River near Lily, Colorado, 

1922–2002.

[Recurrence interval, in years, equals reciprocal of exceedance probability, 

calculated with annual instantaneous discharge peak; streamflow duration in 

percentage of time specific discharge is equaled or exceeded, calculated with 

daily mean discharge; ft3/s, cubic foot per second; %, percentage]

Recurrence interval 

of peak discharge

Duration of daily 

mean discharge

Recurrence 

interval 

(years)

Discharge 

(ft3/s)

Duration 

(% time)

Discharge 

(ft3/s)

1.05 2,171 95 2.15

1.11 2,626 90 12.3

1.25 3,283 85 27.8

2 4,934 80 44.6

5 7,225 75 57.6

10 8,730 70 69.0

25 10,600 65 81.3

50 11,970 60 95.2

100 13,320 55 109.0

200 14,650 50 130.2

500 16,390 45 159.0

40 196.0

35 249.1

30 342.6

25 515.8

20 818.4

15 1,279.0

10 1,968.7

5 3,032.7

Yampa River at Deerlodge Park, Colorado 15
16 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002 Table 5. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 09260000 Little Snake River near Lily, Colorado, 1994–2002. [dd mm yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; nd, no data] Sample date (dd mm yy) Instanta- neous discharge (ft3/s) Hydro- graph season Suspended- sediment load (tons/d) Bedload (tons/d) Total sediment load (tons/d) Bedload percentage of total load (%) Total load <0.062 mm (tons/d) Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks

12 Oct 93 248 Base flow 3,070 nd nd nd nd nd 2,824 246 nd nd nd No bedload, water year 199401 Nov 93 157 Base flow 170 nd nd nd nd nd 95 75 nd nd nd22 Feb 94 85 Base flow 21 nd nd nd nd nd nd nd nd nd nd No sand break analysis28 Mar 94 387 Rising 653 nd nd nd nd nd 438 215 nd nd nd26 Apr 94 2,070 Falling 12,100 nd nd nd nd nd 7,623 4,477 nd nd nd Peak 25 April 199410 May 94 1,760 Falling 6,270 nd nd nd nd nd 3,511 2,759 nd nd nd21 May 94 1,790 Falling 2,330 nd nd nd nd nd 1,515 816 nd nd nd24 May 94 1,270 Falling 1,950 nd nd nd nd nd 605 1,346 nd nd nd22 June 94 105 Falling 27 nd nd nd nd nd 7 20 nd nd nd28 June 94 52 Base flow 6.5 nd nd nd nd nd nd nd nd nd nd No sand break analysis13 July 94 1.6 Base flow 0.33 nd nd nd nd nd nd nd nd nd nd No sand break analysis22 July 94 1.0 Base flow 0.03 nd nd nd nd nd nd nd nd nd nd No sand break analysis03 Aug 94 121 Base flow 11,600 nd nd nd nd nd 11,484 116 nd nd nd19 Sept 94 25 Base flow 1,470 nd nd nd nd nd 1,470 nd nd nd nd06 Oct 94 239 Base flow 8,880 nd nd nd nd nd 8,791 89 nd nd nd No bedload, water year 199525 Nov 94 82 Base flow 83 nd nd nd nd nd 66 17 nd nd nd30 Jan 95 116 Base flow 168 nd nd nd nd nd 34 134 nd nd nd28 Feb 95 495 Rising 4,620 nd nd nd nd nd 2,911 1,709 nd nd nd31 Mar 95 228 Rising 520 nd nd nd nd nd 78 442 nd nd nd13 Apr 95 468 Rising 1,640 nd nd nd nd nd 951 689 nd nd nd01 May 95 513 Rising 658 nd nd nd nd nd 658 nd nd nd nd31 May 95 4,900 Rising 28,500 nd nd nd nd nd 21,090 7,410 nd nd nd08 June 95 5,840 Rising 12,000 nd nd nd nd nd 11,160 840 nd nd nd Peak June 7 and 8, 199512 June 95 3,340 Falling 17,600 nd nd nd nd nd 5,456 12,144 nd nd nd17 July 95 1,370 Falling 2,130 nd nd nd nd nd 2,130 nd nd nd nd31 Aug 95 38 Base flow 1.6 nd nd nd nd nd nd nd nd nd nd No sand break analysis20 Sept 95 49 Base flow 195 nd nd nd nd nd 137 59 nd nd nd30 Oct 95 351 Base flow 6,250 nd nd nd nd nd 6,188 63 nd nd nd No bedload, water year 199606 Dec 95 196 Base flow 151 nd nd nd nd nd 112 39 nd nd nd07 Dec 95 178 Base flow 102 nd nd nd nd nd 90 12 nd nd nd07 Feb 96 77 Base flow 20 nd nd nd nd nd nd nd nd nd nd No sand break analysis28 Mar 96 369 Rising 643 nd nd nd nd nd 579 64 nd nd nd01 Apr 96 477 Rising 744 nd nd nd nd nd 707 37 nd nd nd10 Apr 96 909 Rising 6,430 nd nd nd nd nd 5,401 1,029 nd nd nd15 Apr 96 1,110 Rising 1,830 nd nd nd nd nd 238 1,592 nd nd nd10 May 96 3,440 Rising 2,420 nd nd nd nd nd 2,372 48 nd nd nd21 May 96 3,960 Falling 6,060 nd nd nd nd nd 5,575 485 nd nd nd Peak 19 May 199605 June 96 2,340 Falling 1,570 nd nd nd nd nd 1,413 157 nd nd nd10 June 96 2,610 Falling 5,590 nd nd nd nd nd 1,621 3,969 nd nd nd
Yampa River at Deerlodge Park, Colorado 17

25 June 96 1,090 Falling 748 nd nd nd nd nd 741 7 nd nd nd24 July 96 61 Base flow 3.6 nd nd nd nd nd nd nd nd nd nd No sand break analysis02 Aug 96 86 Base flow 164 nd nd nd nd nd 157 7 nd nd nd15 Oct 96 60 Base flow 27 nd nd nd nd nd 25 2 nd nd nd No bedload, water year 199718 Nov 96 254 Base flow 1,750 nd nd nd nd nd 1,733 18 nd nd nd23 Dec 96 67 Base flow 31 nd nd nd nd nd 29 2 nd nd nd26 Feb 97 231 Base flow 130 nd nd nd nd nd 126 4 nd nd nd21 Mar 97 1,210 Rising 14,400 nd nd nd nd nd 11,952 2,448 nd nd nd25 Mar 97 958 Rising 4,240 nd nd nd nd nd 4,240 nd nd nd nd03 Apr 97 885 Rising 1,750 nd nd nd nd nd 1,698 53 nd nd nd18 Apr 97 620 Rising 5,360 nd nd nd nd nd 4,181 1,179 nd nd nd07 May 97 3,060 Rising 11,900 nd nd nd nd nd 11,067 833 nd nd nd08 May 97 4,480 Rising 21,400 nd nd nd nd nd 19,260 2,140 nd nd nd14 May 97 4,410 Rising 13,300 nd nd nd nd nd 11,172 2,128 nd nd nd27 May 97 4,290 Rising 5,680 nd nd nd nd nd 4,771 909 nd nd nd10 June 97 4,880 Falling 12,900 nd nd nd nd nd 10,965 1,935 nd nd nd Peak 4 June 199707 July 97 603 Falling 130 nd nd nd nd nd 100 30 nd nd nd15 July 97 327 Falling 26 nd nd nd nd nd 23 3 nd nd nd06 Aug 97 128 Falling 52 nd nd nd nd nd 50 2 nd nd nd21 Oct 97 288 Base flow 284 nd nd nd nd nd 162 122 nd nd nd No bedload, water year 199815 Dec 97 82 Base flow 14 nd nd nd nd nd 4 10 nd nd nd06 Mar 98 182 Base flow 128 nd nd nd nd nd 61 67 nd nd nd01 Apr 98 833 Rising 2,700 nd nd nd nd nd 2,565 135 nd nd nd09 Apr 98 587 Rising 872 nd nd nd nd nd 532 340 nd nd nd22 Apr 98 675 Rising 1,130 nd nd nd nd nd 463 667 nd nd nd27 Apr 98 1,850 Rising 5,990 nd nd nd nd nd 5,631 359 nd nd nd07 May 98 3,270 Rising 10,900 nd nd nd nd nd 6,540 4,360 nd nd nd20 May 98 3,450 Rising 9,690 nd nd nd nd nd 5,330 4,361 nd nd nd29 May 98 2,490 Rising 2,710 nd nd nd nd nd 1,870 840 nd nd nd01 June 98 2,920 Rising 6,090 nd nd nd nd nd 2,436 3,654 nd nd nd11 June 98 1,710 Rising 2,530 nd nd nd nd nd 784 1,746 nd nd nd15 June 98 1,320 Rising 7,810 nd nd nd nd nd 625 7,185 nd nd nd19 June 98 3,900 Falling 45,100 nd nd nd nd nd 35,178 9,922 nd nd nd Peak 18 June 199801 July 98 1,270 Falling 1,630 nd nd nd nd nd 375 1,255 nd nd nd06 July 98 950 Falling 285 nd nd nd nd nd 242 43 nd nd nd09 July 98 749 Falling 5,720 nd nd nd nd nd 286 5,434 nd nd nd19 Aug 98 96 Base flow 173 nd nd nd nd nd 157 16 nd nd nd

