Long Term Resource Monitoring Program

Technical Report

2000-T001

August 2000

Response of Vegetation and Fish

During an Experimental Drawdown

In Three Pools, Upper Mississippi River
Long Term Resource Monitoring Program Technical Reports

provide Long Term Resource Monitoring Program

partners with scientific and technical support.

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Upper Midwest Environmental

Sciences Center

CENTER DIRECTOR

Leslie E. Holland-Bartels

PROGRAM MANAGER

Robert L. Delaney

CHIEF, AQUATIC SCIENCES BRANCH

James G. Wiener

CHIEF, SUPPORT SERVICES

Barbara A. Deml

REPORT EDITOR

Jerry D. Cox

Mention of trade names or commercial products does not constitute endorsement

or recommendation for use by the U.S. Department of the Interior, U.S. Geological Survey.
Response of Vegetation and Fish

During an Experimental Drawdown

In Three Pools, Upper Mississippi River

by

Joseph H. Wlosinski, James T. Rogala, Thomas W. Owens, Kenneth L. Dalrymple,

David Busse, Claude N. Strauser, and Elmer Atwood

August 2000

U.S. Geological Survey

Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, Wisconsin 54603
Findings, views, and recommendations are those of the authors and should not be construed as official department positions

unless so designated by other authorizing documents.

Suggested citation:

Wlosinski J. H., J. T. Rogala, T. W. Owens, K. L. Dalrymple, D. Busse, C. N. Strauser, and E. Atwood. 2000. Response of

vegetation and fish during an experimental drawdown in three pools, Upper Mississippi River. U.S. Geological Survey, Upper

Midwest Environmental Sciences Center, La Crosse, Wisconsin, August 2000. LTRMP 2000-T001. 18 pp. + Appendixes

A – B

Additional copies of this report may be obtained from the National Technical Information Service, 5285 Port Royal Road,

Springfield, VA 22161 (1-800-553-6847 or 703-487-4650). Also available to registered users from the Defense Technical

Information Center, Attn: Help Desk, 8725 Kingman Road, Suite 0944, Fort Belvoir, VA 22060-6218 (1-800-225-3842 or

703-767-9050).
iii

Contents

Page

Preface ....................................................................................................................................................... v

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

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

Methods ...................................................................................................................................................... 2

Water Levels ........................................................................................................................................... 2

Ground Surveys ....................................................................................................................................... 3

Vegetation Mapping ................................................................................................................................. 3

Fish .......................................................................................................................................................... 4

Spatial Model ........................................................................................................................................... 7

Results and Discussion ............................................................................................................................... 7

Water Levels ........................................................................................................................................... 7

Ground Surveys ....................................................................................................................................... 9

Vegetation Mapping ............................................................................................................................... 10

Fish ........................................................................................................................................................ 10

Spatial Model ......................................................................................................................................... 11

Benefits of Vegetation ........................................................................................................................... 14

Conclusions and Recommendations .......................................................................................................... 16

Acknowledgment ...................................................................................................................................... 16

References................................................................................................................................................ 17

Appendix A. Pool 25 Natural Resources Committee Members.............................................................A-1

Appendix B. Definitions of Terms Used in this Report .......................................................................... B-1
iv

Tables

Page

1. Location of vegetation surveys in the three pools affected by a drawdown ....................................... 4

2. Fish sampling locations, habitat and substrate types, and the number of seine hauls per pool and

year ..................................................................................................................................................... 5

3. Amount of drawdown at Pools 24 and 25 and Melvin Price Pool in 1995 and 1996 .......................... 9

4. Amounts of vegetation estimated from aerial photographs taken on July 27, 1995............................13

Figures

1. Location of Pools 22, 24, and 25 and the Melvin Price Pool on the Upper Mississippi River.............. 2

2. Water elevation relative to discharge according to the water-level management plan for Pool 25 ..... 3

3. Measured water-level elevations (feet above sea level) immediately upriver of Lock and Dam 24

in 1995 and 1996. ................................................................................................................................. 7

4. Measured water-level elevations (feet above sea level) immediately upriver of Lock and Dam 25

in 1995 and 1996................................................................................................................................... 8

5. Measured water-level elevations (feet above sea level) immediately upriver of Melvin Price Locks

and Dam in 1995 and 1996 ................................................................................................................... 8

6. Measured water-level elevations (feet above sea level) immediately upriver of Lock and Dam 22

in 1995 .................................................................................................................................................. 8

7. Estimated discharges at Keokuk, Iowa, in 1995 (a) and 1996 (b) ....................................................... 9

8. Estimated discharges at Grafton, Illinois, in 1995 (a) and 1996 (b) ..................................................... 9

9. Frequency of occurrence of vegetation at all sampling sites in 1995 ................................................. 10

10. Average height of Echinochloa spp. (millet) at all sampling sites .................................................... 11

11. Average height of Cyprus spp. (chufa) at all sampling sites ............................................................. 11

12. Average height of Polygonum spp. (smartweed) at all sampling sites .............................................. 11

13. Acres of vegetation near the waterline in 1995 estimated from aerial photography .......................... 12

14. Areas of vegetation (black) in Pools 22 (a), 24 (b), 25 (c), and Melvin Price Pool (d) thought to

be caused by a drop in water levels ................................................................................................... 12

15. Mean total numbers of fish (all species) per seine haul in Pool 24 .................................................... 13

16. Mean total numbers of fish (all species) per seine haul in Pool 25 .................................................... 13

17. Mean total numbers of fish (all species) per seine haul in Pool 26 .................................................... 14

18. Mean total numbers of fish (all species) per seine haul in the upriver and down river portions of

Pools 24, 25, and 26 ............................................................................................................................ 14

19. Simpson’s Diversity Index for fishes sampled by seining in Pool 24 .................................................. 15

20. Simpson’s Diversity Index for fishes sampled by seining in Pool 25 .................................................. 15

21. Simpson’s Diversity Index for fishes sampled by seining in Pool 26 .................................................. 15

22. A comparison of acreage of dewatered areas predicted by the model to acreage of vegetation

estimated from photointerpretation ..................................................................................................... 16

23. A map of dewatered areas as predicted by the model in comparison with areas with vegetation

estimated from photointerpretation in the lower stretch of Pool 25 ................................................... 16

Number
v

Preface

The Long Term Resource Monitoring Program (LTRMP) was authorized under the Water Resources

Development Act of 1986 (Public Law 99-662) as an element of the U.S. Army Corps of Engineers’ (Corps)

Environmental Management Program. The LTRMP is being implemented by the U.S. Geological Survey’s

Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin, in cooperation with the five Upper

Mississippi River System (UMRS) States of Illinois, Iowa, Minnesota, Missouri, and Wisconsin. The U.S.

