Prepared in cooperation with Environment and Natural Resources Trust Fund, U.S. Army Corps 

of Engineers, Lower Minnesota River Watershed District, Minnesota Pollution Control Agency, 

and Minnesota Department of Natural Resources

Using Acoustic Doppler Velocity Meters to Estimate 

Suspended Sediment along the Lower Minnesota and 

Mississippi Rivers

Scientific Investigations Report 2018–5165

U.S. Department of the Interior

U.S. Geological Survey
Cover: J. William Lund (U.S. Geological Survey) installing an acoustic Doppler velocity meter at 

the Minnesota River near Jordan, Minn., from a Minnesota Department of Transportation Snooper. 

Brett Savage and Joshua Ayers (U.S. Geological Survey) are looking on from a boat. 
Using Acoustic Doppler Velocity Meters to 

Estimate Suspended Sediment along the 

Lower Minnesota and Mississippi Rivers

By Joel T. Groten, Jeffrey R. Ziegeweid, J. William Lund, Christopher A. Ellison, 

Samuel B. Costa, Erin N. Coenen, and Erich W. Kessler

Prepared in cooperation with Environment and Natural Resources Trust Fund, 

U.S. Army Corps of Engineers, Lower Minnesota River Watershed District, Minnesota Pollution Control Agency, and Minnesota Department of Natural Resources 

Scientific Investigations Report 2018–5165

U.S. Department of the Interior

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

DAVID BERNHARDT, Acting Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2019

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

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For an overview of USGS information products, including maps, imagery, and publications, 

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U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Groten, J.T., Ziegeweid, J.R., Lund, J.W., Ellison, C.A., Costa, S.B., Coenen, E.N., and Kessler, E.W., 2019, Using 

acoustic Doppler velocity meters to estimate suspended sediment along the lower Minnesota and Mississippi Rivers: 

U.S. Geological Survey Scientific Investigations Report 2018–5165, 30 p., https://doi.org/10.3133/sir20185165.

ISSN 2328-0328 (online)
iii

Acknowledgments

 This report presents a compilation of information, resources, and expertise supplied by 

many agencies and individuals. The authors would like to thank the Environment and Natural 

Resources Trust Fund, U.S. Army Corps of Engineers, Lower Minnesota River Watershed District, 

Minnesota Pollution Control Agency, and Minnesota Department of Natural Resources for their 

assistance with this study.

Gerald Storey, Joshua Ayers, Brent Mason, Trent Sherman, Camille Buckley, and Bradley 

Claggett of the U.S. Geological Survey are acknowledged for assistance with equipment installation, maintenance, data management, and (or) report preparation. Molly Wood and Faith Fitzpatrick of the U.S. Geological Survey are acknowledged for their technical reviews of the report.

v

Contents

Acknowledgments........................................................................................................................................iii

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

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

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

Description of the Study Area ............................................................................................................3

Sampling Sites..............................................................................................................................4

Precipitation..................................................................................................................................4

Streamflow....................................................................................................................................6

Methods of Data Collection and Analysis .................................................................................................6

Sampling Methods................................................................................................................................6

Acoustic Backscatter Data.................................................................................................................6

Streamflow Data ...................................................................................................................................9

Laboratory Analysis..............................................................................................................................9

Statistical Analysis for Suspended Sediment..................................................................................9

Development of Linear Regression Models ............................................................................9

Daily and Annual Suspended-Sediment Load Estimates......................................................9

Streamflow, Suspended-Sediment Concentrations, and Surrogate Relations .................................10

Surrogate Relations for Suspended-Sediment Concentrations ..........................................................10

Suspended-Sediment Loads......................................................................................................................21

Summary and Conclusions.........................................................................................................................26

References Cited..........................................................................................................................................27
vi

Figures

1. Map showing location of the study area and sampling sites in the Mississippi

River Basin.....................................................................................................................................2

2. Graph showing stream gradients along the Mississippi River and two tributaries ..........5

3. Hydrographs and collection dates of suspended-sediment samples at nine sites

in the Mississippi River Basin, water years 2016 through 2017 ............................................7

4. Graph showing measured suspended-sand and suspended-fines concentrations

at nine sites in the Mississippi River Basin............................................................................12

5. Graphs showing relations among suspended-sediment concentrations, acoustic

surrogate metrics, and streamflow at nine sites in the Mississippi River Basin.............14

6. Map showing precipitation totals in the Mississippi River Basin and upper

Minnesota River and Blue Earth River subbasins on August 17, 2017...............................18

7. Graphs showing streamflow and estimated 15-minute suspended-sediment

concentrations during the open-water season at six sites in the Mississippi

River Basin...................................................................................................................................19

8. Graphs showing daily mean streamflow and daily estimated suspendedsediment loads at nine sites in the Mississippi River Basin................................................22

9. Graph showing estimated annual suspended-sediment loads at nine sites in the

Mississippi River Basin, water years 2016 through 2017 .....................................................24

10. Graphs showing possible sediment sources and sinks with stream gradients

along the Minnesota and Mississippi Rivers at eight sites, water years 2016

and 2017........................................................................................................................................25

11. Graph showing annual sediment yield at nine sites in the Mississippi River Basin,

water years 2016 and 2017 ........................................................................................................26

Tables

1. Study area sediment monitoring sites in the Mississippi River Basin.................................5

2. Summary statistics for streamflow, suspended sediments, and acoustic surrogate

model metrics..............................................................................................................................11

3. Summary of linear regression models for selected sites in the Mississippi River

Basin .............................................................................................................................................13

4. Estimated annual suspended-sediment loads for the lower Minnesota, St. Croix,

and Mississippi Rivers ...............................................................................................................17
vii

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

pint (pt) 0.4732 liter (L) 

quart (qt) 0.9464 liter (L) 

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Mass

ton, short (2,000 lb) 0.9072 metric ton (t) 

ton per year per square mile 

(tons/yr)/mi2 

0.3503 metric ton per year per square 

kilometer

International System of Units to U.S. customary units

Multiply By To obtain

Length

millimeter (mm) 0.03937 inch (in.)

Volume

liter (L) 2.113 pint (pt)

liter (L) 1.057 quart (qt)
viii

Supplemental Information

Concentrations of chemical constituents in water are given in milligrams per liter 

(mg/L).

Water year (WY) is the 12-month period, October 1 through September 30, and is 

designated by the calendar year in which it ends.

Abbreviations

ADVM acoustic Doppler velocity meter 

MPCA Minnesota Pollution Control Agency

p-value probability value

R2 coefficient of determination

SAC sediment attenuation coefficient 

SCB sediment-corrected backscatter

SSC suspended-sediment concentration

SSL suspended-sediment load

TSS total suspended solids

USGS U.S. Geological Survey

WY water year
Using Acoustic Doppler Velocity Meters to Estimate 

Suspended Sediment along the Lower Minnesota and 

Mississippi Rivers

By Joel T. Groten,1 Jeffrey R. Ziegeweid,1 J. William Lund,1 Christopher A. Ellison,1 Samuel B. Costa,2 Erin N. 

Coenen,1 and Erich W. Kessler1

1

 U.S. Geological Survey.

2

 Institute for Technological Research.

Abstract

Lake Pepin is the largest naturally formed lake on the 

Mississippi River and has complex management needs to 

satisfy economic, environmental, and cultural demands. Lake 

Pepin is filling in with sediment at a rapid rate compared to 

conditions before settlement by European immigrants and 

intense agricultural cultivation. Accordingly, the Minnesota 

Pollution Control Agency has developed aggressive plans to 

prioritize sediment sources, understand transport mechanisms, 

and implement large-scale strategies to reduce sedimentation 

in Lake Pepin.

The Minnesota River is the primary sediment source 

to Lake Pepin, and reductions in sediment loading from the 

Minnesota River are needed to reduce sedimentation in Lake 

Pepin. Current loading estimates were calculated from grab 

sampling and total suspended solids laboratory methods that 

greatly underestimate the actual concentrations in the rivers 

when compared to U.S. Geological Survey width and depth 

integrated sampling and laboratory methods for determining suspended-sediment concentration (SSC). Therefore, the 

U.S. Geological Survey, with funding from the Environment 

and Natural Resources Trust Fund and in cooperation with 

the U.S. Army Corps of Engineers, Lower Minnesota River 

Watershed District, Minnesota Pollution Control Agency, and 

Minnesota Department of Natural Resources, collected SSCs 

and acoustic backscatter data from acoustic Doppler velocity 

meters over a 2-year period at nine sites. The purpose of the 

study was to improve understanding of sediment-transport 

processes and increase accuracy of estimating SSCs and 

suspended-sediment loads for the lower Minnesota River and 

the Mississippi River compared to traditional measures.

The study results indicated that acoustic backscatter 

worked well in estimating SSCs at sites not regulated by locks, 

dams, and lakes. The results also confirmed previous studies 

that determined most of the suspended-sediment loading into 

the Mississippi River is from the Minnesota River and the 

largest sediment sink is Lake Pepin. Suspended-sediment loading from site to site and year to year was often variable when 

compared to streamflow, which has been traditionally used to 

estimate SSC. As a result, this study demonstrates the value 

in having high temporal and spatial resolution of continuous 

sediment monitoring from acoustic devices to help manage the 

sources of sediment into Lake Pepin.

Introduction

Sediment-laden rivers in Minnesota cost river users 

millions of dollars each year (U.S. Army Corps of Engineers, 

2006; Minnesota Pollution Control Agency, 2009a). Excessive sediment in rivers degrades water quality, is deleterious to aquatic habitat, leads to increased navigation channel 

dredging, reduces recreational opportunities, and can transport 

harmful contaminants (U.S. Army Corps of Engineers, 2006; 

Minnesota Pollution Control Agency, 2009a). The U.S. Army 

Corps of Engineers, St. Paul District, maintains commercial 

navigation channels in the upper Mississippi River and lower 

parts of the Minnesota and St. Croix Rivers (U.S. Army Corps 

of Engineers, 2001, 2007, 2011).

