U.S. Department of the Interior 

Gale A. Norton, Secretary 

U.S. Geological Survey 

Charles G. Groat, Director 

For additional information write to: Copies of this report can be purchased fro

District Chief U.S. Geological Survey


U.S. Geological Survey Information Services


4821 Quail Crest Place Building 810


Lawrence, KS 66049–3839 Box 25286, Federal Center


Denver, CO 80225–0286 
CONTENTS 

Abstract.................................................................................................................................................................................. 

Introduction ........................................................................................................................................................................... 

Methods ................................................................................................................................................................................. 

Channel-Bed Elevation Changes ........................................................................................................................................... 

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

References ............................................................................................................................................................................. 

FIGURES 

1. Map showing location of 24 large Federal reservoirs and selected U.S. Geological Survey streamflow-gaging 

stations in Kansas.................................................................................................................................................... 

2–31. Graph showing change in river/stream stage for mean annual discharge of:


2. Neosho River at Burlington, 1961–97 ............................................................................................................... 

3. Marais des Cygnes River near Pomona, 1968–93 ............................................................................................. 

4. Republican River below Milford Dam, 1963–97 .............................................................................................. 

5. Smoky Hill River near Langley, 1940–97 ......................................................................................................... 

6. Verdigris River near Coyville, 1952–96 ............................................................................................................ 

7. Big Blue River near Manhattan, 1953–97 ......................................................................................................... 

8. Big Hill Creek near Cherryvale, 1957–97 ......................................................................................................... 

9. Elk River below Elk City Lake, 1966–90.......................................................................................................... 

10. North Cottonwood River below Marion Lake, 1968–97 ................................................................................... 

11. Saline River at Wilson Dam, 1965–96............................................................................................................... 

12. South Fork Solomon River below Webster Reservoir, 1963–98 ....................................................................... 

13. Wakarusa River below Clinton Dam, 1972–79 ................................................................................................. 

14. Neosho River at Council Grove, 1944–97......................................................................................................... 

15. Walnut River at Highway 54 east of El Dorado, 1981–94 ................................................................................ 

16. Fall River near Fall River, 1940–79................................................................................................................... 

17. Big Bull Creek near Hillsdale, 1958–95............................................................................................................ 

18. Hundred and Ten Mile Creek near Quenemo, 1963–98 .................................................................................... 

19. Republican River at Clay Center, 1934–99 ....................................................................................................... 

20. Smoky Hill River at Ellsworth, 1949–97........................................................................................................... 

21. Smoky Hill River near Schoenchen, 1964–98................................................................................................... 

22. Fall River at Fredonia, 1947–98 ........................................................................................................................ 

23. Verdigris River near Altoona, 1945–98 ............................................................................................................. 

24. South Fork Solomon River at Woodston, 1978–97 ........................................................................................... 

25. Wakarusa River near Lawrence, 1951–98 ......................................................................................................... 

26. Neosho River near Americus, 1963–97............................................................................................................. 

27. Smoky Hill River at Lindsborg, 1937–65.......................................................................................................... 

28. Cottonwood River at Marion, 1984–96 ............................................................................................................. 

29. North Fork Solomon River at Portis, 1964–97 .................................................................................................. 

30. Prairie Dog Creek near Woodruff, 1955–96...................................................................................................... 

31. Marais des Cygnes River near Ottawa, 1962–94............................................................................................... 

TABLE 

1.	 Change in river or stream stage for mean annual discharge at U.S. Geological Survey streamflow-gaging


stations located downstream from 24 large Federal reservoirs in Kansas for post-dam period of record .............. 

Content
CONVERSION FACTORS AND ABBREVIATIONS


Multiply By To obtain 

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

acre-foot (acre-ft) 43,560 cubic foot 

cubic foot per second (ft3

/s) 0.02832 cubic meter per second 

foot (ft) 0.3048 meter 

foot per year (ft/yr) 0.3048 meter per year 

mile (mi) 1.609 kilometer 

IV Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
Channel-Bed Elevation Changes Downstream From Large


Reservoirs in Kansas 

By Kyle E. Juracek 

Abstract 

Channel-bed elevation changes were assessed 

downstream from 24 large Federal reservoirs in 

Kansas using information from U.S. Geological 

Survey streamflow-gaging stations. Changes in 

river/stream stage associated with mean annual 

discharge indicated that channel-bed lowering had 

occurred downstream from most of the reservoirs. 

The net decrease in channel-bed elevation ranged 

from less than 1 foot to slightly more than 9 feet. 

The magnitude of channel-bed lowering downstream from the reservoirs likely was related to 

the composition of the channel bed. 

INTRODUCTION 

In Kansas, 24 large Federal reservoirs have been 

constructed, mostly in the eastern two-thirds of the 

State (fig. 1). The reservoirs, most of which were completed in the 1950s or 1960s, were built by either the 

U.S. Army Corps of Engineers or the Bureau of Reclamation (U.S. Department of the Interior) initially for 

the primary purposes of providing flood control and 

water for irrigation, respectively. Subsequently, the 

reservoirs have become important for several other 

uses including public water supply, wildlife habitat, 

and recreation. Total capacity of the reservoirs ranges 

from about 40,000 to 3,200,000 acre-ft, with a mean of 

about 650,000 acre-ft. 

The construction and operation of a reservoir can 

have a substantial effect on the stability of the river or 

stream channel downstream from the dam. Primary 

changes introduced by a dam include a reduction in 

the river’s sediment load and an alteration of the flow 

regime. The ability of dams to trap and permanen

store virtually the entire sediment load of the upstr

basin has been widely reported (Petts, 1979; Willi

and Wolman, 1984). Typical changes in the flow 

regime include a reduction in the magnitude of pe

flows and a possible increase in the magnitude of 

flows (Williams and Wolman, 1984). Such artifici

introduced changes may trigger an adjustment by 

river or stream as it attempts to re-establish an app

imate equilibrium between the channel and the di

charge and sediment load being transported (Leop

and Maddock, 1953). Channel adjustments, which 

include such interdependent hydraulic variables a

width, depth, and gradient, may be achieved in sev

ways, including channel degradation [that is, bed 

(or) bank erosion], channel aggradation (that is, 

deposition of material), or changes in channel pat

and shape. 