Army Corps of Engineers provides guidance and has overall Program responsibility. The mode of operation

and respective roles of the agencies are outlined in a 1988 Memorandum of Agreement.

The UMRS encompasses the commercially navigable reaches of the Upper Mississippi River, as well as

the Illinois River and navigable portions of the Kaskaskia, Black, St. Croix, and Minnesota Rivers. Congress

has declared the UMRS to be both a nationally significant ecosystem and a nationally significant commercial

navigation system. The mission of the LTRMP is to provide decision makers with information for maintaining

the UMRS as a sustainable large river ecosystem given its multiple-use character. The long-term goals of the

Program are to understand the system, determine resource trends and effects, develop management

alternatives, manage information, and develop useful products.

This report was prepared under Strategy 1.2.3, Determine Effects of Water Levels and Discharges on

the Upper Mississippi River Ecosystem, and Goal 3, Develop Alternatives to Better Manage the Upper

Mississippi River System, as specified in the Operating Plan of the LTRMP for the Upper Mississippi River

System (U.S. Fish and Wildlife Service 1993). The purpose of this work was to monitor the response of

vegetation from an experimental drawdown during 1995 and 1996 in Pools 24 and 25 and Melvin Price Pool

on the Upper Mississippi River and to refine a previously developed geographic information system model to

predict areas that would be dewatered because of alternative water-level management plans.
1

Response of Vegetation and Fish

During an Experimental Drawdown

In Three Pools, Upper Mississippi River

by

Joseph H. Wlosinski, James T. Rogala, and Thomas W. Owens

U.S. Geological Survey, Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road, La Crosse, Wisconsin 54603

Kenneth L. Dalrymple

Missouri Department of Conservation

Box 201, Elsberry, Missouri 63343

David Busse and Claude N. Strauser

U.S. Army Corps of Engineers, St. Louis District

1222 Spruce Street, St. Louis, Missouri 63103

Elmer Atwood

Illinois Department of Natural Resources

1000 Killarney Drive, Greenville, Illinois 62246

Abstract. An experiment to improve ecological conditions while maintaining a 9-foot (2.74-m) navigation

channel was continued in 1995 and 1996 on the three pools of the Upper Mississippi River managed by the

St. Louis District, U.S. Army Corps of Engineers. Water levels were held from 1 to 3 feet (0.3 to 0.9 m) lower

than maximum regulated elevations at the dam from about mid-June through July in Pools 24 and 25 and

Melvin Price Pool. Water levels were then gradually raised as discharge allowed. Vegetation was surveyed

along an elevational gradient in eight areas in 1995 and six areas in 1996. Seven plant genera were identified in

1995 and five genera in 1996. Amaranthus spp. (pigweed), Cyperus spp. (chufa), Echinochloa spp. (wild

millet), and Polygonum spp. (smartweed) were found in 30–90% of the sites. Plants grew 7–10 inches (17.8–

25.4 cm) in about 30 days and then grew more quickly as water levels were slowly raised. On July 27, 1995,

aerial infrared photographs (1:15,000) were taken of the lower stretches of the three pools. Photographs also

were taken of Pool 22, where no drawdown occurred. These photographs were interpreted, specifically searching

areas near the waterline with signatures representing the above plants. In Pools 24 and 25 and Melvin Price

Pool, between 255 and 880 acres (103 and 356 ha) of plants were measured near the waterline, compared to just

51 acres (20.6 ha) in Pool 22 where water levels near the dam were held at the project pool elevation. A

geographic information system model was also used to predict areas that would be dewatered under various

water-level management options. Minnow seining data collected on the three pools from 1986 to 1996 were

also analyzed. The total numbers of fish per haul and Simpson’s Diversity Index showed no significant detrimental

effects during years when water levels were held on the low side of the operating band. We believe that this

management experiment was successful and that continuation, as conditions allow, would be beneficial.

Keywords: Drawdown, fish, Mississippi, river, upper, vegetation, water-level management, water levels

Introduction

An experiment to improve ecological conditions

while maintaining a 9-foot (2.74-m) navigation

channel was initiated in 1994 on Pools 24 and 25

and Melvin Price Pool (Figure 1) on the Upper

Mississippi River. Instead of holding water levels

on the high side of the operating band as usual, water
2

levels were held on the low side of the operating

band with the goal of increasing plant production.

The experiment was performed in cooperation with

the Pool 25 Natural Resources Management

Committee (Committee), an interagency group

whose goal is to improve habitat in the Upper

Mississippi River floodplain. Committee members

are listed in Appendix A.

 

Figure 1. Location of Pools 22, 24, and 25 and the Melvin

Price Pool on the Upper Mississippi River.

The 1994 experiment was considered successful

by the Committee. Amaranthus spp. (pigweed),

Cyperus spp. (chufa or flatsedge), Echinochloa spp.

(wild millet or cockspur), Leptochloa spp. (sprangle

top), and Polygonum spp. (smartweed or knotweed)

colonized the dewatered area. The plant community

in the dewatered zone grew 2–3 feet (0.6–0.9 m) by

early August. Seed production seemed to be excellent

and substantial numbers of waterfowl used the area

during fall migration. Additional information

concerning the 1994 experiment is in Busse et al.

(1995).

Here we report on the continuation of the waterlevel experiment in 1995 and 1996. Two additional

goals were quantifying plant response and refining

a previously developed geographic information

system (GIS) model to predict areas that would be

dewatered when using alternative water-level

management plans. Plant response would be

estimated from ground surveys and aerial

photography. We also analyzed minnow seining data

collected on all three pools between 1986 and 1996.

This report extends involvement by the U.S.

Geological Survey Upper Midwest Environmental

Sciences Center concerning water-level management

in the St. Louis District. Previous studies summarized

historical discharges and water-level management

practices in Pool 25 (Wlosinski 1996), the effects of

water-level management alternatives on habitats

(Wlosinski and Rogala 1996), and estimating land

ownership requirements in moving the control point

in Pool 25 (Wlosinski and Rogala 1997).

Some of the terminology used in this report may

not be common but is used routinely for water-level

management or analysis with GIS. Definitions for

these terms are included in Appendix B.

Methods

Water Levels

The Committee recognized the fact that the

Mississippi River is put to multiple uses, including

navigation and biological habitat. It also recognized

that water levels and pool slope are highly dependent

on discharge. With those facts in mind, the Committee

made two suggestions in spring 1995 for water-level

management: provide a safe and dependable

navigation channel and provide better opportunities

of reproductive success of fish, vegetation,

invertebrates, and associated organisms.