The Minnesota and St. Croix Rivers are the two largest tributaries to the Mississippi River upstream from Lake 

Pepin, each contributing about 25 percent of the total flow 

into Lake Pepin (Stark and others, 1996; Engstrom and others, 

2009; fig. 1). The lower St. Croix River contributes little sediment to the Mississippi River (Blumentritt and others, 2009; 

U.S. Army Corps of Engineers, 2011). In contrast, sediment 

loads in the Minnesota River have been a concern among Minnesota State agencies. About 85–90 percent of the sediment 

being deposited into Lake Pepin originates from the Minnesota 

River Basin (Engstrom and others, 2009; Minnesota Pollution 

Control Agency, 2015).
2 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

St. Croix Basin

Minnesota River 

Basin

Mississippi River 

Basin

Base and digital elevation model modified from U.S. Geological Survey, U.S. Census Bureau, 

Minnesota Department of Natural Resources, Wisconsin Department of Natural Resources, 

South Dakota Department of Environment and Natural Resources, 

and Iowa GEODATA digital data, variously dated, various scales 

Universal Transverse Mercator, Zone 15 

North American Datum of 1983

50 100 KILOMETERS

100 MILES

75

75

0 25

0 25 50

NORTH 

DAKOTA 

SOUTH

DAKOTA

WISCONSIN 

MICHIGAN 

MINNESOTA

IOWA

CANADA

98° 97° 96° 95° 94° 93° 92° 91° 90°

50°

49°

48°

47°

46°

45°

44°

43°

Minnesota River

Mississippi River

St. Croix R

Blue Earth

River

Lake 

St. Croix Chippewa River

LAKE SUPERIOR

Cannon R

Lake Pepin

Le Sueur River

Judson

Prescott

St. Peter

Red Wing

St. Cloud

Minneapolis

Jordan

St. Paul

Mankato

05317500 05325000

05325300

05330000 05355235

05331000

05344490

05355341

05289900

Sampling site and station 

number (table 1)

Digital elevation model

High: 1993

Low: 650

05317500

EXPLANATION

Figure 1. Location of the study area and sampling sites in the Mississippi River Basin.
Introduction 3

Lake Pepin is an important recreational and commercial 

resource that is about 50 miles (mi) downstream from the 

Minneapolis-St. Paul (hereafter referred to as “Twin Cities”) 

metropolitan area of Minnesota. A sediment coring study demonstrated that sediment loading to Lake Pepin has increased 

by an order of magnitude since 1830, and the highest sediment 

accumulation rates were between 1940 and 1970 (Engstrom 

and others, 2009). Generally poor water quality in Lake 

Pepin reflects the combined effects of urban and agricultural 

developments in the basin (Engstrom and others, 2009). The 

Minnesota Pollution Control Agency (MPCA) is addressing 

sediment-related impairments in Lake Pepin by developing 

total maximum daily loads for total suspended solids (TSS) 

in the Minnesota and the Mississippi Rivers. To help meet 

water-quality targets of the total maximum daily loads, the 

MPCA adopted a Sediment-Reduction Strategy that includes 

90- and 50-percent reductions in sediment loads by 2040 for 

the Minnesota River and the Mississippi River between the 

Twin Cities and Lake Pepin, respectively (Minnesota Pollution 

Control Agency, 2015).

The MPCA began collecting suspended-sediment grab 

samples for analysis of TSS in the early 1970s based on recommendations by the U.S. Environmental Protection Agency. 

From 2007 through 2011, the U.S. Geological Survey (USGS) 

and the MPCA completed a cooperative, statewide study that 

built upon a previous USGS study (Gray and others, 2000) to 

compare sediment loads calculated using the grab sampling 

and TSS laboratory methods to sediment loads calculated 

using standard USGS sampling methods that integrate the 

width, depth, and velocity of the river cross section (Edwards 

and Glysson, 1999) and the suspended-sediment concentration (SSC) laboratory method. The study results indicated that 

grab sampling and TSS laboratory methods underrepresented 

sediment concentrations by about 50 percent (Ellison and 

others, 2014). A subsequent report demonstrated that the grab 

sampling and TSS laboratory methods accurately estimated 

concentrations of fine sediments but underestimated sand 

concentrations compared to the standard USGS sampling and 

SSC laboratory methods (Groten and Johnson, 2018). Underrepresentation of sediment concentrations results in inaccurate 

sediment load computations and subsequent misinterpretations 

of data that inform management decisions.

Physically collected suspended-sediment samples provide 

the most accurate measurements of suspended-sediment loads 

(SSLs) and erosion in a basin, but physical samples do not 

provide accurate, real-time estimates of SSLs. Historically, 

SSLs have been estimated by a rating curve approach that 

relates SSC to streamflow (Crawford, 1991; Horowitz, 2003), 

and continuous streamflow records can be used to estimate 

SSLs for unsampled periods using this approach. However, 

uncertainties in SSLs based on streamflow are high because of 

the effects of hysteresis (Walling, 1997), which means that the 

relation between streamflow and SSC changes between the rising and falling limb of the streamflow hydrograph (Knighton, 

1998). Sediment transport and streamflow also do not correlate well in regulated or supply-limited systems; therefore, 

accurate and cost-effective methods for providing real-time 

sediment information could help the U.S. Army Corps of 

Engineers better maintain the commercial navigation channel. In addition, real-time sediment information can help State 

agencies monitor progress toward sediment reduction goals 

and effectiveness of implemented best management practices 

and other restoration activities.

From water years (WYs) 2015 through 2017, the USGS, 

with funding from the Environment and Natural Resources 

Trust Fund and in cooperation with the U.S. Army Corps 

of Engineers, Lower Minnesota River Watershed District, 

MPCA, and Minnesota Department of Natural Resources, 

installed and operated side-looking acoustic Doppler velocity meters (ADVMs) at nine streamgages in the Minnesota, 

Mississippi, and St. Croix Rivers upstream from Lake Pepin. 

The ADVMs emit sound pulses into the water and measure 

the strength of the returned pulses (called acoustic backscatter) after reflecting off sediment and other particulate matter in 

the water. The measured acoustic backscatter data were used 

as a surrogate for SSCs according to methods in Landers and 

others (2016). The measured acoustic backscatter data were 

corrected for various losses to compute the sediment-corrected 

backscatter (SCB) and sediment attenuation coefficient (SAC) 

and then were correlated to SSCs measured from water 

samples collected using approved USGS depth-integrated, 

isokinetic techniques. Statistical relations among SCB, SAC, 

streamflow, and SSC were combined with streamflow data to 

estimate SSLs at streamgages included in this study.

Purpose and Scope

The purpose of this report is to summarize and interpret collected SSC and acoustic backscatter data to improve 

understanding of the timing and loading of suspended-sediment transport for the lower Minnesota River, the St. Croix 

River, and the Mississippi River between the Twin Cities and 

Lake Pepin. Specifically, the report describes (1) the relations among acoustic backscatter, streamflow, and SSCs in 

the lower Minnesota River and the Mississippi River (WYs 

2012 through 2017); (2) annual and seasonal SSLs (WYs 

2015 through 2017); and (3) suspended-sediment budgets for 

selected reaches on the lower Minnesota River and Mississippi 

River (WYs 2016 through 2017).

Description of the Study Area

The study area includes parts of the Minnesota River, 

Mississippi River, and St. Croix River Basins (fig. 1). The 

outlet of Lake Pepin represents the downstream end of the 

study area and drains 47,400 square miles (mi2). Lake Pepin 

is a natural flood plain lake on the Mississippi River that was 

formed by a tributary fan caused by the confluence with the 

Chippewa River during the end of the last glaciation (Blumentritt and others, 2009).
4 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

Land use in the Mississippi River Headwaters Basin transitions from forest in the northern areas to agricultural areas in 

the central part and finally to the Twin Cities at the southern 

end of the basin marked by the confluence with the St. Croix 

River (fig. 1). The poor water quality in the part of the study 

area from the confluence of the Mississippi and St. Croix 

Rivers to the outlet of Lake Pepin (fig. 1) reflects the combined effects of agricultural and urban development upstream 

(Engstrom and others, 2009).

The Minnesota River Basin drains 16,900 mi2 (fig. 1). 

The Minnesota River flows from the origin along the Minnesota-South Dakota border (fig. 1) across south-central Minnesota for 335 mi to the Mississippi River near the city of 

St. Paul, Minnesota. The Minnesota River valley was formed 

by incision from Glacial River Warren (not shown), and tributaries to the Minnesota River flow through highly erodible 

knickpoints made up of fine-grained till (Minnesota Pollution 

Control Agency, 2011).

Land use in the Minnesota River Basin is about 

85–90 percent agriculture (Engstrom and others, 2009; Minnesota Pollution Control Agency, 2015), and modifications in the 

watershed have altered the manner in which water moves from 

the landscape to the river channel. Previous work by Schottler 

and others (2014) in the Minnesota River Basin demonstrated 

that artificial drainage was the primary factor for an increase 

in streamflow since 1940 and that climate and crop conversion explained less than one-half of the observed increase in 

streamflow. Belmont and others (2011) indicated that most of 

the sediment loading in the Minnesota River Basin has shifted 

from agricultural erosion to bluff and streambank erosion in 

the past three decades; furthermore, the increase in streamflow 

from artificial drainage in the Minnesota River has increased 

channel erosion and widened channels (Schottler and others, 

2014). Finally, Lenhart and others (2013) determined that the 

Minnesota River has widened by 52 percent and shortened by 

7 percent between Mankato and St. Paul, Minn., since 1938.

The St. Croix Basin (fig. 1) drains 7,700 mi2 in Minnesota and Wisconsin (Lenz and others, 2001). Before European 

settlement, the St. Croix Basin was dominated by forests, 

peatlands, and prairie grasslands (Niemela and Feist, 2000; 

Payne and others, 2002). Currently, the St. Croix Basin is 

dominated by forest, pastures, and croplands, with most of the 

urban lands concentrated in the areas around the lowest 25 mi 

of the St. Croix River (Heiskary and Vavricka, 1993; Larson 

and others, 2002). The final 25 mi of the river forms Lake 

St. Croix, a natural flood plain lake formed by a tributary fan 

at the confluence of the Mississippi River during the end of 

the last glaciation (Robertson and Lenz, 2002; Blumentritt and 

others, 2009). Sediment deposition in Lake St. Croix further 

reduces sediment loads from the St. Croix River into the Mississippi River.