In general, rivers or streams downstream from 

dams initially adjust by channel degradation. Typi

cally, a river or stream will scour, and thus lower, 

channel bed as the sediment-depleted water emerg

from the dam attempts to replenish its sediment lo

Concurrently, the reduced magnitude of peak flow

emerging from the dam eventually may result in c

nel narrowing as vegetation encroaches. An excep

is the case where the channel bed is armored (with 

coarse material) or situated on bedrock. Unable to 

effectively scour the resistant channel bed, the rive

stream may instead erode laterally and thus widen 

channel (Petts, 1977; Bradley and Smith, 1984). T

cally, channel degradation begins near the dam fol

ing closure and eventually may migrate a consider

distance downstream. Although Williams and Wol

(1984) stated that most channel changes occur dur

the first 5 or 10 years after dam closure, others ha

speculated that the complete adjustment of a chan

Introductio
2 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas

0 20 40 60 KILOMET

0 20 40 60 

South Fork

Republican River

Prairie

Dog

Creek

North Fork

South

Fork

Saline River

Smoky

Hill

River

ARKANSAS

RIVER

Cimarron

Walnut

Pawnee

River

Creek

River

Cimarron

River

Rattlesnake

Creek

Medicine

Lodge

River

Chikaskia

River

North

Fork

South Ninnescah

Fork

River

ARKANSAS

RIVER

Little

Arkansas

River

Walnut

River

Cottonwood

River

Verdigris

River

Neosho

River

Marais

des Cygnes

Wakarusa R.

KANSAS

RIVER

Stranger

Creek

Delaware

River

Blue

River

Little

Big

Republican

River

White Rock Creek

Solomon

River

Saline

River

Smoky

Hill

River

MISSOURI

R

6

7

6

7

6

7

Basin boundary

U.S. Geological Survey 

 streamflow-gaging station 

 and number—Map index

 number used in table 1

Name of reservoir and 

 year storage began

Drainage basin

 Missouri River Basin

 Arkansas River Basin

6

7

EXPLANATION

18

19

20

21 36

37

22

34

38

17

2

3

15

16

4

4

24 23

7 8

14

9

11

31

12 32

10

1

28

27

33

29

5

6

25

26

30

1

35

Keith Sebelius

(1964) Kirwin

(1955) Lovewell

(1957)

Milford

(1967)

Tuttle

Creek

(1962)

Perry

(1969)

Pomona

(1963) Clinto

(1977

Melvern

(1972)

Fall River

(1949) Toronto

(1960)

Elk City

(1966)

Big Hill

(1981)

John Redm

(1964) El Dorado

(1981)

Council

Grove

(1964)

Waconda

(1967)

Marion

(1968)

Cheney

(1964)

Wilson

(1964)

Wilson

(1964)

Kanopolis

(1948)

Webster

(1956)

Cedar

Bluff

(1950)

37°

38°

39°

40°

102° 101° 100° 99° 98° 97° 96° 95°

Base map from U.S. Geological Survey digital data, 1:2,000,000, 1994

Albers Conic Equal-Area projection,

Standard parallels 29°30' and 45°30', central meridian 96°

NEBRASKA

COLORADO

OKLAHOMA

may require 100 years or more (Kellerhals, 1982;

Andrews, 1986; Knighton, 1988).

The type, rate, duration, and extent of channel

degradation downstream from dams are controlled by

many factors, including discharge, sediment load, bedand bank-material composition, local bed-elevation

control (for example, armoring or bedrock), channel

geometry, climate, tributary inflow, and vegetation

(Simons and Li, 1982; Knighton, 1984, 1987; Williams and Wolman, 1984). Also, human-caused

changes such as grade-control structures (for example,

weirs) and bank stabilization may affect the geomorphic response of a river or stream. Considerable variation in the type and rate of channel degradation may

occur even between sites located close together due to

the variability of the controlling factors (Thornes,

1977; Hooke, 1980; Pizzuto, 1994). Downstream from

the degradation zone, channel aggradation may result.

Channel change is a concern for several important

reasons including bridge-site selection, design, and

maintenance; protection of property and structures in

and along the affected channel; protection of riparian

and aquatic habitat for threatened and endang

species; channel capacity; ground-water level

eral aesthetics; and recreation. A substantial l

of the channel bed poses a threat to bridge-pi

dations as well as pipelines and cables buried 

the channel. In addition, bed lowering increas

height and bank instability. Such instability m

ger bank erosion and channel widening that m

a threat to bridge abutments and other structu

Channel aggradation raises the bed elevation, 

channel capacity, and increases the likelihood 

ing. Any channel adjustments that occur on th

stem rivers or streams also may migrate upstr

the tributaries where additional property and s

may be at risk. Finally, any long-term channe

adjustment processes (such as the downstream

response of a river or stream to upstream regu

also may instigate or worsen local scour prob

(Robbins and Simon, 1983).

In addition to reservoirs, several other na

human factors also may cause changes in cha

elevation over time. gion

Figure 1. 

Examples include re

Location of 24 large Federal reservoirs and selected U.S. Geological Survey streamflow-gaging stations in Kansas.
climate change, a change in base level (level below 

which erosion cannot occur) of a river or stream, landuse changes within the basin, and channelization. 