Table 5. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 09260000 Little Snake River near Lily, Colorado, 1994–2002.—Continued[dd mm yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; nd, no data]

Sample

date 

(dd mm yy)

Instantaneous

discharge

(ft3/s)

Hydrograph

season

Suspendedsediment

load

(tons/d)

Bedload

(tons/d)

Total

sediment

load

(tons/d)

Bedload

percentage

of total 

load

(%)

Total load

<0.062 mm

(tons/d)

Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks
27 Mar 00 271 Rising 2,350 nd nd nd nd nd 2,348 2 nd nd nd No bedload, water year 2000

4 Apr 00 250 Rising 448 nd nd nd nd nd 207 241 nd nd nd18 Apr 00 792 Rising 5,260 nd nd nd nd nd 4,618 642 nd nd nd27 Apr 00 1,160 Rising 1,940 nd nd nd nd nd 1,810 130 nd nd nd2 May 00 1,970 Rising 7,070 nd nd nd nd nd 3,280 3,790 nd nd nd25 May 00 3,070 Rising 1,820 nd nd nd nd nd nd nd nd nd nd No suspended size analysis6 June 00 1,270 Falling 665 nd nd nd nd nd 344 321 nd nd nd Peak May 2716 Mar 01 533 Rising 2,480 302 2,782 10.8 1,513 1,269 1,513 967 12 229 60 First bedload26 Mar 01 709 Rising 43,100 nd nd nd nd nd 42,669 431 nd nd nd No bedload16 Apr 01 485 Rising 852 255 1,107 23.1 417 690 417 435 13 199 43 Peak 3 May 200115 May 01 2,040 Falling 7,580 nd nd nd nd nd 3,259 4,321 nd nd nd No bedload24 May 01 1,280 Falling 1,730 495 2,225 22.2 588 1,636 588 1,142 608 969 5912 June 01 766 Falling 521 249 770 32.4 198 572 198 323 234 291 4714 June 01 346 Falling 139 151 290 52.1 42 248 42 97 73 147 2709 July 01 5 Base flow 0 nd nd nd nd nd nd nd nd nd nd No bedload03 Apr 02 468 Rising 2,000 246 2,246 11.0 1,720 526 1,720 280 147 312 6624 Apr 02 527 Falling 1,650 341 1,991 17.1 479 1,513 479 1,172 3 1,188 140 Peak about 18 April 200215 May 02 386 Falling 744 235 979 24.0 141 838 141 603 72 652 4021 May 02 451 Falling 763 145 908 16.0 290 618 290 473 90 423 1505 June 02 695 Falling 1,110 399 1,509 26.5 611 899 611 500 271 520 108

Table 5. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 09260000 Little Snake River near Lily, Colorado, 1994–2002.—Continued[dd mm yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; nd, no data]

Sample

date 

(dd mm yy)

Instantaneous

discharge

(ft3/s)

Hydrograph

season

Suspendedsediment

load

(tons/d)

Bedload

(tons/d)

Total

sediment

load

(tons/d)

Bedload

percentage

of total 

load

(%)

Total load

<0.062 mm

(tons/d)

Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks

18 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002
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Figure 7. Relation of suspended load at 09260000 Little Snake River near Lily, Colorado, 

1994–2002, A, to water discharge; B, by particle size to water discharge; and C, by season 

to water discharge.

Yampa River at Deerlodge Park, Colorado 19
20 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

lower than the R2 of 0.54 that resulted from regression of the 

1982 and 1983 data (Elliott and others, 1984, p. 16). Sediment 

transport appeared to have a seasonal component (fig. 8C), and 

the transport equation for the rising-limb season had an R2 of 

0.89; however, the falling-limb season equation had an R2 of 

0.68.

The recent effort to collect sediment data at Deerlodge 

Park for this analysis increased the number of suspendedsediment measurements by 139 percent and increased the 

number of total-sediment (suspended sediment plus bedload 

sediment) measurements by 71 percent since 1982–83. Based 

only on the relative magnitudes of the R2 value, the additional 

data have resulted in a slightly improved suspended-sediment 

transport equation (0.80 compared to 0.76) and a slightly deteriorated total-load equation (0.72 compared to 0.79) compared 

to those equations published by Elliott and others (1984).

Additional data collection may not improve these transport equations; however, more bedload measurements made 

during streamflows of less than about 700 ft3/s could improve 

the accuracy of both the bedload-transport and total-sediment 

transport equations (fig. 8A). Additional data collection during 

the rising-limb and falling-limb hydrograph periods at streamflows less than about 700 ft3

/s might improve the transport 

equations that describe seasonality (fig. 8C).

Table 7. Streamflow characteristics at streamflow-gaging 

station 09260050 Yampa River at Deerlodge Park, Colorado, 

1982–94 and 1997–2002.

[Recurrence interval, in years, equals reciprocal of exceedance probability, 

calculated with annual instantaneous discharge peak; streamflow duration in 

percentage of time specific discharge is equaled or exceeded, calculated with 

daily mean discharge; ft3/s, cubic foot per second; %, percentage]

Recurrence interval 

of peak discharge

Duration of daily 

mean discharge

Recurrence 

interval 

(years)

Discharge 

(ft3/s)

Duration 

(% time)

Discharge 

(ft3/s)

1.05 4,979 95 128.5

1.11 6,184 90 213.0

1.25 7,963 85 259.7

2 12,550 80 301.8

5 19,040 75 340.6

10 23,350 70 381.5

25 28,710 65 438.5

50 32,620 60 495.5

100 36,450 55 575.8

200 40,230 50 659.1

500 45,160 45 780.1

40 913.9

35 1,132.8

30 1,486.7

25 2,088.7

20 2,867.5

15 4,442.5

10 6,560.3

5 9,912.9

Table 6. Sediment-transport equations derived from sediment 

discharges measured at station 09260000 Little Snake River 

near Lily, Colorado, 1994–2002.

[Qs, sediment discharge in tons per day; Q, water discharge in cubic feet per 

second; R2, coefficient of determination; MSE, mean square error; n, number 

of samples]

Type of 

sediment 

discharge

Regression 

equation R2 MSE n

Total Qs = 6.87 Q0.824 0.22 0.403 10

Suspended Qs = 0.146 Q1.39 0.74 1.94 96

Bedload Qs = 1.82 Q0.788 0.60 0.0662 10

Silt and clay 

(suspended)

Qs = 0.818 Q1.07 0.46 2.14 87

Sand Qs = 0.0387 Q1.35 0.54 2.41 83

(Suspended)

Suspended, rising Qs = 8.35 Q0.85 0.47 0.742 40

Suspended, falling Qs = 0.00953 Q1.71 0.76 0.925 28

Suspended-sediment and bedload measurements were 

made at gaging station 09260050 in 1982, 1983, and 1994, 

and from 1997 through 2001; no sediment measurements were 

made in 2002 (table 8). Annual instantaneous discharge peaks 

for the years when sediment measurements were made ranged 

from 7,670 ft3/s in 1994 to 23,400 ft3/s in 1983. Suspendedand bedload-sediment data were collected near the 1983 

instantaneous peak discharge of 23,400 ft3/s (table 8), but no 

sediment measurements were made the following year during 

the historical instantaneous peak discharge (33,200 ft3/s). 

Suspended sediment was measured 79 times and bedload 

was measured 53 times at discharges ranging from 46 ft3/s 

to 17,600 ft3/s. Concurrent suspended-sediment and bedload 

measurements included 24 measurements made during the 

rising-limb hydrograph season and 29 measurements made 

during the recessional- or falling-limb hydrograph season. 

Bedload as a percentage of total-sediment load ranged from 

0.5 to 38.8 percent and averaged 9.3 percent.

Sediment-transport equations were derived and annual 

sediment loads were estimated from the 1982 and 1983 data 

by Elliott and others (1984). These earliest data were combined with data collected since 1994, and updated transport 

equations were derived (table 9). The updated transport 

equations showed minor changes in R2, slope, and intercept 

when compared to the 1984 equations. The updated transport 

equations for total-sediment load, suspended-sediment load, 

sand-and-gravel load, and fine sand load all had R2 greater 

than 0.72. The updated transport equation for suspendedsediment load may be useful for annual suspended-sediment 

load calculations for discharges ranging from about 40 to 

18,000 ft3/s, whereas the updated transport equations for totalsediment load, sand-and-gravel load, and fine sand load may 

be useful for annual load calculations for discharges ranging from about 600 to 18,000 ft3

/s. The updated equation for 

bedload transport had an R2 of 0.40, which was considerably 
Table 8. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 09260050 Yampa River at Deerlodge Park, Colorado, 1982–2001.