The Committee’s recommendation for waterlevel management for fish reproduction was to

maintain steady to slightly rising water conditions

for at least a 30-day period in the spring. Pool surface

elevation was not considered as important as keeping

fluctuations to less than 0.5 foot (15 cm) in any 10-day

period. Steady pool levels were requested between

May 1 and June 30, with the period between May 15

and June 15 being the most critical. The Committee

also thought it beneficial for the pool selected to have

residual vegetation from a previous year to increase

spawning and nursery habitat.

The request for water-level management for plant

reproduction included a drawdown of 0.5–2.0 feet
3

(0.15–0.6 m) for at least 30 days, starting when the

normal high spring flows recede. This plan would

better mimic a more natural hydrograph. The pool

would then be raised after the drawdown at a rate not

greater than 0.2 feet (6 cm) per day.

The St. Louis District would continue to manage

water levels within the guidelines established in the

Master Water Control Manual and appendixes (U.S.

Army Corps of Engineers 1980a–d) to assure that a

9-foot (2.74-m) navigation channel is maintained. The

guidelines require that water levels be managed as a

function of discharge and allow some flexibility

within certain discharge ranges. Maximum drawdown

below the project pool elevation at the three dams is

between 3.5 and 6.5 feet (1.1 and 2.0 m). A sample

plan for water-level management is presented for

Pool 25 (Figure 2). Flexibility is measured as the

vertical difference between the low and high side of

the operating band. There is little to no water-level

flexibility at either low or high discharges.

Water levels were measured immediately upriver

of the dams at gages previously established by the

St. Louis District. Drawdown values were calculated

as the difference between project pool elevations and

the water surface measured immediately upriver of

each dam. Project pool elevations are 449.0, 434.0,

and 419.0 feet (136.86, 132.28, and 127.71 m) for

Pools 24 and 25 and Melvin Price Pool, respectively.

Water levels at the three St.Louis District dams were

compared to water levels in Pool 22 which is managed

by the Rock Island District. The project pool elevation

for Pool 22 is 459.5 feet. Pool 22 was managed

according to the plan outlined in Appendix 22 of the

Master Reservoir Regulation Manual (U.S. Army

Corps of Engineers 1980e). That plan calls for water

levels between 459.1 and 459.6 feet (139.93 and

140.08 m) at the dam when discharges are below

163,000 cfs (4,613 cm).

Ground Surveys

Eight sampling locations in 1995 and six in 1996

were selected for monitoring among the three pools

(Table 1). The locations were semi-randomly

selected and had to be easily accessible areas with a

gentle slope. In 1995, two or three sites at each

location were established along a transect, each

approximately 0.5 feet (15 cm) apart in elevation. In

1996, two sites were established

at each location with the first site

being 0.8 feet (24 cm) lower in

elevation than the present woody

tree line and the second 0.8 feet

(24 cm) lower than the first. We

measured species presence, plant

height, and the number of stems

in a 1.6 feet (49 cm) square area

at each site. Each site was

measured at about 1-week

intervals in 1995 and 2-week

intervals in 1996. Sampling

commenced on June 22, 1995, and

June 26, 1996. The last sampling

period was August 9 in 1995 and

September 4 in 1996. Photographs

were also taken at each site during

most sampling visits. No ground surveys were

performed in Pool 22 during either year.

Vegetation Mapping

Color infrared, 1:15,000 scale, vertical, stereo,

9- x 9-inch (23- x 23-cm) aerial photographs of

Figure 2. Water elevation relative to discharge according to the water-level

management plan for Pool 25. Wlosinski (1996) includes information on how

discharges were estimated.
4

Pools 22, 24, and 25 and Melvin Price Pool were

taken on July 7, 1995. The photographs covered about

8 miles (12.9 km) of each pool, immediately upriver

of their respective dams. Standard Long Term

Resource Monitoring Program photointerpretation,

cartographic, and automation methods were used to

map and automate the data (Arndt and Olsen 1995;

Owens and Hop 1995; Owens and Robinson 1996;

Owens et al. 1997). Photographs were interpreted

with the standard Long Term Resource Monitoring

Program land cover/land use classification system and

a mirror stereoscope on a light table. The

photointerpreter identified vegetated areas near the

waterline. The interpretation was performed on clear

plastic overlays registered to the photograph with a

0.18-mm drafting pen. The photointerpretation was

checked by a senior photointerpreter and by the field

biologist for accuracy and completeness. The

interpreted data were then transferred to 1:24,000

USGS quadrangle topographic maps with a manual

zoom transfer scope. The transferred data were

checked by a senior cartographer for accuracy and

completeness. The transferred data were automated

with a digitizing table and placed into a spatial

database in vector format.

Fish

Fish monitoring was not performed specifically

to evaluate the drawdown experiment on pools within

the St. Louis District. However,

fisheries data have been routinely

collected in a similar manner since

1986 by the Illinois Department of

Natural Resources (DNR). We used

that data to test for pool-wide

differences between years (1986– 93)

when pools were held on the high side

of the operating band and (1994–96)

when pools were held on the low side

of the operating band during early to

mid-summer.

 Between 1986 and 1990, sampling

was conducted with a 4- x 20-foot

(1.2- x 6.1-m) minnow seine with

0.635-cm ace mesh. After 1990,

sampling was done with a bag seine of the same

dimensions, but with a 4- x 4-foot (1.22- x 1.22-m)

bag. Seines used in the study have been treated with

black net coat. Most seine hauls were made in a

downstream direction (the direction of water flow).

Periodically, when catch rates were low or sampling

area was limited, seine hauls were made in both

upstream and downstream directions. Length of seine

hauls varied with sampling location and substrate

type. When boat ramps were sampled, seine hauls

were limited to the width of the ramp. Seine hauls

made on natural sand beaches were all about 50 feet

(15 m) long. All seine hauls are considered to be

comparable with respect to catch rate.

Sampling locations, habitat and substrate type,

and the number of hauls are shown in Table 2.

Habitats sampled during the study include 7 tailwater

sites, 27 main-channel border sites, 3 side channel

sites, and 11 backwater sites. Among these habitat

types, four substrate types sampled include concrete,

cobble, gravel, and sand. Thirty-one of the sampling

sites were concrete boat ramps, 12 were gravel boat

ramps, 6 were natural sand beaches, and 2 were

cobble. Boat ramps were the preferred sampling

locations because of their accessibility and

consistency of sampling conditions over time. Also,

when biologists with the Illinois DNR’s Reservoirs

Program compared seining data obtained from natural

habitats with that from boat ramps, the results from
5
6

boat ramps were equal to or

better than those from natural

habitats (Cruse 1989). The

number of seine hauls per

pool ranged from 8 to 62 over

the 11-year period.

