Long Term Resource Monitoring Program

Technical Report

99-T002

Pool 13 Drawdown: Predicting

Success Rates and Affected Areas

April 1999
LTRMP Technical Reports provide Long Term Resource Monitoring Program

partners with scientific and technical support.

All reports in this series receive anonymous peer review.

Upper Midwest Environmental

Sciences Center

PROGRAM MANAGER

Robert L. Delaney

ACTING MONITORING SCIENCES AND

COORDINATION DIVISION MANAGER

Kenneth S. Lubinski

CHIEF, SUPPORT SERVICES

Barbara A. Deml

REPORT EDITOR

Jerry D. Cox

Cover graphic by Jim Rogala

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.
Pool 13 Drawdown: Predicting

Success Rates and Affected Areas

by

James T. Rogala, Joseph H. Wlosinski, and Kevin J. Landwehr 1 1 2

U.S. Geological Survey

Upper Midwest Environmental Sciences Center 1

2630 Fanta Reed Road

La Crosse, Wisconsin 54603

U.S. Army Corps of Engineers 2

Rock Island District

Clock Tower Building

Rock Island, Illinois 61204-2004

April 1999

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:

Rogala, J. T., J. H. Wlosinski, and K. J. Landwehr. 1999. Pool 13 drawdown: Predicting success rates and affected areas.

U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin, April 1999. LTRMP

99-T002. 27 pp. + Appendix

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).
iv

Contents

Page

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

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

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

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

Success Rates ................................................................. 2

Affected Areas ................................................................. 3

Results and Discussion ............................................................. 3

Success Rates ................................................................. 3

Affected Areas ................................................................. 5

Acknowledgments ................................................................. 8

References ....................................................................... 8

Appendix. Fish and Wildlife Interagency Committee ...................................... A-1

Tables

Table 1. Definitions of terms used in this report ........................................ 10

Table 2. Predicted water surface elevations (feet above sea level) from the UNET model ......... 11

Table 3. Drawdown amounts (feet) predicted by the UNET model at various river miles when

water levels at Dam 13 are held at 582 feet (1-foot drawdown) and 581 feet (2-foot drawdown) 12

Table 4. Area (acres) dewatered and within 1-foot depth increments at various river miles when

water levels are held at the four conditions at Lock and Dam 13 ..................... 13

Table 5. Average invertebrate numbers (per m ) in Pool 13 between 1992 and 1997 ............. 15 2

Figures

Figure 1. Detail map of Pool 13 .................................................... 16

Figure 2. Percentage of time discharge was exceeded for Clinton, Iowa, between May 1 and

August 15 (upper) and June 15 and August 15 (lower), based on daily values collected

from 1873 to 1996 ...................................................... 17

Figure 3. Estimated success rates for a 1- or 2-foot drawdown between May 1 and August 15 or a 1-foot

drawdown between June 15 and August 15 for Pool 13 based on the annual occurrence of

discharge for the required number of consecutive days ............................ 18

Figure 4. Percentage of drawdown attempts successful for Pool 13 based on the required number

of consecutive days for the periods between May 1 and August 15 for a 1- or 2-foot drawdown

or between June 15 and August 15 for a 1-foot drawdown ......................... 19
v

Figure 5. Drawdown amounts (feet) by river mile when water surface elevations are held at 1 foot

(solid line) and 2 feet (dashed line) lower at Dam 13 for the discharge range required for

the drawdown .......................................................... 20

Figure 6. Acreage dewatered at 50,000 cfs for a 1-foot drawdown (582 feet above sea level at the

dam) and at 70,000 cfs for a 2-foot drawdown (581 feet above sea level at the dam) in Pool 1321

Figure 7. Maps of Pool 13 depicting areas dewatered from a 1-foot drawdown at 50,000 cfs (left) and 2-

foot drawdown at 70,000 cfs (right) .......................................... 22

Figure 8. Acreage (upper) and cumulative acreage (lower) within each 1-foot water-depth range for 583-

foot elevation at 50,000 and 70,000 cfs, 582-foot elevation at 50,000 cfs, and 581-foot

elevation at 70,000 cfs ................................................... 23

Figure 9. Maps of water depth, at 50,000 cfs, for the study area of Pool 13 when water levels at the dam

are held at 583 feet (left) and 582 feet (right) above sea level ....................... 24

Figure 10. Maps of water depth, at 70,000 cfs, for the study area of Pool 13 when water levels at the dam

are held at 583 feet (left) and 581 feet (right) above sea level ....................... 25

Figure 11. Acreage, by river mile, of areas with water depths between 0–1 feet (top), 1–2 feet

(middle), and 2–3 feet (bottom) for each of the four conditions ...................... 26

Figure 12. Acreage, by river mile, of areas with water depths between 3–4 feet (top), 4–5 feet

(middle), and greater than 5 feet (bottom) for each of the four conditions .............. 27
vi

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'

Environmental Management Program. The LTRMP is being implemented by the Upper Midwest

Environmental Sciences Center (formerly the Environmental Management Technical Center), a U.S.

Geological Survey science center, 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 UMRS (USFWS

1993). The purpose of this report is to estimate areas affected by a drawdown on Pool 13. This report was

developed with partial funding provided by the LTRMP and part from the Rock Island District, U.S. Army

Corps of Engineers.
Pool 13 Drawdown: Predicting

Success Rates and Affected Areas

by

 James T. Rogala, Joseph H. Wlosinski, and Kevin J. Landwehr

Abstract

The likelihood of 1- or 2-foot drawdowns, and the area affected by such alternative drawdowns, was estimated

for Pool 13 on the Upper Mississippi River. Minimum water surface (elevation) requirements were compared

to computed water surface profiles to determine a critical low flow that would allow a navigation channel

400 feet wide and 10.5 feet deep. An upper limit on flow was established based on the flow at which open river

conditions would exist for a given drawdown. The range in flows that would allow for a drawdown was used

to estimate success rates using historical daily discharge data. Success rates were determined for a variety of

drawdown durations between two time periods, May 1–August 15 and June 15–August 15. The greatest effect

of the drawdown would be near Lock and Dam 13. Higher discharges, as well as distance from the dam, lessen

the drawdown amount. Areas that would be affected by these two drawdown scenarios were predicted by

overlaying maps of water surfaces with depths using a geographic information system. Although the drawdown

effects on most physical and biotic components of Pool 13 are unknown, some general drawdown effects likely

to occur because of the changes in water surface elevation are presented.

Introduction

The Upper Midwest Environmental Sciences Center (UMESC; formerly the Environmental Management

Technical Center) and the Rock Island District of the U.S. Army Corps of Engineers collaborated to estimate

the likelihood of a successful drawdown in Pool 13 (Figure 1) based solely on historical discharge estimates.

We also quantified areas that would be affected by a drawdown. Pool 13 is controlled by Lock and Dam 13

at river mile 522.5 and extends 34.2 miles upriver to mile 556.7. The Fish and Wildlife Interagency Committee

requested the drawdown (Appendix) as an experiment to evaluate alternative regulation effects on moist soil

plant production, sediment oxidation and compaction, and the photic zone for submersed vegetation. Estimates

of areas, both dewatered and with changed water depths, were used to describe benefits anticipated as a result

of the requested deviation from the current operating plan for Lock and Dam 13.