[dd mm yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; nd, no data]

Sample

date

(dd mm yy)

Instantaneous

discharge

(ft3/s)

Hydrograph

season

Suspendedsediment

load

(tons/d)

Bedload

(tons/d)

Total

sediment

load

(tons/d)

Bedload

percentage

of total 

load

(%)

Total load

<0.062 mm

(tons/d)

Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks

01 Apr 82 1,570 Rising nd nd nd nd nd nd nd nd nd nd nd No loads published for April 127 Apr 82 7,590 Rising 61,550 1,356 62,906 2.2 40,300 22,606 40,008 21,543 12,220 10,200 194 1982 loads as published12 May 82 9,410 Falling 45,862 1,525 47,387 3.2 10,900 36,487 10,548 35,314 11,690 23,410 1,374 Peak 7 May 198213 May 82 8,820 Falling 22,814 1,934 24,748 7.8 8,940 15,808 8,897 13,917 6,730 8,540 57124 May 82 9,700 Falling 26,562 826 27,388 3.0 15,700 11,688 15,672 10,890 8,880 2,745 3625 May 82 10,900 Falling 29,827 936 30,763 3.0 18,800 11,963 18,791 11,036 9,960 1,965 6908 June 82 9,400 Falling 25,981 1,524 27,505 5.5 5,280 22,225 5,196 20,785 6,340 15,850 8024 June 82 10,000 Falling 9,099 1,856 10,955 16.9 4,440 6,515 4,368 4,731 2,620 3,615 28025 June 82 9,600 Falling 23,672 4,736 28,408 16.7 4,210 24,198 4,024 19,648 2,740 20,560 86207 July 82 6,250 Falling 4,733 2,199 6,932 31.7 2,170 4,762 2,130 2,603 1,679 2,450 63608 July 82 6,240 Falling 19,329 1,751 21,080 8.3 1,510 19,570 1,546 17,783 1,080 16,750 1,74829 July 82 2,350 Falling 4,460 897 5,357 16.7 3,770 1,587 3,746 714 466 886 33623 Feb 83 646 Base flow 234 nd nd nd nd nd 124 110 nd nd nd No bedload published Feb. 2310 Mar 83 1,190 Rising 2,675 120 2,795 4.3 2,510 285 2,515 161 138 142 9 1983 loads as published15 Mar 83 3,480 Rising 51,970 nd nd nd nd nd 36,899 15,071 nd nd nd No bedload published March 1529 Mar 83 1,190 Rising 917 139 1,056 13.2 820 236 816 101 72 129 3507 Apr 83 930 Rising 1,403 53 1,456 3.6 946 510 912 491 68 438 408 Apr 83 859 Rising 746 72 818 8.8 684 134 686 60 56 70 819 Apr 83 1,210 Rising 2,781 621 3,402 18.3 2,460 942 2,447 334 243 625 7621 Apr 83 3,620 Rising 23,869 349 24,218 1.4 15,900 8,318 15,754 8,115 3,140 5,130 4722 Apr 83 3,810 Rising 26,810 343 27,153 1.3 21,800 5,353 21,716 5,094 3,680 1,606 5307 May 83 6,530 Rising 24,521 1,157 25,678 4.5 17,300 8,378 17,165 7,356 4,250 4,000 16309 May 83 6,080 Rising 13,264 1,694 14,958 11.3 9,490 5,468 9,417 3,847 2,650 2,590 24612 May 83 11,900 Rising 92,515 1,268 93,783 1.4 60,200 33,583 60,135 32,380 15,710 17,400 54523 May 83 8,620 Rising 34,513 1,068 35,581 3.0 27,600 7,981 27,610 6,903 5,670 1,879 40926 May 83 15,200 Rising 94,975 989 95,964 1.0 78,200 17,764 77,880 17,096 15,480 2,222 10127 May 83 15,800 Rising 87,639 927 88,566 1.0 69,900 18,666 70,111 17,528 16,380 2,180 8028 May 83 17,600 Rising 96,073 992 97,065 1.0 70,600 26,465 70,133 25,940 18,070 8,310 48 Peak 31 May 198308 June 83 14,400 Falling 39,907 805 40,712 2.0 22,000 18,712 25,940 13,967 8,980 2,619 9610 June 83 15,000 Falling 33,115 535 33,650 1.6 26,000 7,650 21,856 11,259 11,530 2,990 16721 June 83 15,800 Falling 26,962 1,259 28,221 4.5 16,900 11,321 16,986 9,976 6,280 4,910 10123 June 83 15,700 Falling 23,367 634 24,001 2.6 15,400 8,601 15,422 7,945 6,460 2,070 4812 July 83 7,180 Falling 10,624 882 11,506 7.7 2,730 8,776 2,656 7,968 2,925 5,760 9414 July 83 5,540 Falling 5,667 761 6,428 11.8 2,680 3,748 2,663 3,004 2,085 1,565 9802 Aug 83 2,130 Falling nd nd nd nd nd nd nd nd nd nd nd No loads published for Aug. 2

Yampa River at Deerlodge Park, Colorado 21
22 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002 26 Oct 93 688 Base flow 526 nd nd nd nd nd 416 110 nd nd nd No bedload, water year 1994 25 Feb 94 460 Base flow 386 nd nd nd nd nd 378 7.7 nd nd nd 28 Mar 94 1,150 Rising 517 nd nd nd nd nd 445 72 nd nd nd 02 May 94 2,770 Falling 3,140 nd nd nd nd nd 1,319 1,821 nd nd nd Peak 25 April 1994 10 May 94 5,500 Falling 12,300 nd nd nd nd nd 5,781 6,519 nd nd nd 24 May 94 5,650 Falling 9,030 nd nd nd nd nd 2,438 6,592 nd nd nd 13 July 94 186 Base flow 10 nd nd nd nd nd nd 10 nd nd nd 22 July 94 114 Base flow 4.9 nd nd nd nd nd nd 4.9 nd nd nd 28 July 94 111 Base flow 6.3 nd nd nd nd nd 4.0 2.3 nd nd nd 03 Aug 94 74 Base flow 31 nd nd nd nd nd 1.9 29 nd nd nd 12 Sept 94 46 Base flow 5.2 nd nd nd nd nd nd 5.2 nd nd nd 19 Sept 94 83 Base flow 1,450 nd nd nd nd nd 1,450 nd nd nd nd 08 Nov 96 633 Base flow 3,930 nd nd nd nd nd 3,930 nd nd nd nd No bedload, water year 1997 20 Mar 97 2,320 Rising 14,500 nd nd nd nd nd 12,615 1,885 nd nd nd 28 May 97 12,500 Rising 21,400 nd nd nd nd nd 15,622 5,778 nd nd nd 03 June 97 17,600 Rising 25,500 nd nd nd nd nd 21,165 4,335 nd nd nd Peak 4 June 1997 19 Aug 97 953 Falling 450 nd nd nd nd nd 216 234 nd nd nd 17 Nov 97 630 Base flow 65 nd nd nd nd nd 49 16 nd nd nd No suspended size breaks 1998 05 Mar 98 661 Base flow 269 nd nd nd nd nd 242 27 nd nd nd No 8-mm bedload sieve 06 May 98 13,500 Rising 48,100 249 48,349 0.5 32,708 15,641 32,708 15,392 nd nd nd 19 May 98 9,940 Rising 16,300 1,100 17,400 6.3 9,617 7,783 9,617 6,683 nd nd nd Peak 22 May 1998 27 May 98 9,460 Falling 36,800 442 37,242 1.2 31,648 5,594 31,648 5,152 nd nd nd 02 June 98 10,200 Falling 10,600 1,285 11,885 10.8 5,936 5,949 5,936 4,664 nd nd nd 03 June 98 10,100 Falling 9,460 1,555 11,015 14.1 4,825 6,190 4,825 4,635 nd nd nd 10 June 98 6,990 Falling 5,270 530 5,800 9.1 3,004 2,796 3,004 2,266 nd nd nd 17 June 98 7,230 Falling 28,900 515 29,415 1.8 23,698 5,717 23,698 5,202 nd nd nd 01 July 98 5,890 Falling 4,710 483 5,193 9.3 1,460 3,733 1,460 3,250 nd nd nd

09 Sept 98 210 Base flow 6.7 nd nd nd nd nd nd nd nd nd nd

Table 8. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 09260050 Yampa River at Deerlodge Park, Colorado, 1982–2001.—Continued[dd mm yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; nd, no data]

Sample

date

(dd mm yy)

Instantaneous

discharge

(ft3/s)

Hydrograph

season

Suspendedsediment

load

(tons/d)

Bedload

(tons/d)

Total

sediment

load

(tons/d)

Bedload

percentage

of total 

load

(%)

Total load

<0.062 mm

(tons/d)

Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks
Yampa River at Deerlodge Park, Colorado 23

04 Mar 99 1,400 Rising 5,180 nd nd nd nd nd 4,766 414 nd nd nd30 Mar 99 2,300 Rising 2,400 1,013 3,413 29.7 1,824 1,589 1,824 576 161 920 50819 May 99 5,690 Rising 7,650 745 8,395 8.9 3,825 4,570 3,825 3,825 1,636 2,792 14225 May 99 12,600 Rising 49,000 3,547 52,547 6.8 26,460 26,087 26,460 22,540 9,835 12,163 4,08827 May 99 12,800 Rising 30,700 337 31,037 1.1 17,499 13,538 17,499 13,201 11,062 2,317 15802 June 99 12,700 Falling 20,500 124 20,624 0.6 9,430 11,194 9,430 11,070 9,657 1,527 10 Peak 1 June 199923 June 99 7,840 Falling 4,950 895 5,845 15.3 2,475 3,370 2,475 2,475 810 2,310 25121 Oct 99 410 Base 20 nd nd nd nd nd nd nd nd nd nd1 Mar 00 641 Base 59 nd nd nd nd nd nd nd nd nd nd05 Apr 00 1,240 Rising 609 255 864 29.5 370 494 370 239 58 332 10419 Apr 00 3,980 Rising 8,030 162 8,192 2.0 5,629 2,563 5,629 2,401 1,358 1,137 6703 May 00 7,780 Rising 16,400 1,047 17,447 6.0 8,086 9,361 8,085 8,315 4,939 4,031 39105 July 00 645 Falling 1,920 178 2,098 8.5 35 2,063 35 1,885 342 1,668 53 Peak 31 May 200015 Dec 00 456 Base 9 nd nd nd nd nd nd nd nd nd nd12 June 01 3,470 Fall 600 381 981 38.8 600 381 600 0 34 335 11 Peak 18 May 200113 June 01 3,300 Fall 1,890 650 2,540 25.6 548 1,992 548 1,342 940 1,032 1919 June 01 1,700 Fall 1,650 226 1,876 12.1 165 1,711 165 1,485 325 1,380 720 June 01 1,650 Fall 276 163 439 37.1 152 287 152 124 120 164 3

