State Water Survey Division GROUND WATER SECTION

Illinois Department of Energy and Natural Resources

SWS Contract Report 352C

PART C. EXISTING AND FUTURE GROUND WATER LEVELS

for the study

GROUND WATER LEVEL ANALYSIS BY COMPUTER MODELING:

AMERICAN BOTTOMS GROUND WATER STUDY

by

Joseph D. Ritchey, Richard J. Schicht, and Linda S. Weiss

Prepared for and funded by the

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

Champaign, Illinois June 1984

ISWS CR Ritchey, J. D. 352c PART C. EXISTING AND Loan FUTURE GROUND WATER Copy 3 LEVELS FOR THE STUDY q 352c GROUND WATER LEVEL

ANALYSIS BY COMPUTER

PREFACE

Groundwater Level Analysis by Computer Modeling is an in-depth investi­gation of groundwater flow in the American Bottoms area. There were five objectives to this study. They were 1) to compile current hydrologic data pertaining to the area, 2) to develop a computer model that could simulate the movement of groundwater, 3) to analyze existing and future groundwater levels in the area, 4) to present alternatives to lower or maintain ground­water levels at specified elevations in a designated area of interest and 5) to provide documentation of the model including a user's guide.

The five objectives of this study are addressed in five separate reports that may be used independently or conjunctively.

Part Title

A Groundwater Levels and Pumpage B American Bottoms Digital Groundwater Flow Model C Existing and Future Groundwater Levels D Evaluation of Alternative Measures E Digital Flow Model Description and User's Guide

A brief summary of each part of the study is given here. Each part has an introduction, an explanation of methods, results and references. Part E, the model user's guide, includes attachments for data and program listings.

Acknowledgments

A project of this size required the cooperation of many Illinois State Water Survey employees. Their efforts were important in the completion of this project. Noteworthy contributions were made by James D. Miller in gathering background information for Part A, by Mark C. Collins in modifying the ISWS aquifer model for Part B and by Anne Klock in making groundwater level probability exceedance calculations for Part C. Graphics were done by John Brother, Bud Motherway and Linda Riggin. Word processing was done by Pamela Lovett and Kathy Brown. A special appreciation was gained for the timely assistance of consultants at the University of Illinois Computer Services Office and the Boeing Computer Service Customer Service.

SUMMARY OF STUDIES

Groundwater Levels and Pumpage

The American Bottoms is a 175 square mile area of the Mississippi River valley lowlands that includes the urban industrial areas of East St. Louis, Granite City and Alton. Groundwater is a major source of water for the area and is used for industrial, public and irrigation supplies. Groundwater levels prior to industrial and urban development were near land surface. Intensive industrial development and construction of a system of drainage

ditches, levees, and canals to protect developed areas have altered the water resources in the area. In recent years, water level rises due to reductions in pumpage, high river stages, and high precipitation producing favorable recharge conditions have caused damage to underground structures. The U.S. Army Corps of Engineers, St. Louis District has sponsored this study to examine groundwater flow in the area and its relationship to Mississippi River stage and precipitation.

Water levels and pumpage information collected over many years by the State Water Survey have been summarized and are presented in Part A. Pumpage is presented for major and minor pumping centers and is classified as public, industrial, domestic or irrigation. Hydrographs are presented for ten different observation wells for their period of record. Mississippi River stages, precipitation at St. Louis airport and pumpage at Granite City are included with the hydrographs to illustrate their interdependence. Piezo-metric surface maps are presented for five different groundwater conditions.

Groundwater Flow Model

The groundwater model used was a modified form of the Illinois State Water Survey aquifer model (Prickett and Lonnquist, 1971). Modifications were made to incorporate the dynamic effects of river stage and precipita­tion. The model was calibrated by historically matching two five-year periods with constant one-month time steps. Hydrographs of actual and simu­lated water levels at ten observation wells and the nearest model cell for the two five-year periods are presented. Two piezometric surface maps of actual and simulated water levels are also presented. The model was found to consistently calculate water levels within two feet of the actual measured water level within a specified area of interest.

Existing and Future Conditions

Groundwater conditions were evaluated by simulating historical Missis­sippi River stage and precipitation and constant pumpage for a thirty-year period. Pumpage was simulated as 1) constant for the thirty-year period at historical 1980 rates and locations, 2) forecast 2000 rates and locations and 3) no pumpage except for a dewatering site maintained by the Illinois Depart­ment of Transportation.