Constraints used for this study include the following: (1) channel dimensions of 400 feet wide and 10.5 feet

deep must be available for the entire pool at all times, (2) the drawdown should not significantly affect

commercial navigation or recreational craft, and (3) no additional dredging should be required. These

constraints limit the chance of success of a drawdown as well as the effective zone of influence. The purpose

of this report is to estimate these factors. Other constraints related to ecological benefits also exist, but are not

evaluated in this report.

This report is a continuation of work performed at the UMESC to determine the effects of water levels and

discharges on the Upper Mississippi River and to develop water-level management alternatives. Eight previous

papers and reports are included in this series (Lubinski et al. 1991; U.S. Army Corps of Engineers 1991;

Wilcox and Willis 1993; Wlosinski and Hill 1995; Wlosinski and Rogala 1995, 1996; Wlosinski 1996; and

Wlosinski and Koljord 1996).
2

Some of the terminology used in this report may not be common but is used routinely for water-level

management or analysis using geographic information systems (GIS). Definitions for these terms are included

in Table 1. All elevations in this report are referenced to sea level, using the 1912 National Geodetic Vertical

Datum.

Methods

Success Rates

Locations in Pool 13 where the navigation channel might first be threatened because of a drawdown were

identified using bathymetric data obtained by the UMESC from 1989 through 1993. The minimum water

surface (elevation) for each critical location was determined assuming minimum, post-drawdown, channel

dimensions of 400 feet wide and 10.5 feet deep. These minimum water surface requirements were then

compared to computed water surface profiles to determine the critical flow for each location. The most

restrictive flow was then selected as the lowest discharge that would allow a 10.5-foot navigation channel. An

upper limit representing the flow at which open river conditions would exist for a given drawdown was also

used to estimate success rates.

Computed water surface profiles and water velocities were estimated from the one-dimensional flow model

UNET under steady flow conditions. Water surface profiles were predicted for three water-level scenarios

representing the current water-level management plan and drawdowns of 1 and 2 feet for discharges ranging

from 25,000 to 110,000 cfs. The current plan calls for holding water levels at Lock and Dam 13 at 583 feet

above sea level when discharges are less than 125,000 cfs. Data for bathymetric transects for the model were

obtained from 1989–1992 hydrographic surveys. Elevation transects for the model were at approximately

1-mile intervals. The model internally interpolates cross sections at approximately half-mile intervals. The

UNET model used in this analysis is the same model presently used for real-time forecasting of water levels

on the Upper Mississippi River. The model has been calibrated and verified against historical flood events as

well as daily observations of the river stage and flow.

The U.S. Geological Survey stream gage near Clinton, Iowa, was used to estimate success rates. Discharges

have been estimated daily at that gage since 1873. The Clinton gage is 10.6 miles below Lock and Dam 13 and

no major tributaries enter the Mississippi River between the gage and the dam. Computed success rates were

determined for two time periods, May 1–August 15 (107 days) and June 15–August 15 (62 days). We

calculated, for the same time periods, the percentage of the time discharges are exceeded.

We computed two independent measures of drawdown success. The first quantifies how often (expressed

as a percentage of years) a drawdown of a given duration could have been conducted during the 123 years of

flow record. This analysis was based on the largest number of consecutive days that the average daily flow

remained within the specified flow range in any given year. In predicting drawdown opportunities, this

represents the chance that a drawdown of a given duration could be accomplished in a random year. The second

measure of drawdown success reflects how often the drawdown process produces a successful result once

initiated. 

The success curves were computed based on the following five assumptions: 

1. The flow must remain within the defined flow limits for 5 consecutive days, else the process (drawdown)

is not initiated and no failure occurs.
3

2. The number of days required for success is firm (e.g., 27 consecutive days is a failure for a 28-day

requirement).

3. The flow boundaries are semiflexible in that if the flow deviates above or below the prescribed range no

more than 5,000 cfs for 1 or, at most, 2 days the string of consecutive days is considered unbroken. 

4. The remaining days in the time window must be sufficient for the drawdown requirement, else the

process is not initiated and no failure occurs.

5. More than one drawdown attempt can be made in a given year, but no additional attempts were made

within a year after a successful result was obtained.

Affected Areas

Water surfaces predicted by the UNET model were transformed into four GIS coverages representing two

water levels (current conditions and the 1-foot drawdown) at 50,000 cfs and two (current conditions and the

2-foot drawdown) at 70,000 cfs. The discharge condition was selected on the basis of the lowest discharge at

which a drawdown could occur successfully, which equates to the maximum water-level change and affected

acreage. The coverages were created using templates containing cells approximately 1 mile long arranged

longitudinally along the river and perpendicular to the direction of flow. However, if off-channel areas are only

contiguous with the main channel at a downstream location, the template cell would have an irregular pattern.

For example, because Spring Lake (Figure 1) is protected by a levee and only connected to the river at mile

532, the model assumed that the water levels in the lake would be controlled by water levels at river mile 532.

We assigned a river mile to each cell and assumed no lateral changes in water surface elevation within the cells.

Each cell was attributed with the water elevation for each river mile as predicted by the UNET model. The use

of a template to generate a water surface coverage is described in Wlosinski and Rogala (1996).

The water surface coverages representing the four water-level management conditions were used in the GIS

to adjust a bathymetry coverage representing conditions with a water surface elevation of 583 feet. The original

bathymetry coverage was generated by interpolation between depth soundings collected between 1989 and

1993. Using the GIS, areas dewatered and changes in water depths as a result of the 1-foot drawdown were

determined by comparing bathymetry representing current management to bathymetry representing the

drawdown conditions at 50,000 cfs. A similar comparison of current and drawdown conditions at 70,000 cfs

estimated changes for the 2-foot drawdown. Bathymetry data did not cover areas that had persistent nonaquatic

vegetation types present in 1989, as interpreted using aerial photographs. Therefore, water-depth changes in

the areas that would be inundated at 50,000 and 70,000 cfs could not be predicted with the available data.

These data gaps, however, cover only a small area in the impounded portion of the pool. Also, these areas are

not covered by submergent vegetation types that would have benefitted by changes in water depth.

Results and Discussion

Success Rates

The permissible flow range at the Clinton gage required for a 1-foot drawdown is 50,000–110,000 cfs and

for a 2-foot drawdown is 70,000–100,000 cfs. The lower flow values represent the minimum flow required to

maintain a reliable navigation channel. The four possible problem areas that could limit a drawdown were near
4

river miles 527.2, 528.5, 531.1, and 533.4. The higher flow values of the permissible range correspond to open

river conditions for the two drawdown conditions. 

For May 1 through August 15, discharges are between 50,000 and 110,000 cfs approximately 48% of the

time and between 70,000 and 100,000 cfs approximately 22% of the time (Figure 2). The percentage of time

when flow is within the ranges is somewhat smaller (40% and 18%, respectively) for the shorter time period,

June 15 through August 15. This suggests that conditions suitable for a drawdown will occur infrequently,

especially for the 2-foot drawdown and the shorter time period. However, the percentage of time within the

required discharge ranges alone does not tell how often a drawdown of a given duration can occur.

A more informative measure of success is the chance, expressed as a success rate, of performing a

drawdown of a given duration each year (Figure 3). On average, discharges will be in the required range for

a 1-foot drawdown for 30 consecutive days between May 1 and August 15, 2 years out of 3. For the shorter

time period, June 15 through August 15, the success rate is 1 year out of 3. With 30 consecutive days of

required discharges occurring 1 year out of 7 for the longer time period, chances of a 2-foot drawdown are far

less.