Table 8. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 09260050 Yampa River at Deerlodge Park, Colorado, 1982–2001.—Continued[dd mm yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; nd, no data]

Sample

date

(dd mm yy)

Instantaneous

discharge

(ft3/s)

Hydrograph

season

Suspendedsediment

load

(tons/d)

Bedload

(tons/d)

Total

sediment

load

(tons/d)

Bedload

percentage

of total 

load

(%)

Total load

<0.062 mm

(tons/d)

Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks
24 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

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Figure 8. Relation of sediment load at 09260050 Yampa River at Deerlodge Park, Colorado, 1982–2001, 

A, to water discharge; B, by particle size to water discharge; and C, by season to water discharge.
Green River above Gates of Lodore, 

Colorado

Site Description

Streamflow was recorded at streamflow-gaging station 

09234500 Green River near Greendale, Utah, 0.5 mi downstream from Flaming Gorge Dam. The gage is located at 

latitude 40o54'30", longitude 109o25'20", in sec. 15, T. 2 N., 

R. 22 E., Daggett County, Utah, 2 mi south of Dutch John. 

Drainage area at the streamflow-gaging station is approximately 19,350 mi2

.

Sediment data were collected at a site (404417108524900 

Green River above Gates of Lodore) near the National Park 

Service Gates of Lodore Ranger Station, approximately 

46 river miles downstream from the streamflow-gaging station. 

The sediment-sampling site is located at latitude 40o44'17", longitude 108o

52'49", in NE1/4 SE1/4 sec. 17, T. 9 N., R. 102 W., 

Moffat County, Colorado, 0.8 mi upstream from the ranger 

station and 18 mi west of Greystone. Because of the great distance between the streamflow-gaging station and the sedimentsampling site, water-discharge measurements were made each 

time suspended sediment and bedload were sampled. Drainage 

area at the sediment sampling site is undetermined.

The sediment-sampling site is downstream from Browns 

Park (fig. 1), a low-gradient reach through a relatively wide 

valley, and just upstream from the beginning of Lodore 

Canyon, where the river gradient increases abruptly (fig. 5C). 

Sediment samples were collected from a boat at most streamflows and by wading at low streamflows.

Streamflow and Sediment Data

Discharge measured at the gaging station downstream 

from Flaming Gorge Dam has been entirely regulated since 

the dam was completed in November 1962. Consequently, 

no peak-flow statistics have been computed for the regulated-flow period. However, streamflow-duration statistics 

are presented in table 10 for comparison to other sites in this 

report. Sediment-load data are presented in table 11. Plots of 

the sediment-load data are presented in figure 9.

Analysis

Streamflow data have been collected 0.5 mi downstream from Flaming Gorge Dam at streamflow-gaging 

station 09234500 Green River, near Greendale, Utah, since 

October 1950. Before the completion of Flaming Gorge Dam 

in November 1962, annual instantaneous discharge peaks 

ranged from 4,660 ft3/s in 1961 to 19,600 ft3/s in 1957. Since 

the dam was completed, annual instantaneous peak discharges 

released from the dam have ranged from 833 ft3/s in 1963 and 

1964 to 13,700 ft3/s in 1983 (Crowfoot and others, 2002). Baseflow conditions at this site are determined by reservoir releases 

and are greater than would be anticipated for an unregulated 

river. For comparative purposes, the streamflow equaled or 

exceeded 50 percent of the time is 1,802.5 ft3/s (table 10).

Table 9. Sediment-transport equations derived from sediment 

discharges measured at station 09260050 Yampa River at 

Deerlodge Park, Colorado, 1982–2001.

[Qs, sediment discharge in tons per day; Q, water discharge in cubic feet per 

second; R2, coefficient of determination; MSE, mean square error; n, number 

of samples]

Type of 

sediment 

discharge

Regression 

equation R2 MSE n

Total Qs = 0.129 Q1.32 0.72 0.534 53

Suspended Qs = 0.129 Q1.57 0.80 1.40 79

Bedload Qs = 1.75 Q0.682 0.40 0.573 53

Silt and clay Qs = 0.0117 Q1.51 0.63 1.08 53

Sand and gravel Qs = 0.0435 Q1.34 0.74 0.523 53

Fine sand Qs = 0.00474 Q1.77 0.80 0.700 45

Medium and 

coarse sand

Qs = 0.252 Q1.05 0.51 0.951 45

Very coarse sand 

and fine gravel

Qs = 0.0904 Q0.816 0.23 2.05 45

Total, rising Qs = 0.0697 Q1.44 0.89 0.280 24

Total, falling Qs = 0.218 Q1.23 0.68 0.424 29

Table 10. Streamflow characteristics at streamflow-gaging 

station 09234500 Green River near Greendale, Utah, 1963–2002.

[Recurrence interval, in years, equals reciprocal of exceedance probability, 

calculated with annual instantaneous discharge peak; streamflow duration in 

percentage of time specific discharge is equaled or exceeded, calculated with 

daily mean discharge; ft3/s, cubic foot per second; %, percentage]

Recurrence interval 

of peak discharge

Duration of daily 

mean discharge

Recurrence 

interval 

(years)

Discharge 

(ft3/s)

Duration 

(% time)

Discharge 

(ft3/s)

Instantaneous discharge peaks 

entirely controlled by Flaming 

Gorge Dam immediately 

upstream

95 763.8

90 830.0

85 896.2

80 986.5

75 1,081.6

70 1,216.9

65 1,354.1

60 1,493.0

55 1,646.0

50 1,802.5

45 1,985.4

40 2,169.5

35 2,352.8

30 2,536.2

25 2,767.3

20 3,005.6

15 3,331.7

10 3,700.4

5 4,209.3

Green River above Gates of Lodore, Colorado 25
26 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002 Table 11. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 404417108524900 Green River above Gates of Lodore, Colorado, 1999–2002. [Instantaneous discharge from streamflow-gaging station 09234500 Green River near Greendale, Utah, 46 river miles upstream; dd mm yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; Susp Sed, suspended sediment; nd, no data] Sample date (dd mm yy) Instanta- neous discharge (ft3/s) Hydro- graph season Suspended- sediment load (tons/d) Bedload (tons/day) Total sediment load (tons/d) Bedload percentage of total load (%) Total load <0.062 mm (tons/d) Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks

24 May 99 4,550 Early 1,880 420 2,300 18.3 793 1,507 793 1,087 nd nd nd26 May 99 6,230 Early 17,000 726 17,726 4.1 2,193 15,533 2,193 14,807 nd nd nd26 May 99 6,230 Early 7,320 527 7,847 6.7 1,632 6,215 1,632 5,688 nd nd nd27 May 99 6,230 Early 4,140 487 4,627 10.5 1,755 2,871 1,755 2,385 nd nd nd31 May 99 6,000 Early 3,810 426 4,236 10.1 1,353 2,884 1,353 2,457 nd nd nd31 May 99 6,000 Early 6,080 386 6,466 6.0 1,192 5,274 1,192 4,888 nd nd nd1 June 99 6,000 Early 3,290 772 4,062 19.0 1,047 3,015 1,046 2,244 nd nd nd Yampa peak 1 June 19994 June 99 8,370 Early 6,170 518 6,688 7.8 2,332 4,356 2,332 3,838 nd nd nd7 June 99 8,270 Early 10,700 304 11,004 2.8 1,487 9,517 1,487 9,213 nd nd nd7 June 99 8,270 Early 5,810 718 6,528 11.0 1,621 4,907 1,621 4,189 nd nd nd8 June 99 8,270 Early 10,500 700 11,200 6.3 1,366 9,835 1,365 9,135 nd nd nd15 June 99 10,200 Late 5,890 533 6,423 8.3 1,673 4,750 1,673 4,217 nd nd nd Daily peak June 12–20, 199915 June 99 10,200 Late 6,170 657 6,827 9.6 1,505 5,321 1,505 4,665 nd nd nd Daily peak June 12–20, 199917 June 99 10,200 Late 24,300 310 24,610 1.3 13,268 11,341 13,268 11,032 nd nd nd Daily peak June 12–20, 199917 June 99 10,200 Late 7,630 331 7,961 4.2 3,289 4,672 3,289 4,341 nd nd nd Daily peak June 12–20, 199918 June 99 10,250 Late 7,970 617 8,587 7.2 2,024 6,562 2,024 5,946 nd nd nd Daily peak June 12–20, 199922 June 99 8,730 Late 3,180 337 3,517 9.6 999 2,519 999 2,181 nd nd nd23 June 99 7,140 Late 2,310 453 2,763 16.4 822 1,941 822 1,488 nd nd nd04 Apr 00 2,350 Early 362 196 558 35.1 221 337 221 141 255 202 10018 Apr 00 1,920 Early 373 336 709 47.4 317 392 317 56 318 281 5402 May 00 2,220 Early 270 248 518 47.9 188 330 188 82 226 149 143 Daily peak 24 May 200001 June 00 4,830 Late 2,060 666 2,726 24.4 631 2,095 630 1,430 1,045 1,525 156 Yampa peak 31 May 200006 July 00 1,340 Late 98 114 212 53.8 72 140 72 26 72 77 3715 May 01 2,980 Early 4,390 1,034 5,424 19.1 1,141 4,283 1,141 3,249 nd nd nd No Susp Sed size data16 May 01 3,340 Early 10,200 812 11,012 7.4 2,040 8,972 2,040 8,160 nd nd nd No Susp Sed size data24 May 01 4,300 Late 1,730 426 2,156 19.8 554 1,602 554 1,176 381 1,090 132 Yampa Peak 18 May 200125 May 01 3,660 Late 4,750 580 5,330 10.9 428 4,903 428 4,323 143 3,400 22028 May 01 2,270 Late 478 372 850 43.8 167 683 167 311 33 523 12603 Apr 02 916 Early 92 59 151 39.2 82 68 82 9 nd nd nd No Susp Sed size data15 May 02 811 Early 31 93 124 75.2 21 103 21 10 nd nd nd No Susp Sed size data21 May 02 3,930 Early 2,980 283 3,263 8.7 1,579 1,684 1,579 1,401 807 791 7905 June 02 859 Late 216 188 404 46.5 28 376 28 188 2 282 83 Yampa Peak 2 June 2002
Figure 9. Relation of sediment load at 404417108524900 Green River above Gates of Lodore, Colorado, 1999–2002, 