Thus, although upstream regulation may be the primary cause, several causes may combine to account 

for the changes in channel-bed elevation determined 

for a given location. 

A study by the U.S. Geological Survey (USGS), in 

cooperation with the Kansas Department of Transportation, was begun in 2000 to assess channel-bed 

elevation changes downstream from 24 large Federal 

reservoirs in Kansas (fig. 1). The specific study objectives were to determine the magnitude (and direction) 

of channel-bed elevation changes as well as the statistical significance of any observed trends in those 

changes. The purpose of this report is to present the 

results of the study. From a national perspective, the 

methods and results presented in this report provide 

guidance and perspective for future studies concerned 

with the issue of channel changes downstream 

from reservoirs. 

METHODS 

The assessment of channel-bed elevation changes 

downstream from the 24 reservoirs involved an analysis of available information from USGS streamflowgaging stations (fig. 1, table 1). The gaging stations 

provide historical, site-specific information that may 

be indicative of channel conditions both upstream and 

downstream of the stations. 

At any given time and location along a river or 

stream, a relation exists between river/stream stage 

(that is, the height of the water in the channel above a 

given datum) and discharge. These relations, quantified on rating curves, are updated as necessary to 

accommodate changes in channel geometry, slope, and 

other factors that can affect the relation. Each rating 

curve represents a best-fit line through the measurement data (that is, paired measurements of 

river/stream stage and discharge). Discharge measurements at, and stage-discharge rating curves for, the 

streamflow-gaging stations were made using standard 

USGS techniques (Buchanan and Somers, 1969; 

Kennedy, 1984) with a typical accuracy of + 5 percent 

(Kennedy, 1983). 

By computing the stage that relates to a reference 

discharge for each rating curve developed during the 

period of record of a gaging station (and correcting to 

a common datum, if necessary), trends in the elevation 

of the channel bed can be inferred by plotting the 

resulting time-series data. In this assessment, the 

river/stream stage for the mean annual discharge 

(rounded to the nearest 10 or 100 ft3/s, as appropr

for the period of record was used as the reference 

charge (Chen and others, 1999). If the stage for t

reference discharge has a downward (negative) tre

it may be inferred that the channel-bed elevation h

lowered over time due to erosion. Conversely, if 

stage for the reference discharge has an upward (p

tive) trend, it may be inferred that the channel-bed 

elevation has risen over time due to aggradation. 

trend indicates that the channel bed has been 

essentially stable. 

In addition to the magnitude and trend of cha

bed elevation changes at each gaging station, info

tion derived from the rating curves also was used 

assess the rate of channel-bed elevation changes (

ing-curve information is on file at the USGS offic

Lawrence, Kansas). For a given trend, the rate of 

channel-bed elevation change was estimated as th

difference in stage between the starting and endin

dates that define the trend divided by the length o

time between the two dates. 

Because channel changes caused by dams are 

ically greatest near the dam, this study initially 

focused on the first gaging station located downstr

from each dam. Of the 24 reservoirs, 22 had a gag

station located less than 6 mi downstream from th

dam. For 16 reservoirs, a gaging station was locat

2 mi or less downstream from the dam. Unfortuna

an analysis of channel-bed elevation change at the 

gaging station downstream from the dam was not 

sible for 7 of the 24 reservoirs either due to concr

control in the channel at or near the gaging station 

an insufficient post-dam period of record. 

For several reservoirs, a second gaging station 

located farther downstream also was included in t

analysis. The inclusion of the second gaging stati

served two purposes. First, for a few reservoirs it 

vided some information where otherwise there wo

have been no information due to the inability to u

the first gaging station downstream. Second, it pr

vided some perspective on the downstream extent 

the channel-bed elevation changes. Also, for selec

reservoirs, an upstream gaging station was includ

the analysis to enable a comparison of channel-be

elevation changes upstream and downstream. 

A statistical test was used to determine the sig

cance of any observed post-dam trends in channel

Method
-- -- 

-- 

Table 1. Change in river or stream stage for mean annual discharge at U.S. Geological Survey (USGS) streamflow-gaging station

downstream from 24 large Federal reservoirs in Kansas for post-dam period of record 

[B, Bureau of Reclamation, U.S. Department of the Interior; C, U.S. Army Corps of Engineers; ft3/s, cubic feet per second; --, not applicable or 

determined] 

Map index 

numberfor 

associated 

USGS Approximate Period of 

stream- Associated distance of continuous Mean annual Post-dam net 

flow- USGS gaging station record at discharge for change 

Reservoir name gaging streamflow- downstream same gaging period of in stage for mean 

(agency that built the dam, station gaging station from dam site record1 annual discharge2 Spearman’s 

year storage began) (fig. 1) number (miles) (years) (ft3/s) (feet) rho 

Big Hill Lake (C, 1981) 1 07170700 0.2 1957–99 30 -2.40 -0.98 

Cedar Bluff Reservoir 2 06862500 12.0 1942–52 (

3

) 

(B, 1950) 3 06862700 21.4 1964–99 20 4-.65, -.50 -.81, 

-.81 

Cheney Reservoir 4 07144795 .3 1964–99 100 (

5) 

(B, 1964) 

Clinton Lake (C, 1977) 5 06891483 3.7 1972–80 300 -1.10 -.94 

6 06891500 6.0 1929–72, 300 +.80 .44 

1980–99 

Council Grove Lake 7 07179500 1.7 1938–99 100 -.70 -.98 

(C, 1964) 8 07179730 37.0 1963–99 300 -.35 -.23 

El Dorado Lake 9 07146830 5.1 1981–98 200 -.25 -.85 

(C, 1981) 