Sampling Sites

A total of 5 sites on the Minnesota River, 3 sites on the 

Mississippi River, and 1 site on the St. Croix River were 

sampled for SSCs during this study (fig. 1; table 1). The 

Minnesota River at Judson, Minn. (USGS station 05317500; 

hereafter referred to as “Judson”), site is positioned highest 

in the basin (fig. 1). The Minnesota River at Mankato, Minn. 

(USGS station 05325000; hereafter referred to as “Mankato”), 

site is downstream from the Judson site and just downstream 

from where the Blue Earth River flows into the Minnesota 

River. The Le Sueur River is a tributary to the Blue Earth 

River (fig. 1). Downstream from the Mankato site are the 

Minnesota River at County Highway 22 in St. Peter, Minn. 

(USGS station 05325300; hereafter referred to as “St. Peter”); 

Minnesota River near Jordan, Minn. (USGS station 05330000; 

hereafter referred to as “Jordan”); and Minnesota River at Fort 

Snelling State Park, Minn. (USGS station 05330920; hereafter referred to as “Ft. Snelling”), sites (fig. 1). Ft. Snelling is 

just above the confluence with the Mississippi River, which is 

below Lock and Dam Number 1 (fig. 2). The Mississippi River 

at St. Paul, Minn. (USGS station 05331000; hereafter referred 

to as “St. Paul”), site is just downstream from the confluence 

of the Minnesota and Mississippi Rivers (fig. 1). The St. Croix 

River at Prescott, Wisconsin (USGS station 05344490; 

hereafter referred to as “Prescott”), site is just above the 

confluence with the Mississippi River (fig. 1). The Mississippi 

River above Red Wing below Diamond Island, Minn. (USGS 

station 05355235; hereafter referred to as “Red Wing”), site 

is below Lock and Dam Number 3 and downstream from the 

Cannon River’s confluence with the Mississippi River (fig. 1). 

The last site at Mississippi River (Lake Pepin) above Reads 

Landing, Minn. (USGS station 05355341; hereafter referred 

to as “Pepin”), is at the outlet of Lake Pepin and above the 

confluence of the Chippewa and Mississippi Rivers (fig. 1).

The nine sampling locations represent a wide range of 

stream gradients that affect relative differences in sedimenttransport capacity throughout the study area (fig. 2; MnTOPO, 

2018). Steeper gradients cause water to flow faster, increasing sediment-transport capacity, and can also cause erosion, 

which can change river geomorphology. Gradual gradients 

can lead to slower moving water, which can decrease the 

sediment transport of the river and lead to sediment deposition. Of the nine sites, Judson had the steepest gradient. The 

gradient decreased downstream along the Minnesota River at 

the Mankato, St. Peter, and Jordan sites. The Ft. Snelling site 

had the most gradual gradient of all Minnesota River sites in 

the study area because its location in the valley bottomlands is 

near the confluence of the Minnesota and Mississippi Rivers. 

Gradients at Mississippi River sites at St. Paul and above Red 

Wing are affected by locks and dams. Finally, the St. Croix 

and Pepin sites are affected by backwater in Lake St. Croix 

and Lake Pepin, respectively.

Precipitation

Precipitation is a primary factor affecting sediment 

transport because of direct effects on streamflow. Precipitation varied from WYs 2015 through 2017 in the study area 

(Minnesota Department of Natural Resources, 2018a). During 
Introduction 5

Table 1. Study area sediment monitoring sites in the Mississippi River Basin.

[USGS, U.S. Geological Survey; Minn., Minnesota; MNDNR, Minnesota Department of Natural Resources; MPCA, Minnesota Pollution Control Agency; St., 

Saint; Ft., Fort; Wisc., Wisconsin; the boldfaced text under station names are station name abbreviations used in the text of this report (see “Sampling Sites” 

section)]

Station name USGS station 

number

Responsible 

for streamgage 

operation

Latitude 

(north)

Longitude 

(west)

Drainage area 

(square 

miles)

Minnesota River at Judson, Minn. 05317500 MNDNR/MPCA 44.20000 −94.19333 11,300

Minnesota River at Mankato, Minn. 05325000 USGS 44.16889 −94.00306 14,900

Minnesota River at County Highway 22 in St. Peter, Minn. 05325300 MNDNR/MPCA 44.30750 −93.95008 15,100

Minnesota River near Jordan, Minn. 05330000 USGS 44.69306 −93.64167 16,200

Minnesota River at Ft. Snelling State Park, Minn. 05330920 USGS 44.89611 −93.18861 16,900

Mississippi River at St. Paul, Minn. 05331000 USGS 44.94440 −93.08806 36,800

St. Croix River at Prescott, Wisc. 05344490 USGS 44.74917 −92.80444 7,700

Mississippi River above Red Wing below Diamond Island, 

Minn.

05355235 USGS 44.60417 −92.57917 45,200

Mississippi River (Lake Pepin) above Reads Landing, Minn. 05355341 USGS 44.41028 −92.09722 47,400

Distance upstream from confluence of Minnesota and Mississippi Rivers, in miles

125 100 75 50 25 0 −25 −50 −75

Elevation, in feet

650

700

750

800

Sampling site and identifer

EXPLANATION

Lock and Dam No. 1

Lock and Dam 

No. 2

Lock and Dam No. 3

Mississippi River 

above Red Wing 

below Diamond 

Island, Minnesota

Mississippi River

at St. Paul, Minnesota

Minnesota River

at Fort Snelling

State Park, Minnesota

St. Croix River 

at Prescott, Wisconsin Minnesota River 

near Jordan, Minnesota

Mississippi River

(Lake Pepin) above

Reads Landing, Minnesota Minnesota River

at County Highway 22

in St. Peter, Minnesota

Minnesota River

at Mankato, Minnesota

Minnesota River

at Judson, Minnesota

City of New Ulm, Minnesota

City of 

Minneapolis, 

Minnesota

City of 

Stillwater, 

Minnesota

St. Croix River

Mississippi River

Minnesota River

Figure 2. Stream gradients (MnTOPO, 2018) along the Mississippi River (from Minneapolis to the outlet of Lake Pepin) and two 

tributaries (Minnesota River and St. Croix River).
6 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

WY 2015, precipitation was less than the historical mean in 

the upper part of the Minnesota River Basin and similar to 

historical means in the rest of the study area, with isolated 

pockets of above average precipitation near the Le Sueur 

River Basin (not shown; Minnesota River subbasin) and the 

confluence of the Mississippi and St. Croix Rivers (Minnesota Department of Natural Resources, 2018a). Precipitation 

during WY 2016 was higher than historical mean precipitation 

throughout Minnesota, and parts of the Blue Earth (not shown) 

and Le Sueur River Basins (not shown) received 16–24 inches 

of precipitation above the historical mean. In the WY 2017, 

precipitation was similar to the historical mean for much of 

the study area; however, the upper Minnesota River Basin 

received more precipitation than the historical mean, whereas 

the Blue Earth and Le Sueur River Basins received average 

amounts of precipitation.

Streamflow

Historical mean streamflows measured at long-term 

streamgages on the Minnesota (the Jordan site; 1935–2017), 

Mississippi (the St. Paul site; 1901–2017), and St. Croix 

(St. Croix River at St. Croix Falls, Wisc., USGS station 

05340500; 1911–2017) Rivers were used to make general 

assessments of streamflow during the study period (U.S. Geological Survey, 2018a). Observed streamflow patterns were 

similar in the Minnesota and Mississippi Rivers, with annual 

mean streamflows being slightly less than the historical mean 

in the WY 2015 and substantially higher than the historical 

mean in WYs 2016 and 2017. In contrast, the annual mean 

streamflows in the St. Croix River were higher than the historical mean for all study years, but the magnitudes of differences 

from the historical mean were lower compared to observed 

differences in the Minnesota and Mississippi Rivers.

Methods of Data Collection and 

Analysis

Field crews attempted to collect samples over the full 

range of observed streamflows during the open-water season at each site (fig. 3). A total of eight sites (table 1) were 

sampled for SSCs during WYs 2016 through 2017, and 

Ft. Snelling was sampled for SSCs during WYs 2012 through 

2017 (table 1). Corresponding acoustic backscatter data were 

collected during SSC sample collection at all sites. Sites were 

at established USGS or Minnesota Department of Natural 

Resources and MPCA cooperative streamgages (table 1), and 

samples were collected 8 to 13 times per year over a range 

of streamflows during the open-water season (March through 

November; fig. 3) when the rivers were not covered by ice. 

Water samples were analyzed for SSC and percentage of fines 

(defined as particle sizes [clay and silt] less than 0.0625 millimeter [mm]). 

Sampling Methods

Water samples were collected using isokinetic samplers 

and depth-integrating techniques at equal-width intervals or 

equal-discharge intervals (Edwards and Glysson, 1999; Davis, 

2005). For collection of water samples, the stream width was 

divided into 10 equal widths for equal-width interval samples 

or 5 equal-discharge increments for equal-discharge interval 

samples. Each isokinetic, depth-integrated sample was collected at the centroid of each increment according to procedures in Edwards and Glysson (1999). Depending on the river 

depth and velocity, samples from each centroid were collected 

from the stream transect with a D–74 or D–96 sampler lined 

with either a 1-pint glass bottle, a 1-quart glass bottle, or a 

3-liter bag. Each sample collected from all the centroids of the 

stream transect were composited into one sample and sent to 

the laboratory for analysis.

Acoustic Backscatter Data

During this study, an ADVM was deployed at each of the 

nine sampling sites (table 1; fig. 1). The ADVMs at Ft. Snelling, St. Paul, and Prescott already were installed to compute 

streamflow using the index velocity method (Levesque and 

Oberg, 2012) because these sites are affected by backwater. 

Because these three ADVMs were installed to assist in streamflow computations, the ADVMs were configured differently 

from methods recommended for using acoustic backscatter 

data as a surrogate for SSCs (Landers and others, 2016). For 

example, these ADVMs were programmed to collect 5 cells 

of acoustic backscatter data, instead of the 10 cells recommended by Landers and others (2016). The other six sites 

(Judson, Mankato, St. Peter, Jordan, Red Wing, and Pepin; 

table 1) were configured according to recommendations made 

by Landers and others (2016) and were programmed with 

10 cells.

The ADVMs were configured to collect and average backscatter measurements over 12 minutes out of each 

15-minute measurement interval. Data were downloaded from 

ADVMs about every 8 weeks during the duration of the study. 

