U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2011–5200

National Water-Quality Assessment Program

Trends in Suspended-Sediment Loads and 

Concentrations in the Mississippi River Basin, 

1950–2009
Cover photograph: U.S. Army Corps of Engineers Digital Visual Library (http://eportal.usace.army.mil/sites/DVL/default.aspx).
Trends in Suspended-Sediment Loads and 

Concentrations in the Mississippi River 

Basin, 1950–2009

By David C. Heimann, Lori A. Sprague, and Dale W. Blevins

National Water-Quality Assessment Program

Scientific Investigations Report 2011–5200

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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Suggested citation:

Heimann, D.C., Sprague, L.A., and Blevins, D.W., 2011, Trends in suspended-sediment loads and concentrations in the 

Mississippi River Basin, 1950–2009: U.S. Geological Survey Scientific Investigations Report 2011–5200, 33 p.
iii

Contents

Acronyms ........................................................................................................................................................v

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

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

Study Methods ...............................................................................................................................................4

Station Selection...................................................................................................................................4

Determination of Annual Suspended-Sediment Loads ..................................................................5

Trend Analyses......................................................................................................................................7

Step Trends ...................................................................................................................................7

Monotonic Trends and Qualitative Temporal Variations in Suspended-Sediment 

Loads, Concentrations, and Streamflow ....................................................................8

Suspended-Sediment Trends in the Mississippi River Basin.................................................................8

Relative Sediment Contributions from Mississippi River Subbasins ...........................................8

Step Trends ............................................................................................................................................9

Monotonic Trends and Qualitative Temporal Relations ...............................................................12

Suspended Sediment 1950–2009.............................................................................................12

Suspended Sand 1950–2004.....................................................................................................17

Suspended Sediment 1976–2009.............................................................................................19

Suspended Sand 1976–2004.....................................................................................................19

Suspended Sediment 1998–2009.............................................................................................27

Summary........................................................................................................................................................29

References Cited..........................................................................................................................................30

Figures

1. Map showing Mississippi River Basin, major subbasins, and U.S. Geological Survey 

streamgaging and sediment stations included in study.........................................................3

2. Graph showing annual suspended-sediment loads of the Missouri, Ohio, upper 

Mississippi, and Arkansas Rivers, 1976–2009..........................................................................9

3. Maps and graphs showing summary of trends in annual suspended-sediment loads, 

flow-weighted concentrations, and streamflows at selected U.S. Geological Survey 

streamgaging stations in the Mississippi River Basin, 1950–2009 .....................................13

4. Graphs showing summary of temporal variations in flow-adjusted concentrations for 

selected U.S. Geological Survey streamgaging stations in the Mississippi River 

Basin, 1950–2009.........................................................................................................................16

5. Graphs showing summary of temporal variations in annual suspended-sand loads 

and annual sand as a percentage of total suspended-sediment loads, 1950–2004. .......18

 6. Graphs showing summary of temporal variations in flow-adjusted sand concentrations, 1950–2004 and 1976–2004 ...............................................................................................20

7. Maps and graphs showing summary of trends in annual suspended-sediment loads, 

flow-weighted concentrations, and streamflows at selected U.S. Geological Survey 

streamgaging stations in the Mississippi River Basin, 1976–2009 .....................................21

8. Map and graphs showing summary of temporal variations in flow-adjusted sediment 

concentrations for selected U.S. Geological Survey streamgaging stations in the 

Mississippi River Basin, 1976–2009 .........................................................................................24
iv

9. Maps and graphs showing summary of trends in annual suspended-sediment loads, 

flow-weighted concentrations, and streamflows at selected U.S. Geological Survey 

streamgaging stations in the Mississippi River Basin, 1998–2009 .....................................26

10. Map and graphs showing summary of temporal variations in flow-adjusted sediment 

concentrations for selected U.S. Geological Survey streamgaging stations in the 

Mississippi River Basin, 1998–2009 .........................................................................................27

Tables

1. Main-stem reservoirs of the upper Missouri River Basin......................................................2

2. U.S. Geological Survey streamgaging stations in the Mississippi River Basin used in 

study................................................................................................................................................6

3. Summary of contributions of suspended-sediment load from gaged tributaries to 

major subbasins of the lower Mississippi River Basin.........................................................10

4. Median annual suspended-sand loads at selected Missouri River Basin streamgaging stations, 1981–91............................................................................................................11

5. Summary of step-trend analyses of suspended-sediment characteristics and streamflows for pre- (pre-1953) and post-Missouri River main-stem impoundment (post-1967) 

periods at selected Missouri River and lower Mississippi River Basin stations.............14

6. Summary of analyses of monotonic trends in annual suspended-sediment loads, flow 

weighted concentrations, and streamflows between 1950 and 2009 at selected 

Mississippi River Basin streamgaging stations.....................................................................15

7. Summary of analyses of monotonic trends in annual suspended-sand loads, flowweighted suspended-sand concentrations, and sand load as a percentage of total 

suspended-sediment load between 1950 and 2004 at selected Missouri River and 

lower Mississippi River Basin stations ...................................................................................17

8. Summary of analyses of monotonic trends in annual suspended-sediment loads, flowweighted concentrations, and streamflows between 1976 and 2009 at selected 

Mississippi River Basin streamgaging stations.....................................................................22

9. Summary of analyses of monotonic trends in annual suspended-sand loads, flowweighted suspended-sand concentrations, and suspended-sand load as a percentage 

of total suspended-sediment loads between 1976 and 2004 at selected Missouri 

River and lower Mississippi River Basin stations .................................................................25

10. Summary of analyses of monotonic trends in annual suspended-sediment loads, flowweighted suspended-sediment concentrations, and streamflows between 1998 and 

2009 at selected Mississippi River Basin streamgaging stations.......................................26
v

Conversion Factors

 SI to Inch/Pound

Multiply By To obtain

Length

millimeter (mm) 0.03937 inch (in.)

kilometer (km) 0.62137 mile (mi)

Area

square kilometer (km2) 0.38610 square mile (mi2)

hectare-meter (ha-m) 8.1071 acre-feet (ac-ft)

Volume

liter (L) 0.26417 gallon (gal)

Flow rate

cubic meter per second (m3/s) 35.3147 cubic feet per second (ft3/s)

Mass

metric ton (t) 1.10231 ton, short (2,000 lb)

Acronyms

FA SSC flow-adjusted suspended-sediment concentration (the positive and negative 

residuals of a linear regression model constructed from streamflow and 

suspended-sediment concentration data pairs, expressed in milligrams per liter)

FA SSDC flow-adjusted suspended-sand concentration (the positive and negative 

residuals of a linear regression model constructed from streamflow and 

suspended-sand concentration data pairs, expressed in milligrams per liter)

FW SCC flow-weighted suspended-sediment concentration (computed as the daily 

suspended-sediment load divided by the corresponding daily mean streamflow)

FW SSDC flow-weighted suspended-sand concentration (computed as the daily 

suspended-sand load divided by the corresponding daily mean streamflow)

SSC suspended-sediment concentration

SSDC suspended-sand concentration

SSDL suspended-sand loads

SSL suspended-sediment loads

Abstract

Trends in loads and concentrations of suspended sediment and suspended sand generally were downward for stations within the Mississippi River Basin during the 60-, 34-, 

and 12-year periods analyzed. Sediment transport in the lower 

Mississippi River has historically been, and continues to be, 

most closely correlative to sediment contributions from the 

Missouri River, which generally carried the largest annual 

suspended-sediment load of the major Mississippi River subbasins. The closure of Fort Randall Dam in the upper Missouri 

River in 1952 was the single largest event in the recorded 

historical decline of suspended-sediment loads in the Mississippi River Basin. Impoundments on tributaries and sediment 

reductions as a result of implementation of agricultural conservation practices throughout the basin likely account for much 

of the remaining Mississippi River sediment transport decline. 

Scour of the main-stem channel downstream from the upper 

Missouri River impoundments is likely the largest source 

of suspended sand in the lower Missouri River. The Ohio 

River was second to the Missouri River in terms of sediment 

contributions, followed by the upper Mississippi and Arkansas 

Rivers. Declines in sediment loads and concentrations continued through the most recent analysis period (1998–2009) at 

available Mississippi River Basin stations. Analyses of flowadjusted concentrations of suspended sediment indicate the 

recent downward temporal changes generally can be explained 

by corresponding decreases in streamflows. 

Introduction 

Suspended-sediment concentrations (SSCs) were first 

recorded in the Mississippi River Basin in 1804 along the 

Missouri River by William Clark during the Lewis and Clark 

Expedition (Moulton, 1986; Blevins, 2006), and in 1838 near 

the mouth of the Mississippi River by Andrew Talcott (U.S. 

Army Corp of Engineers, 1930; Keown and others, 1981). 

Monitoring of sediment transport within the Mississippi River 

Basin has continued through the present day (2011), which 

has led to an increasingly better understanding of its role and 

importance in the geomorphic and ecological integrity of the 

river channels and riparian resources throughout the basin. 

Present-day suspended-sediment loads (SSLs) of the Mississippi River delivered to the Gulf of Mexico are about onehalf of the pre-1950s loads (Tuttle and Comb, 1981; Keown 

and others, 1986; Meade and Parker, 1985; Meade, 1995). 

This reduced Mississippi River sediment transport has been 

attributed to impoundments, implementation of soil conservation practices, and bank-stabilization efforts that have reduced 

contributions from the Missouri River Basin (Keown and 

others, 1981; Tuttle and Combe, 1981; Kesel, 1988; Meade 

and Moody, 2010), but other possible causes of the reductions 

include numerous engineering structures and channel modifications in the Mississippi River (Keown and others, 1981; 

Keown and others, 1986; Smith and Winkley, 1996; Biedenharn and others, 2000). 

Substantial State and Federal funds have been spent to 

address multiple concerns resulting from the reduced SSLs 

in the Missouri and Mississippi River Basins, yet funds also 

are spent to reduce soil erosion and limit contributions of 

sediment to the Missouri and Mississippi Rivers. Reductions 

in SSLs in the Missouri River have lead to bed degradation 

in long reaches of the lower part of the river, which, in turn, 

has had large economic effects owing from the necessary 

alterations of river structures, increased pumping costs for 

water requirements, and modifications to aggregate mining 

operations (United States Army Corp of Engineers, 2009a) 

along with adverse effects on aquatic and riparian habitat 

(U.S. Fish and Wildlife, 2003). Reduced sediment transport 

from the Mississippi River Basin is cited as a factor in the 

loss of coastal wetlands in Louisiana (Kesel, 1988, 1989; 

van Heerden and DeRouen, 1997). Sediment transport is an 

important factor in assessing opportunities and constraints of 

several large-scale ecosystem restoration programs within the 

Mississippi River Basin including the Louisiana Coastal Area 

Restoration Program (U.S. Army Corps of Engineers, Louisiana Coastal Area Restoration Program, accessed August 2010, 

http://www.lca.gov/.), Missouri River Recovery Program (U.S. 

Army Corps of Engineers, Missouri River Recovery Program, 

accessed November 2010, http://www.moriverrecovery.org/

mrrp/f?p=136:1:1186003470123021), and Upper Mississippi River Environmental Management Program (U.S. Army 

Corps of Engineers, Upper Mississippi River Environmental 

Trends in Suspended-Sediment Loads and Concentrations 

in the Mississippi River Basin, 1950–2009

By David C. Heimann, Lori A. Sprague, and Dale W. Blevins
2 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Management Program, accessed November 2010, http://www.

mvp.usace.army.mil/environment/default.asp?pageid=74). At 

the same time, sediment transport is closely associated with 

nutrient transport and the reduction of nutrient transport in the 

Mississippi River Basin to mitigate hypoxia (dissolved oxygen 

reductions) in the northern Gulf of Mexico is an objective of 

current State and Federal programs, including the Mississippi 

River Basin Healthy Watersheds Initiative (National Resources 

Conservation Service, Mississippi River Basin Healthy Watersheds Initiative, accessed November 12, 2010, http://www.

nrcs.usda.gov/wps/portal/nrcs/detailfull/national/programs/

farmbill/initiatives/?&cid=nrcsdev11_024120). Quantifying 

sediment and nutrient transport is a means of assessing the 

effectiveness of erosion control and conservation practices 

at multiple scales. Therefore, information on the spatial and 

temporal variability in the quantity of sediment transport at 

locations throughout the Mississippi River Basin is necessary 

to assess the feasibility of management alternatives of multiple 

local, State, and Federal interests. 

Concerns related to sediment transport in the Mississippi 

River Basin and the need for an assessment of that transport 

prompted a study, as described in this report, of the changes in 

SSLs and SSCs at selected stations throughout the Mississippi 

River Basin and analyses of the relative contributions of sediment from the major subbasins. The Mississippi River Basin 

(fig. 1) is the largest river basin in the United States (U.S.) 

[3.21 million square kilometers (km2)] draining 41 percent of 

the conterminous United States. The Mississippi River transports more sediment than any other river in North America 

(Meade and others, 1990). The river extends 3,700 km from 

its headwaters in northern Minnesota to the mouth at the Gulf 

of Mexico. The upper Mississippi River main stem (upstream 

from the junction of the Mississippi River with the Ohio River 

near Cairo, Illinois) has been substantially altered by the construction of 29 navigation locks and dams between Minneapolis, Minnesota and Saint Louis, Missouri, most of which were 

completed during the 1930s (O’Brien and others, 1992; Knox, 

2007). A primary tributary to the upper Mississippi River, the 

Illinois River/Illinois Waterway, has eight locks and dams that 

were constructed by 1933 between Chicago and the junction 

of the Illinois River with the Mississippi River at Grafton, 

Illinois (West Consultants Inc., 2000). 

The lower Mississippi River was modified by bank stabilization, levees, meander cutoffs, and channel constrictions 

between 1930 and 1955 (Smith and Winkley, 1996). About 

58 percent of the total Mississippi River Basin is regulated by 

hundreds of reservoirs (Tuttle and Combe, 1981). In 1963, the 

U.S. Army Corps of Engineers (USACE) completed a flowcontrol structure on the lower Mississippi River that controls 

flows between the Mississippi River and the Atchafalaya 

River through the Old River Outflow Channel (Mossa, 1996). 

The diversion maintains the flow in the Atchafalaya River at 

about 30 percent of the combined Mississippi and Red River 

flows. Total sediment transport from the Mississippi River 

Basin is, therefore, measured as the combined SSLs of the 

Mississippi and Atchafalaya Rivers. 

Major tributaries to the lower Mississippi River include 

the Missouri (44.6 percent of contributing area), upper Mississippi (16.5 percent), Arkansas (15.4 percent), and Ohio 

(15.2 percent) Rivers (Knox, 2007). The lower Mississippi 

River receives a disproportionately large influx of sediment 

from the Missouri River and a disproportionately large contribution of its flow from the Ohio River (Meade, 1995; Knox, 

2007).

The Missouri River Basin is the largest tributary to the 

Mississippi River Basin and the second largest river basin in 

the United States draining about one-sixth of the conterminous 

United States (1.37 million km2). The Missouri River is 

3,770 km long from its headwaters in western Montana to its 

mouth at Saint Louis, Missouri, which also makes it the longest river in the United States. Bank stabilization and channel 

modifications to the Missouri River, associated with the Bank 

Stabilization and Navigation Project (BSNP), began in earnest 

in the 1930s and continued through the 1980s (U.S. Army 

Corp of Engineers, 2009a). Six major impoundments that 

regulate the flow from 53 percent of the basin area upstream 

from Saint Louis, Missouri also were constructed in the upper 

Missouri River (upstream from Yankton, South Dakota) 

between the beginning of construction in 1933 and the filling 

of the last impoundment in 1966 (table 1). These engineered 

modifications, along with land-use changes including changes 

in agricultural practices, and other engineered structures in 

the lower Mississippi River (meander cutoffs, river-training 

structures, bank revetments) have resulted in a reported 70 

percent decline in sediment transported by the Missouri River 

to the Mississippi River (Meade and Moody, 2010) since the 

early 1950s. 

The principal tributaries to the Missouri River include the 

Yellowstone, Platte (Nebraska), and Kansas Rivers. The Yellowstone River, the largest tributary to the Missouri in terms 

Table 1. Main-stem reservoirs of the upper Missouri River Basin.

[Table modified from National Research Council, 2011]

Reservoir Dam Year started Year closed Year

completed

Storage

(hectare meter)

Fort Peck Fort Peck 1933 1937 1940 1,210,000

Sakakawea Garrison 1946 1953 1954 2,840,000

Oahe Oahe 1948 1958 1962 2,900,000

Sharpe Big Bend 1959 1963 1966 234,000

Francis Case Fort Randall 1946 1952 1953 678,000

Lewis and Clark Gavins Point 1952 1955 1957 60,700
Introduction 3

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MISSOURI RIVER BASIN

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29

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Base Map from USGS Digital Data, 1:2,000,000, 1990Albers Equal-Area Conic projection

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EXPLANATION

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Mississippi River Basin and Major Subbasins

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Figure 1. Mississippi River Basin, major subbasins, and U.S. Geological Survey streamgaging and sediment stations included in study.
4 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

of discharge (Missouri Basin Inter-Agency Committee, 1969), 

with a drainage area of 182,000 km2, flows through Wyoming 

and Montana before it joins the Missouri River in western 

North Dakota. The lack of reservoirs on the Yellowstone River 

main stem makes it one of the longest free-flowing rivers in 

the United States. Hundreds of small impoundments, however, 

have been built on major tributaries (Zelt and others, 1999) of 

the Yellowstone River that were constructed for water supply, 

recreation, energy production, and flood control purposes. The 

Platte River originates in Colorado and Wyoming and flows 

eastward through Nebraska draining 230,000 km2 (Galat and 

others, 2005). Beginning in the early 1900s, many impoundments were built on the North and South Platte Rivers for 

public supply and irrigation. The Kansas River Basin is about 

159,000 km2 and drains parts of Colorado, Nebraska, and 

Kansas. Eighteen Federal reservoirs have been constructed in 

the Kansas River Basin beginning in 1946, with 7 of the 18 

completed by 1953. Present-day impoundments on the major 

tributaries of the Kansas River and regulate about 85 percent 

of the flow from the basin (Perry, 1994).