Elk City Lake (C, 1966) 10 07170060 .1 1965–99 500 -1.70 -.73 

Fall River Lake 11 07168500 .3 1939–89 300 -.30 -.91 

(C, 1949) 12 07169500 28.9 1938–99 500 -.30 -.89 

Hillsdale Lake (C, 1981) 13 06915000 2.0 1958–99 100 -.25 -.88 

John Redmond Reservoir 14 07182510 5.3 1961–99 1,700 -.15 -.21 

(C, 1964) 

Kanopolis Lake 

(C, 1948) 

Keith Sebelius Lake 

(B, 1964) 

Kirwin Reservoir 

(B, 1955) 

Lovewell Reservoir 

(B, 1957) 

15 06865500 .8 1940–99 300 -5.80 -.99 

16 06866000 38.0 1930–65 400 +1.05 -.16 

17 06864500 -- 1928-98 200 +.80 .85 

18 06848000 .9 1943–99 20 (

5

) -- 

19 06848500 48.4 1944–99 30 +1.95 .77 

20 06871800 .6 1941–99 30 (

5

) -- 

21 06872500 40.8 1945–99 100 +.45 .40 

22 06854000 .3 1945–99 40 (

5

) -- 

Marion Lake (C, 1968) 23 07179795 .25 1968–99 80 -2.15 -.99 

24 07180200 4.55 1984–99 200 +.05 -.23 

Melvern Lake (C, 1972) 25 606913000 713.5, 1968–99 600 +0.30 .72 

28.2 

26 6

06913500 733.5, 1962–99 700 +.45 .67 

48.2 

4 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
--

-- -

-- -

-- -

Table 1. Change in river or stream stage for mean annual discharge at U.S. Geological Survey (USGS) streamflow-gagin

stations located downstream from 24 large Federal reservoirs in Kansas for post-dam period of record—Continued 

Map index 

numberfor 

associated 

USGS Approximate Period of 

stream- Associated distance of continuous Mean annual Post-dam net 

flow- USGS gaging station record at discharge for change 

Reservoir name gaging streamflow- downstream same gaging period of in stage for mean Trend 

(agency that built the dam, station gaging station from dam site record1 annual discharge2 Spearman’s 0.05 le

year storage began) (fig. 1) number (miles) (years) (ft3/s) (feet) rho signifi

Milford Lake (C, 1967) 27 06857100 1.7 1963–99 1,000 -9.05 -0.99 nega

28 06856600 1917–99 1,000 -.25 -.34 no t

Perry Lake (C, 1969) 29 06890900 0 1969–99 700 (

5

) 

Pomona Lake (C, 1963) 30 06912500 .2 1963–99 200 -.50 -.43 nega

Toronto Lake (C, 1960) 31 07166000 3.5 1939–97 500 -3.35 -.97 nega

32 07166500 43.6 1938–99 800 -.55 -.79 nega

Tuttle Creek Lake 33 06887000 2.5 1954–99 2,500 -3.70 -.98 nega

(C, 1962) 

Waconda Lake (B, 1967) 34 06875900 3.6 1964–99 300 (

5) 

35 06876070 57.0 1990–99 600 (

5) 

Webster Reservoir 36 06873200 .4 1956–99 40 -1.75 -.74 nega

(B, 1956) 37 06873460 28.3 1978–99 50 -.70 -.70 nega

Wilson Lake (C, 1964) 38 06868200 .5 1963–99 90 -2.20 -.98 nega

1

Discharges less than 100 ft3/s are rounded to the nearest 10 ft3/s, whereas discharges greater than 100 ft3/s are rounded to the nearest 100 ft3/s

2 In some cases, the period of record does not extend back to the date of dam completion.


3

 Analysis was not possible due to insufficient post-dam period of record.


4

 Gage moved 1.2 miles downstream in 1985. Net changes in stage are for 1964–84 and 1985–98, respectively.


5

 Analysis was not possible due to concrete control at or near gage site. 

6

 Gage site located downstream from both Pomona and Melvern Lakes. 

7 Distance downstream from Pomona and Melvern Lakes, respectively. 

elevation. For this purpose, a nonparametric Spearman’s rho correlation coefficient was computed. An 

advantage of Spearman’s rho is that, because it is 

based on ranks of the data, it is more resistant to outlier effects than the more commonly used Pearson’s r 

correlation coefficient (Helsel and Hirsch, 1992). Statistical significance of trends was tested using a level 

of significance of 0.05. 

CHANNEL-BED ELEVATION CHANGES 

For 15 of the 17 reservoirs for which analysis for 

the first gaging station downstream from the dam was 

possible, a statistically significant negative trend (that 

is, decreasing stage with time) was indicated. Thus, at 

these locations, channel-bed lowering was indicated 

by the decreasing stage. The two exceptions were the 

Neosho River at Burlington downstream from John 

Redmond Reservoir (fig. 2), which had no statisti

significant trend in channel-bed elevation downstr

and the Marais des Cygnes River near Pomona do

stream from Melvern Lake (fig. 3), for which a sta

cally significant positive trend (that is, increasing s

with time) was indicated (table 1). However, for M

vern Lake, the gaging station is located a consider

distance downstream (28.2 mi) and thus may not 

indicative of conditions immediately downstream 

from the dam. Also, artificial control is provided b

overflow dam located 4.7 mi downstream from th

gaging station. The presence of the overflow dam 

cause backwater effects and deposition of materia

the channel bed in the vicinity of the gaging statio

In figures 2–31, each data point represents the sta

date for an individual rating curve. 

For several of the gaging stations for which a 

tistically significant negative trend was indicated, 

Channel-Bed Elevation Change
15 

14 

13 

12 

11 

10 

9 

8 

7 

6 

5 

Pomona Dam completed 

Melvern Dam completed 

John Redmond Dam completed 

1960 1970 1980 1990 2000 

Figure 2. Change in river/stream stage for mean annual discharge (1,700 cubic feet per second) 

of Neosho River at Burlington (gaging station 07182510, map index number 14, downstream from 

John Redmond Reservoir), 1961–97. 

