Design of a Sediment-Monitoring Gaging Network on 

Ephemeral Tributaries of the Colorado River in Glen, 

Marble, and Grand Canyons, Arizona

Open File Report 2014–1137

U.S. Department of the Interior

U.S. Geological Survey
COVER: House Rock Wash above Emmett Wash gaging station looking downstream. Photography by Ronald 

Griffiths, 2010
Design of a Sediment-Monitoring Gaging Network on 

Ephemeral Tributaries of the Colorado River in Glen, 

Marble, and Grand Canyons, Arizona

By Ronald E. Griffiths, David J. Topping, Robert S. Anderson, Gregory S. Hancock, and Theodore S. Melis

Open File Report 2014–1137

U.S. Department of the Interior

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

Sally Jewell, Secretary

U.S. Geological Survey

Suzette Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia 2014

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Suggested citation: 

Griffiths, R.E., Topping, D.J., Anderson, R.S., Hancock, G.S., and Melis, T.S., 2014, Design of a sedimentmonitoring gaging network on ephemeral tributaries of the Colorado River in Glen, Marble, and Grand Canyons, 

Arizona: U.S. Geological Survey Open File Report 2014–1137, 21 p., http://dx.doi.org/10.3133/ofr20141137. 

ISSN 2331-1258 (online)

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iii

Contents

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

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

Purpose and Scope....................................................................................................................................................4

Lesser Tributary Gaging Stations...................................................................................................................................4

Generalized Station Design........................................................................................................................................6

Station Placement Considerations............................................................................................................................11

Discharge Calculations.............................................................................................................................................12

Station Visits and Maintenance ................................................................................................................................13

Summary......................................................................................................................................................................13

Acknowledgments........................................................................................................................................................14

References Cited .........................................................................................................................................................14

Appendix: Campbell Scientific CR10X, SR50, and Onset Rain Gage..........................................................................16

CR10X instructions...................................................................................................................................................17

Instructions for setup of PC208W 3.3 ...................................................................................................................17

CR10X program....................................................................................................................................................17

Instructions for downloading the CR10X datalogger.............................................................................................19

Instructions on deleting all data stored on the CR10X ..........................................................................................20

Onset rain gage and HOBOTM event logger instructions ..........................................................................................20

Figures

1. Digital elevation map showing the lesser tributary stage and suspended-sediment gaging stations........5

2. Photographs of stations along the lesser tributaries.. ..............................................................................7

3. A U-59 single-stage suspended-sediment sampler..................................................................................9

4. Digital elevation map showing the rain-gage network. ...........................................................................11

Tables

1. Equipment present at each sediment-monitoring gaging station. ............................................................10
iv

Conversion Factors

Multiply By To obtain

centimeter (cm) 0.3937 inch (in)

millimeter (mm) 0.03937 inch (in)

micron (μ) 0.00003937 inch (in)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

liter (L) 0.2642 gallon (gal)

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Abbreviations

ABS acrylonitrile butadiene styrene

GCMRC Grand Canyon Monitoring and Research Center

GCNP Grand Canyon National Park

MMT Million metric tons

NPS National Park Service

Reclamation U.S. Department of the Interior, Bureau of Reclamation

USGS U.S. Geological Survey
Design of a Sediment-Monitoring Gaging Network on 

Ephemeral Tributaries of the Colorado River in Glen, 

Marble, and Grand Canyons, Arizona

By Ronald E. Griffiths, David J. Topping, Robert S. Anderson, Gregory S. Hancock, and Theodore S. Melis

Abstract

Management of sediment in rivers downstream from dams requires knowledge of both the 

sediment supply and downstream sediment transport. In some dam-regulated rivers, the amount of 

sediment supplied by easily measured major tributaries may overwhelm the amount of sediment 

supplied by the more difficult to measure lesser tributaries. In this first class of rivers, managers need 

only know the amount of sediment supplied by these major tributaries. However, in other regulated 

rivers, the cumulative amount of sediment supplied by the lesser tributaries may approach the total 

supplied by the major tributaries. The Colorado River downstream from Glen Canyon has been 

hypothesized to be one such river. If this is correct, then management of sediment in the Colorado River 

in the part of Glen Canyon National Recreation Area downstream from the dam and in Grand Canyon 

National Park may require knowledge of the sediment supply from all tributaries. Although two major 

tributaries, the Paria and Little Colorado Rivers, are well documented as the largest two suppliers of 

sediment to the Colorado River downstream from Glen Canyon Dam, the contributions of sediment 

supplied by the ephemeral lesser tributaries of the Colorado River in the lowermost Glen Canyon, and 

Marble and Grand Canyons are much less constrained. Previous studies have estimated amounts of 

sediment supplied by these tributaries ranging from very little to almost as much as the amount supplied 

by the Paria River. Because none of these previous studies relied on direct measurement of sediment 

transport in any of the ephemeral tributaries in Glen, Marble, or Grand Canyons, there may be 

significant errors in the magnitudes of sediment supplies estimated during these studies. To reduce the 

uncertainty in the sediment supply by better constraining the sediment yield of the ephemeral lesser 

tributaries, the U.S. Geological Survey Grand Canyon Monitoring and Research Center established eight 

sediment-monitoring gaging stations beginning in 2000 on the larger of the previously ungaged 

tributaries of the Colorado River downstream from Glen Canyon Dam. The sediment-monitoring gaging 

stations consist of a downward-looking stage sensor and passive suspended-sediment samplers. Two 

stations are equipped with automatic pump samplers to collect suspended-sediment samples during flood 

events.