The Arkansas River, the third largest tributary to the Mississippi River, drains an area of 505,000 km2

. Reservoir and 

flood control projects on the Arkansas began in the late 1930s 

and modifications continued with the construction of 18 

navigation locks and dams in the McClellan-Kerr Arkansas 

River Navigation System between 1967 and 2004 (17 of 

18 were complete by 1970; The Encyclopedia of Arkansas History and Culture, McClellan-Kerr Arkansas River 

Navigation System (MKARNS) accessed June 2010, http://

encyclopediaofarkansas.net/encyclopedia/entry-detail.

aspx?entryID=2309). More than 40 large reservoirs were constructed between 1936 and the late 1960s within the Arkansas 

River Basin in Colorado, Kansas, Oklahoma, and Arkansas. 

Most of the major reservoirs on the lower Arkansas River 

in Oklahoma that reinforce the McClellan–Kerr Navigation 

System were completed by 1964. 

The Ohio River is formed at the junction of the Allegheny and Monongahela Rivers at Pittsburgh, Pennsylvania, and 

is 1,580 km long to its mouth at the Mississippi River near 

Cairo, Illinois. The Ohio River Basin is the smallest of the four 

major lower Mississippi River contributing subbasins in terms 

of area, 490,000 km2, but the largest in terms of contributing 

flow volume (Knox, 2007). A concrete lock and dam system 

for navigation has been in place on the Ohio River since the 

1950s (Meade, 2004), and currently (2010) there are 21 locks 

and dams. Eighty-three reservoirs, about 95 major local floodprotection projects, and numerous small flood-control projects 

have been built on tributaries in the basin. Construction of the 

reservoirs and flood-control projects began in the late 1930s 

and most were completed by the 1950s (U.S. Army Corp of 

Engineers, 2009b). 

The Tennessee River is the largest tributary of the Ohio 

River with a basin area of 106,000 km2 (White and others, 

2005). The river is regulated by numerous impoundments 

including nine main-stem dams operated by the Tennessee 

Valley Authority that were completed between 1913 and 1967, 

although most were completed by the mid-1940s. 

The Wabash River is the second largest tributary to the 

Ohio River (85,340 km2), and whereas the upper 103 km has 

been regulated by a Corps of Engineers reservoir since 1968, 

the lower 661 km is the longest stretch of free-flowing river 

east of the Mississippi River (Karns and others, 2006). Despite 

the free-flowing status of the lower Wabash River main stem, 

Pyron and Neumann (2008) note that the hydrology of the 

river has been substantially altered by the construction of 

reservoirs and by land-cover changes within the basin during 

the past century.

Assessments of changes in water-quality constituents 

over time are a primary goal of the U.S. Geological Survey’s 

(USGS) National Water-Quality Assessment (NAWQA) 

program (Gilliom and others, 2001). Previous studies have 

documented analyses of suspended-sediment trends in the 

Missouri (Sprague and others, 2006), upper Mississippi and 

Ohio (Lorenz and others, 2009), Tennessee (Hoos and others, 

2000) and lower Mississippi and Atchafalaya Rivers (Rebich 

and Demcheck, 2007) for various periods between 1974 and 

2004. Horowitz (2010) also examined trends in SSLs and 

flow-weighted (FW) SSCs at selected USGS streamgaging stations in the Mississippi River Basin for the 1981–2007 period. 

The primary objective of the study described here, and 

the purpose of this report is to augment existing information by computing the relative sediment contributions from 

Mississippi River subbasins and determine temporal trends in 

streamflow, suspended sediment loads and concentrations at 

multiple Mississippi River main-stem and tributary stations, 

and for multiple time scales. The sediment contributions and 

trends in sediment contributions from subbasins could then 

be used to determine which tributaries, subbasins, or regions 

affect recent suspended-sediment trends near the mouth of 

the Mississippi River and in large receiving rivers such as the 

Missouri.

Study Methods

Station Selection

Station selection began with an assessment of published 

SSLs or SSCs and daily streamflow data at USGS streamgaging stations within the major subbasins of the Mississippi 

River Basin. The USGS National Water Information System (NWIS) database (http://waterdata.usgs.gov/nwis) was 

searched for main-stem and primary tributary stream stations 

with a drainage area of at least 2,500 km2 and for which daily 

sediment loads or discrete sediment concentrations and concurrent daily streamflow record of at least 10 years were available. Further selection criteria for those stations with sediment 

loads that were not already determined included selecting 

stations with SSC and suspended-sand concentration (SSDC) 

samples distributed throughout the water year (Oct. 1 to 
Study Methods 5

Sept. 30) and over the range of observed streamflows. At a 

minimum, the most downstream station with adequate suspended-sediment record from each major subbasin of the Mississippi River Basin (fig. 1) was selected for trend analyses. 

Impoundments on the upper main stem of the Missouri 

River have had a substantial effect on sediment transport in 

the lower Missouri and Mississippi River downstream from 

Saint Louis, Missouri. To conduct step-trend analyses to assess 

changes in sediment transport in main-stem and tributary 

stations between pre- and post-impoundment periods, available stations with continuous or non-continuous sediment 

record spanning both periods were selected for analysis. As 

in previous studies (Keown and others, 1986; Jacobson and 

others, 2009) the pre-impoundment period in this study was 

defined as pre-1953—before the closure of the downstream 

Fort Randall Dam. The post-impoundment period was defined 

as post-1967—after the last completed reservoir, Lake Sharpe 

(impounded by Big Bend Dam), was filled.

Final station selection and trend analysis periods were 

determined by maximizing the number of stations within multiple, selected analysis periods based on record availability. 

Stations were selected from the Missouri, upper Mississippi, 

Ohio, Arkansas, lower Mississippi, and Atchafalaya River 

Basins as shown in figure 1 and table 2 for trend analysis 

periods encompassing the last 60 years (1950–2009), the last 

34 years (1976–2009), and the last 12 years (1998–2009) 

of available record. The multiple time periods used in trend 

analysis also provide a long-term context within which to view 

the more recent changes in streamflows and in the concentrations and loads of suspended sediment.

Determination of Annual Suspended-Sediment 

Loads

Annual SSLs and SSDLs described in this report refer to 

the suspended portion of transported sediment, and, therefore, 

do not include bedload. Bedload in large, low gradient rivers 

has been estimated to range from less than 5 percent (Holmes, 

1996; Nittrouer and others, 2008) to 8 percent (Gaeuman and 

Jacobson, 2007) of the total sediment load. 

The data for annual SSLs and suspended-sand loads 

(SSDLs) used in the analyses were obtained from preexisting 

USGS and USACE published or unpublished daily or annual 

loads, or were calculated specifically for this study using 

concentration and daily streamflow data. Sources of sediment load, sediment concentration, and streamflow data used 

in this study are provided by Heimann and others (2010) and 

Heimann and others (2011). Annual SSL and SSDL values 

were computed for this study using the LOADEST program 

and technique (Runkel and others, 2004). The S-LOADEST 

version of the program, written for the commercial statistical 

package TIBCO Spotfire S+ (TIBCO Software Inc., version 

8.1), was used to compute load estimates as described by Heimann and others (2010). LOADEST incorporates explanatory 

variables of streamflow (a linear or quadratic relation), time 

(a linear or quadratic relation), and season into one of nine 

predefined regression models.

The analysis of trends in annual loads (and corresponding annual flow-weighted concentrations) can be problematic 

when the loads are estimated from a single model. In such 

situations, the estimated loads are not independent from one 

another and are likely to be less variable over time than the 

actual loads. As a result, the probability of a Type I error 

(false positive) in the subsequent test for trend is inflated (the 

probability of detecting a trend is inflated). In this study, a 

moving-window approach was used in the estimation of the 

annual LOADEST sediment loads to address these two issues. 

The load model for a given year was developed using 3, 5, or 

7 years (determined by data availability) of suspended-sediment or suspended-sand concentration data centered about the 

computation year. For example, assuming a 3-year window, 

the model for the load estimate for 1975 used calibration data 

from 1974–1976; the model for the 1976 estimate used calibration data from 1975–1977; the model for the 1977 estimate 

used calibration data from 1976–1978; the model for the 1978 

estimate used calibration data from 1977–1979, and so forth. 

Only those load estimates derived from unique calibration 

data sets were used in the trend analyses. In this example, 

estimates from every third year (1975, 1978, and so forth) 

were included. The calibration data set used in the computation of each of the annual loads included in statistical analyses 

was unique; no calibration data point was used in more than 

one window. As a result, the loads used in the trend analysis 

all were independent from one another. The use of unique 

models for each window also allowed the model coefficients 

to change over time, thereby incorporating variability in the 

relation between load and streamflow and season over time. 

As a result, the loads used in the trend analysis also were more 

variable over time than if they had been derived from a single 

model with fixed coefficients. The moving-window approach 

likely only partially addressed the variability issue; because 

the loads are modeled estimates, some of the variability present in actual loads may still be missing. Because data used in 

the computation of annual loads by the tabular day-by-day 

method (U.S. Army Corp of Engineers, 1976; Porterfield, 

1977) and turbidity surrogate methods (Rasmussen and others, 

2009) were from the year of computation, all annual loads 

computed using these methods were included in the statistical 

analyses. 

To determine if trends in sediment loads could be affected 

by combining results from multiple sediment-load computation methods, annual loads within overlapping periods of 

published and calculated loads were compared. Computed 

(LOADEST) and published (day-by-day method) SSLs from 

seven stations with a total of 223 years of overlapping record 

were compared by station. When the same SSC data used in 

computing the published loads were used in the LOADEST 

computations, there were no statistically significant differences 

in the annual SSLs. The lack of significant difference was 

based on the Wilcoxon signed rank test (Helsel and Hirsch, 

2002) using a significance level of 0.05. The probability 
6 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Table 2. U.S. Geological Survey (USGS) streamgaging stations in the Mississippi River Basin used in study.

[km2, square kilometer]

Map

reference 

number 

(fig. 1)

USGS station name Period of available record Drainage area (km2) Trend 

analysesa 

Ohio River Basin

1 Muskingum River at McConnelsville, Ohio 1979–91 19,223 --

2 Ohio River at Greenup Dam near Greenup, 

Kentucky

1974–85, 1997–2007 160,579 D, F

3 Scioto River at Higby, Ohio 1954–74, 1979–93 13,289 --

4 Kentucky River at Lock 2 at Lockport, Kentucky 1974–94 16,000 --

5 Ohio River at Cannelton Dam at Cannelton, 

Indiana

1976–86,1996–2009 251,229 D

6 Green River at Munfordville, Kentucky 1952–94, 2004–08 4,333 D

7 White River at Hazleton, Indiana 1974–84,1991–2009 29,280 D

8 Wabash River at New Harmony, Indiana 1975–86, 1997–2008 75,716 D

9 Tennessee River at Highway 60 near Paducah, 

Kentucky

1974–86, 1997–2009 104,454 D

10 Ohio River at Dam 53 Near Grand Chain, Illinois1973–2009 526,027 D

Upper Mississippi River Basin

11 Minnesota River at Mankato, Minnesota 1968–2009 38,591 D, F

12 Wisconsin River at Muscoda, Wisconsin 1976–93 26,936 --

13 Mississippi River at Clinton, Iowa 1943–87, 1991–2009 221,703 D

14 Iowa River at Wapello, Iowa 1978–2009 32,375 D, F

15 Skunk River at Augusta, Iowa 1976–2009 11,168 D, F

16 Des Moines River near Saylorville, Iowa 1978–2004 15,128 --

17 Illinois River at Valley City, Illinois 1975–2009 69,264 D, F

18 Mississippi River below Grafton, Illinois 1975–2009 443,665 D, F

19 Mississippi River at Saint Louis, Missouri 1949–2009 1,805,222 A, B, D, F

20 Mississippi River at Chester, Illinois 1983–2009 1,835,266 F

21 Mississippi River at Thebes, Illinois 1983–2009 1,847,180 F

Missouri River Basin

22 Missouri River near Landusky, Montana 1949–51, 1959–62, 1964–65, 

1969, 1971–2006

106,156 A, B, D, F

23 Yellowstone River near Sidney, Montana 1948–2009 178,924 A, B, D

24 Little Missouri River near Watford, North 

Dakota

1948–76 21,522 A

25 Missouri River at Yankton, South Dakota 1940–59, 1961–68, 2001–08 723,902 A

26 James River near Scotland, South Dakota 1975–95 53,491 --

27 Big Sioux River at Akron, Iowa 1941–51, 1971–94 21,818 A

28 Missouri River at Sioux City, Iowa 1955–2000, 2004–09 814,810 D, F

29 Boyer River at Logan, Iowa 1940–51, 1969–74, 2004–09 2,256 A

30 Missouri River at Omaha, Nebraska 1940–2009 836,048 A, B, D, F

31 Platte River at Louisville, Nebraska 1940–51, 1953–71, 1973–

2009

221,107 A, B, D

32 Missouri River at Nebraska City, Nebraska 1958–2009 1,061,895 D, F

33 Nishnabotna River above Hamburg, Iowa 1940–51, 1982–93, 2004–09 7,268 A
Study Methods 7

values of the comparison tests (0.07–1.0) exceeded the significance level of 0.05 indicating that the chances the differences 

between the distributions were not true were greater than the 

specified significance level. Therefore, the LOADEST moving 

window approach allowed for the use of independent, annual 

SSL estimates in determining trends in loads and produced 

annual loads that were statistically comparable to previously 

published values. 

Trend Analyses

Temporal changes in streamflow and suspended-sediment 

loads and concentrations were assessed using statistical 

analyses of step trends (test to determine if median differences 

between data values for two time periods are significantly 

different than zero), statistical analyses of monotonic trends 

(test to determine if the average rate of change of the data for 

a specified time period is significantly different than zero), and 

qualitative presentations of temporal relations. Such analyses provide an indication of the magnitude and direction of 

changes in sediment transport characteristics and streamflows 

at specific stations that, when taken collectively, can explain 

net changes in transport on a basin scale.

Step Trends 

Step-trend analyses were conducted on the annual SSL, 

flow-weighted (FW) SSC (the ratio of the annual sediment 

load and annual streamflow, expressed in milligrams per liter), 

and streamflow data to identify and evaluate the effects of the 

Missouri River Basin—Continued

34 Nodaway River at Clarinda, Iowa 1970–74, 1976–92 1,974 --

35 Missouri River at Saint Joseph, Missouri 1949–2009 1,104,630 A, B, C, D, E, F

36 Platte River at Sharps Station, Missouri 1980–92 6,164 --

37 Kansas River at DeSoto, Kansas 1949–74, 1976–91, 2000–05 154,767 A

38 Missouri River at Kansas City, Missouri 1949–81, 1988–2009 1,253,813 A, B, C, D, E

39 Grand River near Sumner, Missouri 1974–93 17,819 --

40 Chariton River near Prairie Hill, Missouri 1978–86 4,843 --

41 Osage River below Saint Thomas, Missouri 1975–94 37,772 --

42 Gasconade River at Jerome, Missouri 1978–92 7,356 --

43 Missouri River at Hermann, Missouri 1949–2009 1,353,269 A, B, C, D, E, F

Arkansas River Basin

44 Arkansas River at Tulsa, Oklahoma 1950–95 193,252 B

45 Arkansas River at David D. Terry Lock and Dam 

below Little Rock, Arkansas 

1941–2009 410,329 B, D

Lower Mississippi River Basin

46 Mississippi River at Tarbert Landing, Mississippi1950–2009 2,913,478 A, B, D, F

47 Old River Outflow Channel near Knox Landing, 

Louisiana

1966–2009 Indeterminate D, F

48 Atchafalaya River at Simmesport, Louisiana 1952–2009 226,805b B, D, F

a

Analysis Categories:

A – Step trends in suspended sediment and suspended sand, pre-1953 and post-1967 periods

B – Trends in suspended sediment, 1950–2009

C – Trends in suspended sand, 1950–2004

D – Trends in suspended sediment, 1976–2009

E – Trends in suspended sand, 1975–2004

F – Trends in suspended sediment 1998–2009

b

Drainage area does not include that area apportioned to the river based on the fraction of streamflow diverted from the Mississippi River main stem.

Table 2. U.S. Geological Survey (USGS) streamgaging stations in the Mississippi River Basin used in study.—Continued

[km2, square kilometer]

Map

reference 

number 

(fig. 1)

USGS station name Short name

 Period of 

available

record

Drainage

area

(km2)

Trend 

analysesa
8 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

construction of main-stem Missouri River impoundments and 

other land-use and channel modifications in the Missouri River 

Basin, on suspended-sediment transport characteristics at 

selected stations in the Missouri and lower Mississippi Rivers. 