Groundwater levels were evaluated with the aid of groundwater level exceedance probability plots. Groundwater level exceedance probability plots were constructed for ten model cells by compiling the maximum yearly water level from monthly simulated values. Plots were based on simulation of the thirty-year period from 1951 to 1980. The Weibold formula was used for probability calculations.

Mississippi River stage and precipitation records were available from 1905 to the present. One simulation was conducted for a period of 75 years to compare the period of simulation with the length of the exceedance plot. The longer period of record was desirable; however, because low river stages

as well as high river stages and low and high precipitation occur during the thirty-year period from 1951 to 1980, the impact on exceedance is minimal. Also, the cost of simulations dictated use of the shorter period.

Alternative Measures

Pumpage systems and gravity drainage collectors to maintain water levels were evaluated by the same methods used in evaluation of existing and future conditions. Two pumpage and one gravity collector systems were designed to meet three specified groundwater levels. Systems were designed for forecast 2000 pumpage and no pumpage conditions. In all, twenty systems were simu­lated. Systems were designed to meet the specified target elevation in all cells for 90 percent of the months simulated. Exceedance probability was calculated for ten cells, but is illustrated for only five cells. Piezo-metric surface maps are presented for June 1973 conditions for designs with year 2000 pumpage.

Digital Flow Model Description and User's Guide

The computer model is documented by sections describing model capabili- ties, theory and assumptions. Explanation for preparing data files and understanding output is also included, as are three sample problems. Four attachments are provided to: 1) list and explain file names supplied on magnetic tape, 2) list data of all inputs to the model, 3) list the Fortran V source code for the model, and 4) define all variables in the computer code.

The text for Part C, Existing and Future Groundwater Levels, follows.

PART C. EXISTING AND FUTURE GROUNDWATER LEVELS

This report on existing and future groundwater levels was prepared by

the Illinois State Water Survey (ISWS) as part of the study entitled, Ground­

water Level Analysis by Computer Modeling, American Bottoms Groundwater Study

funded by the U.S. Department of the Army, St. Louis District, Corps of

Engineers. This report is Part C in the final report.

INTRODUCTION

This section presents a method for evaluating historical groundwater and

future groundwater levels based on forecasts of future groundwater pumpage

without introducing groundwater level control measures. Water level exceed-

ance probability curves are presented using historical river stage, precipi­

tation, and groundwater pumpage. Future groundwater pumpage was forecast and

used to prepare water level exceedance curves for future conditions.

Exceedance probability curves of historical conditions are presented for

the ten wells described in Part A. These are presented to illustrate poten­

tial uses and problems that may be encountered in this method of study.

Exceedance probability curves of existing and future conditions are presented

for ten nodes located in the area of interest.

Water Level Exceedance Probability Curves

An exceedance probability curve is a graphical presentation of a statis­

tical method of analysis. They are constructed to evaluate the probability

that a particular groundwater level would be equalled or exceeded during a

given period of time. Exceedance probability curves have been a tool in

determining the stage of floods for many years (Benson, 1962); however, study

of groundwater conditions has not been done.

Plotting position was determined by using a formula presented by Weibull

(1939). This is:

where p = exceedance probability, in percent

n = number of years of record

m = rank of the event in order of magnitude, th'e largest event

having m = 1 .

Many other formulas have been used for analysis (Benson, 1962): the Weibull

formula is used because of its popularity and simplicity.

Groundwater level, exceedance probability curves were constructed using

available historical records. Water levels in the American Bottoms are

measured by the ISWS monthly or, for a limited number of wells, continuously.

For those wells with continuous record, the yearly maximum water level is

known; however, other wells only supply the maximum of 12 month-end values.

The data series consisted of the maximum month-end values for each year even

if maximum water levels were available. As justification for this, a com­

parison and explanation of using maximum month-end values versus maximum

values is presented.

Both the number of years of record used in the analysis and the period

of record have an impact on the determination of exceedance probability.

Because observation wells have a finite life, usually less than 30 years of

record and water levels predicted by computer simulation are restricted by

the expanse of the model when simulating long periods of time, it is neces­

sary to determine an adequacy of available data. Three different lengths of

record were examined and are presented determining data adequacy. Plots were

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made of elevation of groundwater levels above mean sea level against exceed-

ance probability, in percent. Figures 1 through 6 present water level

exceedance probability curves for selected observation wells in the American

Bottoms area. A brief explanation is presented with each curve to illustrate

the uses of or problems with water level exceedance probability curves.