6 

5 

4 

3 

2 

1 

0 

1960 1970 1980 1990 2000 

Figure 3. Change in river/stream stage for mean annual discharge (600 cubic feet per second) of 

Marais des Cygnes River near Pomona (gaging station 06913000, map index number 25, 

downstream from Melvern and Pomona Lakes), 1968–93. Stage, in feet Stage, in feet 

6 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
substantial net decrease in stage was determined. 

Downstream from Milford (fig. 4) and Kanopolis 

(fig. 5) Lakes, the net decrease in stage was 9.05 and 

5.80 ft, respectively. A decrease in stage of about 3.5 ft 

was determined downstream from Toronto (fig. 6) and 

Tuttle Creek (fig. 7) Lakes. Downstream from Big Hill 

(fig. 8), Elk City (fig. 9), Marion (fig. 10), and Wilson 

(fig. 11) Lakes, and Webster Reservoir (fig. 12), a 

decrease in stage of about 2 ft was determined. The 

decrease in stage determined for the gaging station 

downstream from Big Hill Lake may be attributable, 

in part, to other disturbances (bridge construction, 

channel modifications) that occurred prior to and during the construction of the dam. Also, outflow channel 

repair in the vicinity of the gaging station downstream 

from Elk City Lake may have contributed to the 

decrease in stage determined for this site. With the 

exception of Clinton Lake (-1.10 ft) (fig. 13), the 

decrease in stage at the first gaging station downstream from the remaining reservoirs (for which a statistically significant negative trend was indicated) was 

less than 1 ft (table 1) (figs. 14–18). 

The geomorphic response of a channel downstream from a reservoir depends on the local conditions. For example, downstream from Kanopolis and 

Milford Lakes, the readily erodible sand and gravel 

channel beds have lowered continuously since the 

dams were completed in 1948 and 1967, respectively. 

In comparison, downstream from El Dorado and Hillsdale Lakes, minimal channel-bed lowering has 

occurred due to bedrock control (information on the 

composition of the channel bed at gaging stations is on 

file at the USGS office in Lawrence, Kansas). At the 

locations where the channel bed is actively lowering, 

the channel bed eventually will stabilize due to one or 

more possible causes including armoring, bedrock, 

flattening of the channel gradient, and downstream 

base-level control provided by grade-control structures 

or the confluence with a larger river or stream. 

The pronounced lowering of the Republican River 

channel bed downstream from Milford Lake (fig. 4) 

began immediately after completion of the dam in 

1967. From 1967 to 1997, the channel bed lowered at 

an average rate of about 0.3 ft/yr. However, as indicated by the slope of the data points (fig. 4), the rate of 

lowering appears to have slowed in recent years. 

Ideally, the period of record for the first gaging 

station located downstream from a dam would extend 

back 10 or more years prior to dam construction. Such 

pre-dam information may be used to help ascertain 

whether or not the post-dam changes in channel-b

elevation are due primarily to the effects of regula

or to some combination of causes that may includ

regulation. Unfortunately, in most cases the first 

ing station located downstream from a dam was 

installed to measure the discharge released from t

dam. Thus, in such cases, the desired pre-dam in

mation was limited or did not exist. 

Such was the case for the first gaging station 

the Republican River located downstream from M

ford Lake, for which the period of record extende

back only 3 years prior to the completion of the d

(fig. 4). Such limited pre-dam information was n

sufficient to assess pre-dam changes in channel-b

elevation. However, pre-dam information for a ga

station upstream from Milford Lake at Clay Cent

(figs. 1 and 19) was available. At this upstream 

location, the Republican River channel bed has be

stable since about 1938, with only minor fluctuati

due to scour and fill processes. The stability of th

channel bed at this upstream location provided ad

tional evidence that the effects of regulation are a 

mary, though not necessarily only, cause of chann

bed lowering in the Republican River downstream 

from Milford Lake. 

The lowering of the Smoky Hill River channe

downstream from Kanopolis Lake (fig. 5) has bee

ongoing since completion of the dam in 1948. Fro

1948 to 1952, the channel bed lowered at a relativ

rapid average rate of about 0.7 ft/yr. Then, from 1

to 1997, the channel-bed lowering continued at an 

average rate of about 0.07 ft/yr. Because only 7 y

of pre-dam information was available for this site 

(fig. 5), pre-dam changes in channel-bed elevation 

could not be meaningfully evaluated. Upstream f

Kanopolis Lake at Ellsworth (figs. 1 and 20), the 

Smoky Hill River channel bed has been stable or 

slowly aggrading since 1950. The upstream versu

downstream contrast in channel-bed elevation cha

since completion of the dam indicated that regula

is likely a primary cause of channel-bed lowering 

downstream from Kanopolis Lake. 

The channel bed of the Big Blue River downstream from Tuttle Creek Lake lowered at an aver

rate of about 0.1 ft/yr from 1962 (year of dam com

tion) to 1997 (fig. 7). Downstream from Toronto 

Lake, the channel bed of the Verdigris River lowe

at an average rate of about 0.09 ft/yr from 1960 (y

of dam completion) to 1996 (fig. 6). The pre-dam 

period of record for both of these locations was c

Channel-Bed Elevation Change
16 

15 

14 

13 

12 

11 

10 

9 

8 

7 

6 

5 

4 

3 

2 

1 

0 

Kanopolis Dam completed 

Milford Dam completed 

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 

Figure 4. Change in river/stream stage for mean annual discharge (1,000 cubic feet per second) 

of Republican River below Milford Dam (gaging station 06857100, map index number 27, 

downstream from Milford Lake), 1963–97. 