Directly measuring discharge and collecting suspended-sediment samples in these remote 

ephemeral streams during significant sediment-transporting events is nearly impossible; most significant 

run-off events are short-duration events (lasting minutes to hours) associated with summer 

thunderstorms. As the remote locations and short duration of these floods make it prohibitively 

expensive, if not impossible, to directly measure the discharge of water or collect traditional depthintegrated suspended-sediment samples, a method of calculating sediment loads was developed that 

includes documentation of stream stages by field instrumentation, modeling of discharges associated 

with these stages, and automatic suspended-sediment measurements. The approach developed is as 

follows (1) survey and model flood high-water marks using a two-dimensional hydrodynamic model, (2) 
2

create a stage-discharge relation for each site by combining the modeled flood flows with the measured 

stage record, (3) calculate the discharge record for each site using the stage-discharge relation and the 

measured stage record, and (4) calculate the instantaneous and cumulative sediment loads using the 

discharge record and suspended-sediment concentrations measured from samples collected with passive 

US U-59 samplers and ISCOTM pump samplers. This paper presents the design of the gaging network 

and briefly describes the methods used to calculate discharge and sediment loads. The design and 

methods herein can easily be used at other remote locations where discharge and sediment loads are 

required. 

Introduction

In arid and semi-arid environments, short-duration, high-intensity rainfall events are the primary 

driver of sediment transport in ephemeral streams (for example, Wolman and Miller, 1960; Graf, 1983; 

Sharma and Murthy, 1994; Coppus and Imeson, 2002). The spatial and temporal variability of these 

rainfall events results in episodic and irregular stream flow and resultant sediment transport. For longterm geomorphic studies, the episodic nature of the sediment-transporting events may be irrelevant, but 

for shorter duration studies, especially sediment mass balance studies, knowing the actual short-term 

sediment yield, as opposed to the average sediment yield, is essential. Whereas sediment yield data may 

be important, measuring discharge and collecting suspended-sediment samples on ephemeral streams in 

arid regions is difficult and time-consuming. Limited-flow durations require that field technicians 

closely monitor weather conditions to promptly respond to possible flow events. Because of these 

limitations, few sediment-monitoring programs on ephemeral streams have been developed. Examples 

of sediment-monitoring gages and gaging networks constructed on arid ephemeral streams include 

Walnut Gulch, United States (Graf, 1983), Nahal Yael, Israel (Schick and Lekach, 1996; Schick, 2000), 

and the Luni River Basin, India (Sharma and others, 1984; Sharma and Murthy, 1994). 

The difficulty in making measurements of discharge and suspended-sediment concentration on 

arid ephemeral streams has led many researchers to use methods such as regional sediment-yield 

equations (Webb and others, 2000), sediment-rating curves (Sutherland and Bryan, 1990), and peak 

discharge to total-sediment load relations (Rankl, 2002). These methods can provide a cost-effective 

estimation of sediment yield from ungaged tributaries. However, these approaches are limited by, among 

other factors, time averaging, hysteresis, and differences in local and regional geology, rainfall, and 

vegetation. For small drainage basins, monthly sediment loads have been found to vary up to two orders 

of magnitude from those predicted by sediment rating curves (Walling, 1977). Because of the limitations 

of indirect methods for calculating sediment yield discussed above, methods to measure discharge and 

sediment concentrations must be employed for streams where real-time sediment loads, rather than 

averaged sediment loads, are needed.

The Colorado River in Grand Canyon National Park (GCNP) experienced a dramatic reduction 

in the quantity of fine sediment (sand, silt, and clay) entering the river reach after completion of the Glen 

Canyon Dam; this reduction in sediment supply resulted in a net export of fine sediment (Schmidt and 

others, 2004). Currently, as a part of the U.S. Department of the Interior’s Glen Canyon Dam Adaptive 

Management Program (Campbell and others, 2010), near real-time suspended-sediment monitoring 

occurs at multiple locations on the Colorado River (Topping and others, 2004; Griffiths and others, 

2012). Change in the quantity of sediment stored within each reach bounded by suspended-sediment 

monitoring stations is now calculated in near real-time. In addition to the quantity of fine sediment 

entering and exiting each reach via the Colorado River, the tributary inputs of fine sediment must also be 

quantified to construct these mass balance sediment budgets. The Paria and Little Colorado Rivers are 

currently the major sources of fine sediment to the Colorado River in GCNP and sediment input from 

these tributaries is well constrained. The other lesser tributaries described in this report contribute a 

likely smaller, but perhaps still important, quantity of sand and finer sediment. 
3

A number of workers have investigated sediment yield to Colorado River from the lesser 

tributaries. The first such study was completed by the U.S. Department of the Interior, Bureau of 

Reclamation (Reclamation) in preparation for the construction of Marble Canyon Dam. Reclamation 

conducted field work in the 1950s, making observations of geology, geomorphology, vegetation, and 

sedimentation of stock tanks to establish average sediment yield from the lesser tributaries upstream 

from the proposed dam site (U.S. Department of the Interior, Bureau of Reclamation, 1958). The study 

concluded that the annual average sediment yield from the lesser tributaries to the Colorado River 

between the Glen Canyon Dam and the proposed dam site at river mile 32.5 was of ~800,000 metric 

tons (including gravel). In (1981), Howard and Dolan published a study in which they estimated the 

average combined annual sediment yield from the lesser tributaries upstream from the Grand Canyon 

gage (river mile 87, USGS 09402500) to be 34 percent of the combined contribution of the Paria and 

Little Colorado rivers, or ~4 million metric tons (MMT). Randle and Pemberton (1987) used a regional 

sediment yield regression to calculate lesser tributary annual average sediment yields of ~1.3 MMT 

above the Grand Canyon gage. A similar approach was used by Webb and others (2000), who also

employed a flood-frequency rating-curve method, and a reservoir sedimentation study combined with a 

runoff model to calculate three estimates of average annual sediment yield from the lesser tributaries. 

They estimated an annual sediment yield of 600,000 to 800,000 metric tons above the Grand Canyon 

gage.

The previous studies calculated average sediment yield and, in many cases, used sediment yield 

equations that were derived from drainages with substantially different geologic and climatic conditions. 