A step-trend approach was selected because the impoundment 

completion dates were well defined (table 1) and spanned a 

relatively short time period. Similar step-trend analyses were 

not made with data for the remaining major subbasins of the 

Mississippi River Basin because the sediment-altering event 

was not well defined, available pre-event sediment data were 

limited, or the sediment-altering event predated the available 

sediment record entirely. The step trends in SSLs, FW SSCs, 

and streamflows were determined for the periods corresponding to pre- and post-Missouri River main-stem impoundment 

construction. The statistical comparison of the sediment and 

streamflow data for the pre- and post-impoundment periods 

was conducted using a Wilcoxon Rank Sum test at a significance level of 0.05. Whereas the Missouri River impoundments would directly affect only the Missouri and downstream 

Mississippi River main-stem stations, Missouri River tributary stations with available record also were included in the 

step-trend analyses to assess the occurrence and magnitude of 

secondary factors (for example, tributary impoundments or 

implementation of conservation practices) on sediment transport during the analysis periods. 

Monotonic Trends and Qualitative Temporal 

Variations in Suspended-Sediment Loads, 

Concentrations, and Streamflow

Monotonic trends (increases or decreases without reversals) in SSL, FW SSC, and streamflow data were determined 

for selected stations and for three trend periods—1950–2009, 

1976–2009, and 1998–2009— using the Mann-Kendall test 

(Mann, 1945; Kendall, 1975) at a significance level of 0.05 

and Sen slope estimates (Sen, 1968) within the TIBCO Spotfire S+ (TIBCO Software Inc., version 8.1) statistical package. 

The computed Kendall rank correlation coefficients (Kendall’s 

tau) range from 1 to -1 with a value of 1 indicating the ranking 

of the two variables are the same, a value of -1 indicating the 

rankings are the reverse of each other, and a value of 0 indicating the absence of association. Only stations with a minimum 

of seven annual load, concentration, and streamflow values 

spanning the trend period were used in the analyses. 

Monotonic trends in SSDL, FW SSDC (the ratio of the 

annual sand load and annual streamflow, expressed in milligrams per liter), and SSDL percentage of SSL data were 

computed for three stations with available continuous sandfraction record including the Missouri River at Saint Joseph, at 

Kansas City, and at Hermann, Missouri. Trends were computed for two periods—1950–2004 and 1976–2004—using the 

Mann-Kendall test and Sen slope estimates. 

Qualitative temporal variations in annual SSL and SSDL 

and flow-adjusted (FA) SSC (the positive and negative residuals of SSC values, expressed in milligrams per liter, resulting 

from a linear regression model of observed streamflow and 

SSC pairs) and FA SSDC (the positive and negative residuals of SSDC, expressed in milligrams per liter, resulting from 

a linear regression model of observed streamflow and SSDC 

pairs) data also were assessed using locally estimated scatterplot smoothing (LOESS) curves (Cleveland and Devlin, 

1988). Qualitative temporal relations in FA concentrations 

were determined to evaluate the changes in SSC (for the 

1950–2009, 1976–2009, and 1998–2009 periods) and SSDCs 

(for the 1950–2004 and 1976–2004 periods) resulting from 

effects other than changes in flow. These effects were determined by calculating the residuals of streamflow–sediment 

concentration regression models developed using the observed 

streamflow and concentration data for the entire trend-analysis 

period at a station. A LOESS curve then was fit to the positive 

and negative residuals of the models to qualitatively assess 

changes in the FA concentrations with time. 

Suspended-Sediment Trends In The 

Mississippi River Basin

The relative sediment contributions from and within each 

major Mississippi River subbasin including the Missouri, 

Ohio, upper Mississippi and lower Mississippi River Basins 

were computed. The temporal trends and qualitative temporal 

relations in sediment characteristics and streamflow were then 

assessed at multiple selected stations and for multiple time 

periods. 

Relative Sediment Contributions from 

Mississippi River Subbasins

During the period 1976 through 2009, of the four primary 

contributing subbasins to the lower Mississippi River, the Missouri River provided the greatest median suspended-sediment 

load (56.9 Mt/yr (million metric tons per year)) followed by 

the Ohio (32.5 Mt/yr), upper Mississippi (22.5 Mt/yr), and 

Arkansas Rivers (2.4 Mt/yr). The Missouri River provided the 

largest annual SSLs during 26 of the 34 years analyzed and 

the Ohio River transported the largest annual SSLs during the 

remaining 8 years (fig. 2). The large sediment contributions of 

the Missouri River to the lower Mississippi River have been 

well documented (Keown and others, 1981; Meade and Parker, 

1985; Meade and others, 1990; Meade and Moody, 2010) and 

overall, sediment transport in the lower Mississippi River is 

most closely correlative with the contributions of suspended 

sediment from the Missouri River Basin.

Annual SSLs were computed for gaged tributary streams 

within the Missouri, Ohio, and upper Mississippi Basins to 

further determine major sediment-contributing sources within 

the subbasins. SSLs were computed for 12 primary Missouri 

River tributary stations for the period 1975–91. The Grand 

River near Sumner, Missouri had the largest median annual 
Suspended-Sediment Trends In The Mississippi River Basin 9

SSL (10.8 Mt) and the next largest sediment contributors were 

the Platte River at Louisville, Nebraska (9.6 Mt), and Yellowstone River at Sidney, Montana ( (9.0 Mt) (table 3). 

The median load from these tributary rivers represented 

14-16 percent of the 1975–91 median load of the Missouri River at Hermann, Missouri. Such comparisons are 

not meant to imply that all sediment transported from the 

tributary stations will pass the outlet station in a continuous 

manner because the sediment may be temporarily deposited 

or “trapped”, in this case, in intervening navigation dams, 

and sediment likely is transported episodically between the 

stations.

Data from six gaged Ohio River tributary stations were 

analyzed for sediment load contributions during the record 

period of 1979–86. The Wabash River, with a median annual 

load of 11.5 Mt, provided the largest sediment contribution 

to the Ohio River (table 3). The Wabash River accounted for 

about 23 percent of the sediment load of the Ohio River at 

Grand Chain, Illinois, whereas the next largest contributors 

(Tennessee and Muskingum Rivers) each accounted for about 

2 percent of the total Ohio River sediment load. 

Analyses of records of sediment contributions from 

five, gaged, upper Mississippi River tributary stations for the 

1978–93 period indicated that the Illinois River at Valley City, 

Illinois was the largest sediment contributor (table 3). The 

median annual sediment load of 5.9 Mt was about 22 percent 

of the upper Mississippi River Basin suspended-sediment load 

during the period. The Iowa River at Wapello, Iowa (2.9 Mt), 

and Skunk River at Augusta, Iowa (2.6 Mt), each accounted 

for more than 8 percent of the median annual SSL at the upper 

Mississippi River outlet station at Grafton, Illinois. 

All four major subbasins contributing sediment to the 

lower Mississippi River have main-stem and tributary structures that retard sediment transport and increase the relative 

contributions of sediment from tributaries downstream from 

primary channel control structures. Of the 22 gaged major tributary basins included in the sediment contribution analyses, 

15 were impounded by major structures on their main stems 

(table 3). 

The largest contributor of suspended sand to the lower 

Missouri River between 1981 and 1991 was estimated to 

be the main-stem reach from the Gavins Point Dam, South 

Dakota, to Sioux City, Iowa, followed by contributions from 

the Platte River in Nebraska (table 4). Much of the transported 

suspended sand in the Gavins Point to Sioux City reach likely 

is from scour of the main channel as the SSDL increased from 

near zero in Gavins Point Dam outflows (Paul Boyd, U.S. 

Army Corp of Engineers, personal commun., 2011) at Yankton, South Dakota, to 6.36 Mt/yr at Sioux City, Iowa (table 

4), about 122 km downstream, with little or no input from the 

small interim tributaries. SSDL estimates for the Platte River 

near Louisville, Nebraska, station were about 4.6 Mt/yr. The 

6.36 Mt/yr estimated SSDL from channel scour, along with the 

4.6 Mt/yr estimate contribution from the Platte River, alone 

account for about 50 percent of the 19.7 Mt/yr median SSDL 

at Hermann, Missouri. If additional potential diversions that 

substantially reduce flows take place in the Platte River (Sidle 

and Faanes, 1997) there likely will be a substantial reduction 

in SSDLs from this primary tributary. About 3.0 Mt/yr (on 

average) of sand were contributed to the Missouri River from 

tributaries between Kansas City and Hermann, Missouri, with 

the Grand River near Sumner, Missouri, and Chariton River 

near Prairie Hill, Missouri, stations having estimated median 

SSDLs in excess of 1.2 Mt/yr. 

The longitudinal gradient in Missouri River sand transport is evident in the results as the 1981–91 median sand load 

as a percentage of total load decreased from 62 percent at the 

Missouri River at Sioux City, Iowa, station to 25 percent at 

the Missouri River at Hermann, Missouri (table 4). Reported 

sand fractions of total loads during 1981–91 at the Mississippi 

River at Tarbert Landing, Mississippi, were 15 percent (U.S. 

Army Corp of Engineers, New Orleans District, unpub. data, 

1950–2006).

Step Trends

Results of step-trend analyses to examine changes in 

annual SSLs, SSDLs, FW SSCs, FW SSDCs, and streamflows between the pre-and post-Missouri River main-stem 

impoundment periods indicated decreases in SSLs and SSCs 

at most stations. Significant (Wilcoxon Rank Sum test, p 

<0.001–0.042) decreases in SSLs were determined at all stations except one Missouri River main-stem station upstream 

from the impoundments and one Missouri River tributary station (table 5). Differences in pre- and post-impoundment SSLs 

could not be explained simply by corresponding differences in 

flows as changes in flows between the two periods generally 

were not statistically different (table 5). 

The greatest difference in median SSLs between the two 

periods (-99.8 percent) was recorded at the Missouri River 

at Yankton, South Dakota, about 8 km downstream from 

Gavins Point Dam. The difference of about 126 Mt between 

0

20

40

60

80

100

120

140

160

180

Missouri River

Ohio River

Upper Mississippi River

Arkansas River

 Annual suspended-sediment load,

in millions of metric tons

Water year

1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009

EXPLANATION

Figure 2. Annual suspended-sediment loads of the Missouri, 

Ohio, upper Mississippi, and Arkansas Rivers, 1976–2009.
10 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Table 3. Summary of contributions of suspended-sediment loads from gaged tributaries to major subbasins of the lower Mississippi 

River Basin.

[SSL, suspended-sediment load; SSC, suspended-sediment concentration; mg/L, milligrams per liter; km2, square kilometer; m3/s, cubic meters per second]

USGS station name

Map

reference

number 

(fig. 1)

Medianannual SSL

(metric tons)

Percent of basin 

outlet gaging 

station sediment 

loada

Median annual 

flow-weighted 

SSC (mg/L)

Median-annual 

yield (metric 

tons/km2)

Median-annual 

streamflow 

(m3/s)

Ohio River Basin 1979–86

Muskingum River at McConnelsville, 

Ohio

1 986,000 2.2 124 51.3 263

Scioto River at Higby, Ohiob 3 935,000 1.9 216 70.4 140

Kentucky River at Lock 2 at Lockport, 

Kentuckyb

4 741,000 1.6 112 46.3 203

Green River at Munfordville, Kentuckyb6 486,000 1.1 188 112 81.5

Wabash River at New Harmony, 

Indianab

8 11,500,000 22.6 372 152 967

Tennessee River at Highway 60 near 

Paducah, Kentuckyb

9 1,140,000 2.1 19.0 10.9 1,850

Upper Mississippi River Basin 1978–93

Minnesota River at Mankato, Minnesota11 1,120,000 4.6 314 29.0 126

Wisconsin River at Muscoda, Wisconsinb12 294,000 1.4 43.3 10.9 271

Iowa River at Wapello, Iowab 14 2,890,000 8.2 285 89.3 296

Skunk River at Augusta, Iowab 15 2,580,000 8.8 909 231 99.0

Illinois River at Valley City, Illinoisb 17 5,910,000 22.2 317 85.3 765

Missouri River Basin 1975–91

Yellowstone River near Sidney, 

Montana

23 9,020,000 16.0 901 50.4 347

James River near Scotland, South 

Dakotab

26 36,800 .1 151 .69 7.72

Big Sioux River at Akron, Iowa 27 334,000 .6 390 15.3 22.5

Platte River at Louisville, Nebraskab 31 9,600,000 13.8 1,270 43.4 166

Nishnabotna River above Hamburg, 

Iowab

33 4,540,000 6.4 3,490 625 46.5

Nodaway River at Clarinda, Iowa 34 2,220,000 3.2 5,160 1,130 9.85

Platte River at Sharps Station, 

Missourib,d

36 1,480,000 2.2 1,710 239 34.8

Kansas River at DeSoto, Kansasb 37 5,970,000 11.7 1,160 38.6 180

Grand River near Sumner, Missouri 39 10,800,000 16.0 2,820 604 123

Chariton River near Prairie Hill, 

Missourib,e

40 2,690,000 4.0 1,820 555 67.9

Osage River below Saint Thomas, 

Missourib

41 583,000 1.0 66.8 15.4 328

Gasconade River at Jerome, Missouric 42 165,000 .2 65.9 22.5 81.6

a

Outlet gage for the Ohio River is the Ohio River at Grand Chain, Illinois; upper Mississippi River is the Mississippi River at Grafton, Illinois; and the 

Missouri River is the Missouri River at Hermann, Missouri.

b

Main-stem upstream from gaging station is controlled by at least one permanent impoundment.

c

1982–91 median.

d

1980–91 median.

e

1989–91 median.
Suspended-Sediment Trends In The Mississippi River Basin 11

the pre-1953 and post-1967 periods at this station provides a 

median annual estimate of sediment trapped by the upstream 

reservoirs. This represents about 56 percent of the 224 Mt 

post-impoundment median annual “deficit” at Hermann, Missouri. The remaining 98 Mt, or 44 percent, of the Hermann 

load reduction can be attributed to other factors including 

reductions in sediment from tributaries. Although the stations on the Missouri River near Landusky, Montana, and the 

Yellowstone River near Sydney, Montana, are upstream from 

the impoundments, the post-impoundment values of SSL and 

SSC at the stations showed reductions from pre-impoundment 

values of about 50 percent. The most likely cause for the 

reduction in sediment transport in these tributaries/reaches is 

trapping of sediment by impoundments as there is little (<8 

percent) cropland agriculture in these basins (Zelt and others, 

1999; U.S. Department of Agriculture, 2009). Similarly, the 

SSL values for the Kansas River at Desoto, Kansas, showed an 

89 percent reduction in SSLs between the two periods as 

Table 4. Median annual suspended-sand loads at selected Missouri River Basin streamgaging stations, 1981–91.

[--, not applicable]

USGS station name

Map 

reference 

number 

(fig. 1)

Median annual 

suspended-sand 

load 1981–91

Median annual interim loada

1981–91 (metric 

ton)

Median annual 

percent suspendedsand

Probable source of 

interim suspended-sand 

load contributions

Yellowstone River near Sidney, 

Montana

23 1,620,000 -- 16.0 --

Gavins Point Dam, South Dakota -- -- -- -- --

-- -- 6,360,000 -- Main-stem channel, 

James, Big Sioux 

Rivers

Missouri River at Sioux City, 

Iowa

28 6,360,000 -- 62.0

-- 2,260,000 -- Little Sioux, Boyer 

Rivers

Missouri River at Omaha, Nebraska

30 8,630,000 -- 55.3 --

Platte River at Louisville, Nebraska 31 4,590,000 -- -- --

-- -- --

Missouri River at Nebraska City, 

Nebraska

32 11,100,000 -- 48.1 --

-- -- 1,500,000 -- Nishnabotna, Nodaway 

Rivers

Missouri River at Saint Joseph, 

Missouri

35 11,000,000 -- 34.5 --

Platte River at Sharps Station, Missouri

36 160,000 -- 5.7 --

-- -- 870,000b -- Kansas River

Missouri River at Kansas City, 

Missouri

38 8,390,000b -- 32.2b --

Grand River near Sumner, Missouri 39 1,230,000 -- 15.5 --

Chariton River near Prairie Hill, 

Missouri

40 1,260,000c -- 40.2c --

Osage River below Saint Thomas, 

Missouri

41 154,000 -- 41.3 --

Gasconade River at Jerome, Missouri

42 36,400 -- 26.0 --

-- -- 2,970,000b -- --

Missouri River at Hermann, Missouri

43 19,700,000 -- 25.1 --

a

Median difference between main-stem stations (shown in bold).

b

1981, 1988–91 median.

c

1981–86 median.
12 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

11 major reservoirs were completed in this basin between 

1953 and 1967 (U.S. Army Corp of Engineers, 2009a). 

Records from only five tributaries to the lower Missouri River 

were sufficient to be included in the step-trend analysis, but 

the median reduction in SSLs from these tributaries alone was 

about 69 Mt/yr or 70 percent of the remaining 98 Mt/yr load 

reduction at Hermann, Missouri. About 47 percent of the post1967 SSL reduction of the lower Mississippi River (Mississippi River at Tarbert Landing, Mississippi, and the Atchafalaya River at Simmesport, Louisiana) could be accounted for 

by post-impoundment reductions from the Missouri River at 

Hermann, Missouri.

Post-impoundment Mississippi River SSDLs were significantly lower than pre-impoundment values at the Mississippi River at Tarbert Landing, Mississippi (table 5), although 

the decline in sand loads (-55 percent) and FW SSDCs 

(-55 percent) were not as great as the decline in SSLs 

(-73 percent) and FW SSCs (-65 percent). Declines in postimpoundment sand loads and concentration also were less than 

corresponding declines in total loads and concentrations at the 

Missouri River at Saint Joseph, Kansas City, and Hermann.