To conduct a drawdown of a given duration, several attempts may be necessary. The percentage of attempts

successful was low, especially for a 2-foot drawdown (Figure 4). The percentage of attempts successful is

important information when assessing the effects of drawdown regulations because it measures negative effects

related to attempted drawdowns. One such negative effect would be greater than normal water-level

fluctuations, especially at the dam. For example, 1-foot drops in water levels at the dam would occur an

average more than 2 times per year to achieve a single 1-foot drawdown for 30 days. The percentage of

attempts successful are much lower for a 2-foot drawdown, with an average of 10 2-foot fluctuations needed

to achieve a single 2-foot drawdown for 30 days. The high percentage of failure while attempting a 2-foot

drawdown, in combination with the infrequent potential for a 2-foot drawdown, suggests the 2-foot drawdown

management alternative is less suitable than a 1-foot drawdown given the constraints in this study.

Predicted water surface elevations from the UNET model are included in Table 2 for the existing regulation,

1-foot drawdown, and 2-foot drawdown scenarios. The drawdown amount is presented in Table 3 and is shown

for selected discharges in Figure 5. This drawdown amount is the difference between the water surface

elevation at the existing regulation and each of the two drawdown schemes. Although the model predicted

surface elevations for the entire pool, (river miles 522.5–556.7), we are only including predictions to river

mile 535 because the drawdown amounts upriver of this area were considered insignificant (<0.25 foot change

in water levels). The small drawdown amount is most likely because of the constriction of the river near Spring

Lake that results in greater water surface elevation slope in this region. Table 2 shows that the effects of the

drawdown decreases upriver and are negatively correlated to flow. This is significant when attempting to

estimate the acreage of dewatered land because affected areas change as a function of discharge.

At higher flows, increases in computed (average) channel velocities are greatest immediately upriver of the

dam. At lower flows (less than 50,000 cfs), the maximum velocity increase occurs at river mile 533.0, at the

head of Big Cook Island. Although these average velocities generated from a one-dimensional hydrodynamic

model provide some general information, velocities predicted from a two-dimensional model are needed to

better assess the velocity effects of a drawdown.
5

Affected Areas

Discharges of 50,000 cfs for a 1-foot drawdown and 70,000 cfs for a 2-foot drawdown would result in the

maximum amount of dewatering and loss of water depth. If the discharges are less than these amounts, the

navigation channel could be maintained only if water levels at the dam were raised. Discharges greater than

these amounts would cause higher water surface elevations at all points within the pool. Therefore, the total

dewatered acreages predicted during the drawdown are estimates of maximum amounts. Fewer areas would

be exposed during the drawdown periods because discharges above the 50,000 and 70,000 cfs conditions will

certainly occur. Interpretation of the dewatered amounts should also consider that although a 2-foot drawdown

will provide larger amounts of dewatering and loss of water depth, a 2-foot drawdown would be far less likely

to occur under the constraints of this study. In contrast, the 1-foot drawdown could be achieved more

frequently, but the magnitude of vertical exposure of sediments would be less.

In Table 4, the predicted amount of dewatered area and distribution of water depth (1-foot increments) for

the four water-level conditions are presented by river mile. No areas upriver of river mile 533 were predicted

to be dewatered, therefore predicted acreages are only presented to river mile 533. A maximum of about

440 acres would be dewatered with the 1-foot drawdown and about 530 acres with a 2-foot drawdown.

Respectively for the 1- and 2-foot drawdowns, the dewatered acreage represents about 1.6% and 1.9% of the

total surface area of normally aquatic areas of Pool 13 and about 3.1% and 4.5% of the total area of the

impounded area below river mile 530. In general, dewatered acreage is greater near Dam 13 (Figure 6) because

of the greater drawdown effect illustrated in Figure 5. Dewatered area near the dam was greater for the 2-foot

drawdown, but the effect of the 2-foot drawdown does not extend upriver as far as does the effect of the 1-foot

drawdown. 

The effect of the drawdown is not solely a function of discharge and distance upriver of the dam. The

amount of land dewatered at each river mile is also affected by shoreline slope and shoreline length. This is

evident in lateral variability of dewatering across the river (Figure 7). For example, the large amount of

dewatered area at river mile 532 for a 1-foot drawdown (Figure 6) is the result of exposure of shallow aquatic

areas in Spring Lake. The presence of Spring Lake increases the shoreline length, and the lake has less slope

than channel shorelines in adjacent areas, resulting in the increase in dewatered acreage at river mile 532.

Both the 1- and 2-foot drawdowns produced increased acreage of each 1-foot depth range less than 3 feet

deep and a decrease in acreage of the deeper depth ranges (Figure 8). This is because of a peak at 3.6 feet in

the distribution of water depths at low water conditions. Nonetheless, there is still a substantial increase in the

cumulative acreage of areas less than 4 feet deep as a result of the drawdown (Figure 8). Change in acreage,

both increase and decrease, of each depth range was greater for the 2-foot drawdown. The spatial changes in

water depth are depicted as maps in Figures 9 and 10.

A somewhat different longitudinal pattern was predicted for increases of shallow water depths as compared

to predictions of previously described dewatered areas near Dam 13. Predicted areas with water depths less

than 1 foot increased only slightly for a 1-foot drawdown with a greater increase farther from the dam

(Figure 11). A 2-foot drawdown produced a similar pattern, but with greater magnitude and a greater increase

in area with depths less than 1 foot near the dam. The longitudinal slope of the water surface at this discharge

is much less than the longitudinal slope of the bed elevation of shallow impounded areas and, therefore, changes

in water surface elevation have more effect on water depth. This relation has a more pronounced effect on the

1- to 2-foot depth range. For this depth range, both drawdown conditions result in a large increase in acreage

within the impounded area at river miles 526 and 527.
6

 In contrast to the increases in acreage of shallow areas, the drawdown decreased acreage of areas deeper

than 2 feet in the impounded area nearest the dam. Up to river mile 526, acreage of areas 2–4 feet deep

increased as a result of drawdown, but acreage either decreased or was unchanged upriver in the impounded

area (Figures 11 and 12). The drawdown also decreased the acreage of areas with 3–4 foot depths in most of

the impounded area (Figure 12). We predicted less acreage of areas 4–5 feet deep for all river miles within the

impounded portion of Pool 13.

As was found for dewatered areas, changes in water depth resulting from drawdown were different at river

mile 532, which includes Spring Lake. Large increases in the area with depths less than 1 foot were predicted

for both the 1- and 2-foot drawdown (Figure 11). Also, increased acreage was predicted for water depths up

to 3 feet, as well as largely decreased acreage for depths greater than 3 feet.

Earlier, we described the success of the drawdown in terms of dewatered areas and reduced water depth (and

the frequency at which these could be obtained), as well as having no effect on navigation. However, the

ecological success, although not entirely predictable, can be estimated by conditions present in the affected

areas. The sediment characteristics play a large role in the success of moist soil plant production, sediment

oxidation and compaction, and submersed vegetation response to photic zone changes. In addition to sediment

suitability, sediment types also provide an indication of hydraulic conditions and disturbance over a long time

period (>10 years), which also affects ecological response.