13 

12 

11 

10 

9 

8 

7 

6 

5 

4 

3 

1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 

Figure 5. Change in river/stream stage for mean annual discharge (300 cubic feet per second) of 

Smoky Hill River near Langley (gaging station 06865500, map index number 15, downstream from 

Kanopolis Lake), 1940–97. Stage, in feet Stage, in feet 

8 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
11 

10 

Toronto Dam completed 

9 

8 

7 

6 

5 

4 

1950 1960 1970 1980 1990 2000 

Figure 6. Change in river/stream stage for mean annual discharge (500 cubic feet per second) of 

Verdigris River near Coyville (gaging station 07166000, map index number 31, downstream from 

Toronto Lake), 1952–96. 

10 

9 

8 

7 

6 

5 

4 

3 

1950 1960 1970 1980 1990 2000 Tuttle Creek Dam completed 

Figure 7. Change in river/stream stage for mean annual discharge (2,500 cubic feet per second) 

of Big Blue River near Manhattan (gaging station 06887000, map index number 33, downstream 

from Tuttle Creek Lake), 1953–97. Stage, in feet Stage, in feet 

Channel-Bed Elevation Change
9 

8 

Big Hill Dam completed 

7 

6 

5 

4 

3 

2 

1950 1960 1970 1980 1990 2000 

Figure 8. Change in river/stream stage for mean annual discharge (30 cubic feet per second) of 

Big Hill Creek near Cherryvale (gaging station 07170700, map index number 1, downstream from 

Big Hill Lake), 1957–97. 

12 

11 

10 

9 

8 

7 

1960 1970 1980 1990 2000 Elk City Dam completed 

Figure 9. Change in river/stream stage for mean annual discharge (500 cubic feet per second) of 

Elk River below Elk City Lake (gaging station 07170060, map index number 10, downstream from 

Elk City Lake), 1966–90. Stage, in feet Stage, in feet 

10 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
10 

9 

Marion Dam completed 

8 

7 

6 

5 

4 

1960 1970 1980 1990 2000 

Figure 10. Change in river/stream stage for mean annual discharge (80 cubic feet per second) of 

North Cottonwood River below Marion Lake (gaging station 07179795, map index number 23, 

downstream from Marion Lake), 1968–97. 

9 

8 

7 

6 

5 

4 

3 

2 

1 

Wilson Dam completed 

1960 1970 1980 1990 2000 

Figure 11. Change in river/stream stage for mean annual discharge (90 cubic feet per second) of 

Saline River at Wilson Dam (gaging station 06868200, map index number 38, downstream from 

Wilson Lake), 1965–96. Stage, in feet Stage, in feet 

Channel-Bed Elevation Changes 
6 

5 

Webster Dam completed in 1956 

Culverts (installed in 1983) just downstream from gage were 

temporarily clogged by logs or beaver dam (source: Dennis 

L. Lacock, U.S. Geological Survey, written commun., 2000) 4 

3 

2 

1 

0 

1960 1970 1980 1990 2000 

Figure 12. Change in river/stream stage for mean annual discharge (40 cubic feet per second) of 

South Fork Solomon River below Webster Reservoir (gaging station 06873200, map index 

number 36, downstream from Webster Reservoir), 1963–98. 

12 

11 

10 

9 

8 

7 

6 

5 

4 

Clinton Dam 

completed 

1950 1960 1970 1980 1990 2000 

Figure 13. Change in river/stream stage for mean annual discharge (300 cubic feet per second) 

of Wakarusa River below Clinton Dam (gaging station 06891483, map index number 5, 

downstream from Clinton Lake), 1972–79. Stage, in feet Stage, in feet 

12 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
11 

10 

Council Grove 

Dam completed 

Concrete weir installed across channel in 1997 

about 0.25 mile downstream from gage 

9 

8 

7 

6 

5 

1940 1950 1960 1970 1980 1990 2000 

Figure 14. Change in river/stream stage for mean annual discharge (100 cubic feet per second) of 

Neosho River at Council Grove (gaging station 07179500, map index number 7, downstream from 

Council Grove Lake), 1944–97. 

6 

5 

4 

3 

2 

1 

0 

1970 1980 1990 2000 El Dorado Dam completed 

Figure 15. Change in river/stream stage for mean annual discharge (200 cubic feet per second) of 

Walnut River at Highway 54 east of El Dorado (gaging station 07146830, map index number 9, 

downstream from El Dorado Lake), 1981–94. Stage, in feet Stage, in feet 

Channel-Bed Elevation Changes 
8 

7 

Fall River Dam completed 

6 

5 

4 

3 

2 

1930 1940 1950 1960 1970 1980 1990 

Figure 16. Change in river/stream stage for mean annual discharge (300 cubic feet per second) 

of Fall River near Fall River (gaging station 07168500, map index number 11, downstream from 

Fall River Lake), 1940–79. 

6 

5 

4 

3 

2 

1 

0 

1950 1960 1970 1980 1990 2000 Hillsdale Dam completed 

Figure 17. Change in river/stream stage for mean annual discharge (100 cubic feet per second) 

of Big Bull Creek near Hillsdale (gaging station 06915000, map index number 13, downstream 

from Hillsdale Lake), 1958–95. Stage, in feet Stage, in feet 

14 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
8 

7 

Pomona Dam completed 

6 

5 

4 

3 

2 

1 

1960 1970 1980 1990 2000 

Figure 18. Change in river/stream stage for mean annual discharge (200 cubic feet per second) 

of Hundred and Ten Mile Creek near Quenemo (gaging station 06912500, map index number 30, 

downstream from Pomona Lake), 1963–98. 