Corresponding differences in pre- and post-impoundment 

distributions of FW SSCs were significant at most stations, 

whereas differences in the distributions of streamflow were not 

significant at most stations (table 5). Decreases in median values of FW SSCs ranged from 29 to more than 99 percent, with 

the largest decline again at the Missouri River at the Yankton, 

South Dakota station. Changes in annual streamflows during 

these periods were significant at only 4 of the 15 stations listed 

in table 5. 

Monotonic Trends and Qualitative Temporal 

Relations

Monotonic trends and qualitative temporal relations were 

determined for suspended-sediment and streamflow data for 

the last 60 years of available record (1950–2009), 34 years 

(1976–2009) and 12 years (1998–2009). Similarly, monotonic 

trends and qualitative temporal relations for suspended-sand 

concentrations and loads were determined for the last 55 years 

of available record (1950–2004) and 29 years (1976–2004).

Suspended Sediment 1950–2009 

By 1950, some channel modifications or navigation structures already were in place, or in progress, in all major subbasins of the Mississippi River Basin, but most of the mainstem Missouri River impoundments and Arkansas River Basin 

navigation structures and reservoirs had yet to be constructed. 

Also, land-conservation practices were in place because of 

the passage of the Soil Conservation Act of 1935 (Steiner, 

1987). The 1950s and 1960s were a channel-modification 

period in the Missouri, Arkansas, and lower Mississippi 

Rivers. 

The results of the trend analyses of data for the period 

1950 through 2009 indicate that downward trends in SSLs 

and FW SSCs were widespread throughout the Missouri and 

lower Mississippi River Basin main-stem stations. There were 

significant (Mann-Kendall test; p <0.001–0.032) downward 

trends in SSLs and FW SSCs at most stations (fig. 3A, 3B,

table 6). Downward trends in SSLs were significant at all 

stations within the Missouri and lower Mississippi River subbasins but not at the representative stations within the upper 

Mississippi, Ohio, or Arkansas River subbasins. Cumulative 

reductions in sediment transport in the Missouri and lower 

Mississippi Rivers resulted in an overall reduction of about 

-1.3 percent/yr at the Mississippi River at Tarbert Landing, 

Mississippi, and -1.8 percent/yr at the Atchafalaya River at 

Simmesport, Louisiana, over the 60-year period. Downward 

trends in FW SSCs were significant at all but one upper Missouri River station (fig. 3B, table 6). Median slopes in streamflow temporal changes generally were upward, with significant 

trends in streamflow detected at about one-half of the stations 

(fig. 3C, table 6). 

Decreasing SSLs, despite concurrent increases in streamflow indicate, at most stations, that sediment declines can be 

explained by a decline in source material. Abrupt declines 

in suspended sediment in the Missouri River as a result of 

impoundments on the upper Missouri River have been well 

documented (Keown and others, 1981; Meade and others,

1990; Meade 1995; Jacobson and others, 2009; National 

Resource Council, 2011) as has the resulting effects of these 

reduced contributions at downstream Mississippi River stations (Keown and others, 1986; Kesel, 1988; Mossa, 1996). 

Kesel (1988) notes estimated declines in SSLs in the lower 

Mississippi River between 1850 and 1952 of about 25 percent; 

therefore, pre-dam SSLs likely represent declines from earlier 

transport conditions but are still greater than presettlement 

conditions (Knox, 1977). Even the earliest pre-impoundment 

record used in the trend analyses made here was collected following the closing of the Fort Peck Dam in 1937 and following early channel modifications on the Missouri, Ohio, upper 

Mississippi and lower Mississippi Rivers. Temporal variations 

in annual SSLs indicated that the Missouri River impoundments accounted for the most abrupt declines during the 

1950–2009 period, and the effects of reduced contributions 

from the Arkansas River in the mid-1960s also are evident 

in SSLs at the Mississippi River at Tarbert Landing, Mississippi. The steady declines in SSLs at lower Mississippi River 

stations that followed the 1953 declines from the Missouri 

River and mid-1960s declines from the Arkansas River are 

not as easily explained. Other factors that have been cited 

as contributing to the reduction of SSLs in the Mississippi 

River Basin, in addition to the closing of Missouri main-stem 

impoundments, include the decreases in sediment contributions from the Missouri River tributaries (Meade and Moody, 

2010), depletion of stored sediments in the system (Knox, 

1977, 1987; Trimble, 1983; Beach, 1994; Meade and Moody, 

2010), and implementation of conservation measures throughout the Mississippi River Basin (Knox, 1977; Meade and 
Suspended-Sediment Trends In The Mississippi River Basin 13

-

-

!

!

0

20

40

60

80

100 Missouri River at 

Hermann, Missouri

44

31

22

38

23

19 35 43

30 13

6

Missouri River near 

Landusky, Montana

!-

!-

!- !-

!-

!-

!- !- !-

!!- -

80°

90°

100°

110°

45°

40°

35°

30°

40°

35°

30°

110°

45°

40°

35°

30°

!-

22 23

30

31

35

38

43 19

46

6

13

48

22

23

30

31

35

38

43 19

46

6

48

13 80°

90°

100°

45°

40°

35°

30°

45°

40°

35°

30°

80°

90°

100°

110°

45°

40°

35°

30°

!

!

0 250 500 KILOMETERS

0 250 500 MILES

0

100

200

300

400

500 Mississippi River at Tarbert 

Landing, Mississippi

0

50

100

150

200

Arkansas River at T

ulsa, Oklahoma

Arkansas 

River at 

Little Rock, 

Arkansas

48

 46

19(

G Missouri River Basin

 Upper Mississippi River Basin

 Ohio River Basin

 Arkansas River Basin

 Lower Mississippi River Basin

-

B. Flow-weighted sediment concentration C. Streamflow

A. Sediment loads

0

0.2

0.4

0.6

0.8

1.0

!G

!-

p less than 0.05, downward slope

p greater than 0.05, downward slope

Mann-Kendall trend test, Sen slope

p less than 0.05, upward slope

p greater than 0.05, Upward Slope

0

5

10

15

20

25

30

0

100

200

300

400

0

4

8

12

1950 1978 2009

1950 1978 2009

1950 1978 2009

1950 1978 2009 1950 1978 2009 1950 1978 2009

1950 1978 2009

!

!

!

0–1.00

1.01–2.00

2.01–3.00

Greater than 3.00

Trend (in percent/year) River basins

Locally estimated scatterplot 

 smoothing (LOESS) fit curve

Annual load

Annual suspended-sediment load, in millions of metric tons

Base Map from USGS Digital Data, 1:2,000,000, 1990

Albers Equal Area Conic projection

Mississippi River at 

Clinton, Iowa

Green River at 

Munfordville, Kentucky

Atchafalaya River at 

Simmesport, Louisiana

U.S.Geological Survey streamgaging 

 stations and identifier (table 2)

!-

!

!

!G

!-

!!

-

-

!-

!- !-

!

!

!-

!

- !

- -

!-

!-

!-

!- !-

!-

!

!! !-

!

!- -

!G

!G

!G

!

!

!

!G

G

!G

!G !G

!G

!G

Water year Water year

Water Year

EXPLANATION

Figure 3. Summary of trends in annual suspended-sediment loads, flow-weighted concentrations, and streamflows at selected 

U.S. Geological Survey streamgaging stations in the Mississippi River Basin, 1950–2009.
14 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Table 5. Summary of step-trend analyses of suspended-sediment characteristics and streamflows for pre- (pre-1953) and postMissouri River main-stem impoundment (post-1967) periods at selected Missouri River and lower Mississippi River Basin stations.

[SSL, suspended–sediment load; SSDL, suspended-sand load; FW SSC, flow-weighted suspended-sediment concentration; FW SSDC, flow-weighted 

suspended-sand concentration mg/L, milligrams per liter; p-value, statistical probability level; m3/s, cubic meters per second; <, less than; --, not computed]

USGS station name

Map reference number 

(fig. 1)

Number of values used 

in analysis Median annual SSL, SSDL (metric tons) Change in SSL, 

SSDL (percent) pre-1953 post-1967 pre-1953 post-1967 p-value

Mississippi River at Saint Louis, Missouri 19 4 42 278,000,000a 91,100,000 <0.001 -67.2

Missouri River near Landusky, Montana 22 3 37 8,440,000 4,400,000 1.00 -47.8

Yellowstone River near Sidney, Montana 23 5 16 21,600,000 13,000,000 .015 -39.8

Little Missouri River near Watford, North Dakota 24 4 9 6,714,000 6,829,000 .825 1.71

Missouri River at Yankton, South Dakota 25 13 4 126,000,000 233,000 <.001 -99.8

Big Sioux River at Akron, Iowa 27 11 5 1,060,000 461,000 .038 -56.5

Boyer River at Logan, Iowa 29 12 8 9,010,000 989,000 <.001 -89.0

Missouri River at Omaha, Nebraska 30 13 24 143,000,000 17,300,000 <.001 -87.9

Platte River at Louisville, Nebraska 31 12 16 14,600,000 7,230,000 .042 -50.5

Nishnabotna River above Hamburg, Iowa 33 12 4 10,200,000 2,960,000 .008 -71.0

Missouri River at Saint Joseph, Missouri 35 4 26 215,000,000 33,900,000 <.001 -84.2

3 31 52,200,000 11,000,000 -- -78.9

Kansas River at DeSoto, Kansas 37 4 18 51,200,000 5,550,000 .001 -89.2

Missouri River at Kansas City, Missouri 38 4 21 261,000,000 48,400,000 <.001 -81.5

4 27 45,700,000 12,900,000 -- -71.8

Missouri River at Hermann, Missouri 43 4 26 284,000,000 60,200,000 <.001 -78.8

3 42 62,800,000 19,000,000 -- -69.7

Mississippi River at Tarbert Landing, Mississippi 46 3 42 497,000,000 133,000,000 <.001 -73.2

3 39 67,000,000 29,900,000 .004 -55.4

Atchafalaya River at Simmesport, Louisiana 48 1 42 178,000,000 64,900,000 -- -61.1

1 39 44,400,000 15,200,000 -- -65.8

USGS station name

Map 

reference 

number 

(fig. 1)

Median FW SSC, SSDC (mg/L) Change in

FW

SSC, SSDC

(percent)

Annual median streamflow (m3/s) Change

in flow

pre-1953 post-1967 p-value pre-1953 post-1967 p-value (percent)

Mississippi River at Saint Louis, Missouri 19 1,650 492 <0.001 -70.2 6,120 5,920 0.807 -3.27

Missouri River near Landusky, Montana 22 984 694 1.00 -29.5 294 261 .750 -4.51

Yellowstone River near Sidney, Montana 23 1,880 994 <.001 -47.1 370 363 .780 -1.89

Little Missouri River near Watford, North Dakota 24 8,000 11,100 .199 38.8 24.1 12.8 .699 -46.9

Missouri River at Yankton, South Dakota 25 4,170 13.8 <.001 -99.7 937 557 .045 -40.6

Big Sioux River at Akron, Iowa 27 968 390 .006 -59.7 33.2 41.9 .827 26.3

Boyer River at Logan, Iowa 29 29,900 2,020 <.001 -93.2 8.42 11.0 .427 30.6

Missouri River at Omaha, Nebraska 30 4,520 521 <.001 -88.5 1,030 1,010 .938 -1.94

Platte River at Louisville, Nebraska 31 2,950 1,330 <.001 -54.9 150 197 .037 31.6

Nishnabotna River above Hamburg, Iowa 33 11,500 1,990 .001 -82.7 31.1 47.2 .521 51.6

Missouri River at, St. Joseph, Missouri 35 4,960 791 <.001 -84.1 1,560 1,290 .108 -17.3

999 246 -- -75.4 -- -- -- --

Kansas River at DeSoto, Kansas 37 5,500 1,050 <.001 -80.9 297 169 .042 -43.1

Missouri River at Kansas City, Missouri 38 4,840 873 <.001 -82.0 1,910 1,490 .047 -22.0

732 246 -- -66.4 -- -- -- --

Missouri River at Hermann, Missouri 43 3,190 791 <.001 -75.2 2,800 2,400 .170 -14.3

566 213 -- -62.4 -- -- -- --

Mississippi River at Tarbert Landing, Mississippi 46 832 289 <.001 -65.3 17,400 14,700 .122 -15.5

137 61.6 .003 -55.0 -- -- -- --

Atchafalaya River at Simmesport, Louisiana 48 907 334 -- -63.2 6,250 6,530 -- 4.48

226 72.6 -- -67.9 -- -- -- --

a

Values in bold are statistically significant (p<0.05).

b

Record from 1949–68 from Missouri River near Power Plant Ferry, Montana and from 1969–71 from Missouri River at Robinson Bridge near Landusky, Montana.
Suspended-Sediment Trends In The Mississippi River Basin 15

Table 6. Summary of analyses of monotonic trends in annual suspended-sediment loads, flow-weighted concentrations, and 

streamflows between 1950 and 2009 at selected Mississippi River Basin streamgaging stations. 

[p-value, statistical probability level; mg/L, milligrams per liter; <, less than; yr, year; m3/s, cubic meter per second]

USGS station name

Map

reference

number (fig. 1)

Number of

values used

in analysis

Suspended-sediment loads Trendb

(in percent/

yr)

Mann-Kendall

tau p-value Sen slope(metric tons/yr)

Median

(metric tons)

Green River at Munfordville, Kentucky 6 33 -0.227 0.062 -3,520 363,000 -0.97

Mississippi River at Clinton, Iowa 13 40 .076 .499 12,100 3,360,000 .36

Mississippi River at Saint Louis, Missouri 19 60 -.190a .032 -791,000 91,500,000 -.86

Missouri River near Landusky, Montana 22 45 -.271 .009 -103,000 4,530,000 -2.27

Yellowstone River near Sidney, Montana 23 34 -.305 .012 -236,000 15,200,000 -1.55

Missouri River at Omaha, Nebraska 30 42 -.524 <.001 -422,000 23,300,000 -1.81

Platte River at Louisville, Nebraska 31 33 -.311 .012 -169,000 8,910,000 -1.90

Missouri River at Saint Joseph, Missouri 35 39 -.457 <.001 -829,000 37,300,000 -2.22

Missouri River at Kansas City, Missouri 38 44 -.439 <.001 -1,380,000 56,500,000 -2.44

Missouri River at Hermann, Missouri 43 44 -.332 .002 -1,170,000 63,600,000 -1.84

Arkansas River at Tulsa, Oklahomac 44 20 -.232 .163 -46,300 1,390,000 -3.33

Mississippi River at Tarbert Landing, Mississippi 46 60 -.401 <.001 -1,890,000 142,000,000 -1.33

Atchafalaya River at Simmesport, Louisiana 48 58 -.412 <.001 -1,170,000 66,200,000 -1.77

USGS station name

Map

reference

number

Number of

values used

in analysis

Flow-weighted suspended-sediment concentrations Trendb

(in percent/

yr)

Mann-Kendall

tau p-value Sen slope((mg/L)/yr)

Median

(mg/L)

Green River at Munfordville, Kentucky 6 33 -0.591 <0.001 -3.74 167 -2.24

Mississippi River at Clinton, Iowa 13 40 -.699 <.001 -8.76 362 -2.42

Mississippi River at Saint Louis, Missouri 19 60 -.513 <.001 -8.50 538 -1.58

Missouri River near Landusky, Montana 22 45 -.164 .115 -6.41 572 -1.12

Yellowstone River near Sidney, Montana 23 34 -.401 <.001 -22.5 1,360 -1.65

Missouri River at Omaha, Nebraska 30 42 -.738 <.001 -23.2 765 -3.03

Platte River at Louisville, Nebraska 31 33 -.468 <.001 -43.6 1,812 -2.41

Missouri River at Saint Joseph, Missouri 35 39 -.605 <.001 -33.4 1,050 -3.18

Missouri River at Kansas City, Missouri 38 44 -.644 <.001 -41.7 1,220 -3.42

Missouri River at Hermann, Missouri 43 44 -.643 <.001 -27.4 993 -2.76

Arkansas River at Tulsa, Oklahoma 44 20 -.558 <.001 -13.7 97.6 -14.00

Mississippi River at Tarbert Landing, Mississippi 46 60 -.666 <.001 -5.74 313 -1.84

Atchafalaya River at Simmesport, Louisiana 48 58 -.699 <.001 -8.76 362 -2.42

USGS station name

Map

reference

number

Number of

values used

in analysis

Streamflow Trendb

(in percent/

yr)

Mann-Kendall

tau p-value Sen slope((m3/s)/yr)

Median

(m3/s)

Green River at Munfordville, Kentucky 6 33 0.138 0.260 0.375 78.2 0.48

Mississippi River at Clinton, Iowa 13 40 .280 .011 9.26 1440 .64

Mississippi River at Saint Louis, Missouri 19 60 .197 .027 30.0 5,410 .55

Missouri River near Landusky, Montana 22 45 -.337 .001 -2.51 267 -.94

Yellowstone River near Sidney, Montana 23 34 -.034 .790 -.425 360 -.12

Missouri River at Omaha, Nebraska 30 42 .228 .035 4.36 866 .50

Platte River at Louisville, Nebraska 31 33 .141 .263 .716 168 .43

Missouri River at Saint Joseph, Missouri 35 39 .197 .061 5.12 1,130 .45

Missouri River at Kansas City, Missouri 38 44 .169 .134 6.55 1,410 .46

Missouri River at Hermann, Missouri 43 44 .200 .057 14.4 2,220 .65

Arkansas River at Tulsa, Oklahoma 44 20 -- -- -- -- --

Mississippi River at Tarbert Landing, Mississippi 46 60 .199 .025 62.2 14,000 .44

Atchafalaya River at Simmesport, Louisiana 48 58 .233 .010 30.3 6,060 .50

a

Values in bold are statistically significant (p<0.05).

b

Trend in percent/yr is calculated as the ratio of the Sen slope and median constituent values.

c

Sediment load and record information from Arkansas River at Tulsa, Oklahoma from 1951 through 1993 and from Arkansas River at Little Rock, Arkansas from 1994 through 2006.
16 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Moody, 2010). Most gaged tributaries within major Mississippi River subbasins have main-stem impoundments (table 3) 

that could account for much of the sediment transport deficit 

not accounted for directly by the Missouri River main-stem 

impoundments. 