Although detailed sediment data were not collected in the affected areas, we did limited sediment mapping

in Pool 13 in 1996. According to the data collected, backwater lake sediments had higher moisture content than

sediments in channels and the impounded area. Within the impounded areas, some areas sheltered from windgenerated waves had higher moisture sediments relative to the open areas of the impounded area and,

conversely, shallow alluvial deposits near islands had very low (<30%) moisture sediments. Overall for the

pool, we found most sediments to have low moisture content (<50%) and very few areas to have sediments with

moisture content greater than 60%. Similar patterns were found in a study of Pools 4 and 8 (Rogala 1996).

The sediment distribution patterns described earlier suggest what type of sediments would be exposed. Three

predicted dewatered areas that would likely contain high moisture sediments (>50% moisture) are Thomson

Slough, Gomer’s Lake, and Spring Lake (Figure 1). These areas of high moisture sediments total about

120 acres for the 1-foot drawdown and 170 acres for the 2-foot drawdown. Several areas predicted to be

dewatered would result in exposure of low moisture sediments (<30% moisture); most of which were shallow

areas adjacent to remnant islands around river miles 527 to 529. Areas of exposed low moisture sediments total

about 65 acres for both the 1- and 2-foot drawdowns. Although moist soil plant response to exposure of low

versus high moisture sediments is varied, the sediment oxidation and compaction would certainly be less on

the low moisture sediments. Therefore, dewatered acreage that would provide for sediment oxidation and

compaction would be only a fraction of the predicted dewatered acreage. 

Those areas only slightly dewatered will likely retain water through capillary action and remain moist,

thereby reducing impacts on the sediment characteristics. This is important when assessing the advantages of

a 1-foot drawdown compared to 2-foot drawdown. The 2-foot drawdown, although occurring less frequently,

would provide for greater drying of sediments in the areas nearest the dam, which includes Thomson Slough

and Gomer’s Lake. Most of the sediment exposed during a 1-foot drawdown would remain moist for the

duration of the drawdown.

The effects of reduced water depth on the photic zone for submersed plants should be positive and the

acreage of reduced water depths appears substantial (Figure 8). However, the reduced water depths may have
7

additional impacts in the form of disturbances in the water column. For example, the impounded area where

most of the reduction in water depth is predicted has measurable velocity at current conditions. These velocities

may increase as a result of reduced cross sectional area and increased water surface slope during drawdown.

Also, the impounded area is a large expanse of water subject to wind wave action. The narrow band of

dewatered area would not reduce fetch values greatly, but the areas susceptible to the wave disturbances would

increase because of reduced water depths. Resuspension of sediments may be greater if the shallow depths do

not reduce wave energy and impede wave propagation.

Biotic response to the predicted physical changes is far less predictable. The short-term effects of dewatering

on highly mobile aquatic biota such as fish (e.g. stranding) is expected to be less than for biota incapable of

retreating with the dewatering. However, areas that do not dewater from the shoreline outward may more likely

strand fish. The drawdown conditions we investigated show little area that may strand fish by formation of

pockets of water. In addition, the rather narrow band that is dewatered (generally <250 feet) would not require

movement over long distances to avoid stranding. With a larger drawdown, areas such as Thompson Slough

may likely dewater in a manner that would strand fish. Fish eggs laid just prior to attempted drawdowns would

probably become non-viable in the dewatered zone, but that likelihood would be reduced during the shorter

period of June 15–August 15. 

Positive effects from a drawdown have been suggested by data collected in Pools 24 and 25 and Melvin

Price Pool. In these pools, the number and diversity of young-of-the-year fish were similar between 1986 and

1993, when no drawdown occurred, as compared to 1994 through 1996, when water levels were held lower

than in earlier years (Butch Atwood, Illinois Department of Natural Resources, personal communication).

Opinions differ concerning drawdown effects on invertebrates. In a literature search by Wlosinski and

Koljord (1996), factors found to affect invertebrate populations during a drawdown included 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) suggest that management for specific plant communities may be the

most practical way of increasing invertebrate production. Although information concerning invertebrate

populations in the predicted drawdown areas are not available, we compared average invertebrate numbers in

Pool 13 samples taken at depths greater than 1 foot to samples taken at depths less than 1 foot (Table 5). Based

on a small sample size in the near shore regions, average density in shallower areas were less for mayflies and

fingernail clams, but greater for midges.

The effects of a drawdown on native mussels in Pool 13 will also depend on many variables. As the water

is lowered, some mussels will move to deeper water whereas some will burrow into the substrate. The mussels

that bury themselves will be subjected to low moisture, elevated temperatures, and predation. The mussels in

dewatered areas that survive will be stressed. Mussels in shallow, but not exposed areas, will be more

vulnerable to predation. High mussel mortality has been observed in the Tennessee River System during

periodic drawdowns (Steve Ahlstedt, U.S. Geological Survey, personal communication). Some mussel species

appear to be more susceptible than others. 

The effects of a drawdown on aquatic and emergent vegetation have been documented on many aquatic

systems. The U.S. Fish and Wildlife Service routinely manipulates water levels to enhance moist-soil plant

production (Fredrickson 1991). The St. Louis District of the U.S. Army Corps of Engineers has held water

levels 1–2 feet lower than historical levels in Pools 24 and 25 and the Melvin Price Pool for at least 30 days.

Between 255 and 881 acres of preferred plants were found near the shoreline during the drawdown years as

compared to little acreage of the preferred plants in Pool 22, which was not drawn down. The preferred species
8

responding to the drawdown include Polygonum spp. (Smartweed), Cyperus spp. (Chufa), Echinochloa spp.

(Wild Millet), Amaranthus spp. (Pigweed), Setaria spp. (Yellow Foxtail), Panicum, and Leersia (Rice

Cutgrass). However, these pools are about 300 miles south of Pool 13 and water levels in those pools have been

managed differently than in Pool 13. At Small Bay West in Pool 5, a drawdown with similar duration and

magnitude to that proposed for Pool 13 was conducted. Minnesota Department of Natural Resources personnel

found that the number of plant taxa increased from 22 to 42 species and the acreage of vegetation increased

following this drawdown.

In a system as complex as a large impounded floodplain river, ecological effects of a drawdown are

unpredictable. However, the information provided here suggests some effects from a drawdown in Pool 13. The

monitoring of components of the ecosystem before and after a drawdown may provide valuable information

on the effects of the drawdown. That information, with the use of models, could be used to better predict

drawdown effects. Nevertheless, spatial and temporal variability in the river system would prohibit highly

accurate predictions of ecological effects of a drawdown.

The physical effects we estimated are within the constraints currently established for potential drawdown

management. The effects could be much greater if some constraints were less strict. For example, nearly twice

the dewatered area (1,071 compared to 530 acres) could be attained with a 2-foot drawdown at 50,000 cfs.

This drawdown would require lowering the minimum channel depth to less than 10.5 feet in a limited number

of areas. Failure to obtain ecological benefits, as measured during drawdowns occurring under current

drawdown options, should lead to investigating the potential for altering constraints in the future.

Acknowledgments

We thank Jennie Sauer for analysis of the invertebrate data, Butch Atwood for fisheries data on pools in

the St. Louis District, Pamela Thiel for information on potential effects to native mussels, and Jenny

Winkelman for her results on effects of a drawdown from Small Bay West.

References

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.

