Groundwater Occurrence & Movement:An Introductory Discussion with Application toAn Introductory Discussion with Application to

East-Central Illinois

East-Central Illinois Regional Water Supply Planning CommitteeJuly 27, 2007

Allen Wehrmann, P.E., P.H.(GW), D.WRE, DirectorCenter for Groundwater Science, Illinois State Water Survey

Special thanks to:

Ed Mehnert, Ph.D.Hydrogeology Section

Steve Burch & George Roadcap, Ph.D.Center for Groundwater ScienceHydrogeology Section

Illinois State Geological SurveyCenter for Groundwater Science

Illinois State Water Survey

East-Central Illinois Water Supply Planning AreaWater Supply Planning Area

Topical Presentation OutlineBasic Concepts and Definitions

Th H d l i C lThe Hydrologic CycleWhat is groundwater?

Concepts & DefinitionsConcepts & DefinitionsPorous Flow vs. Fractured FlowAquifers vs. Aquitardsq qArtesian vs. Water Table Conditions

Regional Groundwater Flow SystemsWell & Aquifer HydraulicsGroundwater Modeling

The Hydrologic Cyclee yd o og c Cyc eClimate, surface water, and groundwater are linked

Porous Systems

Porosity = volume of pore space / total volume of porous material

Fractured Systems

FracturedLimestoneor Dolomite

Porosity & Effective Porosity Ranges

Material Porosity (%) Eff. Porosity (%)

Silt 34 - 61 0.1 – 10

Clay 34 - 60 0.1 – 10

Sand/Gravel 24 – 55 10 - 55

Limestone/dolomite 5 - 15 0.1 – 5

Shale 1 - 10 0.5 – 5Shale 1 10 0.5 5

Sandstone 5 - 15 0.5 – 10

Aquifers vs. Aquitards

An aquifer is a saturated bed, formation, or group of formations which yields water in sufficient quantityto be of consequence as a source of supply.to be of consequence as a source of supply.

An aquitard yields inappreciable quantities of water to wells compared to an aquifer but through whichleakage of water is possible. Aquitards often act as confining beds.confining beds.

Unconfined vs. Confined Groundwater

An unconfined aquifer is one in which groundwaterAn unconfined aquifer is one in which groundwaterpossesses a free surface open to the atmosphere.The upper surface of the zone of saturation is calledthe water table.

A confined aq ifer is one in hich gro nd ater isA confined aquifer is one in which groundwater isconfined under pressure by overlying and underlyingaquitards or aquicludes and water levels in wells riseabove the top of the aquifer. Also called an artesianaquifer.

Unconfined Aquifers

Land Surface

Unsaturated (Vadose) Zone

Water Table

( )

Saturated

UnconfinedAquifer

Saturated Zone

Bedrock

Confined Aquifers

Land Surface

Water Table

Unsaturated (Vadose) Zone

Unconfined Aquifer

Water Table

Saturated Zone

Confining Layer - AquitardPotentiometric Surface

Confined Aquifer

Confining Layer - Aquitard

Bedrock

Confined Aquifers & Artesian Wells

Land surfaceFlowing artesian well

Land surface

Water table

Aquifer

Regional Groundwater Flow Systems

0.1 mileDepth

20 milesDepth

0’

100’10’

200’20’

Groundwater – Stream Interaction

Regional Flow Systems

Groundwater – Stream Interaction

Regional Flow Systems

Groundwater – Stream Interaction

Regional Flow Systems

Groundwater – Stream Interaction

Regional Flow Systems

Groundwater Flow Velocities

Material VelocityGravel 5-10 feet per day

Clean sand 1 – 5 feet per dayClean sand 1 – 5 feet per day

Clayey sand 0.1 – 0.5 feet per day

Clay < 0.1 feet per day

Sandstone < 0 5 feet per daySandstone < 0.5 feet per day

Highly fractured limestone

10 – 1000’s feet per dayy

Regional Bedrock TopographyGreen= higher elevationsGreen= higher elevationsLight violet= lower elevations