A, to water discharge; B, by particle size to water discharge; and C, by season to water discharge.

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Green River above Gates of Lodore, Colorado 27
28 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

Sediment and water-discharge measurements were 

made 46 river miles downstream from the dam and 

streamflow-gaging station in 1999 through 2002 (table 11). 

Annual instantaneous discharge peaks for the years when 

sediment measurements were made ranged from 4,050 ft3/s 

in 2002 to 11,200 ft3/s in 1999 (Crowfoot and others, 2002). 

Suspended and bedload sediment was measured 32 times 

at discharges ranging from 811 to 10,250 ft3/s. There is 

little hydrograph seasonality at this site because main-stem 

streamflow is almost completely regulated by Flaming Gorge 

Reservoir. However, to test for possible seasonal hysteresis 

in sediment loads originating upstream from the dam and in 

tributaries entering downstream from the dam in the 46-mi 

reach upstream from the Lodore Ranger Station, the data 

were subdivided into “early” and “late” periods based on the 

rising-limb and falling-limb seasons of the Yampa River at 

Deerlodge Park. This subdivision resulted in 19 early season 

and 13 late season sediment measurements at the Gates of 

Lodore site.

Bedload as a percentage of total-sediment load ranged 

from 1.3 to 75.2 percent with the higher percentages generally occurring at lesser discharges and averaged 19.9 percent. 

Bedload was greater than suspended-sediment load for two 

of eight measurements made at discharges less than about 

2,400 ft3/s. The wide range in bedload as a percentage of total 

load may be a reflection of the widely different streamflow 

magnitudes occurring when sediment was sampled. Water 

discharge and, consequently, suspended- and total-sediment 

loads, were much greater in 1999 than in other years.

Sediment-transport equations for total-sediment load, 

suspended-sediment load, silt-and-clay load, and sand-andgravel load had R2

 values of 0.74 or greater (table 12) and 

indicate that these transport equations may be useful for annual 

load estimation or sediment budget calculations for discharges 

ranging from about 800 to 10,000 ft3/s. The equation for 

bedload had an R2 value of 0.47, possibly due to a relatively 

small range in bedload magnitude typical of river reaches with 

a limited supply of transportable bed material, such as rivers

downstream from dams. The seasonal transport equations 

(early and late) had R2 values of 0.81 but were based on small 

numbers of samples and, therefore, may not accurately reflect 

true seasonal conditions. One-half of the sediment measurements were made at discharges greater than 6,000 ft3

/s (fig. 9), 

streamflows that occur less than 5 percent of the time at this 

site (table 10). Additional sediment measurements made at less 

than about 3,000 ft3/s or greater than 10,000 ft3/s in both the 

early and late seasons would make the seasonal transport equations more representative of conditions at this site. Additional 

measurements also might result in a better understanding of 

the variation in dominant transport mode (bedload compared 

to suspended load) for a wide range of streamflows.

Green River near Jensen, Utah

Site Description

Streamflow was recorded at streamflow-gaging station 

09261000 Green River near Jensen, Utah. The gage is located 

at latitude 40o24'34", longitude 109o14'05", in sec. 5, T. 5 S., 

R. 24 E., Uintah County, 300 ft upstream from the county road 

bridge, 6.5 mi northeast of Jensen. Sediment measurements 

were made from the county road bridge or from the cableway at 

the gage in 1996 and 1998. During 1999 through 2002, all sediment measurements were made from a boat at a site approximately 1 mi upstream from the gage. The sampling site is in a 

broad alluvial valley just downstream from the mouth of Split 

Mountain Canyon, a steep, confined reach (figs. 1, 2). Drainage 

area at the gaging station is approximately 29,660 mi2.

Streamflow data have been collected at gaging station 

09261000 Green River near Jensen, Utah, since October 1946. 

Streamflow at the Jensen site has been partly regulated by 

Flaming Gorge Reservoir, 93 river miles upstream, since 

November 1962; however, the streamflow of the Yampa River, 

which joins the Green River 28 mi upstream from the Jensen 

site, has remained largely unregulated and has a strong effect 

on the hydrograph at the Jensen site.

Streamflow and Sediment Data

Streamflow characteristics from discharge data collected 

at the streamflow-gaging station since completion of Flaming 

Gorge Dam in 1962 are presented in table 13, and sedimentload data are presented in table 14. Plots of the sediment-load 

data are presented in figure 10.

Analysis

Representative peak-flow or streamflow-duration statistics for both the pre-dam period (1947–62) and the postdam period (1963–present) are presented in table 13. Annual 

instantaneous discharge peaks ranged from 11,900 ft3/s in 

1955 to 36,500 ft3/s in 1957 during the pre-dam period. 

Table 12. Sediment-transport equations derived from sediment 

discharges measured at station 404417108524900 Green River 

above Gates of Lodore, Colorado, 1999–2002.

[Qs, sediment discharge in tons per day; Q, water discharge in cubic feet per 

second; R2, coefficient of determination; MSE, mean square error; n, number 

of samples; early and late hydrograph seasons at this site arbitrarily based on 

the rising and falling hydrograph seasons at Yampa River at Deerlodge Park]

Type of 

sediment 

discharge

Regression 

equation R2 MSE n

Total Qs = 0.00419 Q1.60 0.78 0.434 32

Suspended Qs = 0.000198 Q1.94 0.80 0.584 32

Bedload Qs = 3.04 Q0.578 0.47 0.230 32

Silt and clay Qs = 0.000689 Q1.65 0.81 0.378 32

Sand and gravel Qs = 0.00259 Q1.62 0.74 0.548 32

Total, early Qs = 0.000620 Q1.85 0.81 0.432 19

Total, late Qs = 0.0190 Q1.40 0.81 0.360 13
Annual instantaneous discharge peaks since Flaming Gorge 

Dam was constructed have ranged from 7,090 ft3/s in 1989 to 

40,000 ft3/s in 1984 (Crowfoot and others, 2002). Base-flow 

conditions since 1963 occur at discharges of less than about 

3,500 to 3,800 ft3/s and are equaled or exceeded about 35 to 

40 percent of the time (table 13).

Suspended sediment was measured 218 times at gaging station 09261000 from 1948 through 1979, 161 times 

before October 1962, and 57 times since October 1962. 

Suspended sediment and bedload sediment were measured 

in 1996 and from 1998 through 2002 as part of this study 

(table 14). Annual instantaneous discharge peaks for the years 

when the more recent sediment measurements were made 

ranged from 7,570 ft3/s in 2002 to 22,400 ft3/s in 1996. Forty 

suspended-sediment and 40 bedload measurements were made 

at discharges ranging from 965 to 22,000 ft3/s during the more 

recent sampling period beginning in 1996. These data included 

18 measurements during the rising-limb hydrograph season 

and 18 measurements during the recessional- or falling-limb 

hydrograph season. Bedload as a percentage of total-sediment 

load ranged from 0.1 to 29.9 percent and averaged 4.0 percent.

Sediment-transport equations for total-sediment, 

suspended-sediment, and transport by all particle-size ranges 

except medium and coarse sand and very coarse sand and 

gravel had R2 values of 0.75 or greater (table 15) and may be 

useful for annual load estimations or sediment budget calculations for discharges ranging from about 1,000 to 22,000 ft3

/s. 

The equation for bedload transport had an R2 value of 0.54, the 

equation for medium and coarse sand had an R2 value of 0.64, 

and the equation for very coarse sand and gravel had an R2

value of 0.40. Rising-limb and falling-limb seasonal equations 

had R2 values of 0.77 and 0.90, respectively, but these equations were based on relatively small numbers of samples (18 

for each equation).

