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!
Visit us on the web for updates:
http://www sws uiuc eduhttp://www.sws.uiuc.eduOr Google: Illinois State Water Survey
Top Related