Acoustic backscatter data were processed and corrected for 

signal losses using the Surrogate Analysis and Index Developer software tool (Domanski and others, 2015; available at 

https://water.usgs.gov/osw/SALT/SAID/downloads.html). 

Acoustic backscatter data were adjusted through three separate 

corrections: (1) attenuation of the acoustic signal because 

of beam spreading, (2) acoustic absorption by water, and 

(3) attenuation of the acoustic signal by suspended sediment. 

The two acoustic surrogate metrics produced by these corrections were SCB, in decibels, and SAC, in decibels per meter; 

SCB, SAC, and streamflow were tested as explanatory variables for SSC in the development of linear regression models. 

Data generated during this study are available as a USGS data 

release (Groten, 2018).
Methods of Data Collection and Analysis 7

0

5,000

10,000

15,000

20,000

25,000

0

10,000

20,000

30,000

40,000

03/01 09/01 03/01 09/01 

Streamflo

w, in cubic feet per second

0

10,000

20,000

30,000

40,000

03/01 09/01 03/01 09/01 

0

10,000

20,000

30,000

40,000

50,000

03/01 09/01 03/01 09/01 

Streamflo

w, in cubic feet per second

0

10,000

20,000

30,000

40,000

Minnesota River at Judson, Minnesota Minnesota River at Mankato, Minnesota

Minnesota River at St. Peter, Minnesota Minnesota River near Jordan, Minnesota 

Minnesota River at Ft. Snelling Park, Minnesota 

2016 2017 2016 2017

03/01 09/01 03/01 09/01 03/01 09/01 03/01 09/01 

2016 2017 2016 2017

2016 2017

Streamflow

Sampling event

EXPLANATION

Figure 3. Hydrographs and collection dates of suspended-sediment samples at nine sites (table 1) in the Mississippi River Basin, water 

years 2016 through 2017.
8 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

0

10,000

20,000

30,000

40,000

50,000 St. Croix River at Prescott, Wisconsin 

03/01 09/01 03/01 

03/01 

09/01 

0

20,000

40,000

60,000

80,000

Mississippi River (Lake Pepin) above Reads Landing, 

Minnesota

2016 2017

03/01 09/01 03/01 09/01 

0

20,000

40,000

60,000

80,000

Mississippi River above Red Wing below Diamond Island, 

Minnesota 

2016

Streamflow, in cubic feet per second

0

10,000

20,000

30,000

40,000

50,000

60,000 Mississippi River at St. Paul, Minnesota 

2017

03/01 09/01 09/01 

2016 2017

03/01 09/01 03/01 09/01 

2016 2017

Streamflow

Sampling event

EXPLANATION

Figure 3. Hydrographs and collection dates of suspended-sediment samples at nine sites (table 1) in the Mississippi River Basin, water 

years 2016 through 2017.—Continued
Methods of Data Collection and Analysis 9

Streamflow Data

Suspended-sediment sampling sites for this study were 

collocated at established streamgages (table 1; fig. 1). Instantaneous and daily mean streamflow data obtained from USGS 

and Minnesota Department of Natural Resources/MPCA 

streamgages are available at the USGS National Water Information System web page (https://doi.org/10.5066/F7P55KJN;

U.S. Geological Survey, 2018) and https://www.dnr.state.

mn.us/waters/csg/index.html (Minnesota Department of Natural Resources, 2018), respectively.

Laboratory Analysis

Water samples were analyzed for SSC following method 

D3977–97 (Guy, 1969; American Society for Testing and 

Materials, 2000) by the USGS Sediment Laboratory in 

Iowa City, Iowa. Percentage of fines (particle sizes less than 

0.0625 mm) also were determined for SSC samples at the 

same laboratory by wet sieving (Guy, 1969). Particles that 

measure greater than or equal to 0.0625–2.0 mm are sands. 

Results from laboratory analyses are available at the USGS 

National Water Information System web page (U.S. Geological Survey, 2018).

Statistical Analysis for Suspended Sediment

Data analyses included the computation of summary 

statistics, the development of linear regression models, and 

the computation of daily and annual SSL estimates. Data 

analyses also included the identification of outliers (Groten, 

2018) in the datasets, which represent random errors. Outliers 

were identified by a low percentage of fines (particle sizes less 

than 0.0625 mm), which indicated a high sand content in the 

sample. Sample outliers can exist during data collection when 

the streambed is inadvertently sampled because the sampler 

disturbed and entrained deposited bed sediment or when the 

sampler nozzle accidentally contacted a sand dune. Identified 

outliers were removed before data analysis.

Development of Linear Regression Models

The suitability of acoustic surrogate relations was tested 

at each site by completing ordinary least squares regression 

analyses (Helsel and Hirsch, 2002) using acoustic surrogate metrics (SCB and SAC) and streamflow as explanatory 

variables and SSC as the response variable. Different combinations of simple and multiple linear regressions on untransformed and transformed data were tested. A level of significance (α) of 0.05 was used for all statistical analyses presented 

in this study. For sites that used acoustic surrogate metrics in 

the linear regression models, gaps in continuous acoustic data 

caused by equipment malfunctions were filled using SSC values estimated using streamflow as an explanatory variable in 

linear regression models to estimate SSC. Gaps in continuous 

acoustic backscatter data (less than 18 percent of the time) are 

identified and described in detail in a corresponding USGS 

data release (Groten, 2018).

For all nine sites in the study area, Surrogate Analysis 

and Index Developer was used to develop regression models 

and evaluate the accuracy of developed models for estimating 

SSCs. Diagnostic plots, residual errors, and probability values 

(p-values) were examined to ensure models met the assumptions of ordinary least squares regression analyses (Helsel and 

Hirsch, 2002). Streamflow and SSC were log transformed 

(base-10 logarithms), and bias-correction factors were applied 

(Duan, 1983) after SSC data were retransformed into the 

original units. The final linear regression models were used to 

generate a time series of estimated SSC values and prediction 

intervals (Helsel and Hirsch, 2002). The following model form 

was used to predict SSC:

SSC BCF b b x b xk k      10 0 1 1  (1)

where

SSC is suspended-sediment concentration, in 

milligrams per liter; 

b0 is the intercept; 

b1 is the slope for the first explanatory variable; 

x1 is the first explanatory variable; 

bk is the slope for the kth explanatory variable; 

xk is the kth explanatory variable (when multiple 

linear regression is used); and

BCF is the bias-correction factor (Duan, 1983).

Daily and Annual Suspended-Sediment Load 

Estimates

Daily mean SSC values and 90-percent prediction intervals were calculated from the time series (15-minute interval) 

of SSCs estimated from linear regression models, and daily 

SSLs were estimated using the following equation (Porterfield, 

1972):

SSL=Q×SSC×cf (2)

where 

SSL is the daily mean suspended-sediment load, in 

tons per day;

Q is the daily mean streamflow, in cubic feet per 

second;

SSC is the daily mean suspended-sediment 

concentration, in milligrams per liter; and

cf is a coefficient (0.0027) that converts the units 

of streamflow and SSC into tons per day 

and assumes a specific gravity of 2.65 for 

sediment. 

When regression equations were deemed not accurate enough 

to use as predictive surrogate models (coefficient of determination [R2

]less than [<] 0.5), the mean SSC of the collected 
10 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

samples was used with the daily mean streamflow to compute 

daily mean SSL. A 90-percent confidence interval of each 

mean SSC was computed (Helsel and Hirsch, 2002). The daily 

mean SSL estimates were summed for the WY to obtain the 

annual SSL estimates.

Streamflow, Suspended-Sediment 

Concentrations, and Surrogate 

Relations

Summary statistics of streamflow, SSCs, and acoustic 

metrics (SCB and SAC) for the nine sites in the study area 

(table 2; fig. 1) demonstrate considerable variability in sediment transport that is likely affected by many factors such as 

sediment sources, sediment supply, rate of erosion, magnitude, intensity and duration of storm events, and antecedent 

conditions. The increase in median SSC for the Minnesota 

River between Judson and Mankato (table 2) likely is a result 

of sediment from the Blue Earth River entering the Minnesota River just upstream from Mankato (fig. 1). The Le Sueur 

River (fig. 1) flows into the Blue Earth River near the town of 

Rapidan, Minn. (not shown), upstream from where the Blue 

Earth River joins the Minnesota River. The Le Sueur and Blue 

Earth Rivers previously have been determined to transport 

elevated SSCs (Minnesota Pollution Control Agency, 2009b; 

Ellison and others, 2014; Groten and others, 2016; Groten and 

Johnson, 2018).

Median suspended-sand concentrations generally 

decreased downstream, similar to how the stream gradients decreased downstream (table 2; figs. 2 and 4). Median 

suspended-sand concentrations increased in the Minnesota 

River from Judson to Mankato (table 2; fig. 4), whereas 

suspended-sand concentrations were similar for the Minnesota 

River between Mankato and St. Peter (table 2; fig. 4). In contrast, suspended-sand concentrations decreased in the Minnesota River between Mankato and Ft. Snelling (table 2; fig. 4), 

and suspended-sand concentrations were substantially lower 

at Prescott and substantially decreased from St. Paul to Red 

Wing and to Pepin (table 2; fig. 4). This observed decrease 

in suspended-sand concentrations corresponds to a transition 

from higher gradient stream sites to lower gradient stream 

sites (fig. 2), indicating that higher gradients may provide the 

velocities required to keep sand particles in suspension. When 

the stream gradient decreases, the suspended sands likely 

settle out and deposit in the river channel and (or) flood plain. 

Also, suspended-fines concentrations followed similar patterns 

as suspended-sands concentrations.

The Mississippi River upstream from the confluence with 

the Minnesota River generally is low in SSC. Downstream 

from the confluences of the Minnesota and Mississippi Rivers 

and the St. Croix and Mississippi Rivers, streamflows increase 

because of the contribution of streamflow from these two 

tributaries (table 2). The combination of low SSCs and high 

streamflow volumes helps to dilute high concentrations of suspended sediment entering the Mississippi River from the Minnesota River. Median SSC drops from Ft. Snelling (221 milligrams per liter [mg/L]; table 2) to St. Paul (119 mg/L; 

table 2), which is just downstream from the confluence of the 

Minnesota and Mississippi Rivers (fig. 1). The median SSC 

at Prescott was low (2.00 mg/L; table 2), and the median SSC 

of Red Wing is less than one-half (46.0 mg/L; table 2) of the 

observed median SSC at St. Paul (119 mg/L; table 2). Finally, 

the stream gradient decreases furthest downstream in Lake 

Pepin, and the median SSC at Pepin decreased to 5.00 mg/L 

(table 2).