Andrews (1986) evaluated the earlier suspended-sediment 

data at the Jensen site and derived regression equations for 

several suspended particle-size ranges for both pre-dam and 

post-dam periods. Andrews’ equation for “all (suspended) 

sizes” in the post-dam period (1963–79) was:

Qs = 0.0172 Q1.56 (3)

where

Qs is suspended-sediment discharge, in tons per day;

and

Q is water discharge, in cubic feet per second.

Andrews’ equation was derived from 57 measurements and 

had a correlation coefficient of 0.62 (or R2 = 0.38). By comparison, the suspended-sediment transport equation derived 

from the 40 measurements made since 1996 in this study 

(table 15) has a slightly steeper slope (2.00), a smaller intercept, and, based on the R2

 value, much less variance.

Possible explanations for the difference between the 

1963–79 and 1996–2002 transport equations could include 

climate and land-use changes, a change in the availability of 

transportable sediment, or a change in Flaming Gorge reservoir operation between the two periods.

Table 13. Streamflow characteristics at streamflow-gaging station 09261000 Green River near Jensen, Utah, 1947–62 

and 1963–2002.

[Recurrence interval, in years, equals reciprocal of exceedance probability, calculated with annual instantaneous discharge peak; streamflow duration 

in percentage of time specific discharge is equaled or exceeded, calculated with daily mean discharge; ft3/s, cubic foot per second; %, percentage]

Recurrence interval of peak discharge Duration of daily mean discharge

Recurrence 

interval 

(years)

Pre-dam discharge 

1947–62 

(ft3/s)

Post-dam discharge 

1963–2002 

(ft3/s)

Duration 

(% time)

Pre-dam discharge 

1947–62 

(ft3/s)

Post-dam discharge 

1963–2002 

(ft3/s)

1.05 12,320 8,184 95 722.0 1,143.7

1.11 14,390 9,673 90 831.0 1,354.8

1.25 17,190 11,740 85 923.2 1,541.4

2 23,410 16,560 80 1,006.1 1,736.7

5 30,610 22,580 75 1,095.6 1,934.9

10 34,690 26,220 70 1,187.9 2,132.7

25 39,200 30,460 65 1,301.4 2,352.5

50 42,180 33,390 60 1,434.9 2,564.2

100 44,880 36,140 55 1,599.7 2,755.7

200 47,350 38,750 50 1,780.4 2,956.2

500 50,340 42,020 45 2,024.1 3,194.0

40 2,308.1 3,453.6

35 2,769.5 3,791.8

30 3,652.0 4,186.7

25 5,116.7 4,650.7

20 7,048.3 5,360.2

15 9,586.6 6,936.2

10 12,744.4 9,724.2

5 18,021.2 13,006.6

Green River near Jensen, Utah 29
30 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002 Table 14. Summary of discharge and sediment loads by transport mode, particle-size range, and season, 09261000 Green River near Jensen, Utah, 1996–2002. [dd mm yy, day month year; ft3/s, cubic feet per second; tons/d, tons per day; %, percent; <, less than; >, greater than; mm, millimeter; Sand&Gvl, sand and gravel; M&C, medium and coarse; VCS & FG, very coarse sand and fine gravel; Susp Sed, suspended sediment; nd, no data] Sample date (dd mm yy) Instanta- neous discharge (ft3/s) Hydro- graph season Suspended- sediment load (tons/d) Bedload (tons/d) Total sediment load (tons/d) Bedload percentage of total load (%) Total load <0.062 mm (tons/d) Sand&Gvl

load

>0.062 mm

(tons/d)

Suspended

load

<0.062 mm

(tons/d)

Suspended

load

>0.062 mm

(tons/d)

Fine 

sand

0.062 to

<0.250 mm

(tons/d)

M&C 

sand

0.250 to

<1.00 mm

(tons/d)

VCS & FG

1.00 to

>8.00 mm

(tons/d)

Remarks

30 Apr 96 9,580 Rising 14,100 nd nd nd nd nd 6,768 7,332 nd nd nd No bedload sample 30 April 199607 May 96 12,000 Rising 26,300 98 26,398 0.7 14,729 11,669 14,728 11,572 8,093 3,572 5 Mean of 7 suspended measurements10 May 96 14,900 Rising 31,900 780 32,680 2.4 17,545 15,135 17,545 14,355 9,912 5,082 140 Mean of 7 suspended measurements16 May 96 18,500 Rising 32,800 519 33,319 1.6 20,008 13,311 20,008 12,792 9,856 3,388 67 All 1996 measurements from bridge20 May 96 22,000 Falling 41,200 477 41,677 1.1 25,132 16,545 25,132 16,068 11,138 5,340 67 Mean of 7 suspended measurements23 May 96 16,000 Falling 20,100 285 20,385 1.4 9,648 10,737 9,648 10,452 7,448 3,263 2603 June 96 12,800 Falling 8,020 199 8,219 2.4 4,331 3,888 4,331 3,689 2,889 971 28 Mean of 7 suspended measurements27 June 96 9,380 Falling 5,930 121 6,051 2.0 2,906 3,145 2,906 3,024 2,377 758 1101 July 96 6,610 Falling 3,030 41 3,071 1.3 1,576 1,495 1,576 1,454 1,243 250 213 Aug 96 1,770 Base flow 64.0 1.4 65.4 2.2 nd nd nd nd nd nd nd No suspended sand break analysis07 May 98 15,700 Rising 44,900 25 44,925 0.1 28,736 16,189 28,736 16,164 nd nd nd No suspended size fractions, 199820 May 98 13,700 Rising 24,400 285 24,685 1.2 15,860 8,825 15,860 8,540 nd nd nd 8 measurements made from bridge28 May 98 13,400 Falling 16,000 263 16,263 1.6 8,800 7,463 8,800 7,200 nd nd nd Peak 24 May 199801 June 98 14,700 Falling 15,600 188 15,788 1.2 8,268 7,520 8,268 7,332 nd nd nd04 June 98 14,400 Falling 12,700 178 12,878 1.4 8,001 4,877 8,001 4,699 nd nd nd09 June 98 11,200 Falling 9,560 886 10,446 8.5 5,832 4,615 5,832 3,728 nd nd nd Bedload sampled 0.5 mile upstream11 June 98 11,100 Falling 8,480 190 8,670 2.2 4,664 4,006 4,664 3,816 nd nd nd18 June 98 10,300 Falling 27,000 144 27,144 0.5 23,490 3,654 23,490 3,510 nd nd nd Snowmelt30 June 98 8,010 Falling 3,500 94 3,594 2.6 1,960 1,634 1,960 1,540 nd nd nd31 Mar 99 5,520 Rising 6,100 402 6,502 6.2 3,111 3,391 3,111 2,989 1,963 1,424 4 All 1999 measurements from boat20 May 99 10,800 Rising 9,650 413 10,063 4.1 5,404 4,659 5,404 4,246 2,836 1,778 4525 May 99 18,300 Rising 46,000 1,145 47,145 2.4 29,900 17,245 29,900 16,100 12,040 4,998 206 Sedigraph analysis28 May 99 19,700 Rising 37,200 788 37,988 2.1 20,832 17,156 20,832 16,368 9,735 7,326 95 Sedigraph analysis02 June 99 20,400 Falling 29,200 597 29,797 2.0 16,060 13,737 16,060 13,140 9,672 3,928 137 Sedigraph analysis, peak 2 June 200024 June 99 13,800 Falling 10,600 140 10,740 1.3 4,452 6,288 4,452 6,148 5,101 1,175 1306 Apr 00 3,360 Rising 735 18 753 2.4 623 130 623 112 113 16 0.420 Apr 00 6,270 Rising 15,659 108 15,767 0.7 9,693 6,074 9,693 5,966 5,067 1,006 0.203 May 00 8,910 Rising 15,733 1,500 18,733 8.0 8,891 9,842 8,889 6,844 3,834 4,489 2002 June 00 16,000 Falling 22,939 1,783 24,722 7.2 10,300 14,422 10,300 12,639 7,558 6,432 431 Daily mean peak 1 June 200005 July 00 2,160 Base flow 321 39 360 10.9 188 172 188 133 74 94 426 Mar 01 3,500 Rising 11,700 56 11,756 0.5 10,296 1,460 10,296 1,404 nd nd nd Questionable bedload size05 Apr 01 4,170 Rising nd 59 nd nd nd nd nd nd nd nd nd Susp Sed sample contaminated17 Apr 01 2,600 Rising 878 14 892 1.6 834 58 834 44 nd nd nd No Susp Sed size data13 June 01 4,650 Falling 1,160 115 1,275 9.0 684 591 684 476 245 221 4419 June 01 2,590 Falling 266 114 380 29.9 218 161 218 48 nd nd nd No Susp Sed size data02 Apr 02 2,470 Rising 3,550 128 3,678 3.5 3,408 270 3,408 142 112 153 523 Apr 02 3,080 Rising 3,680 106 3,786 2.8 1,509 2,277 1,509 2,171 75 1,779 1914 May 02 2,700 Rising 561 64 625 10.2 544 81 544 17 18 55 822 May 02 6,960 Rising 15,200 272 15,472 1.8 5,776 9,696 5,776 9,424 3,667 5,383 3804 June 02 4940 Falling 2,650 234 2,884 8.1 1,935 950 1,935 716 571 367 1203 July 02 965 Base flow 37 3 40 8.1 33 6 33 3 nd nd nd No Susp Sed size data
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Figure 10. Relation of sediment load at 09261000 Green River near Jensen, Utah, 1996–2002, A, to water 

discharge; B, by particle size to water discharge; and C, by season to water discharge.