Fredrickson, L. H., and F. A. Reid. 1988. Invertebrate response to wetland management. In Waterfowl

management handbook. Fish and Wildlife Leaflet 13.3.1. U.S. Fish and Wildlife Service, Washington, D.C.

6 pp.

Fredrickson, L. H. 1991. Strategies for water level manipulations in moist-soil systems. In Waterfowl

management handbook. Fish and Wildlife Leaflet 13.4.6. U.S. Fish and Wildlife Service, Washington, D.C.

8 pp.

Lubinski, K. S., G. Carmody, D. Wilcox, and B. Drazkowski. 1991. Development of water level regulation

strategy for fish and wildlife, Upper Mississippi River System. Regulated Rivers: Research & Management

6:117–124.
9

Rogala, J. T. 1996. Surficial sediment characteristics in Pools 4 and 8, Upper Mississippi River.

U.S. Geological Survey, Environmental Management Technical Center, Onalaska, Wisconsin, November

1996. LTRMP 96-T006. 22 pp. (NTIS #PB97-129365) 

U.S. Army Corps of Engineers. 1991. Identification of constraints on regulation of Upper Mississippi River

System Lock and Dam 18. Report by the U.S. Army Corps of Engineers, Rock Island, Illinois, for the

U.S. Fish and Wildlife Service, Environmental Management Technical Center, Onalaska, Wisconsin,

September 1991. EMTC 91-07. 54 pp. (NTIS # PB92 104728)

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-P002R. 179 pp. (NTIS #PB94-160199)

Wilcox, D. B., and K. W. Willis. 1993. Identification of constraints on river regulation. Lock and Dam 9 near

Lynxville, Wisconsin, Upper Mississippi River 9-Foot Channel Project. Report by the U.S. Army Corps

of Engineers, St. Paul District-Minnesota, for the U.S. Fish and Wildlife Service Environmental

Management Technical Center, Onalaska, Wisconsin, August 1993. EMTC 93-S012. 91 pp. (NTIS #

PB94-103603) 

Wlosinski, J. H. 1996. Pool 25: Analysis of water levels and discharge. National Biological Service,

Environmental Management Technical Center, Onalaska, Wisconsin, March 1996. LTRMP 96-T001.

88 pp. (NTIS #PB96-165907)

Wlosinski, J. H., and L. Hill. 1995. Analysis of water level management on the Upper Mississippi River

(1980–1990). Regulated Rivers: Research & Management 11(2):239–248.

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. T. Rogala. 1995. Pool 25: Effects of water level and levee management alternatives

on present habitats. Pages 41–48 in Proceedings of the fifty-first annual meeting of the Upper Mississippi

River Conservation Committee, Rock Island, Illinois.

Wlosinski, J. H., and J. T. Rogala. 1996. Integrating hydraulic, statistical, and spatial models for predicting

the effects of water level management alternatives. Pages 235–237 in Proceedings Rivertech96, 1st

International Conference on New/emerging Concepts for Rivers–Volume 1. International Water Resources

Association, Urbana, Illinois.
10

Table 1. Definitions of terms used in this report.

Term Definition

Attributed The process of defining information about specific parts of a geographic information

system (GIS) map or coverage

Bathymetric data The water depth at a particular location in the river for a specific water-level elevation

Control point A specific location in a pool where the U.S. Army 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

GIS 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 As used in this report, a mathematical model that predicts water-level elevations from

upriver to downriver using bottom geometry, gate elevation settings at the downstream

dam, and discharge data 

Impounded area The area of the pool immediately upriver of the dam with little change in water surface

elevations; in Pool 13 this area is between the dam and river mile 530

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

which would still allow a 9-foot 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

Overlay A GIS process which 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

Project pool elevation The water-level elevation needed to maintain a 9-foot channel at zero discharge and for

which each dam was designed

Vector A GIS data structure that represents map features as a list of ordered x,y coordinates
11

Table 2. Predicted water surface elevations (feet above sea level) from the UNET model.

Drawdown (cfs)

Discharge

River mile

522.5 523 525 527 529 531 533 535

Existing 50,000 583.00 583.04 583.23 583.37 583.52 583.68 584.33 585.36

regulation

60,000 583.00 583.06 583.32 583.50 583.71 583.91 584.70 585.90

70,000 583.00 583.08 583.43 583.66 583.92 584.17 585.06 586.42

80,000 583.00 583.10 583.54 583.82 584.13 584.42 585.43 586.90

90,000 583.00 583.13 583.66 583.99 584.35 584.68 585.78 587.36

100,000 583.00 583.16 583.79 584.17 584.56 584.93 586.13 587.79

110,000 583.00 583.19 583.93 584.35 584.77 585.19 586.45 588.20

1-foot 50,000 582.00 582.07 582.38 582.61 582.86 583.06 583.89 585.13

60,000 582.00 582.10 582.53 582.82 583.12 583.37 584.34 585.72

70,000 582.00 582.13 582.68 583.03 583.38 583.69 584.77 586.27

80,000 582.00 582.17 582.84 583.25 583.65 584.01 585.18 586.79

90,000 582.00 582.21 583.01 583.47 583.92 584.32 585.56 587.25

100,000 582.00 582.26 583.19 583.69 584.18 584.61 585.94 587.71

110,000 582.00 582.31 583.36 583.91 584.44 584.90 586.29 588.12

2-foot 70,000 581.00 581.20 582.06 582.58 583.03 583.38 584.60 586.19

80,000 581.00 581.26 582.29 582.85 583.34 583.74 585.03 586.72

90,000 581.00 581.33 582.51 583.11 583.64 584.09 585.43 587.20

100,000 581.00 581.39 582.71 583.34 583.92 584.40 585.81 587.65
12

Table 3. Drawdown amounts (feet) predicted by the UNET model at various river miles when water levels at Dam 13

are held at 582 feet (1-foot drawdown) and 581 feet (2-foot drawdown).

Discharge

(cfs)

River mile

Drawdown 522.5 523 525 527 529 531 533 535

1-foot 50,000 1.00 0.97 0.85 0.75 0.67 0.62 0.43 0.23

 60,000 1.00 0.96 0.80 0.69 0.60 0.54 0.35 0.18

 70,000 1.00 0.95 0.75 0.63 0.54 0.48 0.30 0.15

 80,000 1.00 0.93 0.70 0.57 0.48 0.42 0.25 0.12

 90,000 1.00 0.91 0.65 0.53 0.43 0.36 0.22 0.11

100,000 1.00 0.90 0.61 0.48 0.38 0.32 0.19 0.08

110,000 1.00 0.88 0.57 0.44 0.34 0.28 0.17 0.07

2-foot 70,000 2.00 1.88 1.37 1.08 0.89 0.79 0.46 0.23

 80,000 2.00 1.84 1.25 0.97 0.79 0.68 0.40 0.18

 90,000 2.00 1.80 1.15 0.88 0.71 0.59 0.35 0.16

100,000 2.00 1.77 1.08 0.83 0.64 0.53 0.32 0.14
13

Table 4. Area (acres) dewatered and within 1-foot depth increments at various river miles when water levels are held

at the four conditions at Lock and Dam 13.