The Arkansas River is the primary tributary sediment 

contributor to the lower Mississippi River Basin and there 

were significant decreases in SSLs in this basin during the 

1950–2009 period. SSLs at the Arkansas River at Tulsa, 

Oklahoma, station decreased abruptly in the mid-1960s and 

this likely was the result of the construction of impoundments 

and navigation structures associated with the McClellan-Kerr 

navigation system. Keown and others (1986) noted substantial 

declines in SSLs at a downstream station, the Arkansas River 

at Little Rock, Arkansas, at which the 1941–62 average SSL 

was about 93 Mt/yr and the 1970–78 average was about 

11.4 Mt/yr. This represents about an 88 percent reduction 

in SSLs from the Arkansas River Basin and exceeds the 79 

percent reduction in SSLs in the Missouri River Basin (Missouri River at Hermann, Missouri, station; table 5) that followed channel modifications. 

Decreases in SSLs in the lower Mississippi River corresponding to the declines in the Missouri and Arkansas Rivers 

were immediate and substantial. Pre-1953 (pre-Missouri River 

impoundment) SSLs in the lower Mississippi River (Mississippi River at Tarbert Landing, Mississippi, and Atchafalaya 

River at Simmesport, Louisiana) averaged 641 Mt/yr. This 

average declined to 296 Mt/yr during the 1953–64 period and 

to 198 Mt/yr following declines in contributions from the 

Arkansas River Basin in the mid-1960s (fig. 3)—a total SSL 

reduction of about 69 percent. 

FA SSCs for Missouri River and Arkansas River 

stations decreased during the 1950–2009 analysis period 

(fig. 4). Plots of FA SSCs show downward changes in the 

fitted LOESS curves for each Missouri River station indicating deviations from the overall streamflow-SSC relation. At 

1950 1980 2009

-5,000

-7,500

-2,500

2,500

0

5,000

7,500

10,000

12,500

1950 1980

-5,000

0

5,000

10,000

-10,000

15,000

17,500

-7,500

-2,500

2,500

7,500

12,500

2009

Three data points not shown 

1950 1980 2009

-2,000

-4,000

-5,000

0

2,000

4,000

6,000

8,000

10,000

No data

Two data points not shown 

Two data points not shown Missouri River at St. Joseph, Missouri

Missouri River at

Kansas City, Missouri

Missouri River at Hermann, Missouri

1950 1980 2009

Arkansas River at Tulsa, Oklahoma

No data

Flow-adjusted concentration, in milligrams per liter

-6,000

-4,000

-2,000

0

2,000

4,000

6,000

8,000

10,000

11,000

Water year

Locally estimated scatterplot smoothing (LOESS) fit curve

Residuals of observed suspended-sediment concentration 

 values compared to estimated values using a linear regression 

 model of streamflow and suspended-sediment concentration 

 for 1950–2009

EXPLANATION

Figure 4. Summary of temporal variations in flow-adjusted concentrations for selected U.S. Geological Survey streamgaging 

stations in the Mississippi River Basin, 1950–2009.
Suspended-Sediment Trends In The Mississippi River Basin 17

each station there were changes in the transport relation in 

about 1962 and 1972 with no substantial changes thereafter. 

The large negative FA SSCs in 1951, 1952, 1973, 1993, and 

1995 correspond with large floods in those years, but these 

events had no apparent long-term effects on FA SSCs. FA 

SSCs for the available 1950–95 period at the Arkansas River 

at Tulsa, Oklahoma, also show apparent sediment transport 

relation changes around 1963 and 1974 with stable relations 

thereafter (fig. 4). Whereas abrupt changes in annual SSLs 

were evident following the closing of Fort Randall Dam in 

1952, the changes in FA SSCs at Saint Joseph, Kansas City, 

and Hermann, Missouri, were lagged and subtle. The decrease 

in FA SSCs at these stations indicate less suspended material 

was being transported for a given flow condition and likely 

corresponds to adjustments in the system from a transportlimited to a supply-limited system, as suggested by Horowitz 

(2010), and by Meade and Moody (2010). The magnitude of 

variability of FA SSCs declined during the mid-1960s, likely 

a result of regulated flows and limitations in sediment supply. The decrease in FA SSCs at the Arkansas River at Tulsa, 

Oklahoma, also is a likely indication of adjustments in this 

sediment conveyance system from a transport-limited towards 

supply-limited conditions. 

Suspended Sand 1950–2004

Trends in SSDLs, SSDCs, and SSDL percentage of SSLs 

were determined for three Missouri River and two lower Mississippi River stations for 1950–2004. Significant downward 

trends in SSDLs were determined for the Missouri River at 

Saint Joseph and Kansas City, Missouri and for the Mississippi River at Tarbert Landing, Mississippi, and Atchafalaya River at Simmesport, Louisiana, stations (table 7). The 

downward change in SSDLs at Hermann, Missouri, however, 

was not significant (p = 0.055). Decreases in FW SSDCs were 

Table 7. Summary of analyses of monotonic trends in annual suspended-sand loads, flow-weighted suspended-sand concentrations, 

and sand load as a percentage of total suspended-sediment load between 1950 and 2004 at selected Missouri River and lower 

Mississippi River Basin stations.

[p-value, statistical probability level; yr, year; mg/L, milligrams per liter; m3/s, cubic meter per second; <, less than;]

USGS station name

Map reference 

number 

(fig. 1)

Number 

of values 

used in 

analysis

Suspended-sand load 

Trend (in 

percent/yr)

MannKendall

tau

 p-value

Sen slope 

(metric tons/

yr)

Median (metric tons)

Missouri River at Saint Joseph, Missouri 35 20 -0.537a 0.001 -323,000 15,200,000 -2.13

Missouri River at Kansas City, Missouri 38 19 -.491 .004 -298,000 14,200,000 -2.10

Missouri River at Hermann, Missouri 43 22 -.299 .055 -270,000 19,400,000 -1.39

Mississippi River at Tarbert Landing, Mississippi 46 55 -.282 .002 -550,000 31,900,000 -1.72

Atchafalaya River at Simmesport, Louisiana 48 53b -.232 .014 -246,000 16,600,000 -1.48

USGS station name

Map reference 

number 

(fig. 1)

Number 

of values 

used in 

analysis

Flow-weighted suspended-sediment concentrations

Mann-Kendall tau p-value Sen slope 

((mg/L)/yr)

Median 

(mg/L)

Trend (in 

percent/yr)

Missouri River at Saint Joseph, Missouri 35 20 -0.747 <0.001 -10.8 340 -3.18

Missouri River at Kansas City, Missouri 38 19 -.790 <.001 -8.69 346 -2.51

Missouri River at Hermann, Missouri 43 22 -.533 <.001 -4.26 221 -1.93

Mississippi River at Tarbert Landing, Mississippi 46 55 -.410 <.001 -1.61 73.7 -2.18

Atchafalaya River at Simmesport, Louisiana 48 53 -.441 <.001 -2.24 90.7 -2.47

USGS station name

Map reference 

number 

(fig. 1)

Number 

of values 

used in 

analysis

Suspended-sand load percentage of suspended-sediment load

Trend (in 

percent/yr) MannKendall

tau

 p-value Sen slope

((m3/s)/yr)

Median 

(m3/s)

Missouri River at Saint Joseph, Missouri 35 20 -0.179 0.284 -0.393 33.3 -1.18

Missouri River at Kansas City, Missouri 38 19 -.076 .675 -.125 27.1 -.46

Missouri River at Hermann, Missouri 43 22 -.013 .955 -.008 27.6 -.03

Mississippi River at Tarbert Landing, Mississippi 46 55 .017 .861 0 20.0 0

Atchafalaya River at Simmesport, Louisiana 48 53 -.003 .982 0 23.0 0

a

Values in bold are statistically significant (p <0.05).

b

Available sediment record is from 1952–2004.
18 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Figure 5. Summary of temporal variations in annual suspended-sand loads and annual sand as a percentage 

of total suspended-sediment loads, 1950–2004.

Missouri River at 

St. Joseph, Missouri 

Missouri River at 

Hermann, Missouri

Mississippi River at 

Tarbert Landing, 

Mississippi

Suspended-sand load

 

0

20

40

60

80

0

10

20

30

40

50

60

0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

0

10

20

30

40

50

60

0

10

20

30

40

50

60

1950 1968 1986 2004

No Data

No data

Sand as a percent of total load

 

0

20

40

60

80

100

0

10

20

30

40

0

10

20

30

40

50

0

10

20

30

40

Sand as a percent of total load 

1950 1968 1986 2004

1950 1968 1986 2004

1950 1968 1986 2004

1950 1968 1986 2004

1950 1968 1986 2004

1950 1968 1986 2004

1950 1968 1986 2004

1950 1968 1986 2004

1950 1968 1986 2004

1950–2004

 

Missouri River at 

Kansas City, Missouri 

Atchafalaya River at

Simmesport, Louisiana

Water year

Suspended-sand load, in millions of metric tons

Locally estimated scatterplot 

 smoothing (LOESS) fit curve
Suspended-Sediment Trends In The Mississippi River Basin 19

significant at all five stations, but there were no significant 

monotonic trends in the sand percentage of total sediment 

loads at any of the five stations for the 1950–2004 period 

(table 7). Qualitative temporal relations in SSDLs and SSDCs 

indicate the declines in SSDLs were abrupt following the 1952 

dam closure, but SSDL declines (fig. 5) were more gradual 

than declines in SSLs 

(fig. 3). The corresponding temporal changes in SSDL percentage of SSLs showed increases in the portion of total loads 

comprised of sand between 1950 and about 1978 at all three 

Missouri River stations, followed by a decline in the portion of 

total loads comprised of sand from 1978 through 2004 

(fig. 5). Similar temporal changes were not evident at the Tarbert Landing, Mississippi, or Simmesport, Louisiana, stations.

In addition to being the largest contributor of total suspended sediment to the Mississippi River, the Missouri River 

also is likely the largest contributor of suspended sand to the 

Mississippi River. The stations at Saint Joseph and Kansas 

City, Missouri, receive the majority of sand from the upstream 

main-stem channel of the Missouri and from the Platte River 

in Nebraska. The lack of a discernable trend in SSDLs at Hermann, Missouri, could be a consequence of the longitudinal 

distance from this primary source and the moderating effects 

in sediment transport over a great distance. Another possible 

moderating effect could be the substantial contributions of 

sand from major, and relatively unaltered, tributaries between 

Kansas City and Hermann (Grand and Chariton Rivers, 

Missouri). 

An increase in SSDL percentage of SSLs from 1950 

through about 1980 at the three Missouri River stations 

coincided with a period of declining SSLs and SSDLs 

(fig. 3, fig. 5) and indicated the silt and clay fractions of total 

load declined more than the sand fraction during this period. 

Further evidence of the larger declines in silt and clay fraction is indicated in the larger declines in SSLs and SSCs than 

SSDLs and SSDCs at several Missouri and Mississippi River 

stations (table 5), in the post-impoundment period. A larger 

decline in silt and clay fractions of sediment transport in the 

system could possibly reflect the effects of conservation practices in the basin that would target topsoil containing more silt 

and clay than sand. The reversal of this trend from 1980–2004 

could be explained by the increased downward change in sand 

transport at these stations that began about 1980 (fig. 5), but 

the direct cause is unclear. The source of the change in the 

trend originates upstream from the Saint Joseph station and 

does not seem to be the result of a change in the streamflowSSDC transport relation. The larger relative decline in SSDLs 

may simply be the result of a low-flow period in the sand-supply reach, downstream from Gavins Point Dam, as the Sioux 

City station showed significant downward trends in streamflow during the 1976–2009 period (table 8).

FA SSDCs at the Missouri River at Saint Joseph, Kansas City, and Hermann, Missouri for the 1950–2004 period 

showed subtle but apparent slope changes in LOESS fitted 

curves around 1956–58 and again around 1963–70 depending on the station (fig. 6). These slope changes, therefore, 

preceded the changes in FA SSCs for the 1950–2009 period 

at these stations by about 5 years. Unlike FA SSCs, however, 

which showed downward slope breaks between 1950 and 

1975, there was at least one period of increases in FA SSDCs 

between 1950 and 1970 at each of the three stations. The specific causes of the transport relation transitions are difficult to 

determine with available information and likely include lagged 

channel adaptations to the main-stem impoundments. 

Suspended Sediment 1976–2009 

By 1976, most of the channel modifications in the major 

Mississippi River subbasins had been completed, although 

work continued on the Missouri River through the 1980s, the 

McClellan–Kerr navigation system on the Arkansas River 

through the early 2000s, and the Red River through the early 

2000s. There were downward changes in SSLs at 19 of 27 

Mississippi River Basin stations and statistically significant 

downward monotonic trends at 9 of 27 stations during the 

1976 through 2009 analysis period, including stations in all 

major subbasins except the Arkansas River Basin (fig. 7, 

table 8). Eight stations, at least one within each major subbasin, showed upward changes in SSLs although none were significant (p= 0.102– 0.940). Downward changes in FW SSCs 

were significant at 13 stations including stations in each of the 

major subbasins except the Arkansas River Basin (fig. 7, table 

8). Two stations, the Missouri River near Landusky, Montana 

and Sioux City, Iowa, showed significant downward trends in 

streamflow during the 34-year analysis period (fig. 7, table 8).

During 1976–2009, most stations had stready declines in 

sediment loads including stations within the upper Mississippi, 

Missouri, Ohio, and lower Mississippi River subbasins 

(fig. 7). Exceptions included the Wabash River at New Harmony, Indiana, which showed variable SSLs ending with an 

increase, and the Iowa River at Wapello, Iowa, which also 

ended the period with increasing SSLs. 

Although not expressed in the fitted 1950–2009 FA SSC 

LOESS curves for the stations on the Missouri River at Saint 

Joseph and Kansas City, Missouri (fig. 4), subtle downward 

changes appear in the fitted 1976–2009 FA SSC curves for 

these stations, indicating a change in the streamflow-SSC relation coinciding with the 1993 and 1995 floods (fig. 8). There 

was a subsequent increase in the FA SSCs beginning in about 

1997 and continuing through 2003, indicating a system recovery from the 1993 and 1995 floods. There were large negative 

FA SSCs at the Missouri River at Hermann, Missouri, in 1993 

and 1995, but these declines were not expressed in the fitted 

LOESS curve. 

Suspended Sand 1976–2004

Trends in SSDL, FW SSDCs, and SSDL percentage of 

SSLs during the 1976–2004 post-impoundment period were 

analyzed at seven stations including four Missouri River Basin 

and three lower Mississippi River stations for the 1976–2004 
20 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

post-impoundment period (table 9). Of the five stations with 

downward changes in SSDLs during this time period, two 

(Missouri River at Saint Joseph and Kansas City, Missouri) 

had significant downward trends. The remaining two stations 

(Mississippi River at Tarbert Landing, Mississippi, and Atchafalaya River at Simmesport, Louisiana) had upward, but not 

statistically significant, changes in SSDLs and SSDCs 

(table 9). Downward monotonic trends in FW SSDCs and the 

SSDL percentage of SSLs were significant at all three Missouri River main-stem stations (table 9) but not at any other 

stations. 

Sand from the Missouri River main-stem reach between 

Gavins Point Dam and Sioux City, Iowa, likely was the primary contributor to SSDLs in the Missouri River during the 

1981–1991 analysis period (table 4). The downward trends 

in SSDLs, FW SSDCs, and SSDL percentage of SSLs at the 

Missouri River at Sioux City, Iowa, for the 1976–2004 period 

are likely the result of downward trends in flows rather than a 

depletion of readily available upstream sand sources. The U.S. 

Army Corps of Engineers (2004) reported a 3.3-meter (m) 

decline in stage for a reference flow at the Gavins Point Dam 

outflow and at the Sioux City station between 1955 and the 

early 1980s. During the dry period of 1985–1991, sand loads 

at Sioux City were reduced and the river stage increased by 

0.3 m. A succession of high-flow years in the 1990s, however, 

resulted in a further 1-m decline in stage at a reference flow at 

this station through 2003, indicating a continued availability of 

source material. 