16 

14 

12 

10 

8 

6 

4 

2 

0 

Milford Dam completed 

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 

Figure 19. Change in river/stream stage for mean annual discharge (1,000 cubic feet per second) 

of Republican River at Clay Center (gaging station 06856600, map index number 28, upstream 

from Milford Lake), 1934–99. Stage, in feet Stage, in feet 

Channel-Bed Elevation Changes 
8 

7 

6 

5 

4 

3 

2 

1 

0 

Kanopolis Dam completed 

1940 1950 1960 1970 1980 1990 2000 

Figure 20. Change in river/stream stage for mean annual discharge (200 cubic feet per second) 

of Smoky Hill River at Ellsworth (gaging station 06864500, map index number 17, upstream from Stage, in feet 

Kanopolis Lake), 1949–97. 

sidered too short (less than 10 years) to meaningfully 

evaluate pre-dam changes in channel-bed elevation. 

Sufficient information to evaluate pre-dam 

changes in channel-bed elevation at the first gaging 

station downstream from the dam was available for 

Hillsdale, Big Hill, and Council Grove Lakes. Downstream from Hillsdale Lake (fig. 17), the stability of 

the Big Bull Creek channel bed due to bedrock control 

is evident throughout the period of record. Downstream from Big Hill Lake (fig. 8), pre-dam changes in 

the Big Hill Creek channel-bed elevation were caused, 

in part, by multiple disturbances including bridge construction and channel modifications. Downstream 

from Council Grove Lake (fig. 14), lowering of the 

Neosho River channel bed was ongoing before, during, and after the construction of the dam. The channel bed has been stable since the late 1980s due to 

bedrock control. 

Changes in channel-bed elevation upstream from 

most of the reservoirs was not investigated because 

either the change in channel-bed elevation at the first 

gaging station downstream from the dam was relatively minor or unknown, no upstream gaging station 

existed, the upstream gaging station was located 

upstream from one or more major tributaries, or the 

period of record for the upstream gaging stati

too short. 

Although channel-bed lowering was typic

first gaging station downstream from the dam

results were more mixed for the second gagin

tions located farther downstream. For the seco

ing station located downstream from Cedar B

Reservoir (fig. 21), Fall River Lake (fig. 22), 

Lake (fig. 23), and Webster Reservoir (fig. 24

tistically significant negative trend in stage w

cated. For these gaging stations, which were l

from about 21 to 44 mi downstream from the 

the net decrease in stage was about 1 ft or les

No statistically significant trend in stage w

cated for the second gaging station located do

stream from Clinton (fig. 25), Council Grove 

Kanopolis (fig. 27), and Marion (fig. 28) Lak

Kirwin Reservoir (fig. 29). These gaging stati

located from about 5 to 41 mi downstream fro

dams. A statistically significant positive trend 

was determined for the second gaging station 

about 48 mi downstream from both Keith Seb

(fig. 30) and Melvern (fig. 31) Lakes. For Wa

Lake, analysis was not possible for either of t

downstream gaging stations due to concrete c

or near the gage sites. It is uncertain if the tre

16 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
A. 

7 

6 

5 

4 

3 

2 

1 

0 

B. 

7 

6 

5 

4 

3 

2 

1 

0 

1960 1970 1980 1990 2000 

Note: This site was established 1.2 miles 

downstream from original site in 1985 

due to beaver dams, which caused 

backwater problems at the original site. 

Cedar Bluff Dam completed in 1950 

Figure 21. Change in river/stream stage for mean annual discharge (20 cubic feet per second) of 

Smoky Hill River near Schoenchen (gaging station 06862700, map index number 3, downstream 

from Cedar Bluff Reservoir), 1964–98. 

Cedar Bluff Dam completed in 1950 

Stage, in feet 

Channel-Bed Elevation Changes 
8 

7 

Fall River Dam completed 

6 

5 

4 

3 

2 

1940 1950 1960 1970 1980 1990 2000 

Figure 22. Change in river/stream stage for mean annual discharge (500 cubic feet per second) 

of Fall River at Fredonia (gaging station 07169500, map index number 12, downstream from Fall 

River Lake), 1947–98. 

8 

7 

6 

5 

4 

3 

2 

1940 1950 1960 1970 1980 1990 2000 Toronto Dam completed 

Figure 23. Change in river/stream stage for mean annual discharge (800 cubic feet per second) 

of Verdigris River near Altoona (gaging station 07166500, map index number 32, downstream 

from Toronto Lake), 1945–98. Stage, in feet Stage, in feet 

18 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
9 

8 

Webster Dam completed in 1956 

7 

6 

5 

4 

3 

2 

1960 1970 1980 1990 2000 

Figure 24. Change in river/stream stage for mean annual discharge (50 cubic feet per second) of 

South Fork Solomon River at Woodston (gaging station 06873460, map index number 37, 

downstream from Webster Reservoir), 1978–97. 

11 

10 

9 

8 

7 

6 

5 

4 

3 

Clinton Dam completed 

1950 1960 1970 1980 1990 2000 

Figure 25. Change in river/stream stage for mean annual discharge (300 cubic feet per second) 

of Wakarusa River near Lawrence (gaging station 06891500, map index number 6, downstream 

from Clinton Lake), 1951–98. Stage, in feet Stage, in feet 

Channel-Bed Elevation Changes 
8 

7 

Council Grove 

Dam completed 

6 

5 

4 

3 

2 

1 

1960 1970 1980 1990 2000 

Figure 26. Change in river/stream stage for mean annual discharge (300 cubic feet per second) 

of Neosho River near Americus (gaging station 07179730, map index number 8, downstream from 

Council Grove Lake), 1963–97. 