Acreage at each management condition

River mile (feet) @50,000 cfs @70,000 cfs @50,000 cfs @70,000 cfs

Depth 583 feet 583 feet 582 feet 581 feet

523 Dewatered 11 12 62 133

0 51 52 84 239

1 84 86 257 197

2 257 263 182 231

3 182 177 243 225

4 243 237 209 93

5 541 541 332 250

524 Dewatered 0 0 93 146

0 102 96 91 95

1 88 92 143 137

2 149 144 389 547

3 433 421 403 367

4 390 381 303 227

5 677 705 417 319

525 Dewatered 0 0 45 70

0 57 50 87 84

1 82 84 68 85

2 76 70 260 616

3 412 308 733 558

4 683 718 337 159

5 465 545 245 203

526 Dewatered 0 0 47 60

0 62 45 75 79

1 77 75 457 499

2 514 422 477 513

3 498 493 395 335

4 342 397 128 105

5 373 434 289 275

527 Dewatered 0 0 61 77

0 101 69 140 148

1 199 138 693 747

2 803 714 543 500

3 413 525 265 256

4 257 265 163 145

5 407 469 315 306
Table 4. Continued.

Acreage at each management condition

River mile (feet) @50,000 cfs @70,000 cfs @50,000 cfs @70,000 cfs

Depth 583 feet 583 feet 582 feet 581 feet

14

528 Dewatered 0 0 30 30

0 67 32 120 120

1 172 117 265 265

2 252 265 228 228

3 228 228 211 211

4 167 211 68 68

5 241 273 205 205

529 Dewatered 0 0 18 12

0 34 18 74 58

1 80 72 164 151

2 216 158 271 270

3 256 272 157 182

4 134 165 85 88

5 370 405 320 329

530 Dewatered 0 0 7 2

0 20 7 42 31

1 48 33 71 56

2 88 60 108 113

3 105 114 95 94

4 95 98 72 87

5 291 335 252 264

531 Dewatered 0 0 16 0

0 53 12 128 105

1 156 121 116 132

2 119 121 144 127

3 136 142 120 136

4 92 123 67 74

5 314 352 279 295

532 Dewatered 0 0 64 0

0 217 0 385 229

1 441 358 558 430

2 673 517 950 701

3 956 817 571 928

4 306 773 124 310

5 433 562 376 428

533 1 20 14 24 24

2 18 20 17 17

3 14 15 14 14

4 19 14 20 20

5 322 330 318 318
15

Table 5. Average invertebrate numbers (per m ) in Pool 13 between 1992 and 1997. 2 a

Invertebrate

species

Samples less than 1 foot deep Samples greater than 1 foot deep

Mean Sample size Mean Sample size

Mayflies 48 8 177 750

Fingernail clams 17 8 707 750

Midges 234 6 141 627

Data collected by the Long Term Resource Monitoring Program. a
16

Figure 1. Detail map of Pool 13. Inset: Map of the Upper Mississippi River System and the relative position of Pool 13.
0 50 100 150 200 250 300

Discharge (thousands of cubic feet per second) 

0

10

20

30

40

50

60

70

80

90

100

Percent of time exceeded

0 50 100 150 200 250 300

Discharge (thousands of cubic feet per second) 

0

10

20

30

40

50

60

70

80

90

100

Percent of time exceeded

17

Figure 2. Percentage of time discharge was exceeded for Clinton, Iowa, between May 1 and August 15 (upper) and

June 15 and August 15 (lower), based on daily values collected from 1873 to 1996. The hatched area represents

frequency of discharge needed for a 2-foot drawdown and the shaded plus the hatched area represents frequency of

discharge needed for a 1-foot drawdown.
















































0 10 20 30 40 50 60 70 80 90 100

Success rate

0

10

20

30

40

50

60

70

Consecutive days between discharge limits

 1 foot drawdown (May 1 - August 15)

 2 foot drawdown (May 1 - August 15)

1 foot drawdown (June 15 - August 15)







18

Figure 3. Estimated success rates for a 1- or 2-foot drawdown between May 1 and August 15 or a 1-foot drawdown

between June 15 and August 15 for Pool 13 based on the annual occurrence of discharge for the required number of

consecutive days.
















































0 10 20 30 40 50 60 70 80 90 100

Percent of attempts successful

0

10

20

30

40

50

60

70

Required number of consecutive days

1 foot drawdown (May 1 - August 15)

2 foot drawdown (May 1 - August 15)

1 foot drawdown (June 15 - August 15)







19

Figure 4. Percentage of drawdown attempts successful for Pool 13 based on the required number of consecutive

days for the periods between May 1 and August 15 for a 1- or 2-foot drawdown or between June 15 and August 15 for

a 1-foot drawdown.
 523 525 527 529 531 533 535

River mile

0

0.5

1

1.5

2

Drawdown (feet)

70,000 cfs

80,000 cfs

90,000 cfs

100,000 cfs

50,000 cfs

70,000 cfs

90,000 cfs

110,000 cfs

20

Figure 5. Drawdown amounts (feet) by river mile when water surface elevations are held at 1 foot (solid line) and 2

feet (dashed line) lower at Dam 13 for the discharge range required for the drawdown.








 













523 524 525 526 527 528 529 530 531 532 533

River mile

0

50

100

150

200

Acres dewatered

 582@50,000 cfs 581@70,000 cfs 

21

Figure 6. Acreage dewatered at 50,000 cfs for a 1-foot drawdown (582 feet above sea level at the dam) and at

70,000 cfs for a 2-foot drawdown (581 feet above sea level at the dam) in Pool 13.
22

Figure 7. Maps of Pool 13 depicting areas dewatered from a 1-foot drawdown at 50,000 cfs (left) and 2-foot drawdown

at 70,000 cfs (right).




















 

























 0-1 1-2 2-3 3-4 4-5 >5

Depth range (feet)

0

1

2

3

4

5

Acres within depth range (in thousands)

583@50,000 cfs 582@50,000 cfs 583@70,000 cfs 581@70,000 cfs  









































<1 <2 <3 <4 <5

Depth (feet)

0

2

4

6

8

10

12

14

Acres (in thousands)

583@50,000 cfs 582@50,000 cfs 583@70,000 cfs 581@70,000 cfs  

23

Figure 8. Acreage (upper) and cumulative acreage (lower) within each 1-foot water-depth range for 583-foot

elevation at 50,000 and 70,000 cfs, 582-foot elevation at 50,000 cfs, and 581-foot elevation at 70,000 cfs.
24

Figure 9. Maps of water depth, at 50,000 cfs, for the study area of Pool 13 when water levels at the dam are held at

583 feet (left) and 582 feet (right) above sea level.
25

Figure 10. Maps of water depth, at 70,000 cfs, for the study area of Pool 13 when water levels at the dam are held at

583 feet (left) and 581 feet (right) above sea level.




  

 

 











  

    

























0

200

400

600

800

1000

Acres 0 to 1 feet deep

583@50,000 cfs 582@50,000 cfs 583@70,000 cfs 581@70,000 cfs  



























  

 













































0

200

400

600

800

1000

Acres 1 to 2 feet deep

583@50,000 cfs 582@50,000 cfs 583@70,000 cfs 581@70,000 cfs  









 





 































































523 524 525 526 527 528 529 530 531 532 533

River mile

0

200

400

600

800

1000

Acres 2 to 3 feet deep

583@50,000 cfs 582@50,000 cfs 583@70,000 cfs 581@70,000 cfs  

26

Figure 11. Acreage, by river mile, of areas with water depths between 0–1 feet (top), 1–2 feet (middle), and 2–3 feet

(bottom) for each of the four conditions.