Well 01077 (see figure 1) illustrates a well that has a small variance

in maximum water levels. It is located far from the Mississippi River, and

is not affected by any major or minor pumping center so all levels are the

result of recharge. Water level records exist from 1957 through the present

and all were used to prepare the exceedance curve. Maximum water levels show

very small fluctuations, as evidenced by the mild slope. As described in

figure 1, there is limited usefulness of the curves since a small error in

measurement of the water level results in a a very large error in the proba­

bility of exceedance.

Data from well 00181 is used to compare month-end data versus maximum

data in the preparation of exceedance curves (see figures 2a and 2b). As

shown in figures 2a and 2b, the shape and fit of the curves are very similar.

The years designated as high water level years on the curves indicate that

plotting positions do not vary significantly. For the same exceedance proba­

bility, figure 2b gives a slightly (about 0.5 feet) higher groundwater level.

Since the differences are small, month-end data are adequate for the prepara­

tion of probability exceedance curves.

Problems are encountered when constructing probability exceedance curves

for well 01072 (see figure 3) and well 01076 (see figure 4) located close to

the Mississippi River. This problem relates to the unavaila bility of water

level records for wells when the Mississippi River is above flood stage.

When the river is in flood stage, water may be flowing from a well making

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Figure 1. Water level exceedance probability curve for well MAD 3N9W-14.2C, 1958-1981.

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Figure 2a. Water level exceedance probability curve for well STC 2N9W-26.7e, using month-end data, 1952-1981.

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Figure 2b. Water level exceedance probability curve for well STC 2N9W-26.7e, using maximum monthly data, 1952-1981.

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Figure 3. Water level exceedance probability curve for well MAD 5N9W-29.4f, 1957-1981.

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Figure 4. Water level exceedance probability curve for well MAD 3N10W-12.4f, 1958-1981.

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measurement difficult, or high water can make access to the well impossible.

When this occurs, values have to be estimated; in this case, a rating curve

is used for each well. The rating curves were developed using the water

levels at the well and Mississippi River stages adjusted from the St. Louis

gage. This method of estimation is adequate for supplying information during

critical periods of record.

Exceedance probability curves constructed from data from well 01223 (see

figure 5) and well 01165 (see figure 6) reflect changes in pumpage. Because

pumpage changes nearby water levels, a change in pumpage over the period of

time from which the data set is taken will prejudice the probability of water

level exceedance for that period of time. Pumpage in a number of areas has

changed significantly during the period of water level record. The effect on

the probability of exceedance can be great enough to completely invalidate an

evaluation of the probability of future water levels or invalidate portions

such that the record that is usable is too short to be of practical use.

PROBABILITY EXCEEDANCE CURVES FROM SIMULATED DATA

Forecast of Pumpage 1982-2000

This sub-section presents estimates of future groundwater pumpage by

pumping center for the years 1982 through 2000. Accompanying predicted water

pumpage is an explanation of methods and a discussion of the validity of

estimated values. The quantity and distribution of pumpage in the American

Bottoms area for the years 1890 through 1981 have been described in

Part A: Groundwater Levels and Pumpage (pages 8 through 22).

Future water pumpage was forecast for the five major pumping centers

(Alton, Wood River, Granite City, National City and Monsanto) and the five

minor pumping centers (Fairmont City, Troy, Poag, Caseyville and Glen

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Figure 5. Water level exceedance probability curve for well MAD 3N9W-8.5, 1960-1981.

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Figure 6. Water level exceedance probability curve for well STC 2N10W-23.4c, 1943-1974.

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Carbon). Municipal and industrial pumpage were the only uses evaluated.

Pumpage for irrigation and domestic purposes is small compared to municipal

and industrial uses and has little effect on groundwater levels. A more

extensive survey of projected groundwater use was completed recently by

Planning and Management Consultants, Ltd, 1982. The conclusions of that

study are consistent with the findings of this study.

Methods

Future groundwater pumpage was determined by separate methods for short

and long-term forecasts. The period from 1982 to 1985 was considered short-

term and calculations were made according to information obtained from all

known groundwater users withdrawing an average greater than 10,000 gallons

per day. The period from 1986 to 2000 was considered long-term and calcula­

tions were made according to information provided by the area regional

planning commission.