 Two to four sampling trips

were made each year between

May and September. The

count of fish collected from

all hauls at a site were

combined, and the total

number of hauls was also

recorded. Easily identified

fish were recorded and fish

were returned to the river. All

other fish caught were

preserved in 10% buffered

formalin until they were

identified.

 We performed two types

of analysis with the minnow

seining data; total numbers of

fish per haul and Simpson’s

Diversity Index (McGarigal

and Marks 1994). The total

numbers of fish per haul was

calculated pool wide and on

the lower versus upper halves

of each pool. The comparison

for different parts of the pool

was made because the

drawdowns have a greater

effect near the downstream

dam. Both analyses were

performed for every year

within each pool. Data from

all stations were used except

for stations between river

miles 201 and 203. This area

was originally in the tailwater

of Lock and Dam 26 before

Melvin Price Locks and Dam

was constructed.
7

Simpson’s Diversity Index was calculated as

follows:

where:

SDI = Simpson’s Diversity Index, m = number of

individual species, and P = the number of individuals

of species i divided by the total number of individuals

in the sample.

The index ranges from 0 (when only one species

is present in a sample) to less than 1. However, we

arbitrarily assigned an SDI of -0.1 for those instances

where no individuals were found in a sample. Because

the number of species can be a function of the number

of hauls, we subsampled 8 hauls from all hauls in a

pool, for each year, 10 different times, calculating an

SDI for each time. The 10 different SDIs were then

averaged. Fish groups that could not be identified to

species, such as shiners and buffalo, were treated as

species, as were species crosses.

Spatial Model

We integrated a hydrologic and spatial model for

Pool 25 to predict areas that would be dewatered.

The model used was described in Wlosinski and

Rogala (1996). Water surface profiles were predicted

with HEC-2 under steady-state conditions of

19,000 cfs (538 cm) and 56,000 cfs (1,585 cm). The

19,000 cfs figure was selected because it predicts

water surfaces near the flat pool elevation and it was

the discharge that occurred when the original aerial

photographs were taken in 1989. The 56,000 cfs

figure was an arbitrary selection because discharge

varied throughout the drawdown period. It does,

however, result in a drawdown of approximately

1.6 feet (49 cm) at Lock and Dam 25, which was

within the recommendations of the Committee. We

created GIS coverages of water surface elevations

with the HEC-2 generated profiles. A GIS overlay of

the water surface elevation and data representing

bottom geometry was performed to generate landwater data for the two discharge conditions. The

difference between the two land-water coverages was

our predicted area that would be dewatered because

of the drawdown. Models were not developed for

other pools because of a lack of spatial data.

Results and Discussion

Water Levels

Water levels during summers 1995 and 1996 are

presented for Pools 24 and 25 and Melvin Price Pool

in Figures 3, 4, and 5, respectively.

 Figure 6 contains water levels in Pool 22 during

1995 for comparative purposes. The horizontal line

in the figures represent the project pool elevation for

the respective pools. Open river conditions existed

in all four pools at the beginning of June, for both

years, with the drawdown being initiated as soon as

conditions allowed except for Pool 22. Drawdown

amounts vary within and among pools as a function

∋&



∋





Figure 3. Measured water-level elevations (feet above sea

level) immediately upriver of Lock and Dam 24 in 1995

and 1996.
8

of discharge, location in the pool, and water levels

at the dam. Drawdown amounts at the dam for all

three pools for both years are shown in Table 3.

Pool 24 had a 1.2–2.0 foot (37–61 cm) drawdown

Figure 5. Measured water-level elevations

(feet above sea level) immediately upriver of

Melvin Price Locks and Dam in 1995 and

1996.

Figure 4. Measured water-level elevations (feet

above sea level) immediately upriver of Lock and

Dam 25 in 1995 and 1996.

Figure 6. Measured water-level elevations (feet above sea level) immediately

upriver of Lock and Dam 22 in 1995.

for about 30 days in both years.

Drawdowns of about 3 feet

(0.91 m) occurred in Pool 25 and

Melvin Price Pool in both years. A

part of the drawdown amount is due

to lowering water levels at

particular discharge levels, and part

due to holding water levels on the

low side of the operating band.

 All three pools were managed

intensively to assure a 9-foot

(2.7-m) channel was maintained

throughout the experiment. No

barges were reported to have run

aground as a result of the

experiment. High discharges during

the spring of both years were considered adequate

for fish reproductive success, and the flow rate

remained in a range during the summer that allowed

management for increased vegetative growth.
9

Discharge is also being presented for the same

periods for Keokuk, Iowa (Figure 7), and Grafton,

Illinois (Figure 8), for comparative purposes. These

are the two closest gages where discharge is

estimated by the U.S. Geological Survey. The gage

at Keokuk is about 63 miles (101 km) upriver of

Dam 22, and the gage at Grafton is in Melvin Price

Pool about 17 (27 km) miles upriver of the dam.

Ground Surveys

Seven plant genera were identified in the

20 survey sites in 1995 (Figure 9): Polygonum spp.,

Cyperus spp., Echinochloa spp., Amaranthus spp.,

Setaria spp. (yellow foxtail or bristlegrass), Panicum

spp., (panicum), and Leersia (rice cutgrass). The

above species were also present during the 1996

survey except for Setaria and Panicum, with the

dominant plants being found at a greater percentage Figure 7. Estimated discharges at Keokuk, Iowa, in

1995 (a) and 1996 (b).

Figure 8. Estimated discharges at Grafton, Illinois, in

1995 (a) and 1996 (b).
10

Between 255 and 881 acres (91 and

357 ha) of plants were measured

near the water line in Pools 24 and

25 and Melvin Price Pool, compared

to just 51 acres (20.6 ha) in Pool 22.

Less than 60 acres (24 ha) of plants

were found in all four pools in 1989

when water levels were held on the

high side of the operating band.

However, we cannot be sure that the

difference in 1995, between Pool 22

and the other pools, is attributable

solely to water levels in Pool 22 not

being dropped as in the three other

pools. Other factors, such as bottom

geometry and sediment types, may

have also played a role in the

acreage figures among pools. In

addition, estimates of vegetated

areas may be low because narrow

bands of vegetation can be missed by the

photointerpreters. The pens used to transfer

information from photointerpretation represent a

swath on level ground about 15 feet (4.6 m) wide.