The time-averaged nature of the sediment yields calculated from the previous studies make them illsuited for calculation of the shorter time frame sediment budgets needed by river managers for the 

Colorado River. In 2000, to better constrain the total sediment input from the lesser tributaries, and to 

improve sediment budgeting for the Colorado River, the U.S. Geological Survey (USGS) Grand Canyon 

Monitoring and Research Center (GCMRC) established seven suspended-sediment gaging stations on 

previously ungaged ephemeral tributaries to the Colorado River downstream from Glen Canyon Dam. 

This network was expanded in 2006 to include the perennial Bright Angel Creek, which has a long-term 

gaging record beginning in 1923, and is used to provide longer-term hydrologic context to the other 

lesser tributary stations with much shorter periods of record. Each gaging station consists of a stage 

recorder and suspended-sediment point sampler(s). Stage is recorded every 15 minutes from a 

downward-looking ultrasonic stage sensor during zero or base flow conditions, and every minute during 

flood events. Suspended-sediment samples are collected by passive US U-59 samplers (described in 

Edwards and Glysson, 1999) and (or) ISCOTM automatic pump samplers (Teledyne Isco, 2012; 

Teledyne Isco, 2013). 

At each of the gaging stations, channel topography and high-water marks for different peak 

flows have been surveyed. The approach used to calculate discharge for the surveyed high-water marks 

is to (1) generate a topographic map and model grid of the stream channel from survey data, (2) perform 

preliminary model simulations using a “best guess” flood discharge and Z0 Nikuradse (1933) bed 

roughness parameter (based on the measured bed-sediment grain-size distribution) for the first model 

run, (3) perform successive model runs varying the discharge and Z0 to minimize the root-mean-square 

error between the surveyed high-water marks and the modeled water surface and (4) either hold the 

established Z0 constant between different flood events or allow Z0 to increase slightly as peak flood 

stage increases, and model the discharge for different high-water marks to develop stage-discharge 

relations (Griffiths and others, 2010). Unless the characteristics of the bed change as peak flood stage 

increases, Z0 should remain constant; Z0 is only allowed to increase with peak flood stage if there is a 

physical basis for increasing bed roughness with increasing peak flood discharge (as described herein). 

Using the stage sensor and suspended-sediment data from each site, total sediment transport can then be 

determined.
4

Purpose and Scope

This report describes a network of sediment-monitoring gaging stations installed on selected 

smaller tributaries of the Colorado River in Glen, Marble, and Grand Canyons. The gages were installed 

to quantify the yield of fine sediment from what were intended to be a representative subset of smaller, 

or lesser, tributaries to the Colorado River in Glen, Marble, and Grand Canyons. This report provides 

information on the design and maintenance of this sediment-monitoring gaging network, as well as 

providing a possible design framework for use on other streams where an accurate measurement of 

sediment loads is required.

Lesser Tributary Gaging Stations

There are currently eight gaging stations that automatically measure stage and collect suspendedsediment samples on the lesser tributaries of the Colorado River in lower Glen, Marble, and Grand 

Canyons (fig. 1). This monitoring network was established in 2000 and expanded in 2006 to include 

Bright Angel Creek. The major foci of this monitoring network are the ephemeral tributaries of the 

Colorado River in Marble Canyon. Stage, suspended-silt and clay concentration, suspended-sand 

concentration, and suspended-sand grain size data are currently collected on lesser tributaries that drain 

approximately 56 percent of the previously ungaged drainage area of this canyon. All of the lesser 

tributary sediment-monitoring gaging stations, except for those in Water Holes Canyon and on Bright 

Angel Creek, monitor streams that drain into Marble Canyon. Water Holes Canyon is an ephemeral 

tributary of the Colorado River in Glen Canyon and Bright Angel Creek is a perennial tributary of the 

Colorado River in the Grand Canyon. 
5

Figure 1. Digital elevation map showing the stage and suspended-sediment gaging stations along the lesser 

tributaries of the Colorado River, Arizona. Lesser tributary suspended-sediment gaging stations, with informal 

names in parentheses: Water Holes Canyon (Water Holes), Badger Creek (Badger), Tanner Wash (Tanner), 

House Rock Wash above Emmett Wash (House), House Rock Wash in Rider Canyon (Rider), North Canyon 

(North), Shinumo Wash (Shinumo), and Bright Angel Creek.
6

The geology of the lesser tributary drainage basins can broadly be split into two groups, areas of 

high potential fine-sediment yield and areas of lower potential fine-sediment yield. Four of the lesser 

tributary gaging stations, Water Holes Canyon, Badger Creek, House Rock Wash above Emmett Wash 

(herein referred to as House Rock Wash), and House Rock Wash in Rider Canyon (herein referred to as 

Rider Canyon), have drainage basins that are dominated by Mesozoic sandstones and have high 

potential fine-sediment yields. The active channel streambed of Water Holes Canyon consists of sand on 

bedrock, with patches of gravel. Badger Creek has a bed dominated by sand and gravel. The bed of 

House Rock Wash is dominated by sand and fine gravel. The bed of Rider Canyon is composed of 

patches of sand and gravel on bedrock. The Rider Canyon station has the most comprehensive 

suspended-sediment record of the lesser tributary gaging stations; at this station, suspended-sediment 

samples are collected with arrays of US U-59 samplers and an ISCOTM automatic pump sampler.

North Canyon and Shinumo Wash drain areas that consist primarily of Paleozoic limestone and 

have lower potential fine-sediment yields. These two tributaries have streambeds that are almost 

exclusively angular gravel with minor amounts of interstitial sand. The Tanner Wash drainage basin is a 

combination of high and lower fine-sediment yield areas; the bed of Tanner Wash consists of bedrock, 

sand, and gravel. 