Short-term (1982-1985) forecasts of pumpage were made by telephone

interviews with representatives of each industry and municipality that report

water use annually to the Illinois State Water Inventory Program (Kirk

et al., 1979, and Kirk et al., 1982). These representatives were, in most

cases, managers responsible for plant operations including monitoring water

use and maintenance of water pumping, distribution and treatment equipment.

Their knowledge of the amount of water use and its purpose was apparent.

However, they acknowledged uncertainty of future water use. No effort was

made to contact planners at each industry as to water use projections. This

was because of difficulty making contact with the correct individual, the

reluctance of the spokesman to divulge pertinent information, and question­

able benefit of the information once obtained.

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Industry responded to questions of future water use by indicating that

plant production and water conservation are primary indicators of future

water use. Apparently, depressed economic environment in the area has

resulted in many responses that future use would be similar or less than

current use.

Municipalities responded to questions of future water use by indicating

that population growth and weather are primary indicators of future use.

Since long term climate changes are difficult to predict, future use is based

on population growth.

Long-term (1986-2000) forecasts of water use were made with the assist­

ance of the Southwestern Illinois Metropolitan and Regional Planning Commis­

sion (SMRPC). The SMRPC indicated that expansion of industrial facilities

requiring large supplies of water is unlikely in the next five years. This

prediction is based on: the current poor economic climate in combination

with aging industrial facilities and the availability of Mississippi River

water. However, by 1990 a revitalization is likely to begin. Industrial

water use was projected to remain constant for the period 1985-1990, at which

time water use would increase at a rate of approximately 5% per year through

the year 2000. The rate of 5% was selected because it provided values con­

sistent with historical periods of industrial expansion.

The pumping center at National City was considered separately because it

includes a dewatering facility located at the junction of interstate highways

70-55 and 64. This facility, maintained by the Illinois Department of

Transportation (IDOT), withdraws groundwater as necessary to prevent flooding

of the underpass.

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Municipal water use has continued to increase regardless of the economic

climate of local industry. As a result, water use is forecast to increase at

a rate of 2% per year from 1986 through 2000.

The total forecast, municipal and industrial water use for the American

Bottoms area, is illustated in figure 7. Figures 8 through 17 illustrate

water use forecasts for each of the ten pumping centers.

Evaluation of Pumpage Forecasts

Prediction of future pumpage is, at best, a qualified guess. The

American Bottoms area is unstable with respect to many factors that impact

the use of groundwater. Factors previously noted include the abundance of

Mississippi River water, loss of industry, and efforts to conserve water.

Other factors are: groundwater quality problems in certain locations which,

in the past, have required excessive well maintenance; increasing service

area of the public water supply utilities; and uncertainty regarding speed of

economic recovery. Little imagination is needed to formulate a scenario of

greater decline or a turn to rapid growth that would result in different

amounts of water withdrawal than those forecast.

Future water use was projected at each pumping center by an arbitrary

constant rate. This rate intends to account for changes in the quantity of

groundwater withdrawal and in the number of groundwater users. Average

industrial groundwater withdrawal has declined slightly from 1.89 MGD in 1960

to 1.83 MGD in 1980 (disregarding withdrawal at the ID0T dewatering site).

Over this same period the number of groundwater users has declined from 47 to

20. This change includes company closings, relocation, and conversion to

surface water sources. Growth in future groundwater use is dependent on

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Figure 7. Total annual forecast pumpage for public and industrial supplies, 1981-2000.

Figure 8. Annual forecast pumpage for the Alton pumping center, 1981-2000.

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Figure 9. Annual forecast pumpage for the Glen Carbon pumping center, 1981-2000.

Figure 10. Annual forecast pumpage for the Troy pumping center, 1981-2000.

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Figure 11. Annual forecast pumpage for the Poag pumping center, 1981-2000.

Figure 12. Annual forecast pumpage for the Caseyville pumping center, 1981-2000.

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Figure 13. Annual forecast pumpage for the Fairmont City pumping center, 1981-2000.

Figure 14. Annual forecast pumpage for the Monsanto pumping center, 1981-2000.

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Figure 15. Annual forecast pumpage for the National City pumping center, 1981-2000.