Green River near Jensen, Utah 31
32 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

Summary and Conclusions

Large amounts of sediment are stored in the lower Little 

Snake, lower Yampa, and lower Green Rivers in the form of 

alluvial banks, bars, and islands. These near-channel areas 

may be important secondary sources of sediment that periodically are entrained by the Green River and its larger tributaries. 

Aerial photographs made in 1988 of the channels of the Little 

Snake River downstream from the Lily streamflow-gaging 

station 09260000, the Yampa River downstream from Cross 

Mountain, and the Green River from the Lodore Ranger 

Station to Jensen were assessed to determine the relative abundance of alluvial deposits in the banks and bars. The relative 

abundance of subaerial alluvial deposits in the photographs 

varied from river to river in the watershed and from subreach 

to subreach along a river. Although the flood-plain width was 

relatively narrow and the surface area of alluvial deposits was 

small, the Little Snake River, a few miles downstream from 

the Lily streamflow-gaging station, had a consistently high 

percentage of alluvial deposits along its boundaries.

The large sediment yield of the Little Snake River is 

reflected in the increase in relative abundance of alluvial 

deposits in the Yampa River immediately downstream from 

the Little Snake River confluence. The relative abundance of 

alluvial material decreases abruptly from more than 80 percent 

to less than 20 percent as the Yampa River flows into the steep 

and narrow Yampa Canyon. Alluvial deposits are relatively 

scarce in Yampa Canyon between river miles 45 and 21. The 

canyon geomorphology in this reach is dominated by the 

massive limestone of the Morgan Formation; also, the river 

is steep and the canyon floor is narrow, providing little area 

suitable for significant alluvial sediment storage. The Yampa 

River flows through the massive Weber Sandstone downstream 

from river mile 21 and, from here to the mouth, the canyon 

floor is wider and more conducive to sediment deposition.

The abundance of subaerial alluvial deposits in the Green 

River downstream from the Lodore Ranger Station is less 

uniform than in the Little Snake or Yampa Rivers. The relative abundance of alluvial deposits varies from less than 10 to 

more than 80 percent of the visible channel boundary between 

the Lodore Ranger Station and the downstream end of the 

study reach at river mile 194. The regional structural geology 

and lithology at river level may be important in determining 

variations in canyon-floor width and gradient, which influence 

the relative abundance of alluvial deposits in the Green River.

Sediment data from five sites in the Yampa River Basin 

and the upper Green River Basin have been collected by the 

USGS in cooperation with the Colorado Division of Wildlife 

and the U.S. Fish and Wildlife Service during an ongoing, 

multiyear study that began in 1998. These data were augmented with sediment data gathered at these sites in earlier 

years as part of other USGS studies and routine data-collection 

activities. The sampling sites are the Yampa River above Little 

Snake River, near Maybell, Colorado, 09251100; the Little 

Snake River, near Lily, Colorado, 09260000; the Yampa River 

at Deerlodge Park, 09260050; the Green River above Gates 

of Lodore, Colorado, 404417108524900 (nearest streamflow 

gage, Green River near Greendale, Utah, 09234500); and the 

Green River near Jensen, Utah, 09261000.

The period of record, number of samples, and type of 

sediment analyses differ at each of the sites. The sites with 

the shortest periods of record are the Yampa River above 

Little Snake River (1998–2002) and the Green River above 

Gates of Lodore (1999–2002); for both sites, data include 

suspended-sediment and bedload measurements. Suspendedsediment measurements were made at the Little Snake River, 

near Lily site in 1983, 1994–98, and 2000–2002. Bedload 

measurements were made in 2001 and 2002. Suspended- and 

bedload-sediment measurements were made at the Yampa 

River at Deerlodge Park site in 1982–83 and 1998–2001, and 

only suspended-sediment measurements were made in 1994 

and 1997. Suspended-sediment measurements were made at 

the Green River near Jensen site from 1948–79. Suspendedand bedload-sediment measurements were made at the Green 

River near Jensen site in 1996 and from 1998 through 2002. 

Sediment load by transport mode, particle-size range, and 

hydrograph season also were computed for all sites.

One objective of this study was to identify future data 

needs for improving the accuracy of sediment-transport relations that can be used in calculating sediment budgets at the 

five sampling sites. Sediment-transport curves were derived 

by least-squares regression of logarithmic-transformed data to 

provide a means to estimate seasonal and annual sediment supply to the principal streams in the upper part of the watershed 

(the Yampa River, the Little Snake River, and the Green River 

upstream from the Gates of Lodore) and on the Green River 

just upstream from a critical spawning habitat near Jensen, 

Utah. These transport curves can be revised as additional data 

from the ongoing sampling program become available.

Table 15. Sediment-transport equations derived from sediment 

discharges measured at station 09261000 Green River near 

Jensen, Utah, 1996–2002.

[Qs, sediment discharge in tons per day; Q, water discharge in cubic feet per 

second; R2, coefficient of determination; MSE, mean square error; n, number 

of samples]

Type of 

sediment 

discharge

Regression 

equation R2 MSE n

Total Qs = 0.000146 Q1.97 0.81 0.608 39

Suspended Qs = 0.000104 Q2.00 0.81 0.620 40

Bedload Qs = 0.000621 Q1.38 0.54 1.08 40

Silt and clay Qs = 0.000779 Q1.73 0.75 0.625 38

Sand and gravel Qs = 0.00000438 Q2.25 0.85 0.574 38

Fine sand Qs = 0.000000377 Q2.47 0.86 0.532 25

Medium and 

coarse sand

Qs = 0.0000739 Q1.83 0.64 1.04 25

Very coarse sand 

and fine gravel

Qs = 0.0000110 Q1.58 0.40 2.10 25

Total, rising Qs = 0.00483 Q1.64 0.77 0.487 18

Total, falling Qs = 0.0000802 Q2.00 0.90 0.140 18
The relative accuracy and representativeness of the 

transport relations derived in this study were assessed using 

the coefficients of determination (R2) and mean square error 

(MSE) of regression equations, the range of discharges 

sampled, the seasonality of the relations, and the number of 

samples. The transport equations in this report are considered 

to be reasonably representative if the R2 is greater than about 

0.70, if sediment samples are evenly distributed over the likely 

range of nonbase-flow discharges in a year, if the samples are 

distributed between the rising-limb and falling-limb hydrograph seasons, and if the number of samples is large enough to 

reflect the variance in the relation between sediment load and 

water discharge.

The sediment-transport equations presented in this report 

indicate that gravel, sand, silt, and clay transport in these rivers 

is strongly dependent on the streamflow magnitude and, to a 

lesser degree, on the season. The timing of annual runoff and 

consequently the timing of sediment entrainment, transport, 

and deposition affect aquatic habitat and are dependent on 

long-term climate and seasonal weather patterns and on the 

operation of upstream reservoirs. Reach-specific estimates of 

the timing, volume, and particle size of sediment deposited at 

critical aquatic-habitat sites other than at the gaged sampling 

sites require streamflow-routing simulation through the drainage network and are beyond the scope of this report.

Yampa River above Little Snake River, near 

Maybell, Colorado

The relatively large R2 values for all transport equations 

at the Yampa River above Little Snake River near Maybell 

(R2 greater than or equal to 0.80) indicate that the transport 

equations may be useful for annual load estimation or sediment budget calculations for discharges ranging from about 

500 to 10,000 ft3/s; however, the small number of samples 

used to calculate the seasonal transport equations may not be 

representative of flow conditions. These transport equations 

may not adequately reflect transport conditions of higher 

discharges that occurred in 1997 or in the mid-1980s before 

the streamflow-gaging station was established. Additional 

measurements in the 500- to 10,000-ft3/s range from both 

the rising-limb and falling-limb hydrograph seasons and any 

measurements exceeding about 10,000 ft3/s would make these 

equations more representative of flow conditions at this site.

Little Snake River near Lily, Colorado

The suspended-sediment measurements at Little Snake 

River near Lily are relatively evenly distributed at streamflows 

from about 40 to 6,000 ft3/s; however, sediment measurements 

at streamflows approaching the 1984 historical instantaneous 

peak discharge (16,700 ft3/s) have not been made. Bedload 

measurements were made in 2001 and 2002. The transport 

equation for suspended-sediment load (R2 = 0.74) is adequate 

for estimating annual suspended loads for discharges ranging

from about 40 to 6,000 ft3/s and may have some applicability for discharges ranging from about 1 to 40 ft3

/s. The 

suspended-sediment load transport equation must be recomputed with data from discharges greater than 6,000 ft3

/s for it 

to be applicable at extremely high discharges. Transport equations by suspended-particle size are applicable for discharges 

ranging from about 50 to 6,000 ft3/s; however, their R2 values 

are less than 0.55. Although the distribution of data indicate a 

seasonal sediment-load hysteresis may exist, the relatively low 

R2 value for the rising-hydrograph season (R2 = 0.47) could 

be improved with additional data collected in the appropriate 

season. Also, because bedload data have been collected for 

only 2 years at this site, neither the total-annual sediment load 

nor the relative portion of total-sediment load transported as 

bedload is well documented.