Bright Angel Creek is the only lesser tributary gaging station monitoring a stream that drains into

Grand Canyon proper. The Bright Angel Creek drainage basin is dominated by Proterozoic igneous and 

metamorphic rocks, and Paleozoic limestones, sandstones, and siltstones. Bright Angel Creek at the 

gaging station section is a steep, cobble-dominated stream with an average base flow of 12–20 cfs. 

Bright Angel Creek has a historical stream-gaging record from 1923–74 and 1991–93 that provides 

hydrologic context for the other shorter-record stations. Bright Angel Creek is the only lesser tributary 

monitored that has a base-flow; all of the other gaged lesser tributaries are ephemeral. Vegetation at the 

other seven gaging stations consists primarily of sparse, low-lying bushes. The vegetation at the Bright 

Angel Creek site consists of sparse grasses and sedges along the channel, and small willow and other 

brush on the upper channel banks. 

Generalized Station Design

Lesser tributary suspended-sediment gaging stations installed and maintained by USGS GCMRC 

have two main components, several arrays of passive US U-59 single-stage suspended-sediment 

samplers and a Campbell Scientific SR50 (now replaced by the SR50A-L) downward-looking ultrasonic 

stage sensor attached to a Campbell Scientific CR10X (now replaced by the CR1000) data logger (fig. 

2). Although the SR50 was marketed as a snow depth sensor, it provides a cost-effective, lowmaintenance, and sufficiently accurate downward-looking stage sensor ideal for deployment in the 

remote locations of these ephemeral tributaries (an overview of techniques used to measure ephemeral 

stream stage can be found in Bhamjee and Lindsay [2011]). A 12-volt battery attached to a small (10- or 

20-watt) charge-controlled solar panel provides power to the SR50 stage sensor and CR10X data logger. 

Stage is measured and recorded at a 15-min interval during zero- or base-flow conditions, and every 

minute during flood conditions when the stage is above a user-specified threshold. Two of the lesser 

tributary gaging stations are equipped with ISCOTM automatic pump samplers triggered by liquid-level 

(stage) actuators. Rain gages are also co-located with all gaging stations.
7

Figure 2. Photographs of gaging stations along the lesser tributaries of the Colorado River, Arizona. A, Shinumo 

Wash station looking across the channel. Station has two arrays of three US U-59s each. The rain gage is 

located on the opposite stream bank from the station, approximately at the location from where the photograph 

was taken. B, Badger Creek station looking downstream. Station has two arrays of three US U-59s each. The 

rain gage is located on the opposite stream bank from the station (to the left of the photograph). C, Tanner 

Wash station looking upstream. Station has two arrays of three US U-59s each; the second array of US U-59s 

is located behind the point where the photograph was taken. D, Water Holes Canyon station looking upstream. 

Station has two arrays of three US U-59s each. The rain gage is just off the photograph to the right of the 

station.
8

Figure 2. —Continued Photographs of gaging stations along the lesser tributaries of the Colorado River, 

Arizona. E, Rider Canyon station looking across the channel. Station has three arrays of three US U-59s each. 

The third array of US U-59s is located ~50 m upstream (photograph left) of the station. The SR50, CR10X, 

battery, second solar panel, and rain gage are located on the opposite stream bank from the ISCOTM, just 

behind where the photograph was taken. F, North Canyon station looking downstream. Station has two arrays 

of three US U-59s each. G, Bright Angel Creek station looking across the stream. The ISCOTM pump sampler, 

SR50, and CR10X are located under the foot bridge. Power to this station is provided from a National Park 

Service (NPS) building. A weather station, including a rain gage, is maintained by the NPS several hundred 

meters upstream. H, House Rock Wash station looking downstream. Station has two arrays of three U-59s 

each. The second array of US U-59s is located ~50 m upstream (photograph left) of the station. The rain gage 

is just off the photograph to the left of the station. 

The US U-59 is an inexpensive sampler that requires no power and has no moving parts, making 

it useful for remote tributaries where visits are infrequent. The US U-59 consists of a sample container, 

in this case a high-density polyethylene half-liter bottle, attached to an intake hose and an air-exhaust 

hose (Inter-Agency Committee on Water Resources, Subcommittee on Sedimentation, 1961; Edwards 

and Glysson, 1999). The intake hose, attached to the sample container with airtight fittings, extends up 

from the container to the intake nozzle via a gooseneck bend (fig. 3). The intake nozzle is positioned 

near the top of the sample container. The air-exhaust hose ends several centimeters above the bottom of 

the sample container. During tributary floods, suspended-sediment sample flows into the container when 
9

the stream stage increases above the top of the gooseneck bend in the intake hose. The flow into the 

sample container stops when the pressure inside the sample container increases because the rising flood 

blocks the exhaust hose. An ABS (acrylonitrile butadiene styrene) pipe, in which an access hatch has 

been cut, typically houses three US U-59 samplers (fig. 3). Arrays of samplers are bolted to boulders or 

the canyon wall (fig. 2). Two or three arrays of samplers are bolted at progressively higher elevations to 

allow samples to be collected as the stage increases.

Figure 3. A U-59 single-stage suspended-sediment sampler. Bolts, secured with wing nuts, keep the sample 

containers in place during flood events along the lesser tributaries of the Colorado River, Arizona. Cable (zip) 

ties attach the cover and keep the air exhaust hoses in place.

Although US U-59 samplers are cheap and easy to use, problems with sampler operation 

frequently occur. Problems with US U-59 samplers are mostly related to the correct filling of the sample 

container

• The sample bottle may not fill properly because of the small size of the intake hose (0.635 cm 

inside diameter).

• Waterborne debris or insects may clog the intake hose.

• The intake hose may become crimped with age.

• The intake hose may fill with windblown sand during the long periods between flood events. 

• The rising limb of a flood may rise too fast, blocking the exhaust port before a water sample is 

collected.

• The sample container may overfill or collect multiple samples because of a pulsating flood, 

multiple floods between station visits, or as a result of an air leak in the system.