Missouri River at St. Joseph, Missouri Missouri River at Kansas City, Missouri Missouri River at Hermann, Missouri

1950–2004

1976–2004

1976 1983 1990 1997

-500

-750

0

500

1,000

1,500

1,750

One data point

not shown

2004

-1,000

-1,500

0

1,000

2,000

3,000

4,000

Two data points not shown

1950 1968 1986 2004

-500

-750

0

500

1,000

2,000

1976 1983 1990 1997 2004

1950 1968 1986 2004

-1,000

-1,500

-500

0

500

1,000

1,500

2,000

2,500

Two data points

not shown

No data

1950 1968 1986

-1,000

-2,000

0

1,000

2,000

3,000

4,000

5,000

6,000

One data point

not shown

2004

No data

-500

-400

-200

200

0

400

600

1976 1983 1990 1997 2004

No data

Missouri River at St. Joseph, Missouri Missouri River at Kansas City, Missouri Missouri River at Hermann, Missouri

Yellowstone River near Sidney, Montana Platte River at Louisville, Nebraska

Flow-adjusted sand concentration,

in milligrams per liter

Flow-adjusted sand concentration,

in milligrams per liter

-500

-200

-400

0

200

400

600

800

900

1976 1983 1990 1997 2004

-3,000

-1,000

-2,000

1,000

2,000

0

3,000

1976 1983 1990 1997 2004

Water year

Water year

EXPLANATION

Locally estimated scatterplot smoothing (LOESS) 

 fit curve

Residuals of observed suspended-sediment 

 concentration values compared to estimated

 values using a linear regression model of 

 streamflow and suspended-sediment

 concentration for 1950–2009

Figure 6. Summary of temporal variations in flow-adjusted sand concentrations, 1950–2004 and 1976–2004.
Suspended-Sediment Trends In The Mississippi River Basin 21

Figure 7. Summary of trends in annual suspended-sediment loads, flow-weighted concentrations, and streamflows at selected 

U.S. Geological Survey streamgaging stations in the Mississippi River Basin, 1976–2009.

-

-

-

!

-

!

-

-

!

-

!

9

22

23

11

28 30

31

32

35

38

43

13 14

15 17

18

19 8 7

45

Annual suspended-sediment load, in millions of metric tons

10 6

2

5

Water year Water year

Water year

!

!

!

30

G Missouri River Basin

 Upper Mississippi River Basin

 Ohio River Basin

 Arkansas River Basin

 Lower Mississippi River Basin

-

!G

!-

p less than 0.05, downward slope

p greater than 0.05, downward slope

Mann-Kendall trend test, Sen slope

p less than 0.05, upward slope

p greater than 0.05, Upward Slope

!

!

!

0–1.00

1.01–2.00

2.01–3.00

Greater than 3.00

Trend (in percent/year) River basins

Base Map from USGS Digital Data, 1:2,000,000, 1990

Albers Equal Area Conic projection

EXPLANATION

( U.S.Geological Survey streamgaging 

 stations and identifier (table 2)

Locally estimated scatterplot 

 smoothing (LOESS) fit curve

Annual load

46

47

48

!G

- !-

!-

!-

!- !-

!-

!-

-!-

!-

!-

6

2

9

8 7

5

22

14

15

45

31

13

10

38

23

19 43

35 32

30 28

18

17

11

80°

90°

100°

110°

45°

40°

35°

30°

40°

35°

30°

45°

40°

35°

30°

!G 6

2

9

8 7

5

22

14

15

45

31

13

10

38

23

19

43 35

32

30 28

18

17

11

80°

90°

100°

110°

45°

40°

35°

30°

45°

40°

35°

30°

80°

90°

100°

110°

45°

40°

35°

30°

!-

47

48 46

47 48

46

1976 1993 2009

0

20

40

60

80

100

110 Atchafalaya River at

Simmesport, Louisiana

1976 1993 2009

0

10

20

30

40

Missouri River at 

Omaha, Nebraska

1976 1993 2009

0

5

10

15

20

25 Missouri River at 

Landusky, Montana

1976 1993 2009

0

5

10

15

20

25 Illinois River at 

Valley City, Illinois

1976 1993 2009

0

1

2

3

4

5 Iowa River at 

Wapello, Iowa

Wabash River at 

New Harmony, Indiana

1976 1993 2009

0

5

10

15

20

25 Ohio River at 

Greenup, Kentucky

No data

B. Flow-Weighted Sediment Concentration C. Streamflow

1

0

5

9

13

No data

1976 1993 2009

A. Sediment Loads

!

!- !G !-

!G !-

-

!

!

!G

!

!G

!-

!!!

!- !-

-

!!

!!

!G

!G !G

!G

!- !-

!-

!

!- !

- !-

!-

!G !

!- !

!G

!

!- -

! !!!

!

!-

!-

!!! !G

!G !-

!

!

!- - !

!- !

!- !G

!G

!

!G -

!- !-

!G

!G !-

!G

!-

!-

!G

!

!

!-

!

!-

-

!-

!-

!- !G

!-

!- !-

!G !G !

!G

G

0 250 500 KILOMETERS

0 250 500 MILES
22 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Table 8. Summary of analyses of monotonic trends in annual suspended-sediment loads, flow-weighted concentrations, and 

streamflows between 1976 and 2009 at selected Mississippi River Basin streamgaging stations.

[p-value, statistical probability level; yr, year; mg/L, milligrams per liter; <, less than; m3/s, cubic meter per second]

Short name

(table 2)

Map 

reference 

number 

(fig. 1)

Number of 

values used 

in analysis

Suspended-sediment loads Trend (in 

percent/

yr) Mann-Kendall

tau p-value Sen slope (metric tons/yr)

Median (metric 

tons)

Ohio River at Greenup Dam near Greenup, Kentucky 2 21 -0.429a 0.007 -291,000 9,560,000 -3.04

Ohio River at Cannelton Dam at Cannelton, Indiana 5 8 .143 .764 54,500 28,600,000 .19

Green River at Munfordville, Kentucky 6 9 0 1.00 -110 318,000 -.03

White River at Hazleton, Indiana 7 9 .111 .755 14,400 2,030,000 .71

Wabash River at New Harmony, Indiana 8 8 -.143 .711 -229,000 6,060,000 -3.78

Tennessee River at Highway 60 near Paducah, 

Kentucky

9 8 -.357 .266 -20,900 461,000 -4.53

Ohio River at Dam 53 Near Grand Chain, Illinois 10 11 -.236 .350 -645,000 40,300,000 -1.60

Minnesota River at Mankato, Minnesota 11 32 .206 .102 22,300 1,210,000 1.84

Mississippi River at Clinton, Iowa 13 36 .033 .913 1,920 3,450,000 .06

Iowa River at Wapello, Iowa 14 29 -.276 .037 -47,300 2,240,000 -2.11

Skunk River at Augusta, Iowa 15 34 -.123 .313 -28,500 2,300,000 -1.24

Illinois River at Valley City, Illinois 17 12 -.320 .012 -107,000 4,890,000 -2.19

Mississippi River below Grafton, Illinois 18 24 -.261 .078 -451,000 21,200,000 -2.13

Mississippi River at Saint Louis, Missouri 19 34 -.234 .054 -1,640,000 91,100,000 -1.80

Missouri River near Landusky, Montana 22 31 -.290 .023 -162,000 4,320,000 -3.75

Yellowstone River near Sidney, Montana 23 11 -.200 .436 -74,300 5,330,000 -1.39

Missouri River at Sioux City, Iowa 28 13 -.495 .003 -363,000 6,740,000 -5.39

Missouri River at Omaha, Nebraska 30 19 -.368 .030 -430,000 14,700,000 -2.93

Platte River at Louisville, Nebraska 31 11 -.236 .350 -160,000 6,200,000 -2.58

Missouri River at Nebraska City, Nebraska 32 23 -.328 .030 -573,000 23,100,000 -2.48

Missouri River at Saint Joseph, Missouri 35 18 .020 .940 17,500 31,800,000 .06

Kansas River at DeSoto, Kansas 37 20 .103 .669 167,000 41,600,000 .40

Missouri River at Hermann, Missouri 43 18 .046 .820 115,000 55,800,000 .21

Arkansas River at David D. Terry Lock and Dam 

below Little Rock, Arkansas 

45 11 -.200 .436 60,300 2,040,000 2.96

Mississippi River at Tarbert Landing, Mississippi 46 34 -.166 .173 -811,000 124,000,000 -.65

Old River Outflow Channel near Knox Landing, 

Louisiana

47 34 -.244 .044 -427,000 31,800,000 -1.34

Atchafalaya River at Simmesport, Louisiana 48 34 -.355 .003 -1,020,000 58,600,000 -1.74

Short name

Map 

reference 

number 

(fig. 1)

Number of 

values used 

in analysis

Flow-weighted suspended-sediment concentrations Trend (in 

percent/

yr) Mann-Kendall 

tau p-value Sen slope ((mg/L)/yr) Median (mg/L)

Ohio River at Greenup Dam near Greenup, Kentucky 2 21 -0.514 0.001 -4.06 125 -3.25

Ohio River at Cannelton Dam at Cannelton, Indiana 5 8 -.048 1.00 -.528 206 -.26

Green River at Munfordville, Kentucky 6 9 -.167 .602 -1.34 116 -1.16

White River at Hazleton, Indiana 7 9 .056 .917 .247 175 .14

Wabash River at New Harmony, Indiana 8 8 -.429 .174 -3.42 183 -1.87

Mississippi River at Clinton, Iowa 13 36 -.165 .443 -.756 65.3 -1.16

Iowa River at Wapello, Iowa 14 29 -.261 .049 -3.12 231 -1.35

Skunk River at Augusta, Iowa 15 34 -.362 .003 -18.0 785 -2.29

Illinois River at Valley City, Illinois 17 12 -.320 .012 -3.29 200 -1.65

Mississippi River below Grafton, Illinois 18 24 -.297 .045 -4.68 177 -2.65

Mississippi River at Saint Louis, Missouri 19 34 -.447 <.001 -9.84 475 -2.07

Missouri River near Landusky, Montana 22 31 -.187 .144 -8.77 534 -1.64

Yellowstone River near Sidney, Montana 23 11 -0.127 0.640 -8.37 691 -1.21
Suspended-Sediment Trends In The Mississippi River Basin 23

Table 8. Summary of analyses of monotonic trends in annual suspended-sediment loads, flow-weighted concentrations, and 

streamflows between 1976 and 2009 at selected Mississippi River Basin streamgaging stations.—Continued

[p-value, statistical probability level; yr, year; mg/L, milligrams per liter; <, less than; m3/s, cubic meter per second]

Short name

Map 

reference 

number 

(fig. 1)

Number of 

values used 

in analysis

Flow-weighted suspended-sediment concentrations 

Trend (in 

Mann-Kendall percent/yr)

tau p-value Sen slope ((mg/L)/yr)

Median 

(mg/L)

Missouri River at Sioux City, Iowa 28 13 -.547 <.001 -8.32 254 -3.27

Missouri River at Omaha, Nebraska 30 19 -.392 .021 -8.50 493 -1.72

Platte River at Louisville, Nebraska 31 11 -.273 .276 -21.7 831 -2.61

Missouri River at Nebraska City, Nebraska 32 23 -.336 .027 -8.93 632 -1.41

Missouri River at Saint Joseph, Missouri 35 18 .007 1.00 .587 743 .08

Kansas River at DeSoto, Kansas 37 20 .026 .951 1.19 830 .14

Missouri River at Hermann, Missouri 43 18 -.033 .880 -1.24 657 -.19

Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Arkansas 

45 11 -.309 .213 -1.45 59.6 -2.43

Mississippi River at Tarbert Landing, Mississippi 46 34 -.259 .033 -1.85 268 -.69

Old River Outflow Channel near Knox Landing, Louisiana 47 34 -.444 <.001 -2.91 238 -1.22

Atchafalaya River at Simmesport, Louisiana 48 34 -.497 <.001 -5.55 318 -1.75

Short name

Map 

reference 

number 

(fig. 1)

Number of 

values used 

in analysis

Streamflow

Trend (in 

Mann-Kendall percent/yr)

tau p-value Sen slope((m3/s)/yr)

Median 

(m3/s)

Ohio River at Greenup Dam near Greenup, Kentucky 2 21 -0.038 0.838 -3.03 2370 -0.13

Ohio River at Cannelton Dam at Cannelton, Indiana 5 8 .238 .548 6.61 3,970 .17

Green River at Munfordville, Kentucky 6 9 0 1.00 .022 82.1 .03

White River at Hazleton, Indiana 7 9 .278 .348 4.02 408 .99

Wabash River at New Harmony, Indiana 8 8 -.071 .902 -.467 1,020 -.05

Tennessee River at Highway 60 near Paducah, Kentucky 9 8 -.429 .174 -23.2 1,640 -1.42

Ohio River at Dam 53 Near Grand Chain, Illinois 10 11 -.091 .732 -32.0 8,480 -.38

Minnesota River at Mankato, Minnesota 11 32 .130 .286 1.68 142 1.18

Mississippi River at Clinton, Iowa 13 36 .187 .381 16.8 1,720 .98

Iowa River at Wapello, Iowa 14 29 -.143 .285 -2.27 260 -.87

Skunk River at Augusta, Iowa 15 34 .037 .767 .271 85.9 .32

Illinois River at Valley City, Illinois 17 12 -.058 .659 -2.17 740 -.29

Mississippi River below Grafton, Illinois 18 24 -.065 .673 -9.28 3,550 -.26

Mississippi River at Saint Louis, Missouri 19 34 .034 .790 7.55 6,240 .12

Missouri River near Landusky, Montana 22 31 -.372 .004 -4.74 232 -2.04

Yellowstone River near Sidney, Montana 23 11 -.346 .161 -5.45 265 -2.06

Missouri River at Sioux City, Iowa 28 13 -.379 .021 -11.0 784 -1.40

Missouri River at Omaha, Nebraska 30 19 -.275 .108 -10.8 1,020 -1.05

Platte River at Louisville, Nebraska 31 11 -.018 1.00 -1.06 166 -.64

Missouri River at Nebraska City, Nebraska 32 23 -.296 .051 -13.0 1,080 -1.21

Missouri River at Saint Joseph, Missouri 35 18 -.163 .363 -6.76 1,250 -.54

Kansas River at DeSoto, Kansas 37 20 -.026 .951 -2.05 1,460 -.14

Missouri River at Hermann, Missouri 43 18 .111 .545 9.79 2,330 .42

Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Arkansas 

45 11 -.200 .436 -15.2 1,130 -1.35

Mississippi River at Tarbert Landing, Mississippi 46 34 -.037 .767 -24.3 14,700 -.17

Old River Outflow Channel near Knox Landing, Louisiana 47 34 .119 .328 16.6 4,170 .40

Atchafalaya River at Simmesport, Louisiana 48 34 .023 .859 5.71 6,410 .09

a

Values in bold are statistically significant (p <0.05).
24 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

There were downward changes in FA SSDCs at four of 

five Missouri River Basin stations during 1976–2004 

(fig. 6), whereas FA SSDCs at the remaining station were 

relatively unchanged. The FA SSDCs at the Missouri River 

at Saint Joseph, Kansas City, and Hermann, Missouri (fig. 6), 

showed small but steady declines during 1976–2004. There 

was, however, a period of primarily negative FA SSDCs, that 

is, lower measured concentrations for a particular flow than 

would be expected from an overall streamflow-SSC relation, 

at the Missouri River at Kansas City and Hermann, Missouri, 

between 1993 and 1996 (fig. 6). The declines in FA SSDCs 

were short term and were not expressed in the fitted LOESS 

curve. The subtle decline in FA SSDCs at the Platte River at 

Louisville, Nebraska, station may be the result of high flows in 

1987, 1993, and 1995, but the apparent effects in the SSDCstreamflow relation were temporary. There was a subtle “dip” 

in FA SSDCs between 1988 and 1997 at the Platte River at 

Louisville, Nebraska, station but no apparent changes in the 

FA SSDCs at the Yellowstone River at Sidney, Montana. 

#

#

# #

#

#

##

10

37 42

34 17

11

45 47 #

#

Mississippi

Ohio

River

River

Missouri

River

#

8

 U.S. Geological Survey streamgaging station and identifier 

 (table 2)

#47

0 250 500 KILOMETERS

0 250 500 MILES

-2,000

-2,500

0

2,000

4,000

6,000

8,000 Missouri River at 

St Joseph, Missouri

-2,000

-1,000

0

1,000

2,000

3,000

4,000

No data

Missouri River at 

Kansas City, Missouri

-5,000

-3,000

-4,000

-1,000

-2,000

0

1,000

2,000

4,000

3,000 Missouri River at 

Hermann, Missouri

Atchafalaya River at 

Simmesport, Louisiana

1976 1993 2009

-400

-200

0

200

400

600

800

Mississippi River at 

Tarbert Landing, 

Mississippi

-400

0

400

800

1,200 One data point 

not shown

-1,000

-500

0

500

1,000

1,500

2,000

No data

Minnesota River 

at Mankato, 

Minnesota

One data point 

not shown

One data point 

not shown

Illinois River at 

Valley City, 

Illinois

-1,000

0

1,000

2,000

3,000

No data

One data point 

not shown

-200

0

200

400

500

Ohio River at

Grand Chain, 

Illinois

-400

-200

0

200

400

600

800

900

1976 1993 2009

1976 1993 2009

1976 1993 2009

No data

1976 1993 2009

1976 1993 2009

1976 1993 2009

1976 1993 2009

1976 1993 2009

Water year Water year

Water year

EXPLANATION

Locally estimated scatterplot smoothing (LOESS) fit curve

Residuals of observed suspended-sediment concentration 

 values compared to estimated values using a linear 

 regression model of streamflow and suspended-sediment 

 concentration for 1950–2009

Flow-adjusted concentration, in milligrams per liter

Wabash River at 

New Harmony, Indiana

Figure 8. Summary of temporal variations in flow-adjusted sediment concentrations for selected U.S. Geological Survey 

streamgaging stations in the Mississippi River Basin, 1976–2009.
Suspended-Sediment Trends In The Mississippi River Basin 25

Table 9. Summary of analyses of monotonic trends in annual suspended-sand loads, flow-weighted suspended-sand concentrations, 

and suspended-sand load as a percentage of total suspended-sediment loads between 1976 and 2004 at selected Missouri River and 

lower Mississippi River Basin stations.