11 

10 

9 

8 

7 

6 

5 

1930 1940 1950 1960 1970 Kanopolis Dam completed 

Figure 27. Change in river/stream stage for mean annual discharge (400 cubic feet per second) 

of Smoky Hill River at Lindsborg (gaging station 06866000, map index number 16, downstream 

from Kanopolis Lake), 1937–65. Stage, in feet Stage, in feet 

20 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
10 

9 

Marion Dam completed in 1968 

8 

7 

6 

5 

4 

3 

1980 1990 2000 

Figure 28. Change in river/stream stage for mean annual discharge (200 cubic feet per second) 

of Cottonwood River at Marion (gaging station 07180200, map index number 24, downstream 

from Marion Lake), 1984–96. 

8 

7 

6 

5 

4 

3 

2 

1 

1960 1970 1980 1990 2000 

Kirwin Dam completed in 1955 

Figure 29. Change in river/stream stage for mean annual discharge (100 cubic feet per second) 

of North Fork Solomon River at Portis (gaging station 06872500, map index number 21, 

downstream from Kirwin Reservoir), 1964–97. Stage, in feet Stage, in feet 

Channel-Bed Elevation Changes 
7 

6 

Keith Sebelius 

Dam completed 

5 

4 

3 

2 

1 

0 

1950 1960 1970 1980 1990 2000 

Figure 30. Change in river/stream stage for mean annual discharge (30 cubic feet per second) of 

Prairie Dog Creek near Woodruff (gaging station 06848500, map index number 19, downstream 

from Keith Sebelius Lake), 1955–96. 

10 

9 

8 

7 

6 

5 

4 

3 

1960 1970 1980 1990 2000 Pomona Dam completed Melvern Dam completed 

Figure 31. Change in river/stream stage for mean annual discharge (700 cubic feet per second) 

of Marais des Cygnes River near Ottawa (gaging station 06913500, map index number 26, 

downstream from Melvern Lake), 1962–94. Stage, in feet Stage, in feet 

22 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas 
channel-bed elevation determined for some of the second gaging stations are related to the upstream dam. 

An assessment of the downstream extent of channel-bed elevation changes was limited by a lack of 

information. For example, downstream from Kanopolis Lake, the first and second gaging stations are 

located at distances of about 0.8 and 38 mi from the 

dam. For the first gaging station, a statistically significant negative trend was indicated with a net decrease 

in stage of 5.80 ft. No trend was indicated for the second gaging station. Thus, the downstream limit of 

channel-bed lowering was somewhere in the approximately 37-mi-long reach of river channel between the 

two gaging stations. Williams and Wolman (1984) 

determined that about 1.6 ft of channel-bed lowering 

had occurred at a location 3 mi downstream from the 

dam as of 1971. 

Additional information, which may not be available, is necessary to more effectively assess the downstream extent of channel-bed elevation changes. For 

some reservoirs constructed by the U.S. Army Corps 

of Engineers (table 1), multiple-date, cross-sectional 

information may be available for several sites downstream. If available, such information may be used to 

help assess the magnitude and downstream extent 

of post-dam changes in channel depth, width, 

and geometry. 

An assessment of the effect of time on channelbed elevation change was limited to the four reservoirs 

for which the largest downstream changes in channelbed elevation were determined. Downstream from 

Milford Lake, the rate of lowering of the Republican 

River channel bed appeared to slow about 1980 

(13 years after dam closure) but continued at least 

through 1997 (fig. 4). Eventually, the channel bed at 

this location will stabilize due to a combination of factors including reduced slope, bedrock control, and 

base-level control provided by the Kansas River downstream. Downstream from Kanopolis Lake, the rate of 

lowering of the Smoky Hill River channel bed 

decreased substantially in 1952 (4 years after dam closure) but continued at least through 1997 (fig. 5). 

Downstream from Toronto Lake, the rate of lowering 

of the Verdigris River channel bed has decreased gradually over time but continued at least through 1996 

(fig. 6). The rate of lowering of the Big Blue River 

channel bed downstream from Tuttle Creek Lake 

showed no indication of slowing as of 1997 (fig. 7). 

At these locations, the adjustment of the channel 

bed has been ongoing for several decades and is n

yet complete. 

SUMMARY AND CONCLUSIONS 

Available information from USGS streamflow

gaging stations was used to assess channel-bed el

tion changes downstream from 24 large Federal r

voirs in Kansas. For 15 of the 17 reservoirs for w

analysis for the first gaging station downstream fr

the dam was possible, a statistically significant ne

tive trend in channel-bed elevation (represented b

trend in river/stream stage for the mean annual di

charge) was indicated. At these gaging stations (t

cally located 5 mi or less downstream from the da

the net decrease in channel-bed elevation ranged 

between 0.25 (El Dorado and Hillsdale Lakes) to 

9.05 ft (Milford Lake). The magnitude of channel

lowering downstream from the reservoirs likely w

related to the composition of the channel bed and 

be due, in part, to causes other than upstream regu

tion. The spatial and temporal variability of chan

bed elevation changes determined in this study w

indicative of the variability of the factors that con

the geomorphic response of river and stream chan

downstream from reservoirs. 

A determination of the magnitude and rate of 

channel-bed lowering downstream from a reservo

important for understanding the geomorphic resp

of the channel to the changes imposed by the rese

and the possible implications. At locations where 

channel-bed elevation has decreased several feet a

the lowering is ongoing, structures, property, and 

tat may be threatened due to channel-bed and ban

erosion. At locations where channel-bed lowering 

been limited by bedrock, channel widening may b

concern. Thus, the magnitude and rate of channel

lowering may provide an indication of actual and 

potential channel change downstream from a reser

Additional investigation, perhaps involving the us

more streamflow-gage information, surveyed cros

sections, and aerial photography, as well as a com

hensive analysis of channel-bed and bank compos

tion, may provide a more complete understanding 

channel change downstream from reservoirs and h

to prioritize and plan channel stabilization and 

rehabilitation efforts. 

Summary and Conclusions 
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24 Channel-Bed Elevation Changes Downstream From Large Reservoirs in Kansas