Surrogate Relations for SuspendedSediment Concentrations

Statistically significant linear relations (p-value <0.05) 

and high coefficients of determination (R2

 greater than 0.75) 

demonstrated that SAC and SCB could be useful for improving estimates of SSCs at five of the nine study sites: the 

Minnesota River at (1) Mankato, (2) St. Peter, (3) Jordan, 

and (4) Ft. Snelling and the Mississippi River at (5) St. Paul 

(table 3; fig. 5). A significant linear relation could not be 

developed for Judson because of data quality issues caused by 

the ADVM going out of water during low flow periods and 

by low signal return for the vertical elevation beam during 

high flow periods (Xue Fan, Sontek, written commun., 2018). 

For Judson, the linear relation between streamflow and SSC 

(R2

=0.79) was statistically significant (p<0.01) and was used 

in estimating annual SSL (table 4; Groten, 2018). Because 

more samples were collected during the rising limb rather than 

the falling limb of the streamflow hydrograph, there is likely to 

be hysteresis in SSCs with respect to rising- and falling-limb 

flow conditions; therefore, this study likely did not capture the 

full range of variability in SSCs at different streamflows. Thus, 

the streamflow regression statistics (table 3) likely overestimate R2

, underestimate standard error, and produce higher 

biased estimated SSCs for falling-limb conditions. For sites 

that included acoustic surrogate metrics to estimate SSC in 

the linear regression model, the models with acoustic metrics 

consistently explained more variability (had higher R2

 values) 

than streamflow-based models (fig. 5; Groten, 2018).

A pattern was evident when comparing surrogate models 

developed for two sites. Linear regression model forms were 

similar for Mankato and St. Peter and different compared 

to the other sites. Similar elevation gradients (fig. 3) and 

close proximity (13 mi) without an intervening major tributary likely contributed to the similarities in these regression 

models.

Significant linear relations could not be developed to 

predict SSC from acoustic data or streamflow for Prescott, 

Red Wing, or Pepin (fig. 5). Mean SSC values from physically 

collected samples (table 3) at each site were used to estimate 

SSLs at these sites. Samples collected in 2016 at Red Wing 
Surrogate Relations for Suspended-Sediment Concentrations 11

Table 2. Summary statistics for streamflow, suspended sediments, and acoustic surrogate model metrics.

[n, number of samples; Minn., Minnesota; ft3/s, cubic foot per second; mg/L, milligram per liter; St., Saint; Ft., Fort; Wisc., Wisconsin]

Constituent Minimum Mean Median Maximum Total n

Minnesota River at Judson, Minn.

Streamflow, instantaneous (ft3/s) 654 5,170 4,810 15,900 731 

Suspended-sediment concentration (mg/L) 62.0 252 234 558 21.0 

Suspended sands (mg/L) 3.72 49.6 46.6 92.1 21.0 

Suspended fines (mg/L) 58.3 202 178 513 21.0 

Minnesota River at Mankato, Minn. 

Streamflow, instantaneous (ft3/s) 1,020 8,820 8,050 34,700 731 

Suspended-sediment concentration (mg/L) 66.0 407 330 1,190 20.0 

Suspended sands (mg/L) 4.62 85.9 84.7 288 20.0 

Suspended fines (mg/L) 61.4 321 241 1,120 20.0 

Sediment attenuation coefficient (in decibels per meter) 0.170 0.558 0.474 7.35 38,600 

Minnesota River at County Highway 22 in St. Peter, Minn.

Streamflow, instantaneous (ft3/s) 1,160 9,440 8,870 36,000 731 

Suspended-sediment concentration (mg/L) 83.0 398 332 1,620 22.0 

Suspended sands (mg/L) 7.47 89.9 80.5 292 22.0 

Suspended fines (mg/L) 75.5 308 231 1,330 22.0 

Sediment attenuation coefficient (in decibels per meter) 0.189 0.806 0.764 4.59 30,200 

Minnesota River near Jordan, Minn.

Streamflow, instantaneous (ft3/s) 1,320 10,200 9,470 38,300 731 

Suspended-sediment concentration (mg/L) 67.0 370 312 1,390 21.0 

Suspended sands (mg/L) 5.36 54.9 56.8 99.0 21.0 

Suspended fines (mg/L) 61.6 315 244 1,290 21.0 

Sediment-corrected backscatter (in decibels) 22.7 80.1 80.6 94.8 56,600 

Minnesota River at Ft. Snelling State Park, Minn.

Streamflow, instantaneous (ft3/s) 1,120 8,340 7,400 34,500 1,100 

Suspended-sediment concentration (mg/L) 18.0 257 221 1,010 54.0 

Suspended sands (mg/L) 0.360 29.7 17.6 171 54.0 

Suspended fines (mg/L) 17.6 227 189 909 54.0 

Sediment-corrected backscatter (in decibels) 32.4 72.3 74.4 92.4 99,500 

Mississippi River at St. Paul, Minn.

Streamflow, instantaneous (ft3/s) 5,670 22,800 22,000 52,500 731 

Suspended-sediment concentration (mg/L) 13.0 139 119 333 19.0 

Suspended sands (mg/L) 0.520 14.0 13.6 38.3 19.0 

Suspended fines (mg/L) 12.5 125 107 316 19.0 

Sediment-corrected backscatter (in decibels) 46.0 73.0 75.7 93.6 65,200 

St. Croix River at Prescott, Wisc.

Streamflow, instantaneous (ft3/s) 1,750 7,580 6,290 41,500 731 

Suspended-sediment concentration (mg/L) 1.00 3.00 2.00 7.00 19.0 

Suspended sands (mg/L) 0 0.225 0.140 0.810 19.0 

Suspended fines (mg/L) 0.790 2.56 1.90 6.72 19.0 
12 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

Table 2. Summary statistics for streamflow, suspended sediments, and acoustic surrogate model metrics.—Continued

[n, number of samples; Minn., Minnesota; ft3/s, cubic foot per second; mg/L, milligram per liter; St., Saint; Ft., Fort; Wisc., Wisconsin]

Constituent Minimum Mean Median Maximum Total n

Mississippi River above Red Wing below Diamond Island, Minn.

Streamflow, instantaneous (ft3/s) 12,800 33,300 31,500 74,600 731 

Suspended-sediment concentration (mg/L) 20.0 49.6 46.0 89.0 20.0 

Suspended sands (mg/L) 0.230 2.42 2.20 7.70 20.0 

Suspended fines (mg/L) 19.0 47.1 44.4 87.2 20.0 

Mississippi River (Lake Pepin) above Reads Landing, Minn.

Streamflow, instantaneous (ft3/s) 11,100 32,500 30,500 69,700 731 

Suspended-sediment concentration (mg/L) 3.00 5.30 5.00 10.0 20.0 

Suspended sands (mg/L) 0 0.300 0.250 0.870 20.0 

Suspended fines (mg/L) 2.13 5.00 4.63 9.50 20.0 

Site

0.01

0.1

1

10

100

1,000

Fine particle sizes less than 0.0625 millimeter

Sand particle sizes greater than or equal to 0.0625 millimeter

Minnesota River

at Judson, Minnesota 

Minnesota River

at Mankato, Minnesota 

Minnesota River at County

 Highway 22 in St. Peter, Minnesota

Mississippi River

at St. Paul, Minnesota

St. Croix River

at Prescott, Wisconsin

Mississippi River above Red Wing

below Diamond Island, Minnesota

Minnesota River

near Jordan, Minnesota

Minnesota River at

Fort Snelling State Park, Minnesota

Mississippi River (Lake Pepin) 

above Reads Landing, Minnesota 

EXPLANATION

EXPLANATION

75th percentile

50th percentile (median)

25th percentile

Interquartile 

range

10th percentile

90th percentile

Values outside of range did not plot

Number of samples

Concentration, in milligrams per liter

n=21

n=21

n=20

n=22

n=21

n=54 n=19

n=19

n=20

n=20

Figure 4. Measured suspended-sand and suspended-fines concentrations at nine sites in the Mississippi River Basin.
Surrogate Relations for Suspended-Sediment Concentrations 13

Table 3. Summary of linear regression models for selected sites in the Mississippi River Basin.

[n, number of samples; R2, coefficient of determination; p-value, probability value of explanatory variable(s); Minn., Minnesota; --. no data; SSC, suspendedsediment concentration laboratory analysis method; SAC, sediment attenuation coefficient; Q, streamflow; <, less than; St., Saint; SCB, sediment corrected 

backscatter; Ft., Fort]

Station name n Linear regression model Standard 

error

R 

2

Average 

model 

standard 

percentage 

error 

p-value

Acoustic model or acoustic and streamflow model

Minnesota River at Judson, Minn. -- -- -- -- -- --

Minnesota River at Mankato, Minn. 18 a

SSC=10−1.1+0.215×SAC+0.825×Q×1.01b 0.0777 0.94 18 <0.01

Minnesota River at County Highway 22 in St. Peter, Minn.20 a

SSC=100.135+0.405×SAC+0.467×Q×1.02b 0.0833 0.916 19.3 <0.01

Minnesota River near Jordan, Minn. 19 SSC=10−4.76+0.0869×SCB×1.04b 0.13 0.829 30.5 <0.01

Minnesota River at Ft. Snelling 

State Park, Minn.

49 SSC=10−5.27+0.0976×SCB×1.07b 0.165 0.84 38.8 <0.01

Mississippi River at St. Paul, Minn. 17 SSC=10−8.94+0.14×SCB×1.07b 0.166 0.803 39.2 <0.01

Streamflow model

Minnesota River at Judson, Minn. 20 SSC=10−0.598+0.774×Q×1.01b 0.077 0.794 17.8 <0.01

Minnesota River at Mankato, Minn. 19 SSC=10−2.23+1.14×Q×1.06b 0.148 0.781 34.8 <0.01

Minnesota River at County Highway 22 in Saint Peter, Minn.21 SSC=10−1.37+0.931×Q×1.08b 0.167 0.659 39.5 <0.01

Minnesota River near Jordan, Minn. 19 SSC=10−0.78+0.805×Q×1.18b 0.248 0.379 60.3 <0.01

Minnesota River at Fort Snelling 

State Park, Minn.