In addition, if the samplers are located in areas of high stream velocity, the current may tear them 

from the securing bolts during extreme flow events. These problems cause a high rate of sample 

collection failure, which, given the low expense and ease of use, is acceptable at many locations. 

Sediment-monitoring gaging stations where more reliable sampling is required (Rider Canyon and 

Bright Angel Creek) have ISCOTM automatic pump samplers (table 1). The ISCOTM pump samplers hold 
10

24 sample collection bottles. The pump samplers, secured above the foreseeable high-flow stage, have a 

sample tube and a liquid level actuator that extend down to ~30–40 cm above the channel bed. When 

water rises above the elevation of the liquid actuator, the pump samplers collect suspended-sediment 

samples at a programmed interval until the water recedes and the actuator dries. The pump sampler and 

the US U-59 sampler are both point samplers. Analyses of samples collected in similar gradient and 

sediment-concentration streams (for example, the Paria River) have shown that point samples, 

automated pump samples, and dip samples are usually equivalent to more-accurate depth-integrated 

samples in these types of streams where suspended sand, silt, and clay are typically well mixed in the 

cross section.

Table 1. Equipment present at each sediment-monitoring gaging station along the lesser tributaries of the 

Colorado River, Arizona. 

Station

name

SR50 ultrasonic stage 

sensor

Arrays of U-59s ISCOTM pump 

sampler

Rain gage

Water Holes Canyon X 2 arrays of 3 X

Badger Creek X 2 arrays of 3 X

Tanner Wash X 2 arrays of 3 X

House Rock Wash X 2 arrays of 3 X 

Rider Canyon X 3 arrays of 3 X X

North Canyon X 2 arrays of 3 X

Shinumo Wash X 2 arrays of 3 X

Bright Angel Creek X 0 X X 

Stage is measured at the stations with a downward-looking Campbell Scientific SR50 ultrasonic 

sensor attached to a Campbell Scientific CR10X data logger. (See Appendix 1 for a wiring diagram and 

programming instructions.) The data logger records stage measurements every 15 minutes during 

background conditions and every minute during flood conditions. The recording interval changes to one 

minute when the sensor detects that the stage has risen past a pre-programmed level (usually 0.1–0.2 m 

above the elevation of the dry bed). 

To provide meteorological context for flood events and provide insight into sediment sources, 

rain gages were installed in each of the monitoring station drainage basins. A total of 29 tipping-bucket 

rain gages (fig. 4) were installed with rain gages co-located with each of the sediment gaging stations 

and typically 2 rain gages installed upstream from each station. The tipping-bucket rain gages are 

connected to HOBOTM event loggers that are powered by internal batteries. Rain gaging sites are visited 

every six months to collect data and replace batteries. It is anticipated that data from this rain-gage 

network will provide insight into the amount of sediment likely to be supplied from these tributaries 

during future storm events. 
11

Figure 4. Digital elevation map showing the rain-gage network surrounding the lesser tributaries of the Colorado 

River, Arizona. 

Station Placement Considerations

The placement of tributary sediment-monitoring gaging stations directly affects the quality of 

data collected and amount of maintenance required at any given site. Where to place the station along 

the tributary is the first consideration. This decision affects the percentage of the tributary system 

sampled, the frequency of human foot traffic past the station, and the ease of access to the station for 

maintenance. The easier a site is to access, the more likely it is that the site will be vandalized. An 

extremely remote site, while safe from vandals, will increase the time and effort required for 

maintenance. Most of the GCMRC stations are located a short hike, less than a half hour, from 

infrequently used dirt roads. The compromise between remoteness and ease of access allows a 

technician to service several stations a day and, at the same time, reduces vandalism.

Once a general location is identified, a specific station site must be chosen. An ideal station 

location features several hours of direct sunlight during all times of the year (for charging batteries), a 

stable channel near a steep wall or large boulder (above any anticipated high water), a relatively straight 

and uniform channel upstream and downstream (for ease of modeling discharge), and several locations 

to bolt US U-59 samplers. The downward-looking ultrasonic sensor should be mounted directly over a 

stable part of the channel. This is accomplished at the GCMRC stations by mounting the sensor on an 
12

aluminum L-beam that is anchored to the wall or boulder with anchor bolts and guide wires (fig. 2). 

Though it is clearly important to install the stage sensor above the maximum anticipated stage, problems 

can be caused by mounting the sensor too high above the streambed. The Campbell Scientific SR50 

ultrasonic sensor attached to a Campbell Scientific CR10X data logger used at USGS GCRMC 

sediment-monitoring gaging stations will not record data when the sensor is mounted more than 10 m 

above the channel surface. In addition, a higher sensor mount increases the footprint of the ultrasonic 

beam, producing noisier data and a greater chance of beam inference. To ease the modeling of flood 

events, and to develop a stage-discharge relation for the station, the channel near the station should be 

uniform. Stations with large changes in channel roughness or channel width, or that have tight bends, 

will result in poor discharge modeling. Because of the difficulty in meeting all of these requirements in 

one compact location, several of the USGS GCMRC stations have equipment that is spread out over tens 

of meters along the channel (fig. 2).

Discharge Calculations

The remote location of the stations coupled with the short duration of flood events makes it very 

difficult and potentially expensive to measure the discharge of water directly. Discharge of water during 

floods is therefore modeled using the USGS National Research Program multidimensional surface water 

modeling system (McDonald and others, 2005) and the quasi-three-dimensional flow and sediment 

transport with morphological evolution of channels solver. The approach used is to 

1. Select a suitable reach for modeling and complete a base topographic survey. A suitable channel 

reach is stable and relatively straight. The simple channel geometry will result in an easier flow 

modeling process. During the initial survey the position of the stage sensor and any suspendedsediment sampler intakes should also be recorded.

2. Survey multiple sets of high-water marks within the reach corresponding to floods with different 

peak stages. A wide range of high-water marks from flood peak stage will allow the development 

of a comprehensive stage-discharge relation. 