This swath, even if recognized by the

photointerpreter, may be represented as a linear

feature that is not reflected in acreage estimates. In

addition, trees may have obscured some vegetation,

and field biologists noted that large vegetated areas

were under water at the time photographs were taken.

Maps depicting the vegetation beds that we

believe are attributable to water levels in Pools 22,

24, and 25 and Melvin Price Pool are presented in

Figure 14. Over 90% of the beds in all four pools

were classified as a mix of forbs and grasses (Table 4).

Fish

The number of fish per haul is shown in

Figures 15 through 17 for Pools 24 through 26,

respectively. The average number of fish per haul

between 1986 and 1993 was 27.6 in all three pools

combined, as compared with an average of 29.2 fish

between 1994 and 1996. The total number of fish

collected per haul for the upriver and downriver

















	








	





























Figure 9. Frequency of occurrence of vegetation at all sampling sites in

1995.

of sites in 1996. In 1995, stem densities exceeding

100 individuals per plot were measured soon after

germination. Stem densities dropped to, and

remained, around 10 to 40 individuals per plot after

about 30 days. Although not measured, seed

production appeared to be quite high during the late

summers of both 1995 and 1996.

The growth rate of the three dominant species—

Echinochloa, Cyperus, and Polygonum—are

presented in Figures 10, 11, and 12, respectively.

Polygonum and Echinochloa exhibited two different

germination periods in 1996, probably due to the

timing of drawdowns in different pools. About

30 days were required for plants to grow to a height

of about 10 inches (25 cm) during both summers.

Plants then grew more quickly as water levels were

slowly raised. Of the three dominant plants, Cyperus

reached a height of about 40 inches (101 cm),

Echinochloa 50 inches (127 cm), and Polygonum

over 50 inches (127 cm).

Vegetation Mapping

 The estimate of plant coverage from

photointerpretation, for 8-mile (12.8 km) stretches

just upriver of the dams, is shown in Figure 13.
11

portions of the pools is shown in

Figure 18. In the downriver portion of the

three pools, the average number of fish

per haul between 1986 and 1993 was

32.9, as compared with an average of

40.0 fish between 1994 and 1996. The

averages in the upriver portion of the

pools were nearly equal between the two

periods; 22.6 between 1986 and 1993

versus 21.0 between 1994 and 1996.

Similar results were found for

Simpson’s Diversity Index. The average

index was 0.57 for all three pools when

water levels were held on the high side

of the operating band, compared with an

index of 0.58 between 1994 and 1996.

The index for Pools 24 through 26 are

shown in Figures 19 through 21,

respectively.

Our analyses were performed on all

fish species combined. Undoubtably,

analysis on individual species would

probably show that populations for some

species were higher and others lower,

when comparing results of the two waterlevel management conditions.

Considering the variability in fish data

collected between 1986 and 1993, we

believe the lower water levels at the three

dams in the St. Louis District had no

significant detrimental effect on the fish

community.

Spatial Model

The spatial model predicted that

1,046 acres (423 ha) in the lower 8 miles

(12.8 km) of Pool 25 would be dewatered

at 56,000 cfs (1,585 cm) as compared to

19,000 cfs (538 cm). This can be

compared to the 881 acres (357 ha) of

vegetation mapped from

photointerpretation. The dewatering may

seem contrary to normal river

hydrodynamics, but it should be

Figure 11. Average height of Cyprus spp. (chufa) at all sampling sites.

Figure 10. Average height of Echinochloa spp. (millet) at all

sampling sites. Heights were measured for plants that germinated

at two different times (1996A and 1996B).

Figure 12. Average height of Polygonum spp. (smartweed) at all

sampling sites. Heights were measured for plants that germinated at

two different times (1996A and 1996B).
12

remembered that water levels at the

dam are lowered as discharge

increases to moderate levels in pools

where water levels are managed with

a mid-pool control point. This type

of plan was originally devised

because less land had to be acquired

by the Corps of Engineers for

construction of the 9-foot (2.7-m)

channel project.

 The area predicted to be dewatered,

by river mile, followed the same

trend as the acreage of plant growth

Figure 14. Areas of vegetation (black) in Pools 22 (a), 24 (b), and 25 (c), and Melvin Price Pool (d) thought to be

caused by a drop in water levels.

Figure 13. Acres of vegetation near the waterline in 1995 estimated from

aerial photography.

5 1

255

881

417

0

100

200

300

400

500

600

700

800

900

1000

A cres


13

estimated from photointerpretation

(Figure 22). The greatest effect was

near Batchtown at river miles (km) 243

(391.0) through 245 (394.2). However,

although predicted and observed areas

were usually in the same general areas,

they were not necessarily the same exact

areas (Figure 23). About 492 acres

(199 ha) predicted to be dewatered had

vegetation. Another 555 acres (225 ha)

predicted to be dewatered did not have

vegetation, according to the

photointerpreter. In addition, 387 acres

(157 ha) had vegetation observed in

areas not predicted to be dewatered by

the model.

 Most of the differences

can be explained by the lack

of resolution of the data from

the hydrologic model,

relatively low resolution data

for bottom geometry, and

discharges that varied

throughout the growing

season. The hydrologic model

predicts only one value for

water surfaces from one side

of the river to the next,

although minor differences do

occur on the river. The bottom

geometry surface was

estimated from points that

were as much as 200 feet

(61 m) apart. Even the bottom

elevation at the points that

were measured are probably

not exact because the method

used assumes that both the

water surface at the point and

the horizontal location of the

point are known. However,

water surfaces at a particular

location are estimated from

gages that are miles away,

waves can affect

Figure 16. Mean total numbers of fish (all species) per seine haul in Pool 25. measurements, and the

Figure 15. Mean total numbers of fish (all species) per seine haul in Pool 24.
14

Benefits of Vegetation

Aquatic macrophytes are

essential to a healthy Upper

Mississippi River ecosystem.

Fassett (1985) included an

appendix on the use of aquatic

plants by birds and mammals that

was obtained from

95 publications. Specific entries

from Fassett include: the

Cyperaceae, a favorite food of

some wildfowl and eaten by

muskrat, beaver, and deer;

Echinochloa spp., eaten by

wildfowl, upland game birds, song

birds, and muskrats; Leersia spp.,

eaten by ducks and muskrats; and

Polygonum spp., eaten by

wildfowl, upland game birds,

shore birds, song birds, deer, and

muskrat. Martin et al. (1951)

include the following information

concerning the genera found in

our study: Chufa is eaten by

waterfowl, upland gamebirds,

songbirds, and mammals; Rice

cutgrass is eaten by waterfowl,

marshbirds, shorebirds, and

songbirds; Echinochloa is eaten

by waterfowl, marshbirds,

shorebirds, songbirds, upland gamebirds, muskrats,

and rabbits; Panicum is eaten by waterfowl,

marshbirds, shorebirds, songbirds, upland gamebirds,

muskrats, rabbits, and white-tailed deer; Amaranthus

is eaten by waterfowl, upland gamebirds, songbirds,

rabbits, small mammals, and mule deer; and

Polygonum is eaten by waterfowl, marshbirds,

shorebirds, songbirds, upland gamebirds, muskrats,

raccoon, squirrel, and chipmunk.