49 SSC=10−2.46+1.18×Q×1.18b 0.267 0.577 65.6 <0.01

Mississippi River at St. Paul, Minn. 17 SSC=10−3.58+1.28×Q×1.18b 0.262 0.513 64 <0.01

a

Multiple linear regression model.

b

Bias correction factor or “smearing” estimator is used to correct retransformation bias of regression estimates (Duan, 1983).

seemed to indicate that a strong linear relation could be developed between acoustic data and SSC; however, a large rain 

event deposited a substantial amount of sediment around the 

streamgage and buried the ADVM, and the ADVM was repositioned higher in the water column on November 17, 2016. A 

significant linear relation could not be developed using samples 

collected in 2017 after the ADVM was repositioned. The mean 

SSC for this site based on physically collected samples was 

49.6 mg/L (table 2).

Linear regression models for Prescott and Pepin were not 

significant and could not be used to accurately estimate SSCs. 

Because acoustic backscatter and streamflow data were not 

correlated to SSC, mean SSC and daily mean streamflows are 

reasonable to estimate SSLs at these sites. Increased water residence times and lower flow velocities upstream caused by natural reservoirs in Lake St. Croix and Lake Pepin, respectively, 

likely resulted in low suspended sediment in the water column 

and corresponding low acoustic return signals, which limited 

the ability to develop surrogate relations. Mean SSCs based on 

physically collected samples were 3.00 and 5.30 mg/L for the 

outlets of Lake St. Croix and Lake Pepin, respectively (table 2).

During model development, several samples collected 

after a storm event on August 17, 2017 (fig. 6), were outliers 

in regression models (Groten, 2018). The storm was in the 

upper parts of the Minnesota River Basin and did not affect 

sediment-rich tributaries (Blue Earth and Le Sueur Rivers) in 

the lower part of the basin; therefore, the localized nature of 

this storm may have caused sediment-transport patterns to differ in the study area.

Linear regression models were used to produce time 

series estimates of SSCs (fig. 7) at a 15-minute interval for 

six sites. Caution should be taken with interpretations of 

estimates of SSCs that extend beyond the site-specific calibration dataset (table 2). The estimated SSCs at Judson only used 

streamflow as an explanatory variable, so Judson’s estimates 

of SSCs followed the 15-minute time series of streamflow 

pattern more closely. However, regression models for the other 

five sites (Mankato, St. Peter, Jordan, Snelling, and St. Paul) 

included SCB or SAC as one of the explanatory variables, and 

the resulting estimated SSCs did not follow the streamflow 

pattern.
14 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

Minnesota River at St. Peter, Minnesota 

Streamflow, in cubic feet per second

1,000 10,000 100,000

10

100

1,000

10,000

Estimated suspended-sediment concentration, in milligrams per liter, 

from sediment attenuation coefficient, in decibels per meter, 

and streamflow, in cubic feet per second

10 100 1,000

10

100

1,000

1,000 10,000

10

100

1,000 Minnesota River at Judson, Minnesota

Minnesota River at Mankato, Minnesota 

Minnesota River at St. Peter, Minnesota 

10 100 1,000 10,000

10

100

1,000

10,000 Minnesota River at Mankato, Minnesota

1,000 10,000 100,000

10

100

1,000

10,000

Best-fit regression line

1:1 line

Measured value

Modeled value

Outlier 

EXPLANATION

Suspended-sediment concentration, in milligrams per liter

Streamflow models

Acoustic and streamflow models

Figure 5. Relations among suspended-sediment concentrations, acoustic surrogate metrics, and streamflow at nine sites in the 

Mississippi River Basin.
Surrogate Relations for Suspended-Sediment Concentrations 15

Minnesota River near Jordan, Minnesota Minnesota River near Jordan, Minnesota 

Minnesota River at Fort Snelling Park, Minnesota Minnesota River at Fort Snelling Park, Minnesota 

Mississippi River at St. Paul, Minnesota Mississippi River at St. Paul, Minnesota 

1,000 10,000 100,000

1

10

100

1,000

10,000

10 20 60 70 80 90

1

10

100

1,000

10,000

1,000 10,000 100,000

10

100

1,000

10,000

74 76 78 80 82 84 86 88 90 92

10

100

1,000

10,000

Streamflow, in cubic feet per second

10,000 100,000

10

100

1,000

Mean sediment-corrected backscatter, in decibels

70 72 74 76 78 80 82 84

10

100

1,000

Suspended-sediment concentration, in milligrams per liter

Best-fit regression line

Measured value

Measured value

Outlier 

EXPLANATION

Streamflow models Acoustic models

Figure 5. Relations among suspended-sediment concentrations, acoustic surrogate metrics, 

and streamflow at nine sites in the Mississippi River Basin.—Continued
16 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

Sediment attenuation coefficient, in decibels per meter

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

0

2

4

6

8

Mean sediment-corrected backscatter, in decibels

50 60 70 80 90

0

20

40

60

80

100

Mean sediment-corrected backscatter, in decibels

50 55 60 65 70 75 80

0

2

4

6

8

10

12

St. Croix River at Prescott, Wisconsin

Mississippi River above Red Wing below Diamond Island, 

Minnesota

Mississippi River (Lake Pepin) above Reads Landing, 

Minnesota

EXPLANATION

Mean

Measured value 

Suspended-sediment concentration, in milligrams per liter

Mean suspended-sediment concentrations

Figure 5. Relations among suspended-sediment concentrations, acoustic surrogate metrics, and streamflow at nine sites in the 

Mississippi River Basin.—Continued
Surrogate Relations for Suspended-Sediment Concentrations 17

Table 4. Estimated annual suspended-sediment loads for the lower Minnesota, St. Croix, and Mississippi Rivers.

[Minn., Minnesota; St., Saint; Ft., Fort; Wisc., Wisconsin]

Water year

Lower 90-percent prediction or 

confidence interval for 

suspended-sediment load, 

in tons per day

Suspended-sediment load, 

in tons per day

Upper 90-percent prediction or 

confidence interval for 

suspended-sediment load, 

in tons per day

Minnesota River at Judson, Minn.

2016 577,718a 799,361b 1,106,289a

2017 1,133,249a 1,565,415b 2,162,627a

Minnesota River at Mankato, Minn. 

2016 1,491,665a 2,211,463b 3,328,612a

2017 1,626,969a 2,268,078b 3,162,194a

Minnesota River at County Highway 22 in St. Peter, Minn.

2016 1,482,868a 2,281,159b 3,588,246a

2017 1,894,383a 2,745,851b 4,004,410a

Minnesota River near Jordan, Minn.

2016 1,421,022a 2,604,897b 4,949,749a

2017 1,472,402a 2,541,865b 4,389,835a

Minnesota River at Ft. Snelling State Park, Minn.

2015 295,917a 566,605b 1,086,033a

2016 1,389,583a 2,676,231b 5,165,522a

2017 1,545,841a 2,969,812b 5,711,388a

Mississippi River at St. Paul, Minn.

2016 1,027,759a 2,083,186b 4,234,288a

2017 1,277,846a 2,783,848b 6,230,043a

St. Croix River at Prescott, Wisc.

2016 16,781c 24,742d 29,230c

2017 13,649c 20,124d 23,775c

Mississippi River above Red Wing below Diamond Island, Minn.

2016 1,388,773c 1,602,771d 1,816,769c

2017 1,435,699c 1,656,927d 1,878,156c

Mississippi River (Lake Pepin) above Reads Landing, Minn.

2016 146,481c 168,371d 190,262c

2017 149,003c 171,271d 193,538c

a

Upper or lower 90-percent prediction interval for suspended-sediment load by regression.

b

Suspended-sediment load by regression. 

c

Upper or lower 90-percent confidence interval for suspended-sediment load by mean.

d

Suspended-sediment load by mean.
18 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

97° 96° 95° 94° 93° 92° 91° 90°

50°

49°

48°

47°

46°

45°

44°

43°

Upper Minnesota River

Lower Minnesota River

EXPLANATION

Base modified from U.S. Geological Survey, U.S. Census Bureau,and Minnesota Department of 

Natural Resources digital data, variously dated, various scales 

Universal Transver Mercator, zone 15 

North American Datum of 1983

Precipitation, in inches

High: 7.5748

Low: 0.05905

Upper Minnesota 

Watershed

Blue Earth Watershed

0 25 50 75 100 KILOMETERS

0 25 50 75 100 MILES

MINNESOTA

IOWA

WISCONSIN

NORTH

DAKOTA

CANADA

SOUTH

DAKOTA

LAKE

SUPERIOR

MICHIGAN

Precipitation data from the 

National Oceanic and Atmospheric Administration

Figure 6. Precipitation totals in the Mississippi River Basin and upper Minnesota River and Blue Earth River subbasins 

on August 17, 2017.
Surrogate Relations for Suspended-Sediment Concentrations 19

Minnesota River at Fort Snelling, Minnesota Mississippi River at St. Paul, Minnesota 

Minnesota River at Judson, Minnesota Minnesota River at Mankato, Minnesota 

Minnesota River at St. Peter, Minnesota 

 Streamflow, in cubic feet per second

04/01 10/01 

0

10,000

20,000

30,000

40,000

50,000

0

100

200

300

400

500

04/01 10/01 

0

2,000

4,000

6,000

8,000

04/01 10/01 

0

2,000

4,000

6,000

8,000

10,000

0

10,000

20,000

30,000

40,000

50,000

04/01 10/01 

0

500

1,000

1,500

2,000

2,500

3,000 Minnesota River near Jordan, Minnesota 

04/01 10/01 

0

10,000

20,000

30,000

40,000

50,000

60,000

0

2,000

4,000

6,000

8,000

2016

04/01 10/01 

0

1,000

2,000

3,000

4,000

Estimated suspended-sediment concentration, in milligrams per liter

2016

EXPLANATION

Streamflow

15-minute suspended-sediment concentration

Figure 7. Streamflow and estimated 15-minute suspended-sediment concentrations during the open-water season (March through 