The Mahomet Aquifer Region

Morton

Peoria

WatsekaWOODFORDCO

FORD0 8 12 16 204

NORTH

PekinNormal

Bloomington` PaxtonHoopeston

MCLEAN COCHAMPAIGN CO

FORD CO IROQUOIS CO

VERMILION CO

MILESGibson City

TAZEWELL CO

Havana

Lincoln Clinton Champaign Urbana

Rantoul

DanvilleMASON CO

MENARD CO

LOGAN CO

MCLEAN CO

MahometDEWITT CO

Petersburg

Decatur

Monticello

p gCASS CO

MACON CO

PIATT CO

Proposed ethanol plants using

Bedrock “high” – aquifer absent

SpringfieldProposed ethanol plants usingMahomet Aquifer as principal source

Illinois Geology:glacial materials

Glacial Depositional Processes

Major Sand &Gravel AquifersGravel Aquifers

Geology of the Mahomet Aquifer

Withdrawals from Sand & Gravel AquifersSand & Gravel Aquifers

Total use ~ 400 mgd+ ~200 mgd for irrigation

Regional Community Groundwater Use

2004 Water Use (gpd)

Gib Cit ( t M h t A if ) 730 000Gibson City (not Mahomet Aquifer) 730,000IL-American Water Co. 21,000,000Mahomet 500 000Mahomet 500,000Monticello 700,000Normal 4 100 000Normal 4,100,000Paxton 650,000Rantoul 1,600,000Rantoul 1,600,000Stone Ridge Dairy (near Bellflower) ~1,200,000White Heath 50,000,

Cone of Depression

Well/Aquifer Interactions

Overlapping Cones of Depression

Well/Aquifer Interactions

Overlapping Cones of Depression:W ll I t fWell Interference

Well/Aquifer Interactions

Overlapping Cones of Depression:Well Interference

BA

Well/Aquifer Interactions

Overlapping Cones of Depression:Well Interference

BA

Well/Aquifer Interactions

Overlapping Cones of Depression:Well Interference

BA

Well/Aquifer Interactions

Mahomet Aquifer Groundwater Levels

680

10 foot conto r10-foot contourFlow direction

Mahomet Water Levels by the Illinois River28

30Great Flood of 1993

Land Surface = 485’ MSL elevation

32

eet

aa

36

34

Dep

th to

wat

er, f

e

38

D

42

40

1988-1989 Drought

1955 1965 1975 1985 1995 2005Year

Potentiometric Surface of Eastern Mahomet Aquifer, 2005

Rantoul

Ch iChampaign-Urbana

DanvilleMonticello

Mahomet Potentiometric Heads near Champaign

660

640

eet

620

wate

r el

evat

ion,

fe

600

Grou

ndw

5801950 1960 1970 1980 1990 2000 2010

Water Use Trend at Champaign

24

20on

s pe

r day

16

paig

n, m

illio

n ga

llo

12

Pum

page

at C

ham

4

8P

1950 1960 1970 1980 1990 2000 2010

4

Impacts of pumping on water levels (head)Mahomet aquifer pumping headsMahomet aquifer nonpumping (artesian) headMahomet aquifer pumping headsMahomet aquifer nonpumping (artesian) head

P Pump settings

High-capacity well Low-capacity well

Glacialtill

P

P

M h t

P

Mahomet aquifer

Impact of pumping hydraulically linked aquifersGlasford nonpumpingMahomet nonpumping Glasford nonpumpingMahomet nonpumpingGlasford pumpingMahomet pumping

Glacial Till

Glasford Aquifer P

P

Glasford Aquifer

Glacial Till

Mahomet Aquifer

P

ISWS Regional Flow Model Predicted Heads

Model-Predicted DrawdownQ = 23 mgd at ChampaignQ = 23 mgd at Champaign

Thanks!

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