 















 





 







































0

200

400

600

800

1000

Acres 3 to 4 feet deep

583@50,000 cfs 582@50,000 cfs 583@70,000 cfs 581@70,000 cfs  













   



















 































0

200

400

600

800

1000

Acres 4 to 5 feet deep

583@50,000 cfs 582@50,000 cfs 583@70,000 cfs 581@70,000 cfs  



 



 





 



















 





































523 524 525 526 527 528 529 530 531 532 533

River mile

0

200

400

600

800

1000

Acres > 5 feet deep

583@50,000 cfs 582@50,000 cfs 583@70,000 cfs 581@70,000 cfs  

27

Figure 12. Acreage, by river mile, of areas with water depths between 3–4 feet (top), 4–5 feet (middle), and greater

than 5 feet (bottom) for each of the four conditions.
A-1

Appendix. Fish and Wildlife Interagency Committee

GARY ACKERMAN DORIE BOLLMAN * RICHARD EHRLER

IOWA DEPT OF NATURAL RESOURCES US ARMY CORPS OF ENGINEERS WAPSI BOTTOMS DUCKS UNLIMITED

BOX 250 CLOCK TOWER BUILDING 1422 ELM COURT

GUTTENBERG, IOWA 52052-0250 PO BOX 2004 DEWITT, IOWA 52742

ROSS ADAMS NORMAN EMERICK

MARK TWAIN NWR ROGER BOLLMAN ILLINOIS DEPT OF NATURAL

1704 NORTH 24TH STREET US ARMY CORPS OF ENGINEERS RESOURCES

QUINCY, ILLINOIS 62301 LECLAIRE BASE STATION BOX 1137

BUTCH ATWOOD

ILLINOIS DEPT OF NATURAL CHRIS BRESCHIA GORDON FARABEE

RESOURCES MIDWEST AREA RIVER COALITION MISSOURI DEPT OF CONSERVATION

1000 KILLARNEY DRIVE 200 N BROADWAY SUITE 1725 BOX 180

GREENVILLE, ILLINOIS 62246 ST LOUIS, MISSOURI 63102 JEFFERSON CITY, MISSOURI 65102

* MALLORY AUSTIN * ED BRITTON JIM FISHER

DUCKS UNLIMITED CLINTON UPPER MISSISSIPPI RIVER NWFR US FISH AND WILDLIFE SERVICE

CHAPTER SAVANNA DISTRICT UPPER MISSISSIPPI RIVER NW&FR

317 8TH AVENUE POST OFFICE BUILDING 51 EAST FOURTH STREET

CAMANCHE, IOWA 52730 SAVANNA, ILLINOIS 61074 WINONA, MINNESOTA 55987

THOMAS J BEISSEL KEN BRUMMETT * ROBERT GOODWIN

ILLINOIS DEPT OF NATURAL 653 CLINIC ROAD TOWER PLAZA MARITIME ADMINISTRATION

RESOURCES HANNIBAL, MISSOURI 63401 1222 SPRUCE STREET

2612 LOCUST STREET ST LOUIS, MISSOURI 63102

STERLING, ILLINOIS 61081 MIKE COCHRAN

GRETCHEN BENJAMIN RESOURCES IOWA DEPT OF NATURAL RESOURCES

WISCONSIN DEPT OF NATURAL 700 SOUTH 10TH STREET 206 ROSE STREET

RESOURCES HAVANA, ILLINOIS 62644 BELLEVUE, IOWA 52031

3550 MORMON COULEE ROAD

108 STATE OFFICE BUILDING MIKE COCKERILL NICK GULDEN

LA CROSSE, WISCONSIN 54601 US ARMY CORPS OF ENGINEERS MINNESOTA DEPT OF NATURAL

RONALD BENJAMIN PO BOX 2004 51 EAST 4TH STREET

WISCONSIN DEPT OF NATURAL ROCK ISLAND, ILLINOIS 61204-2004 WINONA, MINNESOTA 55987

RESOURCES

3550 MORMON COULEE ROAD JOYCE COLLINS STEVE GUTREUTER

LA CROSSE, WISCONSIN 54601-0108 US FISH AND WILDLIFE SERVICE UMR SCIENCE CENTER

* JAY BENTLEY 8588 Route 148 2630 FANTA ROAD

CLINTON DUCKS UNLIMITED MARION, ILLINOIS 62959 LA CROSSE, WISCONSIN 54603

1512 HARTS AVENUE

CAMANCHE, IOWA 52730 JOE COTHERN * JIM HARING

BILL BERTRAND 726 MINNESOTA AVENUE 1449 25 AVENUE SOUTH

ILLINOIS DEPT OF NATURAL KANSAS CITY, KANSAS 66101 CLINTON, IOWA 52732

RESOURCES

BOX 149 KEN DALRYMPLE MARVIN HUBBELL

ALEDO, ILLINOIS 61231 MISSOURI DEPT OF CONSERVATION ILLINOIS DEPT OF NATURAL

KEITH BESEKE ELSBERRY, MISSOURI 63343-0201 LINCOLN TOWER PLAZA

US FISH AND WILDLIFE SERVICE 524 SOUTH SECOND STREET

51 EAST 4TH STREET ROOM 101 * GLENN DROWNS SPRINGFIELD, ILLINOIS 62706

WINONA, MINNESOTA 55987 MISSISSIPPI BEND NATURE CLUB

DOUG BLODGETT CALAMUS, IOWA 52729 GATEWAY BASS BUSTERS INC

ILLINOIS NATURAL HISTORY SURVEY 1101 26TH AVENUE NORTH

704 NO. SCHRADER AVENUE * DOUG DUFFORD CLINTON, IOWA 52732

HAVANA, ILLINOIS 62644 DEARBORN HALL

* TOM BOLAND MT CARROLL, ILLINOIS 61053 ILLINOIS STATE CHAIRMAN

IOWA DEPT OF NATURAL RESOURCES WATERFOWL USA

24143 HIGHWAY 52 JON DUYVEJONCK 7619 HOLLY ROAD

BELLEVUE, IOWA 52031 US FISH AND WILDLIFE SERVICE FULTON, ILLINOIS 61252

ROCK ISLAND, ILLINOIS 61204-2004

PLEASANT VALLEY, IOWA 52767 GALESBURG, ILLINOIS 61401-1137

ILLINOIS DEPARTMENT OF NATURAL * MIKE GRIFFIN

CLOCK TOWER BUILDING RESOURCES

MARION ILLINOIS SUBOFFICE US GEOLOGICAL SURVEY

US ENVIRON PROTECTION AGENCY CLINTON IZAAK WALTON LEAGUE

BOX 201 RESOURCES

RR 1 BOX 166 * JIM HURLBURT

205 EAST SEMINARY * RON KAUFMAN

4469 48TH AVENUE COURT

ROCK ISLAND, ILLINOIS 61201
A-2

MANAGER MARK TWAIN NWR BERNIE SCHONHOFF RYAN WALDEN

WAPELLO DISTRICT IOWA DEPT OF NATURAL RESOURCES DIRECTOR/NATURALIST

10728 COUNTY ROAD X61 FAIRPORT HATCHERY RR 3 SOARING EAGLE NATURE CENTER

WAPELLO, IOWA 52653 3390 HIGHWAY 22 BOX 95

JIM MATTSON

US FISH AND WILDLIFE SERVICE * TOMMY M SEALS STEVE WATERS

1704 NORTH 24TH STREET BROWN WATER TOWING INC IOWA DEPT OF NATURAL RESOURCES

QUINCY, ILLINOIS 62301 100 NORTH BROADWAY SUITE 2120 SE DISTRICT OFFICE

GARY MENSINGER BRIGHTON, IOWA 52540-9661

415 2ND STREET * BOB SHEETS

CAMANCHE, IOWA 52730 IOWA DEPT OF NATURAL RESOURCES GARY WEGE

JIM MILLIGAN/JO GRADY MAQUOKETA, IOWA 52060 TWIN CITIES ES FIELD OFFICE

US FISH AND WILDLIFE SERVICE 4101 EAST 80TH STREET

608 EAST CHERRY STREET JERRY SKALAK BLOOMINGTON, MINNESOTA 55425-

COLUMBIA, MISSOURI 65201 US ARMY CORPS OF ENGINEERS 1665

COLONEL JAMES V MUDD PO BOX 2004 * WALT WEKHAM

US ARMY CORPS OF ENGINEERS ROCK ISLAND, ILLINOIS 61204-2004 BOX 161