October) at six sites in the Mississippi River Basin.
20 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

Minnesota River at Fort Snelling, Minnesota 

0

10,000

20,000

30,000

40,000

50,000

60,000

2017

Minnesota River at Mankato, Minnesota 

Estimated suspended-sediment soncentration, in milligrams per liter

Minnesota River near Jordan, Minnesota 

Mississippi River at St. Paul, Minnesota 

2017

04/01 10/01 

0

200

400

600

04/01 10/01 

0

100

200

300

400

500

40,000

Minnesota River at Judson, Minnesota 

0

10,000

20,000

30,000

50,000

04/01 10/01 

0

200

400

600

800

1,000

0

20,000

40,000

60,000

80,000 Minnesota River at St. Peter, Minnesota 

 Streamflow, in cubic feet per second

04/01 10/01 

0

200

400

600

800

04/01 10/01 

0

500

1,000

1,500

2,000

2,500

04/01 10/01 

0

500

1,000

1,500

2,000

EXPLANATION

Streamflow

15-minute suspended-sediment concentration

Figure 7. Streamflow and estimated 15-minute suspended-sediment concentrations during the open-water season (March through 

October) at six sites in the Mississippi River Basin.—Continued
Suspended-Sediment Loads 21

The inconsistency of SSC-streamflow relations can be 

illustrated using examples from the WY 2016. At Mankato, 

St. Peter, and Jordan, the highest estimated SSC was in midJune 2016 even though a greater streamflow peak was at the 

end of September 2016; furthermore, both estimated SSC 

peaks were before the corresponding streamflow peaks at all 

3 sites for these 2 events in 2016. However, the estimated 

SSCs seemed to follow the streamflow pattern more closely in 

2017 than in 2016 at Mankato and St. Peter; whereas, Jordan’s 

estimated SSCs diverged from the streamflow pattern by peaking before streamflow more than the other two sites in 2017. 

The estimated SSC at Ft. Snelling and St. Paul more closely 

matched the streamflow pattern except for occasional spikes 

that likely resulted from tow boats and barge traffic causing 

resuspension of bottom sediment.

Suspended-Sediment Loads

Time series of daily estimated SSLs and streamflow are 

shown in figure 8. Estimated daily SSLs were highest from 

March to November. Generally, there was more SSL in the 

spring because of higher precipitation amounts; however, daily 

SSL peaked in fall of 2016 at many sites (fig. 8) because of a 

substantial rainfall event in late September.

Comparing annual estimated SSLs (fig. 9) helped to 

determine differences among sites to determine potential sediment sources and sinks (fig. 10). The 15-minute estimates of 

SSC and daily SSL estimates highlighted the variable nature 

of suspended sediment (figs. 7 and 8) because of the resolution 

of the data; however, annual SSLs gave a coarser resolution of 

annual suspended-sediment budgets. The annual SSLs (fig. 9) 

indicate the variability between the 2 measured years. Annual 

SSLs are greater in 2017 than in 2016 at all sites except Jordan 

and Prescott.

Possible sediment sources (brown triangles) and sinks 

(blue triangles) are illustrated in figure 10 by the longitudinal 

changes in annual SSLs among sites along the Minnesota 

and Mississippi Rivers. The height of the triangle represents 

the amount of suspended sediment gained or lost between 

sampling sites. There were substantial differences in SSLs 

between sites when a major tributary joined the river between 

them; for example, the SSL was larger at Mankato than Judson likely because of the elevated SSL from the Blue Earth 

River. Also, the decrease in SSL from Ft. Snelling to St. Paul 

likely is a result of the upper Mississippi River, which is less 

sediment laden than the Minnesota River, diluting the SSL 

at St. Paul. The second most substantial decrease in SSL was 

a 23- (WY 2016) and 40- (WY 2017) percent decrease from 

St. Paul to Red Wing. The most substantial decrease in SSL 

was a 90-percent decrease from Red Wing to Lake Pepin. 

These sediment sinks from St. Paul to the outlet of Lake Pepin 

likely are linked to storage in the pools upstream from Locks 

and Dams Numbers 2 and 3 and Lake Pepin, respectively.

Comparing the sediment yield (annual load divided by 

basin area) provides insight on the relative measure of erosion 

rates, sediment contributions from tributaries, and amount of 

storage between sites (fig. 11). Longitudinal patterns in sediment yields among the nine sites were similar to the annual 

SSLs (fig. 8). The lower Minnesota River outlet yielded 70 

and 50 times more sediment than the outlets of Lake St. Croix 

and Lake Pepin, respectively (fig. 11). Also, the highest sediment yield was at St. Peter in 2017 (182 tons per year per 

square mile [(tons/yr)/mi2]). In contrast, the lowest sediment 

yield was at Prescott in 2017 (2.6 (tons/yr)/mi2). In WYs 2016 

and 2017, the St. Croix River contributed little SSL to the 

Mississippi River, whereas the Minnesota River contributed a 

substantial part of the total SSL to the Mississippi River.
22 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers

Minnesota River at Mankato, Minnesota 

0

10,000

20,000

30,000

40,000

0

50,000

100,000

150,000

200,000

10/01 02/01 06/01 10/01 02/01 06/01 10/01 

2016 2017

Minnesota River at Judson, Minnesota 

0

10,000

20,000

30,000

40,000

0

10,000

20,000

30,000

40,000

10/01 02/01 06/01 10/01 02/01 06/01 10/01 

2016 2017

Streamflow, in cubic feet per second

Minnesota River at St. Peter, Minnesota 

0

10,000

20,000

30,000

40,000

0

50,000

100,000

150,000

200,000

10/01 02/01 06/01 10/01 02/01 06/01 10/01 

2016 2017

Minnesota River near Jordan, Minnesota 

0

10,000

20,000

30,000

40,000

0

50,000

100,000

150,000

200,000

10/01 02/01 06/01 10/01 02/01 06/01 10/01 

2016 2017

Estimated suspended-sediment load, in tons per day

0

20,000

40,000

60,000

80,000

0

50,000

100,000

150,000

200,000

250,000

300,000 Mississippi River at St. Paul, Minnesota 

10/01 02/01 06/01 10/01 02/01 06/01 10/01 

2016 2017

0

10,000

20,000

30,000

40,000

0

50,000

100,000

150,000

200,000 Minnesota River at Fort Snelling, Minnesota 

11/01 05/01 11/01 

2016 2017

05/01 11/01 05/01 

2015

Daily mean streamflow

 Daily mean suspended-sediment load

EXPLANATION

Figure 8. Daily mean streamflow and daily estimated suspended-sediment loads at nine sites in the Mississippi River Basin.
Suspended-Sediment Loads 23

0

20,000

40,000

60,000

80,000

0

5,000

10,000

15,000

20,000

10/01 02/01 06/01 10/01 02/01 06/01 10/01 

2016 2017

Mississippi River above Reads Landing, Minnesota

Estimated suspended-sediment load, in tons per day

Streamflow, in cubic feet per second

Streamflow, in cubic feet per second

0

20,000

40,000

60,000

80,000

0

5,000

10,000

15,000

20,000 St. Croix River near Prescott, Wisconsin

10/01 02/01 06/01 10/01 02/01 06/01 10/01 

2016 2017

Estimated suspended-sediment load, in tons per day

0

20,000

40,000

60,000

80,000

0

5,000

10,000

15,000

20,000

Mississippi River above Red Wing below Diamond 

Island, Minnesota

10/01 02/01 06/01 10/01 02/01 06/01 10/01 

2016 2017

Daily mean streamflow

Daily mean suspended-sediment load

EXPLANATION

Figure 8. Daily mean streamflow and daily estimated suspended-sediment loads at nine sites in the Mississippi River Basin.—

Continued
24 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers Suspended-sediment load, in tons per day

0

1×106

2×106

3×106

4×106

5×106

6×106

Lower 90-percent prediction interval for suspended-sediment load by regression 

Suspended-sediment load by regression

Upper 90-percent prediction interval for suspended-sediment load by regression

Lower 90-percent confidence interval for suspended-sediment load by mean

Suspended-sediment load by mean

Upper 90-percent confidence interval for suspended-sediment load by mean

EXPLANATION

2016 2017

Water years

Site

2016 2017 2016 2017 2016 2017 2016 2017 2016 2017 2016 2017 2016 2017 2016 2017

Minnesota River

at Judson, Minnesota 

Minnesota River

at Mankato, Minnesota 

Minnesota River at County

 Highway 22 in St. Peter, Minnesota

Mississippi River

at St. Paul, Minnesota

St. Croix River

at Prescott, Wisconsin

Mississippi River above Red Wing

below Diamond Island, Minnesota

Minnesota River

near Jordan, Minnesota

Minnesota River at

Fort Snelling State Park, Minnesota

Mississippi River (Lake Pepin) 

above Reads Landing 

Figure 9. Estimated annual suspended-sediment loads at nine sites in the Mississippi River Basin, water 

years 2016 through 2017.
Suspended-Sediment Loads 25

Distance upstream from confluence of Minnesota and Mississippi Rivers, in miles

125 100 75 50 25 0 −25 −50 −75

650

700

750

800

850

900

0

5.0×105

1.0×106

1.5×106

2.0×106

2.5×106

3.0×106

125 100 75 50 25 0 −25 −50 −75

Elevation, in feet

650

700

750

800

850

900

Suspended-sediment load, in tons per day

0

5.0×105

1.0×106

1.5×106

2.0×106

2.5×106

3.0×106

3.5×106

Mississippi River 

(Lake Pepin) above

Reads Landing, Minnesota

EXPLANATION

Possible sediment source

Possible sediment sink

Sampling site

Water year 2016

Water year 2017

Minnesota River

at Judson, Minnesota

Mississippi River

Minnesota River

Mississippi River above

Red Wing below Diamond

Island, Minnesota

Mississippi River

at St. Paul, Minnesota

Minnesota River

at Fort Snelling

State Park, Minnesota

Minnesota River 

near Jordan, Minnesota

Minnesota River

at County Highway 22

in St. Peter, Minnesota

Minnesota River

at Mankato, Minnesota

Minnesota River

at Judson, Minnesota

Minnesota River

at Fort Snelling

State Park, Minnesota

Minnesota River 

near Jordan, Minnesota

Minnesota River

at County Highway 22

in St. Peter, Minnesota

Minnesota River

at Mankato, Minnesota

St. Croix River

Mississippi River 

(Lake Pepin) above

Reads Landing, Minnesota

Mississippi River

Minnesota River

Mississippi River

at St. Paul, Minnesota

Mississippi River above

Red Wing below Diamond

Island, Minnesota

St. Croix River

Figure 10. Possible sediment sources and sinks with stream gradients along the Minnesota and Mississippi Rivers 

at eight sites, water years 2016 and 2017.
26 Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers Annual sediment yield, in (tons per year) per square mile

0

50

100

150

200

EXPLANATION

 2016

2017

Water year

Site

Minnesota River

at Judson, Minnesota 

Minnesota River

at Mankato, Minnesota 

Minnesota River at County

 Highway 22 in St. Peter, Minnesota

Mississippi River

at St. Paul, Minnesota

St. Croix River

at Prescott, Wisconsin

Mississippi River above Red Wing

below Diamond Island, Minnesota

Minnesota River

near Jordan, Minnesota

Minnesota River at

Fort Snelling State Park, Minnesota

Mississippi River (Lake Pepin) 

above Reads Landing, Minnesota 

Figure 11. Annual sediment 

yield at nine sites in the 

Mississippi River Basin, 

water years 2016 and 2017.