3. Generate a topographic map and model grid of the stream channel from survey data. Survey 

cross sections are typically collected every 2–3 m along the channel. 

4. Enter a “best guess” flood discharge and Z0 roughness parameter (based on the bed-sediment 

grain-size distribution) for the first model run. 

5. Perform successive model runs varying the discharge and Z0 to minimize the root-mean-square 

error between the surveyed high-water marks and the modeled water surface.

6. Attempt to hold the established Z0 constant in the model, and model the discharge associated 

with different high-water marks to develop stage-discharge relations (Griffiths and others, 2010). 

7. Only allow Z0 to increase with increasing peak flood stage if there is physical evidence that the 

roughness characteristics of the bed change with increasing stage, as described below. 

The Nikuradse (1933) Z0 bed roughness parameter is used for flow modeling. This roughness 

parameter was chosen instead of the more commonly used Manning's n roughness parameter because, 

unlike the Manning's n roughness parameter, Z0 does not depend on stage and only depends on the 

characteristics of the bed. As discharge increases in gravel-bedded rivers Z0 should remain constant 

unless the gravel bed becomes fully mobile or rougher areas of the bed and banks become inundated. As 

either vegetated or formerly dry rougher areas of the bed, banks, and canyon walls become inundated 

and added to the model grid, Z0 increases. For an immobile gravel bed, Z0 is approximately equal to 0.1 

D84 (Whiting and Dietrich, 1989; Wiberg and Smith, 1991), where D84 is the 84th percentile grain size 

of the gravel. As the gravel bed becomes fully mobile, Z0 increases to approximately equal 0.5D84 

(Pitlick, 1992) 
13

Modeled peak flood discharges are combined with the corresponding SR50 recorded stages to 

develop a stage-discharge relation for the site. This stage-discharge relation is used for all subsequent 

floods unless major changes in the channel geometry are observed. If significant channel changes occur, 

a new stage discharge relation must be developed using the steps above. Where an insufficient number 

and diversity of floods have been modeled to develop a good stage-discharge relation, any high-water 

marks observed during maintenance visits to the station are flagged for later survey. 

Station Visits and Maintenance

Stations are visited twice a year for general maintenance. Additional visits may occur after 

significant precipitation or flood events. The majority of run-off events on the lesser tributaries occur 

during the southwest monsoon season (July–September). National Weather Service radar is monitored 

daily during this time to provide a precipitation alert and to allow field technicians the opportunity to 

service the suspended-sediment samplers before the next run-off event. Maintenance completed during 

regularly scheduled biannual site visits includes the following 

• downloading the CR10X data logger and the HOBOTM event logger using the vendor provided 

software (Appendix), 

• replacing the HOBOTM event logger internal battery, 

• checking the accuracy of the tipping bucket rain gage, 

• checking for samples in the U-59 samplers and inspecting the condition of the samplers, 

• checking the ISCOTM (if present) for samples and correct operation, 

• load testing the station’s 12-volt battery, and 

• inspecting the station for rodent and other damage. 

Common issues that can arise at stations include the following 

• damage to the U-59 samplers due to extreme flow events, 

• sun damage (UV) to the U-59 bottles and intake hoses, 

• vandalism and theft of parts (mainly batteries and solar panels), 

• rodent damage to wiring, 

• growth of plants blocking the solar panel, and (or) 

• growth of plants in the channel, interfering with the Campbell Scientific SR50 ultrasonic sensor 

signal. 

Summary 

A suspended-sediment monitoring gaging network has been established for remote ephemeral 

tributaries to the Colorado River downstream from Glen Canyon Dam. This monitoring network is 

comprised of eight gaging stations, each of which measures stage and collects suspended-sediment 

samples during flood events. Stage-discharge relations for the gaging stations are developed using a 

numerical flow model to determine discharge for several sets of flood high water marks. Modeled 

discharges are matched with the record of stage for a station to develop the stage discharge relation. 

Stage-discharge relations are used in conjunction with stage record and suspended-sediment data to 

compute sediment loads; sediment loads are the product of discharge and suspended-sediment 

concentration. Prior to the establishment of this gaging network, only relatively crude and likely highly 

inaccurate estimates of the sediment input from the lesser tributaries in lower Glen, Marble, and Grand 

Canyons to the Colorado River existed. The ability to calculate sediment loads in the lesser tributaries 

made possible by this gaging network is providing much-needed information on the relative importance 

of these tributaries in supplying sediment to the Colorado River in both Glen Canyon National 

Recreation Area and Grand Canyon National Park. Furthermore, the methods developed herein are 
14

transferrable and can easily be employed to compute discharge and sediment loads at other remote 

locations where information on discharge and sediment loads is needed. 

Acknowledgments

This project was funded by the U.S. Department of the Interior’s Glen Canyon Dam Adaptive 

Management Program through the USGS Grand Canyon Monitoring and Research Center. Susannah 

Erwin and David Dean both provided thoughtful reviews that improved the quality of this report.

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locations on rivers, with examples from the Colorado River: U.S. Geological Survey Techniques and 

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Journal of Geology, v. 89, p. 269–298. 

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sampler for suspended-sediment in A study of methods used in the measurement and analysis of 

sediment loads in streams: Interagency Report no. 13, 105 p. 

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Randle, T.J., and Pemberton, E.L., 1987, Results and analysis of STARS modeling efforts of the 

Colorado River in Grand Canyon: Glen Canyon Environmental Studies Report, 41 p. 
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02-4150, 12 p. 

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sediment budgets, Nahal Yael, Isreal: Physical Geography, v. 14, p. 225–236. 

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distribution of fine sediment in the Colorado River corridor between Glen Canyon Dam and Bright 

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Flagstaff, Arizona, 107 p. 

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of India: Hydrological Processes, v. 8, p. 567–572. 