In a review of the literature on the interactions

between fish and aquatic macrophytes, Janecek

(1988) listed 84 Upper Mississippi River fish species

reported to use macrophytes for some habitat

horizontal accuracy of establishing a point is about

± 15 feet (4.6 m). Changes in discharge and the

resultant gate settings often produce water levels that

change about 1 foot (30 cm) in a week at the dam

(Figures 3–5), and possibly more as one moves

upriver. In addition, plant growth is affected by many

factors other than the presence or absence of water,

such as substrate, current velocity, and light

penetration. Therefore, we believe the model should

only be used to obtain estimates of dewatered areas

over relatively large areas (e.g., by river mile).

Questions dealing with plant response in a particular

area would need additional data.

Figure 17. Mean total numbers of fish (all species) per seine haul in Pool 26.

Figure 18. Mean total numbers of fish (all species) per seine haul in the

upriver and down river portions of Pools 24, 25, and 26.
15

function. He lists 44 species

reported to spawn in, on, or near

macrophytes. Unfortunately,

Janecek also mentions that

references to specific plants are

scarce.

Opinions differ concerning

drawdown effects on

invertebrates. Factors found in a

literature search (Wlosinski and

Koljord 1996) affecting

invertebrate populations during a

drawdown include season,

duration, vertical drop in water

levels, species,

vegetation, and

sediment type. Becker

et al. (1981) mentioned

that invertebrate losses

in shoreline zones

because of drawdowns

may be of little

importance to overall

ecosystem dynamics.

Fredrickson and Reid

(1988), in the U.S. Fish

and Wildlife Services’

Waterfowl

Management

Handbook, opined that

management for

specific plant communities may

be the most practical way of

increasing invertebrate

production.

We did not examine the

response of other populations

such as waterfowl and shorebirds

to the drawdown. However,

observations in late summer and

fall by the field biologists noted

that, as water levels began to

inundate vegetative growth, fish

rapidly began to use the area.

High invertebrate populations

Figure 19. Simpson’s Diversity Index for fishes sampled by seining in Pool 24.

Figure 20. Simpson’s Diversity Index for fishes sampled by seining in Pool 25.

Figure 21. Simpson’s Diversity Index for fishes sampled by seining in Pool 26.
16

were also noted during casual

observations made about 3 weeks

after vegetation was inundated.

The area was also heavily used by

a variety of bird species during

both the fall and spring

migrations.

Conclusions and

Recommendations

We found that (1) excellent

plant growth occurred at all

dewatered sampling sites during

1995 and 1996; (2) plants covered

a much greater area in 1995 near

the water line in Pools 24 and 25

and Melvin Price Pool, where a

drawdown had occurred, than in Pool 22, where water

levels were more constant; (3) the Pool 25 model

reasonably estimated acreages and locations of plant

growth prior to actual manipulation; (4) the fish

community was not significantly affected during

years when water levels were held on the low side of

the operating band as compared to years when water

levels were held on the high side of the operating

band; and (5) navigation and recreation interests were

not adversely affected by the drawdown and in many

instances sandbars exposed during the drawdowns

were used by numerous recreationalists. These

conclusions lead us to believe that the water-level

drawdown experiment has been successful during

summers 1994, 1995, and 1996. However, results

should be further assessed. Reid et al. (1989), in a

review of moist-soil impoundments in the Upper

Mississippi River, mentioned that Echinochloa spp.

and Cyperus spp. are less likely to germinate or may

produce fewer seeds during successive growing

seasons. However, factors such as sediment

deposition on the Mississippi River may lead to

different results.

 We believe that this experiment represents a step

toward ecosystem management on the Upper

Mississippi River System and recommend further

consideration of drawdown as a management tool for

riverine resources.

Figure 23. A map of dewatered areas as predicted by

the model in comparison with areas with vegetation

estimated from photointerpretation in the lower stretch

of Pool 25.

Figure 22. A comparison of acreage of dewatered areas predicted by the

model to acreage of vegetation
17

Acknowledgment

We thank Laura Carnal for interpreting aerial

photographs.

References

Arndt, L., and D. Olsen. 1995. Long Term Resource

Monitoring Program standard operating

procedures: Production ARCEDIT digitizing.

National Biological Service, Environmental

Management Technical Center, Onalaska,

Wisconsin, August 1995. LTRMP 95-P008-3.

12 pp. + Appendixes A–K.

Becker, C. D., D. H., Fickeisen, and J. C.

Montgomery. 1981. Assessment of impacts from

water-level fluctuations on fish in the Hanford

Reach, Columbia River. Prepared for the U.S.

Department of Energy under contract DE-AC06-

76RLO 1830, Pacific Northwest Laboratory,

Richland, Washington.

Busse, D., K. Dalrymple, and C. N. Strauser. 1995.

Environmental pool management. In Upper

Mississippi River Conservation Committee,

Proceedings of the fifty-first annual meeting of

the Upper Mississippi River Conservation

Committee, Rock Island, Illinois.

Fassett, N. C. 1985. A manual of aquatic plants. The

University of Wisconsin Press, Madison. 405

pp.

Fredrickson, L. H., and F. A. Reid. 1988. Section

13.3.1. Invertebrate response to wetland

management. In Waterfowl Management

Handbook. Fish and Wildlife Leaflet 13. U.S.

Fish and Wildlife Service. Washington, D.C. 6

pp.

Janecek, J. A. 1988. Literature review on fishes

interactions with aquatic macrophytes with

special reference to the Upper Mississippi River

System. Upper Mississippi River Conservation

Committee. Rock Island, Illinois.

Martin, A. C., H. S. Zim, and A. L. Nelson. 1951.

American wildlife and plants, a guide to wildlife

food habits. Dover Publications, Inc., New York.

500 pp.

McGarigal, K., and B. J. Marks. 1994. Fragstats.

Forest Science Department, Oregon State

University, Corvallis. 67 pp. + 3 Appendices.