Summary and Conclusions

Sediment-laden rivers in Minnesota cost river users 

millions of dollars each year (U.S. Army Corps of Engineers, 

2006; Minnesota Pollution Control Agency, 2009a). Excessive sediment in rivers degrades water quality, is deleterious to aquatic habitat, leads to increased navigation channel 

dredging, reduces recreational opportunities, and can transport 

harmful contaminants. Sediment loads in the Minnesota River 

have been a concern among Minnesota State agencies. Most 

of the sediment loading in the Mississippi River between the 

Minneapolis-St. Paul (also referred to as “Twin Cities”) metropolitan area and Lake Pepin originates in the Minnesota River; 

furthermore, most of the sediment being deposited into Lake 

Pepin originates from the Minnesota River Basin. Lake Pepin 

is an important recreational and commercial resource, and 

concerns over its fill rate have led Minnesota State agencies to 

adopt a Sediment-Reduction Strategy.

From 2015 through 2017, the U.S. Geological Survey 

(USGS), with funding from the Environment and Natural 

Resources Trust Fund and in cooperation with the U.S. Army 

Corps of Engineers, Lower Minnesota River Watershed 

District, Minnesota Pollution Control Agency, and Minnesota 

Department of Natural Resources, installed and operated 

side-looking acoustic Doppler velocity meters (ADVMs). 

These ADVMs were used to estimate continuous, real-time 

suspended-sediment concentrations (SSCs) at five streamgages 

in the Minnesota and Mississippi Rivers upstream from Lake 

Pepin. Acoustic backscatter data from ADVMs were correlated to physically collected suspended-sediment samples. 

This information is intended to help State agencies monitor 

progress toward sediment-reduction goals and effectiveness of 

implemented best management practices and other restoration 

activities.

This report documents findings based on suspendedsediment data collected at 5 sites on the lower Minnesota 

River (Minnesota River at Judson, Minnesota [USGS station 05317500; hereafter referred to as “Judson”]; Minnesota 

River at Mankato, Minn. [USGS station 05325000; hereafter 

referred to as “Mankato”]; Minnesota River at County Highway 22 in St. Peter, Minn. [USGS station 05325300; hereafter 

referred to as “St. Peter”]; Minnesota River near Jordan, Minn. 

[USGS station 05330000; hereafter referred to as “Jordan”]; 

and Minnesota River at Fort Snelling State Park, Minn. [USGS 

station 05330920; hereafter referred to as “Ft. Snelling”]), 

1 site on the St. Croix River (St. Croix River at Prescott, 

Wisconsin [USGS station 05344490; hereafter referred to as 
References Cited 27

“Prescott”]), and 3 sites on the Mississippi River (Mississippi 

River at St. Paul, Minn. [USGS station 05331000; hereafter 

referred to as “St. Paul”]; Mississippi River above Red Wing 

below Diamond Island, Minn. [USGS station 05355235; hereafter referred to as “Red Wing”]; and Mississippi River [Lake 

Pepin] above Reads Landing, Minn. [USGS station 05355341; 

hereafter referred to as “Pepin”]) to improve the understanding 

of fluvial suspended-sediment concentrations and suspendedsediment loads (SSLs). Samples were collected for suspended 

sediment at Ft. Snelling during water years 2012 through 

2017, and samples were collected at the rest of the eight sites 

during water years 2016 through 2017.

Suspended-sand concentrations among study sites related 

to stream gradients and indicated that higher gradients may 

provide the velocities needed to keep larger sand particles in 

suspension. Generally, suspended-sand and -fines concentrations decreased moving downstream in the Minnesota and 

Mississippi Rivers. The observed decreases corresponded to 

decreases in stream gradients and to proximity of pools and 

lakes.

The Mississippi River upstream from the confluence with 

the Minnesota River and the St. Croix River upstream from 

the Mississippi River generally are low in SSCs. In addition, 

the confluences of the Minnesota and Mississippi Rivers and 

the St. Croix and Mississippi Rivers substantially increase 

streamflow downstream. The combination of low SSCs and 

high streamflows from the upper Mississippi and St. Croix 

Rivers helped dilute the high SSCs entering the Mississippi River from the Minnesota River and Mississippi River 

upstream from the St. Croix River, respectively. Decreases 

in stream gradients corresponded to decreases in SSCs in the 

Mississippi River from St. Paul to Red Wing and from Red 

Wing to the outlet of Lake Pepin. Decreases in stream gradients and SSCs likely relate to the presence of locks, dams, and 

lakes between sampling sites.

Results from statistically significant linear relations indicated that acoustic backscatter data were useful for improving 

estimates of SSCs for five of the nine study sites: the Minnesota River at (1) Mankato, (2) St. Peter, (3) Jordan, and (4) Ft. 

Snelling and the Mississippi River at (5) St. Paul. A significant 

linear relation could not be developed for Judson because of 

data quality issues caused by the ADVM; however, the linear 

relation between streamflow and SSC was significant and 

useful in estimating annual SSLs. For sites that used acoustic 

backscatter data as an explanatory variable in the linear regression model, the linear relations consistently explained more 

variability than streamflow alone. Significant linear relations 

could not be developed to estimate SSC from acoustic backscatter data or streamflow for Prescott, Red Wing, or Pepin, 

presumably because of consistently low SSCs regardless of 

acoustic backscatter or streamflow magnitudes.

Relations between streamflows and physically collected 

sediment samples traditionally have been used to estimated 

suspended-sediment loads; however, continuous estimated 

SSC data illustrated that changes in SSCs often did not track 

with changes in streamflows at study sites. Furthermore, time 

series comparisons illustrated how duration, time, and extent 

of SSCs can change from site to site and from year to year. 

Daily SSLs were highest at all sites from March through 

November, and results indicated a peak sediment loading 

event at many of the sites in the fall of 2016. Finally, estimated 

SSCs peaked before observed streamflow peaks at many sites.

Comparing annual SSLs helped to determine possible 

sediment sources and sinks. Substantial differences were 

observed between sites that have tributaries entering the 

river between them; for example, Mankato had higher SSLs 

than Judson because of the Blue Earth River flowing into the 

Minnesota River upstream from the Mankato site. Also, the 

decrease in SSLs from Ft. Snelling to St. Paul was due to the 

clearer upper Mississippi River water mixing with and diluting 

the higher SSL at St. Paul and backwater from the Mississippi 

River. The second largest decrease in SSL was from St. Paul 

to Red Wing, and then the largest difference from Red Wing 

to Lake Pepin illustrates the largest sediment sink with a 

90-percent decrease. These sinks along the Mississippi River

are likely linked to storage in pools along the lock and dam

system and Lake Pepin. The sediment yield patterns among

the nine sites were similar to the annual SSLs. The outlet of

the Minnesota River contributed more SSL than the outlets of

Lake St. Croix and Lake Pepin.

This study provides data from which to characterize suspended sediment across the lower Minnesota River, St. Croix 

River, and Mississippi River Basins. The analyses discussed 

in this report will improve the understanding of sedimenttransport relations and sediment budgets. These data provide 

a baseline that can be used in understanding future changes in 

climate, land use, restoration, and best management practices 

that may affect sediment dynamics in the lower Minnesota 

River, St. Croix River, and Mississippi River Basins.

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test methods for determining sediment concentration in 

water samples: West Conshohocken, Pa., American Society 

for Testing and Materials International, D3977–97, v. 11.02, 

Water (II), p. 395–400.

Belmont, P., Gran, K.B., Schottler, S.P., Wilcock, P.R., Day, 

S.S., Jennings, C., Lauer, J.W., Viparelli, E., Willenbring,

J.K., Engstrom, D.R., and Parker, G., 2011, Large shift

in source of fine sediment in the upper Mississippi River:

Environmental Science & Technology, v. 45, no. 20, p.

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Blumentritt, D.J., Wright, H.E., Jr., and Stefanova, V., 2009, 

Formation and early history of Lakes Pepin and St. Croix 

of the upper Mississippi River: Journal of Paleolimnology, v. 41, no. 4, p. 545–562. [Also available at https://doi.

org/10.1007/s10933-008-9291-6.]
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accessed June 14, 2018, at https://www.cocorahs.org/ViewData/StateDailyPrecipReports.aspx?state=MN.

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measurement of fluvial sediment: U.S. Geological Survey 

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rivers in Minnesota, 2007 through 2011: U.S. Geological 

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the upper Mississippi River—Mass-balance reconstructions 

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surrogate measurements, and annual sediment loads for 

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For more information about this publication, contact:

Director, USGS Upper Midwest Water Science Center 

2280 Woodale Drive

Mounds View, MN 55112

763–783–3100

For additional information, visit: https://mn.water.usgs.gov

Publishing support provided by the 

Rolla Publishing Service Center

Groten and others—Acoustic Doppler Velocity Meters to Estimate Suspended Sediment along the Lower Minnesota and Mississippi Rivers—SIR 2018–5165

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20185165