Figure 16. Annual forecast pumpage for the Granite City pumping center, 1981-2000.

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Figure 17. Annual forecast pumpage for the Wood River pumping center, 1981-2000.

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activities that can utilize the benefits of groundwater and on the ability of

local groups to attract new groundwater users to the area.

Probability of Existing and Future Groundwater Levels Without Any Project

Because water levels are determined by aquifer simulation, the require­

ments of the simulation are important. The simulation uses Mississippi

River stage and St. Louis precipitation data. River stage data are available

from 1861 to date and precipitation data are available from 1871 to date.

The use of the model, however, is too costly to justify simulation of

the entire record, from 1871 to the present. Therefore, a brief analysis was

done to determine if a shorter length of record would be acceptable. (Five

locations in the area of interest were examined using a 60-, 40-, and 30-year

length of record for the periods 1910 to 1979, 1940 to 1979, and 1950 to

1979, respectively. These were provided to the Corps of Engineers, St. Louis

District, who determined that the 30-year length was acceptable.) Figures 18

and 19 illustrate water level exceedance curves for the three lengths of

record at two locations. The periods from 1910 to 1939 and from 1940 to 1969

were not examined and compared to the period from 1950 to 1979 because the

highest and lowest groundwater levels for the entire record were measured

during the period from 1950 to 1979.

Figure 18 shows water level exceedance curves for model cell J13 located

in the southwestern part of the American Bottoms for the three lengths of

record: from 1910 to 1979; from 1940 to 1979; and from 1950 to 1979.

Exceedance curves compare well between the 10% and 96% interval.

Figure 19 shows water level exceedance curves for model cell K28

located in the western part of the American Bottoms near the Mississippi

River.

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Figure 18. Groundwater level probability of exceedance curves for three different periods; 1911-1980, 1941-1980 and 1951-1980, for cell J 13.

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Figure 19. Groundwater level probability of exceedance curves for three different periods; 1911-1980, 1941-1980 and 1951-1980, for cell K 28.

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Existing and future groundwater levels were determined by simulating a

30-year period (1951-1980) of Mississippi River stage and precipitation with

water withdrawals fixed at either existing (1980), future (2000), or zero

pumpage conditions. The zero pumpage condition included withdrawals esti­

mated for the Illinois Department of Transportation dewatering site located

in the National City area. Pumpage at the IDOT dewatering site was included

in the zero pumpage condition because pumpage at the site would be maintained

even in the case where all other pumpage ceased. Maximum water levels at

each of ten specified locations were determined for each year and then ranked

from highest to lowest elevation. Water level exceedance curves representing

each location were plotted for each of the three pumpage conditions on one

figure. A summary of all of the water level probability exceedance curves is

presented in table 1.

Table 1 summarizes the water level exceedance curves by presenting

exceedance values at specified target elevations. Target elevations are

specified as 3 ft, 8 ft, and 14 ft below the node elevation, which represents

the land surface elevation within the node area. If the target elevation is

above or below the end points of the exceedance probability curve, the

exceedance is given as less than 4 percent or greater than 96 percent. Also

tabulated is the depth below land surface that yields a 4 percent exceedance

which corresponds to a 25-year event.

The exceedance probability curves for node J13 are illustrated in

figure 21. The three curves coincide because the node is remote from pumpage

and all other factors have remained the same. As with node J13, node V18

(figure 23) is removed from pumpage. The exceedance curves, however, do not

correspond and the relative positions of the curves reverse from high exceed­

ance values to low exceedance values. The cause of this is not known.

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Table 1. Water Level Exceedance Probability

Well No. 1 2 3 4 5 6 7 8 9 10 Name Mousette Camp Center- SWS 2 St. Claire Forest 13th Venice Granite Mary-

Jackson ville City ville Location N12 J13 R15 V18 S20 T23 N21 K28 P33 R37 Node elev. 410 409 415 421 414 416 417 412 420 419

Existing 1980 Pumpage Target* 3 feet <4% <4% <4% <4% <4% <4% <4% 4.5% <4% <4% 8 feet 5% 6% <4% 3.5% 12% <4% <4% 6% <4% <4% 14 feet >96% 66% >96% 91% >96% >96% <4% 40% 8% 82% 4% (25) 8 ft* 7 ft 9 ft 8 ft 7 ft 9 ft 19 ft 1 ft 13 ft 10 ft