Yampa River at Deerlodge Park, Colorado

Suspended- and bedload-sediment data were collected 

at the Yampa River at Deerlodge Park site near the 1983 

instantaneous peak discharge of 23,400 ft3/s, but no sediment measurements were made the following year during the 

historical instantaneous peak discharge (33,200 ft3/s). Data 

collected since 1983 at Deerlodge Park has increased the 

number of suspended-sediment measurements by 139 percent 

and has increased the number of total sediment (suspended 

sediment plus bedload sediment) measurements by 71 percent 

since 1982–83. Based only on the relative magnitudes of 

the R2 value, the additional data have resulted in a slightly 

improved suspended-sediment transport equation, compared to 

a previous USGS study (0.80 compared to 0.76), and a slightly 

deteriorated total-load equation (0.72 compared to 0.79). The 

updated transport equation for suspended-sediment load may 

be useful for annual suspended-sediment load calculations 

for discharges ranging from about 40 to 18,000 ft3/s, whereas, 

the updated transport equations for total-sediment load, 

suspended-sediment load, sand and gravel load, and fine sand 

load may be useful for annual load calculations for discharges 

ranging from about 600 to 18,000 ft3/s.

Unless there is an opportunity to make future measurements above about 18,000 ft3

/s, additional data collection may 

not improve these transport equations. However, more bedload 

measurements made during streamflows of less than about 

700 ft3/s could improve the accuracy of both the bedloadtransport and total-sediment transport equations. Additional 

data collection during the rising-limb and falling-limb hydrograph periods might improve the transport equations that 

describe seasonality.

Green River above Gates of Lodore, Colorado

Sediment-transport equations for total-sediment load, 

suspended-sediment load, silt and clay load, and sand and 

gravel load had R2 values greater than or equal to 0.74. The 

equation for bedload had an R2 value of 0.47, possibly due to 

a relatively small range in bedload magnitude typical of river 

Summary and Conclusions 33
34 Summary of Sediment Data from the Yampa River and Upper Green River Basins, Colorado and Utah, 1993–2002

reaches with a limited supply of transportable bed material, 

such as rivers downstream from dams. The seasonal transport 

equations had R2 values of 0.81 but were based on small numbers of samples and, therefore, may not accurately reflect true 

seasonal conditions. One-half of the sediment measurements 

were made at discharges greater than 6,000 ft3/s, streamflows that occur relatively infrequently. Additional sediment 

measurements made at less than 3,000 ft3/s or greater than 

10,000 ft3/s in both early and late hydrograph seasons could 

improve the accuracy of the transport equations. Additional 

measurements also might result in a better understanding of 

the variation in dominant transport mode (bedload compared 

to suspended load) over a wide range of streamflows.

Green River near Jensen, Utah

Sediment-transport equations for total-sediment, 

suspended-sediment, and transport by all particle sizes except 

medium and coarse sand, and very coarse sand and fine gravel 

had R2 values of 0.75 or greater and may be useful for annual 

load estimations or sediment budget calculations for discharges ranging from about 1,000 to 22,000 ft3

/s. No sediment 

measurements have been made at streamflows approaching the 

1984 historical instantaneous peak discharge of 40,000 ft3/s. 

The equation for bedload transport had an R2 value of 0.54, the 

equation for medium and coarse sand had an R2 value of 0.64, 

and the equation for very coarse sand and fine gravel had an 

R2 value of 0.40. Rising-limb and falling-limb season equations had R2

 values of 0.77 and 0.90, respectively, but these 

equations were based on relatively small numbers of samples 

(18 for each equation).

The suspended-sediment transport equation derived from 

the 40 measurements made since 1996 has a different slope and 

intercept than the post-dam period (1963–79) equation and, 

based on the R2 value, much less variance. Possible explanations for the difference between these two transport equations 

could include climate and land-use changes, a change in the 

availability of transportable sediment, or a change in Flaming 

Gorge Reservoir operation between the two periods.

References Cited

Andrews, E.D., 1978, Present and potential sediment yields 

in the Yampa River basin, Colorado and Wyoming: 

U.S. Geological Survey Water-Resources Investigations 

Report 78–105, 33 p.

Andrews, E.D., 1986, Downstream effects of Flaming Gorge 

Reservoir on the Green River, Colorado and Utah: Geological Society of America Bulletin, v. 97, p. 1012–1023.

Crowfoot, R.M., Boulger, R.W., and O’Neill, G.B., 2002, 

Water resources data, Colorado, water year 2002, v. 2, 

Colorado River Basin: U.S. Geological Survey Water-Data 

Report CO–02–2, 623 p.

Edwards, T.K., and Glysson, G.D., 1999, Field methods for 

measurement of fluvial sediment (Revised): Techniques 

of Water-Resources Investigations of the U.S. Geological 

Survey, book 3, chap. C2, 89 p.

Elliott, J.G., Kircher, J.E., and von Guerard, P.B., 1984, Sediment transport in the lower Yampa River, northwestern 

Colorado: U.S. Geological Survey Water-Resources Investigations Report 84–4141, 44 p.

Evans, Laura, and Belknap, Buzz, 1973, Dinosaur river guide: 

Boulder City, Nevada, Westwater Books, 64 p.

Fischer, N.T., Toll, M.S., Cully, A.C., and Potter, L.D., 1983, 

Vegetation along Green and Yampa Rivers and response 

to fluctuating water levels, Dinosaur National Monument: 

Albuquerque, University of New Mexico, Biology Department, done for the National Park Service under contract 

CX–1200–2–B024, 179 p.

Guy, H.P., and Norman, V.W., 1970, Field methods for 

measurement of fluvial sediment: Techniques of WaterResources Investigations of the U.S. Geological Survey, 

book 3, chap. C2, 59 p.

Harvey, M.D., Mussetter, R.A., and Wick, E.J., 1993, A physical process-biological response model for spawning habitat 

formation for the endangered Colorado squawfish: Rivers, 

v. 4, no. 2, p. 114–131.

Helley, E.J., and Smith, W., 1971, Development and calibration of a pressure-difference bedload sampler: U.S. Geological Survey Open-File Report 73–108, 38 p.

Jansson, M.B., 1985, A comparison of detransformed logarithmic regressions and power function regressions: Geografiska Annaler, v. 67A, no. 1–2, p. 61–70.

Lyons, J.K., Pucherelli, M.J., and Clark, R.C., 1992, Sediment 

transport and channel characteristics of a sand-bed portion 

of the Green River downstream from Flaming Gorge Dam, 

Utah, U.S.A.: Bureau of Reclamation Report No. R–92–08, 

23 p.

Merritt, D.M., and Cooper, D.J., 2000, Riparian vegetation and 

channel change in response to river regulation—A comparative study of the regulated and unregulated streams in the 

Green River basin, USA: Regulated Rivers Research and 

Management, v. 16, p. 543–564.

Miller, D.M., 1984, Reducing transformation bias in curve fitting: The American Statistician, v. 38, no. 2, p. 124–126.
Mussetter, R.A., Harvey, M.D., Zevenbergen, L.W., and 

Tenney, R.D., 2001, A comparison of one- and twodimensional hydrodynamic models for evaluating Colorado 

pikeminnow spawning habitat, Yampa River, Colorado, in

Anthony, D.J., Harvey, M.D., Laronne, J.B., and Mosley, 

M.P., eds., Applying geomorphology to environmental management: Water Resources Publications, LLC, Highlands 

Ranch, Colorado, p. 361–380.

O’Brien, J.S., 1984a, Hydraulic and sediment transport 

investigation, Yampa River, Dinosaur National Monument: 

Fort Collins, Colorado, Colorado State University, National 

Park Service, Water Resources Field Support Laboratory 

Report 83–8, 86 p.

O’Brien, J.S., 1984b, 1983 Yampa River cobble reach morphology investigation: Final Report submitted to Endangered Species Office, U.S. Fish and Wildlife Service, Salt 

Lake City, Utah, 79 p.

Pitlick, John, Cress, Robert, and Van Steeter, M.M., 2001, 

Geomorphic assessment of the potential for expanding the 

range of habitat used by native fishes in the Upper Colorado River Basin, in Anthony, D.J., Harvey, M.D., Laronne, 

J.B., and Mosley, M.P., eds., Applying geomorphology to 

environmental management: Water Resources Publications, 

LLC, Highlands Ranch, Colorado, p. 335–360.

Porterfield, G., 1972, Computation of fluvial-sediment discharge: Techniques of Water-Resources Investigations of the 

U.S. Geological Survey, book 3, chap. C3, 66 p.

Troutman, B.M., and Williams, G.P., 1987, Fitting straight 

lines in the earth sciences, in Size, W.B., ed., Use and abuse 

of statistical methods in the earth sciences: New York, 

Oxford University Press, p. 107–128.

U.S. Interagency Advisory Committee on Water Data, 1982, 

Guidelines for determining flood-flow frequency: Reston, 

Va., U.S. Geological Survey, Office of Water Data Coordination, Bulletin 17B of the Hydrology Subcommittee, 

183 p.

Walling, D.E., 1977, Limitations of the rating curve technique 

for estimating suspended sediment loads, with particular 

reference to British rivers, in Proceedings of the Symposium 

on Erosion and Solid Matter Transport in Inland Waters, 

Paris, July 1977: Washington D.C., International Association of Hydrological Science IAHS–AISH Publications No. 

122, p. 34–48.

Williams, G.P., and Wolman, M.G., 1984, Downstream effects 

of dams on alluvial rivers: U.S. Geological Survey Professional Paper 1286, 83 p.

References Cited 35