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desert streams in India; Journal of Hydrology, v. 64, p. 261–272. 

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district, Kenya: Applied Geography, v. 10, p. 91–109. 

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_Samplers/6712_Fullsize_Portable_Sampler.pdf,. 

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suspended-sediment concentration and grain size in the Colorado River in Grand Canyon using a 

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on River Sedimentation, October 18–21, 2004, Yichang, China, v. 4, p. 2507–2514. [Also available at 

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and S.H. Robeson, September 16, 1958. 

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Water Resources Research, v. 13, p. 531–538. 

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tributaries of the Colorado River in Grand Canyon, Arizona: U.S. Geological Survey Water-Resources 

Investigations Report 00-4055, 67 p. 

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the influence of size heterogeneity and natural packing [abs.]: EOS Transactions, American 

Geophysical Union, v. 70, p. 1109. 

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Journal of Geology, v. 68, p. 54–74. 
16

Appendix: Campbell Scientific CR10X, SR50, and Onset Rain Gage

Wiring connection diagram of the tributary gaging station Campbell Scientific CR10X datalogger and SR50 

stage sensor. The wiring of specific data loggers may differ from the one depicted; wiring ports with the same 

label may be used interchangeably.
17

CR10X instructions

Instructions for setup of PC208W 3.3 so only data collected since last visit are downloaded

Each station must have a uniquely named device/CR10X data logger in the "Station List" in the 

datalogger connection window. 

1. To set up a unique station name in PC208W open "Setup" (first button in, has an icon of a 

phone/power line) from the "PC208W 3.3—Datalogger Support Software" window. 

2. Select the "Add Device" button. 

3. A window will open asking to select type of device to be added, select "CR10X Datalogger", and 

click "ok".

4. In the "Setup Connections" window, next to "CR10X Datalogger Name" name the station.

5. Under the "Data Collection" tab (tabs are on the bottom of the window) make sure the following 

options have been selected 

• Collect – Data logged since last call

• File Mode – Append to end of file

• File Format – ASCII, comma separated

• If large data files are to be downloaded, check under the "Hardware" tab and change the 

"Maximum Time On-line (sec)" to provide sufficient time to complete downloads; 

downloading six months of data can take more than an hour if significant 1-min intervals of 

data have been collected.

• Click the "Save Edits" button and close "Setup Connections" window. 

CR10X program

;{CR10} 

*Table 1 Program

 01: 60.0000 Execution Interval (seconds) 

1: Temp (107) (P11) 

 1: 1 Reps

 2: 1 SE Channel 

 3: 1 Excite all reps w/Exchan 1

 4: 1 Loc [Temp_K] 

 5: 1.0 Mult 

 6: 273.15 Offset

2: SDI-12 Recorder (OS10 1.1) (P105) 

 1: 0 SDI-12 Address 

 2: 1 Start Measurement (aM1!)

 3: 1 Port

 4: 2 Loc [Dist_m]

 5: 1.0 Mult 

 6: 0.0 Offset

3: Batt Voltage (P10)

 1: 6 Loc [Batt_Volt] 

4: Z=F (P30) 

 1: 2.4 F 

 2: 00 Exponent of 10 
18

 3: 7 Z Loc [Thresh_m] 

5: Z=F (P30) 

 1: 0.01 F 

 2: 00 Exponent of 10 

 3: 8 Z Loc [Minimum_m] 

6: Z=F (P30) 

 1: 273.15 F 

 2: 0 Exponent of 10 

 3: 3 Z Loc [RefTemp_K]

7: Z=X/Y (P38)

 1: 1 X Loc [Temp_K] 

 2: 3 Y Loc [RefTemp_K] 

 3: 4 Z Loc [Mult]

8: Z=SQRT(X) (P39)

 1: 4 X Loc [Mult]

 2: 4 Z Loc [Mult]

9: Z=X*Y (P36) 

 1: 2 X Loc [Dist_m]

 2: 4 Y Loc [Mult]

 3: 5 Z Loc [TCDist_m] 

10: If time is (P92)

 1: 0 Minutes (Seconds --) into a 

 2: 15 Interval (same units as above) 

 3: 10 Set Output Flag High

11: Real Time (P77)

 1: 120 (Same as 220) D,Hr/Mn

12: Sample (P70) 

 1: 1 Reps

 2: 1 Loc [Temp_K] 

13: Sample (P70) 

 1: 1 Reps

 2: 5 Loc [TCDist_m] 

14: If (X<=>Y) (P88)

 1: 5 X Loc [TCDist_m]

 2: 3 >=

 3: 8 Y Loc [Minimum_m] 

 4: 30 Then Do 

15: If (X<=>Y) (P88)

 1: 5 X Loc [TCDist_m]

 2: 4 < ;

 3: 7 Y Loc [Thresh_m] 

 4: 30 Then Do 

16: Do (P86) 

 1: 10 Set Output Flag High

17: Real Time (P77)

 1: 120 (Same as 220) D,Hr/Mn

18: Sample (P70) 

 1: 1 Reps

 2: 1 Loc [Temp_K] 
19

19: Sample (P70) 

 1: 1 Reps

 2: 5 Loc [TCDist_m]

20: End (P95) 

21: End (P95) 

22: Serial Out (P96) 

 1: 71 SM192/SM716/CSM1 

*Table 2 Program

 01: 0.0000 Execution Interval (seconds) 

*Table 3 Subroutines 

End Program 

Instructions for downloading the CR10X datalogger

1. Open "PC208W v3.3" and click the "Real-time connection to datalogger" button (second button 

in, has an icon of a computer connected to an instrument) from the "PC208W 3.3–Datalogger 

Support Software" widow. A new window “Datalogger Connection” will open. 