[p-value, statistical probability level; <, less than; yr, year; mg/L, milligrams per liter; m3/s, cubic meter per second]

USGS station name)

Map 

reference 

number 

(fig. 1)

Number of 

values used 

in analysis

Suspended-sand load Trend (in 

percent/

yr)

Mann-Kendall

tau p-value Sen slope (metric tons)

Median (metric tons)

Yellowstone River near Sidney, Montana

23 10 -0.289 0.283 -85,800 1,750,000 -4.90

Missouri River at Saint Joseph, Missouri

35 15 -.448a .023 -333,000 11,300,000 -2.95

Missouri River at Kansas City, Missouri 38 13 -.5 .02 -379,000 14,200,000 -2.67

Missouri River at Hermann, Missouri 43 15 -.181 .373 -105,000 12,800,000 -.82

Mississippi River at Tarbert Landing, 

Mississippi

46 30 .03 .83 101,000 24,900,000 .41

Old River Outflow Channel near Knox 

Landing, Louisiana

47 30 -.136 .301 -83,300 5,140,000 -1.62

Atchafalaya River at Simmesport, 

Louisiana

48 30 .03 .83 50,700 12,600,000 .40

USGS station name

Map 

reference 

number 

(fig. 1)

Number of 

values used 

in analysis

Flow-weighted suspended-sand concentration Trend (in 

percent/

yr)

Mann-Kendall 

tau p-value Sen slope (mg/L)

Median 

(mg/L)

Yellowstone River near Sidney, Montana

23 10 -0.244 0.371 -5.1 192 -2.66

Missouri River at Saint Joseph, Missouri

35 15 -.638 .001 -7.4 291 -2.54

Missouri River at Kansas City, Missouri 38 13 -.795 <.001 -8.09 251 -3.22

Missouri River at Hermann, Missouri 43 15 -.505 .01 -3.74 207 -1.81

Mississippi River at Tarbert Landing, 

Mississippi

46 30 .025 .858 .151 53.3 .28

Old River Outflow Channel near Knox 

Landing, Louisiana

47 30 -.145 .269 -.466 37.6 -1.24

Atchafalaya River at Simmesport, 

Louisiana

48 30 .053 .695 .288 62.3 0.46

USGS station name

Map 

reference 

number 

(fig. 1)

Number of 

values used 

in analysis

Suspended-sand load percentage of uspended-sand load Trend (in 

percent/

yr)

Mann-Kendall 

tau p-value Sen slope (m3/s) Median (m3

/s)

Yellowstone River near Sidney, Montana

23 10 0.244 0.371 0.524 17.6 2.98

Missouri River at Saint Joseph, Missouri 35 15 -.695 <.001 -1.09 36.9 -2.95

Missouri River at Kansas City, Missouri 38 13 -.821 <.001 -.832 32.9 -2.53

Missouri River at Hermann, Missouri 43 15 -.448 .023 -.744 28.0 -2.66

Mississippi River at Tarbert Landing, 

Mississippi 46 30 .214 .099 .214 19.0 1.13

Old River Outflow Channel near Knox 

Landing, Louisiana 47 30 .03 .83 0 15.0 0

Atchafalaya River at Simmesport, 

Louisiana 48 30 .253 .051 .435 21.0 2.07

a

Values in bold are statistically significant (p <0.05).
26 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

!G

!-- !- !- !-

2

21 20

22

14

15

19 35 43

32

30

28

18

17

11

80°

90°

100°

110°

45°

40°

35°

30°

80°

90°

100°

110°

45°

40°

35°

30°

- 2

21

20

22

14

15

19 43 35

32

28 30

18

17

11!-

!-

!-

!-!-

!-

!-

2

21

20

22

14

15

19 43 35

32

28 30

18 17

11

!-

80°

90°

100°

110°

45°

40°

35°

30°

45°

40°

35°

30°

45°

40°

35°

30°

47

48 46 47

48 46

47

48 46 !

!-

-!-

1998 2004 2009

0

50

100

150 Mississippi River at 

Tarbert Landing, Mississippi

1998 2004 2009

0

20

40

60

80 Atchafalaya River at 

Simmesport, Louisiana

1998 2004 2009

0

2

4

6

8

10

12

Missouri River at 

Sioux City, Iowa

1998 2004 2009 0

2

4

6

7 Illinois River at 

Valley City, Illinois

B. Flow-Weighted Sediment Concentration C. Streamflow

A. Sediment Loads

0

0.5

1.0

1.5

2.0

Minnesota River at 

Mankato, Minnesota

1998 2004 2009

0

40

80

120 Mississippi River 

at Thebes, Illinois

Suspended-sediment load, in millions of metric tons

1998 2004 2009

0

2

4

6

8

10

12

1998 2004 2009

No data

Ohio River near 

Greenup, Kentucky

No data

Water year Water year

Water year

!

!

!

G Missouri River Basin

 Upper Mississippi River Basin

 Ohio River Basin

 Arkansas River Basin

 Lower Mississippi River Basin

-

!G

!-

p less than 0.05, downward slope

p greater than 0.05, downward slope

Mann-Kendall trend test, Sen slope

p less than 0.05, upward slope

p greater than 0.05, Upward Slope

!

!

!

0–1.00

1.01–2.00

2.01–3.00

Greater than 3.00

Trend (in percent/year) River basins

EXPLANATION

Base Map from USGS Digital Data, 1:2,000,000, 1990

Albers Equal Area Conic projection

0 250 500 KILOMETERS

0 250 500 MILES

30 (

Locally estimated scatterplot 

 smoothing (LOESS) fit curve

Annual load

U.S.Geological Survey streamgaging 

 stations and identifier (table 2)

!G

!

!G

!

!

!!

!

!- !- !-

!

!G

!

!G

!!

-

!!-

!-

!-

!-

!-

!-

!-

!- !- !- !- !

!

!G

!G

!G

!G!-

!-

!-!-

!-

!

!-

!G

!G !

!G

G!G !G

Figure 9. Summary of trends in annual suspended-sediment loads, flow-weighted concentrations, and streamflows at 

selected U.S. Geological Survey streamgaging stations in the Mississippi River Basin, 1998–2009.
Suspended-Sediment Trends In The Mississippi River Basin 27

Suspended Sediment 1998–2009

Analyses of monotonic trends in SSLs, FW SSCs, and 

streamflows over a recent (1998–2009) post-channel modification period in the subbasins indicate that slopes of these constituents were generally downward but few temporal changes 

were significant (fig. 9, table 10). A significant downward 

trend in SSLs was indicated for the Missouri River at Sioux 

City, Iowa, but temporal changes in SSLs were not significant 

at any of the remaining 17 stations. The downward trends in 

FW SSCs were significant during the 12-year period only at 

the Skunk River at Augusta, Iowa, in the upper Mississippi 

River Basin and the Old River Outflow station in Louisiana. 

Significant downward trends in streamflow were determined 

for two Missouri River stations including the Missouri River 

at Sioux City, Iowa, and at Omaha, Nebraska. 

Figure 10. Summary of temporal variations in flow-adjusted sediment concentrations for selected U.S. Geological 

Survey streamgaging stations in the Mississippi River Basin, 1998–2009.

#

#

###

2

22

45

46

47 ##

#

Missouri

Ohio

River

River

Mississippi River

1998 2003 2009

-200

0

200

400

Old River Outflow 

Channel near Knox 

Landing, Louisiana

1998 2003 2009 -400

-200

0

200

400

600 Atchafalaya River at 

Simmesport, Lowa

1998 2003 2009

-400

-200

0

200

400

600 Mississippi River at 

Tarbert Landing, 

Mississippi

-5,000

0

5,000

10,000

15,000

20,000

25,000

1998 2003 2009

No data

Missouri River at 

Landusky, Montana

-120

-70

-20

30

80

130

1998 2003 2009

No 

data

Ohio River near 

Greenup, Kentucky

#17

#

21

#34

#42

-500

0

500

1,000

1,500

-1,000

0

1,000

2,000

-2,000

-1,000

0

1,000

2,000

-1,000

-500

0

500

1,000

Missouri River at 

Hermann, Missouri

1998 2003 2009

Illinois River at 

Valley City, Illinois

1998 2003 2009

Mississippi River at 

Thebes, Illinois

1998 2003 2009

Missouri River at 

St. Joseph, Missouri

1998 2003 2009

Water year Water year

Water year

0 250 500 KILOMETERS

0 250 500 MILES

Flow-adjusted concentration, in milligrams per liter

 U.S. Geological Survey Streamgaging station and identifier 

 (table 2)

#21

EXPLANATION

Locally estimated scatterplot smoothing (LOESS) fit curve

Residuals of observed suspended-sediment concentration 

 values compared to estimated values using a linear 

 regression model of streamflow and suspended-sediment 

 concentration for 1950–2009
28 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Table 10. Summary of analyses of monotonic trends in annual suspended-sediment loads, flow-weighted suspended-sediment 

concentrations, and streamflows between 1998 and 2009 at selected Mississippi River Basin streamgaging stations.

[p-value, statistical probability level; yr, year; mg/L, milligrams per liter; m3/s, cubic meter per second]

USGS station name

Map 

reference 

number 

(fig. 1)

Number of 

values used in 

analysis

Suspended-sediment load

Trend (in 

Mann-Kendall percent/yr) tau p-value Sen slope (metric tons/yr)Median (metric 

tons)

Ohio River at Greenup Dam near Greenup, 

Kentucky

2 10 0.067 0.858 51,800 7,370,000 0.70

Minnesota River at Mankato, Minnesota 11 11 -.127 .64 -37,000 1,470,000 -2.52

Iowa River at Wapello, Iowa 14 9 -.333 .252 -80,600 1,910,000 -4.22

Skunk River at Augusta, Iowa 15 12 -.091 .732 -35,100 1,930,000 -1.82

Illinois River at Valley City, Illinois 17 12 .061 .837 82,000 4,020,000 2.04

Mississippi River below Grafton, Illinois 18 12 -.182 .451 -644,000 17,800,000 -3.62

Mississippi River at Saint Louis, Missouri 19 12 -.182 .451 -2,770,000 60,600,000 -4.57

Mississippi River at Chester, Illinois 20 12 -.121 .631 -1,020,000 70,200,000 -1.45

Mississippi River at Thebes, Illinois 21 12 -.091 .732 -847,000 60,400,000 -1.40

Missouri River near Landusky, Montana 22 9 -.222 .466 -179,000 3,030,000 -5.91

Missouri River at Sioux City, Iowa 28 9 -.611a .029 -520,000 4,028,000 -12.91

Missouri River at Omaha, Nebraska 30 8 -.429 .174 -1,160,000 10,100,000 -11.49

Missouri River at Nebraska City, Nebraska 32 12 -.152 .537 -590,000 14,200,000 -4.15

Missouri River at Saint Joseph, Missouri 35 7 -.143 .764 -745,000 33,900,000 -2.20

Missouri River at Hermann, Missouri 43 7 -.143 .764 -921,000 55,400,000 -1.66

Mississippi River at Tarbert Landing, 

Mississippi

46 12 -.03 .945 -349,000 119,000,000 -.29

Old River Outflow Channel near Knox 

Landing, Louisiana

47 12 -.091 .732 -381,000 29,200,000 -1.30

Atchafalaya River at Simmesport, Louisiana

48 12 -.242 .304 -1,720,000 46,400,000 -3.71

USGS station name

Map 

reference 

number 

(fig. 1)

Number of 

values used in 

analysis

Flow-weighted suspended-sediment concentration

Trend (in 

Mann-Kendall percent/yr) tau p-value Sen slope 

((mg/L)/yr) Median (mg/L)

Ohio River at Greenup Dam near Greenup, 

Kentucky

2 10 -0.20 0.474 -3.76 91.8 -4.10

Minnesota River at Mankato, Minnesota 11 11 .018 1.00 .247 272 .09

Iowa River at Wapello, Iowa 14 9 .056 .917 1.81 223 .81

Skunk River at Augusta, Iowa 15 12 -.727 .001 -46.4 716 -6.48

Illinois River at Valley City, Illinois 17 12 -.303 .193 -4.67 183 -2.55

Mississippi River below Grafton, Illinois 18 12 -.364 .115 -7.31 162 -4.51

Mississippi River at Saint Louis, Missouri 19 12 -.182 .451 -14.8 352 -4.21

Mississippi River at Chester, Illinois 20 12 -.242 .304 -10.7 399 -2.68

Mississippi River at Thebes, Illinois 21 12 -.121 .631 -5.44 339 -1.60

Missouri River near Landusky, Montana 22 9 -.111 .734 -8.10 480 -1.69

Missouri River at Sioux City, Iowa 28 9 -.389 .175 -7.50 219 -3.43

Missouri River at Omaha, Nebraska 30 8 -.214 .536 -3.84 388 -.99

Missouri River at Nebraska City, Nebraska 32 12 -.03 .945 -5.53 520 -1.06

Missouri River at Saint Joseph, Missouri 35 7 -.238 .548 -7.13 773 -.92

Missouri River at Hermann, Missouri 43 7 -.048 1.00 -2.10 634 -.33

Mississippi River at Tarbert Landing, 

Mississippi

46 12 -.152 .537 -3.20 265 -1.21

Old River Outflow Channel near Knox 

Landing, Louisiana

47 12 -.515 .024 -4.10 222 -1.85

Atchafalaya River at Simmesport, Louisiana

48 12 -.303 .193 -9.75 228 -4.27
Summary 29

The downward temporal changes in streamflow could 

account for the SSL declines as temporal relations in FA 

SSCs at most stations did not show substantial corresponding 

changes in the sediment transport relations (fig. 10). Exceptions included a decline in the sediment concentration for a 

given flow at the Atchafalaya River at Simmesport, Louisiana, 

indicating an adjustment to limitations in sediment supply, and 

an increase in the sediment concentration for a given flow at 

the Missouri River at Saint Joseph, Missouri, station during an 

apparent sediment supply recovery period following the 1993 

and 1995 floods.

Summary 

Of the four primary contributing subbasins to the lower 

Mississippi River, the Missouri River provided the greatest 

median suspended-sediment load followed by the Ohio River, 

upper Mississippi, and Arkansas Rivers during the 1976–2009 

analysis period. The Missouri River provided the largest 

annual suspended-sediment loads during 26 of the 34 years 

analyzed, and the Ohio River transported the largest annual 

loads during the remaining 8 years. Overall, sediment transport in the lower Mississippi River is most closely correlative 

with the contributions of suspended sediment from the Missouri River Basin.

Annual suspended-sediment loads were computed for 

gaged tributary streams within the Missouri, Ohio, and upper 

Mississippi Basins to further determine major sediment-contributing sources within the subbasins. The Grand River near 

Sumner, Missouri and the Platte River at Louisville, Nebraska 

had the largest median annual loads within the Missouri River 

Basin. The Wabash River provided the largest sediment contribution to the Ohio River, whereas the Illinois River was the 

largest sediment contributor to the upper Mississippi River. 

The largest contributor of suspended sand to the lower 

Missouri River between 1981 and 1991 was estimated to be 

sand from the main-stem reach between Gavins Point Dam, 

South Dakota, and Sioux City, Iowa, followed by contributions from the Platte River in Nebraska. If additional potential 

diversions that substantially reduce flows take place in the 

Platte River there likely will be a substantial reduction in sand 

loads from this primary tributary. 

Results of step-trend analyses to examine changes in 

annual loads, concentrations, and streamflows between the 

Table 10. Summary of analyses of monotonic trends in annual suspended-sediment loads, flow-weighted suspended-sediment 

concentrations, and streamflows between 1998 and 2009 at selected Mississippi River Basin streamgaging stations.—Continued

[p-value, statistical probability level; yr, year; mg/L, milligrams per liter; m3/s, cubic meter per second]

USGS station name

Map 

reference 

number 

(fig. 1)

Number of 

values used in 

analysis

Streamflow

Trend (in per- Mann-Kendall cent/yr)

tau p-value Sen slope ((m3/s)/yr) Median (m3

/s)

Ohio River at Greenup Dam near Greenup, 

Kentucky

2 10 0.378 0.152 118 2,310 5.11

Minnesota River at Mankato, Minnesota 11 11 0 1.00 .393 133 .30

Iowa River at Wapello, Iowa 14 9 -.389 .175 -22.1 204 -10.82

Skunk River at Augusta, Iowa 15 12 .152 .537 3.06 87 3.52

Illinois River at Valley City, Illinois 17 12 .212 .373 27.8 677 4.10

Mississippi River below Grafton, Illinois 18 12 -.03 .945 -18.1 3,410 -.53

Mississippi River at Saint Louis, Missouri 19 12 -.061 .837 -37.2 5,480 -.68

Mississippi River at Chester, Illinois 20 12 -.03 .945 -23.5 5,700 -.41

Mississippi River at Thebes, Illinois 21 12 -.061 .837 -16.6 6,040 -.28

Missouri River near Landusky, Montana 22 9 -.222 .466 -4.84 170 -2.84

Missouri River at Sioux City, Iowa 28 9 -.722 .009 -49.2 659 -7.47

Missouri River at Omaha, Nebraska 30 8 -.786 .009 -76.6 812 -9.43

Missouri River at Nebraska City, Nebraska 32 12 -.364 .115 -37.4 955 -3.91

Missouri River at Saint Joseph, Missouri 35 7 -.143 .764 -18.1 1,130 -1.6

Missouri River at Hermann, Missouri 43 7 -.048 1.00 -6.80 2,410 -.28

Mississippi River at Tarbert Landing, 

Mississippi

46 12 0 1.00 .871 15,000 .01

Old River Outflow Channel near Knox 

Landing, Louisiana

47 12 .091 .732 25.0 4,450 .56

Atchafalaya River at Simmesport, Louisiana

48 12 0 1.00 1.89 6,430 .03

a

Values in bold are statistically significant (p<0.05).
30 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

pre- (pre-1953) and post- (post-1967) Missouri River mainstem impoundment periods indicated statistically significant 

declines in loads and concentrations at most stations. The 

greatest difference in median sediment loads between the two 

periods (-99.8 percent) was recorded at the Missouri River at 

Yankton, South Dakota, about 8 kilometers downstream from 

the most downstream main-stem impoundment. The difference of about 126 million metric tons between the pre-1953 

and post-1967 periods at this station provides a median annual 

estimate of sediment trapped by the upstream reservoirs. This 

represents about 56 percent of the median annual load decline 

of 224 million metric tons at Hermann, Missouri in the postimpoundment period. The remaining 98 million metric tons, or 

44 percent, of the Hermann load reduction can be attributed to 

other factors including reductions in sediment from tributaries. 