Owens, T., and K. D. Hop. 1995. Long Term Resource

Monitoring Program standard operating

procedures: Photointerpretation. National

Biological Service, Environmental Management

Technical Center, Onalaska, Wisconsin, July

1995. LTRMP 95-P008-1. 7 pp. + Appendixes

A and B.

Owens, T. W., K. Hop, L. Robinson, L. DeHaan, and

T. Fancher. 1997. Long Term Resource

Monitoring Program standard operating

procedures: Quality control for cartographic

activities. U.S. Geological Survey,

Environmental Management Technical Center,

Onalaska, Wisconsin, May 1997. LTRMP

95-P008-7. 10 pp. + Appendixes A–F.

Owens, T., and L. Robinson. 1996. Long Term

Resource Monitoring Program standard

operating procedures: Manual zoom transfer

scope. U.S. Geological Survey, Environmental

Management Technical Center, Onalaska,

Wisconsin, December 1996. LTRMP

95-P008-5. 3 pp. + Appendix.

Reid, F. A., J. R. Kelly, Jr., T. S. Taylor, and L. H.

Fredrickson. 1989. Upper Mississippi Valley

wetlands-refuges and moist-soil impoundments.

In L. M. Smith, R. L. Pederson, and R. M.

Kaminski, editors. Habitat management for

migrating and wintering waterfowl in North

America. Texas Tech University Press,

Lubbock. 560 pp.
18

U.S. Army Corps of Engineers. 1980a. Mississippi

River, Nine Foot Channel Navigation Project.

Pages 1-1–6-2 in Master Water Control Manual.

St. Louis District, St. Louis, Missouri.

U.S. Army Corps of Engineers. 1980b. Mississippi

River, Nine Foot Channel Navigation Project.

Pages 1-1–6-1 in Appendix 24, Master Water

Control Manual. Lock & Dam No. 24. St. Louis

District, St. Louis, Missouri.

U.S. Army Corps of Engineers. 1980c. Mississippi

River, Nine Foot Channel Navigation Project.

Pages 1-1–6-2 in Appendix 25, Master Water

Control Manual. Lock & Dam No. 25. St. Louis

District, St. Louis, Missouri.

U.S. Army Corps of Engineers. 1980d. Mississippi

River, Nine Foot Channel Navigation Project.

Pages 1-1–6-2 in Appendix 26, Master Water

Control Manual. Lock & Dam 26. St. Louis

District, St. Louis, Missouri.

U.S. Army Corps of Engineers. 1980e. Mississippi

River, Nine Foot Channel Navigation Project.

Appendix 22, Master Reservoir Regulation

Manual. Lock & Dam No. 22. Rock Island

District, Rock Island, Illinois. 38 pp. +

Appendixes A–C.

U.S. Fish and Wildlife Service. 1993. Operating Plan

for the Upper Mississippi River System Long

Term Resource Monitoring Program.

Environmental Management Technical Center,

Onalaska, Wisconsin, Revised September 1993.

EMTC 91-P002. 179 pp. (NTIS #PB94-160199)

Wlosinski, J. H. 1996. Pool 25: Analysis of water

levels and discharge. National Biological

Survey, Environmental Management Technical

Center, Onalaska, Wisconsin, March 1996.

LTRMP 96-T001. 88 pp. (NTIS #PB96-165907)

Wlosinski, J. H., and E. R. Koljord. 1996. Effects of

water levels on ecosystems: An annotated

bibliography. U.S. Geological Survey,

Environmental Management Technical Center,

Onalaska, Wisconsin, December, 1996. LTRMP

96-T007. 261 pp. (NTIS #PB97-134795)

Wlosinski, J. H., and J. Rogala 1996. Pool 25: Water

level management alternatives and their effects

on habitat. National Biological Survey,

Environmental Management Technical Center,

Onalaska, Wisconsin, October, 1996. LTRMP

96-T004. 85 pp.+ Appendixes A–D. (NTIS

#PB97-134738)