CLOCK TOWER BLDG ATTN: OD-MC GRAND MOUND, IOWA 52751

PO BOX 2004 DICK STEINBACH

ROCK ISLAND, ILLINOIS 61204-2004 COMPLEX MANAGER KURT WELKE

DOUG MULLEN 1704 NORTH 24TH STREET RESOURCES

US FISH AND WILDLIFE SERVICE QUINCY, ILLINOIS 62301 MISSISSIPPI RIVER FISHERIES

UPPER MISSISSIPPI RIVER NW&FR 315 EAST CEDAR STREET

BOX 460 CHARLES SURPRENANT PRAIRIE DU CHIEN, WISCONSIN 53821

MCGREGOR, IOWA 52157-0460 CRAB ORCHARD NATIONAL

ERIC NELSON 8588 ROUTE 148 THE AMERICAN WATERWAYS

US FISH AND WILDLIFE SERVICE MARION, ILLINOIS 62959 OPERATORS

51 EAST 4TH STREET ROOM 101 11960 WESTLINE INDUSTRIAL DRIVE

WINONA, MINNESOTA 55987 GARY SWENSON SUITE 255

BILL OHDE MISSISSIPPI RIVER PROJECT OFFICE

IOWA DEPT OF NATURAL RESOURCES BOX 534 * JOE WLOSINSKI

515 TOWNSEND AVENUE PLEASANT VALLEY, IOWA 52767-0534 U.S. GEOLOGICAL SURVEY

WAPELLO, IOWA 52653 575 LESTER AVENUE

* DARYL PARKER IOWA DEPT OF NATURAL RESOURCES

JACKSON COUNTY CONSERVATION WALLACE STATE OFFICE BUILDING SCOTT WRIGHT

201 W PLATT, COURTHOUSE DES MOINES, IOWA 50319-0034 17635 140TH STREET WEST

MAQUOKETA, IOWA 52060 REYNOLDS, ILLINOIS 61279

JOHN PITLO US FISH AND WILDLIFE SERVICE

IOWA DEPT OF NATURAL RESOURCES FISHERIES RESOURCES OFFICES

24143 HIGHWAY 52 555 LESTER AVENUE * = Water level subgroup

BELLEVUE, IOWA 52031 LACROSSE, WISCONSIN 54650

BRAD POULTER UMIMRA

ILLINOIS DEPT OF NATURAL DAVE McMURRY

RESOURCES 10 CASCADE TERRACE

BOX 477 BURLINGTON, IOWA 52601

PITTSFIELD, ILLINOIS 62363-0477

* GEORGE RAES LOCK AND DAM 13

WAPSI VALLEY CHAPTER OF ATTN ERNEST JACKSON,

 IZAAK WALTON LEAGUE LOCKMASTER

WELTON, IOWA 52774 4999 LOCK ROAD

* DAN SALLEE

ILLINOIS DEPT OF NATURAL RICK VALE

RESOURCES US ARMY CORPS OF ENGINEERS

BOX 149 CLOCK TOWER BLDG ATTN: OD-MC

ALEDO, ILLINOIS 61231-0149 PO BOX 2004

MUSCATINE, IOWA 52761 CLINTON, IOWA 52732-0095

ST LOUIS, MISSOURI 63102 110 LAKE DARLING ROAD

COURTHOUSE US FISH AND WILDLIFE SERVICE

CLOCK TOWER BUILDING

MARK TWAIN NWR WISCONSIN DEPT OF NATURAL

WILDLIFE REFUGE PAUL J WERNER

US ARMY CORPS OF ENGINEERS ST LOUIS, MISSOURI 63146

KEVIN SZCODRONSKI ONALASKA, WISCONSIN 54660

PAM THIEL/SCOTT YESS

US ARMY CORPS OF ENGINEERS

FULTON, ILLINOIS 61252

ROCK ISLAND, ILLINOIS 61204-2004
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing

data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or

any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information

Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction

Project (0704-0188), Washington, D.C. 20503

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES

April 1999

COVERED

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Pool 13 drawdown: Predicting success rates and affected areas

6. AUTHOR(S)

James T. Rogala, Joseph H. Wlosinski, and Kevin J. Landwehr 1 1 2

7. PERFORMING ORGANIZATION NAME AND ADDRESS 8. PERFORMING ORGANIZATION

 U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Road, La Crosse, Wisconsin 1

54603.

U.S. Army Corps of Engineers, Rock Island District, Clock Tower Building, Rock Island, Illinois 61204-2004. 2

 REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING

U.S. Geological Survey 

Upper Midwest Environmental Sciences Center 99-T002

2630 Fanta Reed Road

La Crosse, Wisconsin 54603

 AGENCY REPORT NUMBER

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Release unlimited. Available from National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161 

(1-800-553-6847 or 703-487-4650. 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).

13. ABSTRACT (Maximum 200 words)

The likelihood of 1- or 2-foot drawdowns, and the area affected by such alternative drawdowns, was estimated for Pool 13 on the Upper Mississippi River. Minimum

water surface (elevation) requirements were compared to computed water surface profiles to determine a critical low flow that would allow a navigation channel 400 feet

wide and 10.5 feet deep. An upper limit on flow was established based on the flow at which open river conditions would exist for a given drawdown. The range in flows

that would allow for a drawdown was used to estimate success rates using historical daily discharge data. Success rates were determined for a variety of drawdown

durations between two time periods, May 1–August 15 and June 15–August 15. The greatest effect of the drawdown would be near Lock and Dam 13. Higher discharges,

as well as distance from the dam, lessen the drawdown amount. Areas that would be affected by these two drawdown scenarios were predicted by overlaying maps of

water surfaces with depths using a geographic information system. Although the drawdown effects on most physical and biotic components of Pool 13 are unknown, some

general drawdown effects likely to occur because of the changes in water surface elevation are presented.

14. SUBJECT TERMS 15. NUMBER OF PAGES

Dam regulation, drawdown, Mississippi River, Upper Mississippi River, water levels 27 pp. + Appendix

16. PRICE CODE

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY 20. LIMITATION OF ABSTRACT

 OF REPORT OF THIS PAGE CLASSIFICATION

Unclassified Unclassified

 OF ABSTRACT

Unclassified
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.