2. Under the "Station List" select the station to be downloaded. 

3. Click the "connect" button. 

4. Make sure that the "Manual Data Collection" box for "Prompt for data file name" is checked.

5. Set the instrument clock by clicking the "Set Datalogger Clk" button.

6. Click the "COLLECT" button, this will download all data logged since the last station visit; 

browse for the correct save location and name the file.

7. After the data is downloaded click the "Numeric" button and check that the program for the 

station is still set up appropriately for the current conditions. 

8. Under Numeric, make sure that the threshold value for "Inloc_5" / "TCDist_m" (temperature 

corrected distance) is 0.1–0.2 meters greater than the value for "Inloc_7" / "Thresh_m" 

(threshold distance). If the row titles are shown as Inloc_# the proper titles can be displayed by 

first using the "Associate DLD Program" button and selecting the appropriate station program 

(found under \PC208W\CSIPRO~1).

• If the threshold value is not correct, the program must be changed and reloaded. 

• From the "PC208W 3.3–Datalogger Support Software" widow click the "Edit datalogger 

program with Edlog" button (fourth button in, has an icon of a keyboard). 

• Edit the value displayed on line 4: 1: to the appropriate distance (the threshold should be 

LESS than the TCDist); this is the threshold beyond which the instrument will begin logging 

1-min data.

• Save the file, when the confirm window pops up click "yes" compile program. 

• There should be no errors, click "yes" again.

• Open the numeric window to check that the threshold has been set correctly. NOTE: it may 

take several minutes for the new values to appear in the numeric window. 

Once finished, close the window and PC208W, the datalogger is always running and does not need to be 

launched. 
20

Instructions on deleting all data stored on the CR10X

Only follow these directions if all data has been backed up and you want to permanently delete 

all data stored on the datalogger. This option may be useful if the computer used for downloading the 

datalogger will change. The information on the last download date is stored on the download computer, 

if a new computer is used the entire datalogger will be downloaded. 

1. Open "PC208W v3.3" and open the "Datalogger Connection" window by clicking the "Real-time 

connection to datalogger" button. 

2. Under the "Station List" select the name of the current SR50 station. 

3. Click the "Connect" button, and then select the "Terminal" tab. 

4. On the Remote Keyboard Display Terminal click the "Open Port" button. 

5. At the cursor prompt, press the "Enter" key on the keyboard until "*" is displayed. 

6. At the "*" prompt, type (without the quotation marks) "7H" and press "Enter", this will give a 

">" prompt. 

7. At the ">" prompt press the "Shift" key and the number "8" at the same time, this will return the 

word "MODE".

8. At the "MODE" prompt, type the letter "A" and "MODE 10" will appear with a second line 

below it saying "01:0028". 

9. With the cursor at the end of the "01:0028" line type "28" and press enter. This will clear the 

storage in Area 1. 

10. The next line "02:0064" will appear, if "Enter" is pressed too many times the cursor will move to 

line 03, then 04, etc. To move back a line, press the "b" key on the keyboard. (DO NOT change 

any other lines other than 01; the lines should read 01:0028, 02:0064, 03:0, 04:62280, 

05:+2048.0, 06:+1787.0 respectively). 

11. Now at the "02:0064" prompt press the "Shift" key and the number "8" at the same time, this will 

return the word "MODE". 

12. Check to see if Area 1 is clear, at the "MODE" prompt, type the number "7" and "MODE 07 1" 

will appear.

13. With the cursor at the end of the "MODE 07 1" line press "Enter" on the keyboard and "01+255." 

will appear. This indicates that the memory storage has been cleared.

14. Close terminal mode: with the cursor at the end of the "01+255." prompt, press "Enter" on the 

keyboard to verify 01+255 clear signal. 

15. Press the "Shift" button and the number "8" at the same time. This will return "MODE".

16. At the end of "MODE" type "0".

17. Typing "0" will return "MODE 00" on the first line, "LOG 1" on the second line, and "*" on the 

third line with the cursor at the end of it. 

18. Press "Enter" again, get another "*", select the "Tools" tab and click the "Disconnect" button. 

Onset rain gage and HOBOTM event logger instructions

1. Inspect the station to ensure that the rain gage bucket is level and free of debris. 

2. Download data. 

• Connect download cable to HOBOTM Event Logger and computer serial port. 
21

• Open "BoxcarPro" program on the computer. 

• Select the “Logger” pull down menu and select "Readout" (or press “CRTL+R”), a window 

will appear detailing the download status. 

• Unplug the HOBOTM Event Logger from the download cable and save the file with the 

appropriate name.

• Review the data file (it is automatically open after you save the file) to ensure that the full 

range of dates is present and the data looks realistic.

• Backup the data file.

• Replace the CR2032 battery in the HOBOTM Event Logger. 

Test the rain gage.

• Make sure that the HOBOTM Event Logger is connected to the tipping bucket rain gage. 

• Select the "Logger" pull down menu and select "Launch", NOTE: Launching the HOBOTM

Event Logger will erase all data, make sure that the logger has been downloaded and the data 

backed up. 

• Click on the start button. 

• Pour a known quality of water (the tipping bucket rain gages USGS GCMRC uses require 8.237 

ml for one tip) slowly (the loggers are setup to record of maximum of one event per second) 

through the rain gage and count/record the number to tips. 

• Pour water through twice. 

• Download the data to check that the instrument is recording correctly, make sure that the test 

data is saved with a different name than the one used in the “Download data” step.

Launch the HOBOTM Event Logger. 

• Select the "Logger" pull down menu and select Launch", make sure that the "Description" is the 

name of the station, "Event Name" is "Inches of Rain", "Event Value" is 0.01, and the "Lockout 

after event" box is checked and set to 00:00:01. 

• Click on the start button. 

• Disconnect the HOBOTM Event Logger when prompted and close BoxcarPro. 

• The LED light will blink every few seconds after the logger is launched. 

• Close the event logger waterproof case, taking care to ensure that the plug from the tipping 

bucket rain gage is secure and the desiccant pack is in place.