Wlosinski, J. H., and J. Rogala 1997. Pool 25: Land

ownership requirements in moving the control

point to the dam. U.S. Geological Survey,

Environmental Management Technical Center,

Onalaska, Wisconsin, March 1997. LTRMP 97-

T002. 15 pp. (NTIS #PB97-158059)
A-1

Mr. Butch Atwood

Biologist

Illinois Department of Natural Resources

1000 Killarney Drive

Greenville, Illinois 62246

Phone: 618-594-3627 Fax: 608-594-8481

Mr. Carl Becker

Division Chief

Illinois Department of Natural Resources

Division of Natural Heritage

600 North Grand Avenue West

Springfield, Illinois 62706

Phone: 217-785-8774 Fax: 217-785-8277

Mr. Neil Booth

Mississippi River Fish and Wildlife Area

RR 1, Box 182

Grafton, Illinois 62037

Mr. Ken Brummett

Missouri Department of Conservation

Box 428

Hannibal, Missouri 63401

Mr. Dave Busse

U.S. Army Corps of Engineers

St. Louis District ED-HP

1222 Spruce Street

St. Louis, Missouri 63103-2833

Phone: 314-331-8349

Mr. Mike Conlin

Illinois Department of Natural Resources

Division of Fisheries

600 North Grand Avenue West

Springfield, Illinois 62706

Mr. Kenneth Dalrymple

Wildlife Management Biologist

Missouri Department of Conservation

Box 201

Elsberry, Missouri 63343

Phone: 573-898-5905 Fax: 573-898-5298

Appendix A. Pool 25 Natural Resources Committee Members

Ms. K. L. Drews

Refuge Manager

U.S. Fish and Wildlife Service

Mark Twain NWR, Brussels District

HCR Box 107

Brussels, Illinois 62013-9711

Phone: 618-883-2524

Mr. Owen Dutt

Chief, Planning Division

U.S. Army Corps of Engineers

St. Louis District

1222 Spruce Street, ATTN: PD

St. Louis, Missouri 63103-2833

Phone: 314-331-8450

Mr. Jon Duyvejonck

UMRCC Coordinator

U.S. Fish and Wildlife Service

Rock Island Field Office

4469 48th Avenue Court

Rock Island, Illinois 61201

Phone: 309-793-5800 Fax: 309-793-5804

Mr. Gary Dyhouse

U.S. Army Corps of Engineers

St. Louis District

1222 Spruce Street

St. Louis, Missouri 63103-2833

Phone: 314-331-8337

Mr. David Ellis

Refuge Manager

U.S. Fish and Wildlife Service

Mark Twain NWR, Annada District

Box 88

Annada, Missouri 63330

Phone: 314-847-2333

Mr. Dan Erickson

Rivers Project Office

PO Box 337

West Alton, Missouri 63386-0337

Phone: 314-355-6585 Fax: 618-452-4615
A-2

Mr. Gordon Farabee

Missouri Department of Conservation

Fisheries Division, P.O. Box 180

2901 W Truman Blvd.

Jefferson City, Missouri 65102-0180

Phone: 573-751-4115

Dr. Robert Gates

Cooperative Wildlife Research 6504

Southern Illinois University at Carbondale

2160 North Winch Road

Carbondale, Illinois 62901

Dr. Stephen Havera

Director

Illinois Natural History Survey

Forbes Biological Station

P.O. Box 590

Havana, Illinois 62644

Phone: 309-543-3950

Mr. David Leake, PE

U.S. Army Corps of Engineers

St. Louis District, ATTN: PD-F

1222 Spruce Street

St. Louis, Missouri 63103-2833

Phone: 314-331-8480

Dr. Kenneth Lubinski

U.S. Geological Survey

Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, WI 54603

Phone: 608-783-7550 Fax: 608-783-8058

Mr. Deck Major

Illinois Department of Natural Resources

4521 Alton Commerce Parkway

Alton, Illinois 62002

Mr. Pat McGinnis

U.S. Army Corps of Engineers

St. Louis District

Riverlands Area Office, P.O. Box 337

West Alton, Missouri 63386-0337

Phone: 314-899-0405 Fax: 314-899-0514

Mr. Rick Messinger

Region IV Regional Land Manager

Illinois Department of Natural Resources

4521 Alton Commerce Parkway

Alton, Illinois 62002

Phone: 618-462-1181

Mr. T. Miller

2160 North Winch Road

Springfield, Illinois 62707

Mr. Rick Nelson

Field Supervisor

U.S. Fish and Wildlife Service

Rock Island Field Office

4469 48th Avenue Court

Rock Island, Illinois 61201

Phone: 309-793-5800

Mr. Jerry Olmsted

U.S. Fish and Wildlife Service

Mark Twain NWR, Brussels District

HCR Box 107

Brussels, Illinois 62013-9711

Phone: 618-883-2524

Mr. Tom Owens

U.S. Geological Survey

Center for Biological Informatics

Denver Federal Center

Building 810 Room 8000 MS 302

Denver, CO 80225-0046

Phone: 303-202-4259

Mr. Jerry Rasmussen

Mississippi Interstate Cooperative

Resource Association (MICRA)

P.O. Box 774

Bettendorf, Iowa 52722-0774

Phone: 319-359-3029 Fax: 319-252-3053

Dr. Robert Sheehan

Southern Illinois University

Fisheries Research Laboratory

Carbondale, Illinois 62901-6511

Phone: 618-536-7761
A-3

Dr. David Soong

Director, Office of Hydraulics and

River Mechanics, Illinois State Water Survey

2204 Griffith Drive

Champaign, Illinois 61820-7495

Phone: 217-333-1495

Dr. Richard Sparks

Illinois Natural History Survey

Forbes Biological Station

P.O. Box 590

Havana, Illinois 62644

Phone: 309-543-3950 Fax: 309-543-4999

Mr. Dick Steinbach

Complex Manager

U.S. Fish and Wildlife Service

Mark Twain National Wildlife Refuge

1704 N. 24th Street

Quincy, Illinois 62301-3304

Phone: 217-224-8580 Fax: 217-224-8583

Mr. Claude Strauser

U.S. Army Corps of Engineers

St. Louis District

1222 Spruce Street

St. Louis, Missouri 63103-2833

Phone: 314-331-8341

Mr. Norman Stucky

Planning Division Supervisor

Missouri Department of Conservation

2901 N. Truman Boulevard

P.O. Box 180

Jefferson City, Missouri 65102-0180

Phone: 573-751-4115

Mr. Richard Whitton

Division of Wildlife Resources

Illinois Department of Natural Resources

Union County Refuge

RR 2, Box 628

Jonesboro, Illinois 62952

Mr. Dan Wilcox

Fisheries Biologist

U.S. Army Corps of Engineers

St. Paul District

190 5th Street East, CENCS-PE-M-ER

St. Paul, Minnesota 55101-1638

Phone: 612-290-5276 Fax: 612-290-5800

Dr. Don Williams

Planning Division

U.S. Army Corps of Engineers

Great Lakes and Ohio Division

111 North Canal Street

Chicago, Illinois 60606-7205

Phone: 312-886-5470 Fax: 312-886-1205

Dr. Joseph Wlosinski

U.S. Geological Survey

Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, WI 54603

Phone: 608-783-7550
B-1

Appendix B. Definitions of Terms Used in this Report

Term Definition

Control point A specific location in a pool where the Corps of Engineers maintains a target

water level over a range of discharges

Coverage A geographical data set containing attributes for discrete point, line, and/or

polygon features in a vector data set or cell values for raster data sets

Drawdown Water levels that are managed below the project pool elevation

An organized collection of computer hardware, software, geographic data,

and personnel adapted to efficiently capture, store, update, analyze, and

display all forms of geographic information

Hydrologic model A mathematical model that predicts water-level elevations from upriver to

downriver, based on bottom geometry, gate elevation settings at the

downstream dam, and discharge data

Maximum drawdown The maximum drop in water levels at the headwater, below the project pool

elevation, that would still allow a 9-foot (2.74-m) navigation channel

Open river The condition when all of the movable gates at a dam are raised out of the

water and the headwater and tailwater elevations are nearly equal

Operating band The amount of vertical flexibility in holding water levels as a function of

discharge

Overlay A GIS process that operates on two or more data sets based on their

geographic location. Types of operations include combining attributes of

different coverages and performing mathematical functions based on

attributes of multiple coverages

Pool The body of water created upriver of a dam and extending to the next

upriver dam

Project pool elevation The water-level elevation needed to maintain a 9-foot (2.74-m) channel at

zero discharge and the elevation for which each dam was designed

Vector A GIS data structure that represents map features as a list of ordered x,y

coordinates

Geographic Information

 System (GIS)

The Long Term Resource Monitoring Program (LTRMP) for the Upper Mississippi

River System was authorized under the Water Resources Development Act of 1986 as

an element of the Environmental Management Program. The mission of the LTRMP

is to provide river managers with information for maintaining the Upper Mississippi

River System as a sustainable large river ecosystem given its multiple-use character.

The LTRMP is a cooperative effort by the U.S. Geological Survey, the U.S. Army Corps

of Engineers, and the States of Illinois, Iowa, Minnesota, Missouri, and Wisconsin.