Future O Pumpage Target* 3 feet <4% <4% <4% <4% <4% <4% <4% 5% <4% <4% 8 feet 5% 6% <4% 3.5% 10% <4% <4% 7% <4% 3.5% 14 feet >96% 70% >96% 91% >96% >96% <4% 68% 66% 92% 4% (25) 8 ft 7 ft 9 ft 8 ft 7 ft 9 ft 19 ft 1 ft 11 ft 8 ft

Future 2000 Pumpage Target* 3 feet <4% <4% <4% <4% <4% <4% <4% <4% <4% <4% 8 feet 3.5% 5.5% <4% 6% 4% <4% <4% 4% <4% <4% 14 feet 97% 64% >96% 84% >96% 91% <4% 30% <4% 68%

4% (25) 8 ft 7 ft 9 ft 8 ft 8 ft 10 ft 20 ft 8 ft 15 ft 10 ft

*feet below node elevation

Figure 20. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions; existing (1980), forecast (2000) and no pumpage, for cell N 12.

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Figure 21. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions existing (1980), forecast (2000) and no pumpage, for cell J 13.

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Figure 22. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions; existing (1980), forecast (2000) and no pumpage, for cell R 15.

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Figure 23. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions; existing (1980), forecast (2000) and no pumpage, for cell V 18.

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The exceedance probability curves for well T23 are illustrated in

figure 25. The node is proximate to pumpage at node T25 (Fairmont City) so

the three curves are parallel. As with T23, node N21 is proximate to pumpage

(see figure 26). The pumpage is due to the Illinois Department of Transpor­

tation (IDOT) dewatering site (node N23). Table 1 indicates the impact on

water levels in the area because the exceedance probability for all three

target elevations is less than 4 percent.

Exceedance probability curves are illustrated for cell P33 in figure 28

and cell R37 in figure 29. These nodes are at different distances from

pumpage that occurs at cells representing the Granite City pumping center.

Node P33 is closer to the pumpage than cell R37. The probability exceedance

curves for the two nodes demonstrate this in that the difference between

existing, future, and no pumpage is greater at cell P33 than at cell R37.

CONCLUSIONS

Determination of exceedance probability is affected by biases such as

pumpage, weather modification due to industrialization and control structures

on the waterways. These effects can be accounted for, resulting in an

adjusted water level exceedance curve. The length and period of record used

also has been shown to affect the calculated exceedance. In the American

Bottoms area, sufficient data exists such that cost of calculation becomes

the significant consideration. However, costs incurred during calculation

are small when compared to capital development. Therefore, this method of

analysis has merit for this study.

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Figure 24. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping condtions; existing (1980), forecast (2000) and no pumpage, for cell S 20.

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Figure 25. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions; existing (1980), forecast (2000) and no pumpage, for cell T 23.

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Figure 26. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions; existing (1980), forecast (2000) and no pumpage, for cell N 21.

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Figure 27. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions; existing (1980), forecast (2000) and no pumpage, for cell K 28.

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Figure 28. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions; existing (1980), forecast (2000) and no pumpage, for cell P 33.

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Figure 29. Groundwater level probability of exceedance curves for 1951-1980, for three different pumping conditions; existing (1980), forecast (2000) and no pumpage, for cell R 37.

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References

Benson, M. A. 1962. Evaluation of Methods of Evaluating the Occurrence of

Floods. USGS, Water Supply Paper 1580A.

Kirk, J. R., J. Jarboe, E. W. Sanderson, R. T. Sasman, and C. Lonnquist.

1982. Water Withdrawals in Illinois, 1980. Illinois State Water Survey

Circular 152, 47 p.

Kirk, J. R., J. Jarboe, E. W. Sanderson, R. T. Sasman, and R. A. Sinclair.

1979. Water Withdrawals in Illinois, 1978. Illinois State Water Survey

Circular 140, 34 p.

Planning and Management Consultants, Ltd. 1982. Institutional Study of

Large Volume Groundwater Users in the American Bottoms Area, Illinois.

Contract Report to the U.S. Army Engineer District, St. Louis, Corps of

Engineers, 76 p.

Weibull, W. 1939. A Statistical Theory of the Strength of Materials. Ing.

Vetenskapsakad. Handl. (Stockholm), Vol. 151, p. 15.

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