About 47 percent of the post-1967 sediment load reduction 

of the lower Mississippi River (Mississippi River at Tarbert 

Landing, Mississippi, and the Atchafalaya River at Simmesport, Louisiana) could be accounted for by post-impoundment 

reductions from the Missouri River at Hermann, Missouri.

The sediment transport regimes of all five major subbasins within the Mississippi River Basin have been affected by 

channel modifications, navigation structures, and main-stem 

or tributary impoundments. Changes in suspended-sediment 

and suspended-sand loads and concentrations generally were 

downward for the 60-, 34-, and 12-year periods analyzed 

in this study. The downward trend in sediment loads began 

before the construction of main-stem impoundments on the 

Missouri River, but the abrupt and extensive decline in sediment transport following the closure of Fort Randall Dam in 

1952 was the single largest event accelerating the decline in 

sediment from the Mississippi River Basin. The downward 

trend in sediment transport at Missouri River and downstream 

Mississippi River stations has continued since the completion 

of the Missouri River main-stem impoundments.

The results of 1950–2009 trend analyses indicate that 

declines in suspended-sediment loads and flow-weighted 

concentrations were widespread throughout the Missouri and 

lower Mississippi River Basin stations. A decrease in flowadjusted suspended-sediment concentrations at Missouri and 

Arkansas River stations in the 1960s and 1970s indicated that 

less suspended material was being transported for a given flow 

condition and likely correspond to adjustments in the sediment 

conveyance system in these rivers from a transport-limited 

system to a supply-limited system following the construction 

of impoundments. 

There were larger declines in suspended-sediment loads 

and concentrations than sand loads and concentrations in the 

post-impoundment period at several stations in the Missouri 

River Basin and the most downstream station on the Mississippi River. A larger decline in silt and clay fractions of sediment transport in the system could possibly reflect the effects 

of conservation practices in the basin that would target topsoil 

containing more silt and clay than sand. 

All significant trends in suspended-sediment loads and 

flow-weighted concentrations during the 1976–2009 period 

were downward and included stations within each major subbasin in the Mississippi River Basin except the Arkansas River 

Basin. The temporal changes in flow-adjusted suspended-sediment concentrations during the 1976–2009 period indicated 

there were substantial effects of the 1993 and 1995 floods on 

sediment transport at the Missouri River at Saint Joseph and 

Kansas City, Missouri, stations. The downward changes in 

flow-adjusted concentrations recovered at both stations by 

about 2003. 

The majority of Mississippi River Basin stations also 

showed downward but nonsignificant temporal changes in 

suspended-sediment loads, concentrations, and streamflows 

during the post-channel modification analysis period of 1998–

2009. The downward temporal changes in streamflows during 

the analysis period likely account for most of the declines in 

loads and concentrations. 

References Cited

Beach, T., 1994, The fate of eroded soil: Sediment sinks and 

sediment budgets of agrarian landscapes in southern Minnesota, 1851–1988: Annals of the Association of American 

Geographers, v. 84, no.1, p. 5–28.

Biedenharn, D.S., Thorne, C.R., and Watson, C.C., 2000, 

Recent morphological evolution of the Lower Mississippi 

River: Geomorphology, v. 34, p. 227–249.

Blevins, D.W., 2006, The response of suspended sediment, turbidity, and velocity to historical alterations of the Missouri 

River: U.S. Geological Survey Circular 1301, 8 p.

Cleveland, W.S., and Devlin, S.J., 1988, Locally weighted 

regression—An approach to regression analysis by local fitting: Journal of the American Statistical Association, v. 83, 

p. 596–610. 

Galat, D.L., Berry, C.R., Jr., Peters, E.J., and White, R.G., 

2005, Missouri River Basin, in Benke, A.C., and Cushing, C.E., eds., chap. 10, Rivers of North America: Oxford, 

U.K., Elsevier, p. 427–480.

Gaeuman, D., and Jacobson, R.B., 2007, Field assessment of 

alternative bedload transport estimators: Journal of Hydraulic Engineering, v. 133, p. 1,319–1,328.

Gilliom, R.J., Hamilton, P.A., and Miller, T.L., 2001, The 

National Water-Quality Assessment Program—Entering a 

new decade of investigations: U.S. Geological Survey Fact 

Sheet 071–01, 6 p.

Heimann, D.C., Rasmussen, P.P., Cline, T.L., Pigue, L.M., and 

Wagner, H.R., 2010, Characteristics of sediment data and 

annual suspended-sediment loads and yields for selected 

lower Missouri River mainstem and tributary stations, 

1976–2008: U.S. Geological Survey Data Series 530, 58 p., 

accessed September, 2010 at http://pubs.usgs.gov/ds/530/.
References Cited 31

Heimann, D.C., Cline, T.L., and Glaspie, L.M., 2011, Data 

used in analyses of suspended-sediment and suspended-sand 

concentrations and loads for selected streams in the Mississippi River Basin: U.S. Geological Survey Data Report 593, 

6 p.

Holmes, R.R., Jr., 1996, Sediment transport in the lower 

Missouri and the central Mississippi Rivers, June 26 

through September 14, 1993: U.S. Geological Survey 

Circular 1120–I, 23 p.

Hoos, A.B., Robinson, J.A., Aycock, R.A., Knight, R.R., and 

Woodside, M.D., 2000, Sources, instream transport, and 

trends of nitrogen, phosphorus, and sediment in the lower 

Tennessee River Basin, 1980–96: U.S. Geological Survey 

Water-Resources Investigations Report 99–4139, 96 p.

Horowitz, A.J., 2010, A quarter century of declining suspended sediment fluxes in the Mississippi River and the 

effect of the 1993 flood: Hydrological Processes, v. 24, 

p.13–34. 

Jacobson, R.B., Blevins, D.W., and Bitner, C.J., 2009, Sediment regime constraints on river restoration―An example 

from the lower Missouri River: Geological Society of 

America Special Papers 451, p. 1–22.

Karns, D.R., Pyron, M., and Simon, T.P., 2006, The Wabash 

River Symposium: Proceedings of the Indiana Academy of 

Science, v. 115, no. 2, p. 79–81. 

Kendall, M.G., 1975, Rank Correlation Methods, 4th ed.: 

Charles Griffin, London, 196 p.

Keown, M.P., Dardeau, E.A., Jr., and Causey, E.M., 1981, 

Characterization of the suspended-sediment regime and 

bed-material gradation of the Mississippi River Basin: U.S. 

Army Corps of Engineers, Waterway experiment Station, 

Report 1, Potamology Program, 62 p.

Keown, M.P., Dardeau, E.A., Jr., and Causey, E.M., 1986, Historic trends in the sediment flow regime of the Mississippi 

River: Water Resources Research, v. 22, p. 1,555–1,564.

Kesel, R.H., 1988, The decline in the suspended sediment load 

of the lower Mississippi River and its influence on adjacent 

wetlands: Environmental Geology and Water Sciences, 

v. 11, p. 271–281.

Kesel, R.H., 1989, The role of the Mississippi River in wetland loss in southeastern Louisiana, USA: Environmental 

Geology and Water Sciences, v. 13, p. 183–193.

Knox, J.C., 1977, Human impacts on Wisconsin stream channels: Annals of the Association of American Geographers, 

v. 62, no. 3, p. 401–410.

Knox, J.C. 2007, The Mississippi River system, in A. Gupta 

ed., Large Rivers—Geomorphology and Management,: 

Chichester, U.K., John Wiley and Sons, p. 145–182.

Lorenz, D.L., Robertson, D.M., Hall, D.W., and Saad, D.A., 

2009, Trends in streamflow and nutrient and suspenedsediment concentrations and loads in the upper Mississippi, 

Ohio, Red, and Great Lakes River Basins, 1975–2004: U.S. 

Geological Survey Scientific Investigations Report 2008–

5213, 82 p.

Mann, H.B., 1945, Non-parametric test against trend: Econometrica, v. 13, p. 245–259.

Meade, R.H., 1995, Setting—geology, hydrology, sediments, 

and engineering of the Mississippi River. in Meade, R.H, 

ed., Contaminants in the Mississippi River, 1987–92: U.S. 

Geological Survey Circular 1133, p. 13–30.

Meade, R.H., 2004, Engineering works and their effects on 

movement and storage of sediment in Mississippi River and 

its major tributaries in Hu,C., and Tan,Y. eds., Proceedings 

of the Ninth International Symposium on River Sedimentation: Beijing, China, Tsinghua University Press, p. 154–161.

Meade, R.H., and Moody, J.A., 2010, Causes for the decline of 

suspended-sediment discharge in the Mississippi River system, 1940–2007: Hydrological Processes, v. 24, p. 35–49.

Meade, R.H., and Parker, R.S., 1985, Sediment in rivers of the 

United States, National Water Data Summary 1984: U.S. 

Geological Survey Water–Supply Paper 2275, p. 49–60.

Meade, R.H., Yuzyk, T.R., and Day, T.J., 1990, Movement and 

storage of sediment in rivers of the United States and Canada, in Wolman, G., and Riggs, H.C. eds., Surface Water 

Hydrology—The geology of North America, ,v. O–1, M: 

Geological Society of America, Boulder, Colo., p. 255–280.

Missouri Basin Inter-Agency Committee, 1969, Comprehensive framework study: Missouri River Basin, v. 1, Washington, D.C., U.S. Government Printing Office. 

Mossa, J., 1996, Sediment dynamics in the lowermost Mississippi River: Engineering Geology, v. 45, p. 457–479.

Moulton, G., ed., 1986, The Journals of the Lewis & Clark 

Expedition: v. 2, Lincoln, Nebraska, University of Nebraska 

Press, 612 p.

National Research Council, 2011, Missouri River planning—

Recognizing and incorporating sediment management: 

Washington D.C., National Academies Press, 152 p.

Nittrouer, J.A., Allison, M.A., and Campanella, R., 2008, Bedform transport rates for the lowermost Mississippi River: 

Journal of Ecophysical Research, Earth Surface, v. 113, 

16 p.

O’Brien, W.P., Rathbun, M.Y., O’Bannon, P., and Whitacre, 

C., 1992, Gateways to commerce¬—The U.S. Army Corps 

of Engineers’ 9-foot channel project on the upper Mississippi River: U.S. National Park Service, Rocky Mountain 

Region, 238 p.
32 Trends in Suspended-Sediment Loads and Concentrations in the Mississippi River Basin, 1950–2009

Perry, C.A., 1994, Effects of reservoirs on flood discharges in 

the Kansas and Missouri River Basins, 1993: U.S. Geological Survey Circular 1120–E, 20 p.

Porterfield G., 1977, Computation of fluvial-sediment discharge: Techniques of Water–Resources Investigations of 

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

Pyron, M., and Neumann, K., 2008, Hydrologic alterations 

in the Wabash River Watershed, USA: River Research and 

Applications, v. 24, p. 1,175–1,184.

Rasmussen, P.P., Gray, J.R., Glysson, G.D., and Ziegler, A.C., 

2009, Guidelines and procedures for computing time-series 

suspended sediment concentrations and loads from instream turbidity-sensor and streamflow data: U.S. Geological Survey Techniques and Methods, book 3, chap. C4, 

54 p.

Rebich, R., and Demcheck, D.K., 2007, Trends in nutrient and 

sediment concentrations and loads in major river basins of 

the south-central United States, 1993–2004: U.S. Geological Survey Scientific Investigations Report 2007–5090, 

112 p.

Runkel, R.L., Crawford, C.G., and Cohn, T.A., 2004, Load 

Estimator (LOADEST)—A FORTRAN program for 

estimating constituent loads in streams and rivers: U.S. 

Geological Survey Techniques and Methods, book 4, 

chap. A5, 69 p.

Sen, P.K., 1968, Estimates of the regression coefficient based 

on Kendall’s Tau: Journal of the American Statistical Association, v. 63, p. 1,379–1,389.

Sidle, J.G., and Faanes, C.A., 1997, Platte River ecosystem 

resources and management, with emphasis on the Big Bend 

reach in Nebraska: U.S. Fish and Wildlife Service, Grand 

Island, Nebraska, Northern Prairie Wildlife Research Center, accessed December 2010, at http://www.npwrc.usgs.gov/

resource/habitat/plrivmgt/index.htm.

Smith, L.M., and Winkley, B.R., 1996, The response of the 

lower Mississippi River to river engineering: Engineering 

Geology, v. 45, p. 433–455. 

Sprague, L.A., Clark, M.L., Rus, D.L., Zelt, R.B., Flynn, J.L., 

and Davis, J.V., 2006, Nutrient and Suspended-Sediment 

Trends in the Missouri River Basin 1993–2003: U.S. Geological Survey Scientific Investigations Report 2006–5231, 

80 p.

Trimble, S.W., 1983, A sediment budget for Coon Creek Basin 

in the Driftless Area, Wisconsin, 1853–1977: American 

Journal of Science, v. 283, p. 454–474. 

Tuttle, J.R., and Combe, A.J., 1981, Flow regime and sediment load affected by alterations of the Mississippi River 

in Cross, R.D., and Williams, D., eds., Proceedings of the 

National Symposium on Freshwater inflow to Estuaries: 

Fish and Wildlife Service, Office of Biological Services 

report FWS/OBS–81/04, p. 334–348.

U.S. Army Corps of Engineers, 1930, Sediment investigations 

of the Mississippi River and its tributaries prior to 1930, 

paper H: U.S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, Miss.

U.S. Army Corps of Engineers, 1976, Suspended sediment in 

the Missouri River—Daily record for water years 1970–

1974, Kansas City, Missouri: U.S. Army Corps of Engineers, Missouri River Division, 201 p.

U.S. Army Corps of Engineers, 2004, Missouri River stage 

trends, RCC Technical Report A–04: U.S. Army Corps of 

Engineers, Northwest Division, Reservoir Control Center, 

Omaha, Nebraska, 40 p.

U.S. Army Corps of Engineers, 2009a, Missouri River 

bed degradation reconnaissance study: U.S. Army 

Corps of Engineers Kansas City District, 67 p., accessed 

June 2010, at http://www.nwk.usace.army.mil/projects/

MoRiverDegradation/Documents/MORiverBedDegrada

tionReconStudy.pdf.

U.S. Army Corps of Engineers, 2009b, Ohio River Basin 

Comprehensive Reconnaissance Report, Great Lakes and 

Ohio River Division, 211 p., accessed August 2010, at 

http://www.ohioriverbasin.org/pdfs/ORBStudy.pdf.

U.S. Department of Agriculture, Natural Resources Conservation Service, 2009, Phase II sedimentation assessment for 

the upper Missouri River Basin: U.S. Department of Agriculture Assessment Report, 51 p., accessed February 2010, 

at http://www.msaconline.com/Missouri%20River%20

Phase%20II%20%20Report.pdf.

U.S. Fish and Wildlife Service, 2003, Amendment to the 2000 

Biological Opinion on the Operation of the Missouri River 

Main Stem Reservoir System, Operation and Maintenance 

of the Missouri River Bank Stabilization and Navigation Project, and Operation of the Kansas River Reservoir 

System: U.S. Fish and Wildlife Service, 308 p., accessed 

December 2010, at http://www.nwd-mr.usace.army.mil/

mmanual/FinalBO2003.pdf.

van Heerden, I., and K. DeRouen, K., Jr., 1997, Implementing 

a barrier island and barrier shoreline restoration program—

the state of Louisiana’s perspective: Journal of Coastal 

Research, v. 13, p. 679–685.

West Consultants Inc., 2000, Upper Mississippi River and 

Illinois Waterway Cumulative Effects Study, Volume 1—

Geomorphic assessment, Final Report: Contract DACW25–

97–R–0012 and ENV Report 40–1, 244 p.
References Cited 33

White, D., Johnston, K., and Miller, M., 2005, Ohio River 

basin, in Benke, A.C., and Cushing, C.E., eds., Rivers of 

North America: Burlington, Vt., Elsevier Academic Press, 

p. 375–424.

Zelt, R.B., Boughton, G., Miller, K.A., Mason, J.P., and Gia-

nakos, L.M., 1999, Environmental setting of the Yellow-

stone River Basin, Montana, North Dakota, and Wyoming: 

U.S. Geological Survey Water-Resources Investigations 

Report 98–4269, 113 p.
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