Groundwater Occurrence & Movement: An Introductory Discussion with Application to Northeastern Illinois

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1 Groundwater Occurrence & Movement: An Introductory Discussion with Application to Northeastern Illinois H. Allen Wehrmann, P.E., Director Center for Groundwater Science Illinois State Water Survey April 24, 2007

2 Acknowledgments Martin Jaffe, University of Illinois, Chicago Scott Meyer, Center for GW Science, ISWS Steve Burch, Center for GW Science, ISWS IL State Geological Survey Kane County Water Resources Department

3 Topical Presentation Outline Basic Concepts and Definitions The Hydrologic Cycle What is groundwater? Concepts & Definitions Porous Flow vs. Fractured Flow Aquifers vs. Aquitards Artesian vs. Water Table Conditions Regional Groundwater Flow Systems Well & Aquifer Hydraulics Groundwater Modeling

4 The Hydrologic Cycle Climate, surface water, and groundwater are linked

5 Porous Systems Groundwater flows through pore spaces between grains

6 Porosity & Effective Porosity Ranges Silt Clay Material Porosity (%) Eff.. Porosity (%) Sand/Gravel Limestone/dolomite Shale Sandstone

7 Fractured Systems

8 Fractured Limestone or Dolomite

9 Aquifers vs. Aquitards An aquifer is a saturated bed, formation, or group of formations which yields water in sufficient quantity to be of consequence as a source of supply. An aquitard yields inappreciable quantities of water to wells compared to an aquifer but through which leakage of water is possible. Aquitards often act as confining beds.

10 Unconfined vs. Confined Groundwater An unconfined aquifer is one in which groundwater possesses a free surface open to the atmosphere. The upper surface of the zone of saturation is called the water table. A confined aquifer is one in which groundwater is confined under pressure by overlying and underlying aquitards or aquicludes and water levels in wells rise above the top of the aquifer. Also called an artesian aquifer.

11 Unconfined Aquifers Land Surface Unsaturated (Vadose) Zone Water Table Saturated Zone Unconfined Aquifer Bedrock

12 Confined Aquifers Land Surface Unsaturated (Vadose) Zone Water Table Unconfined Aquifer Saturated Zone Confining Layer - Aquitard Potentiometric Surface Confined Aquifer Bedrock

13 Confined Aquifers & Artesian Wells Flowing artesian well Land surface Water table Aquifer

14 Regional Groundwater Flow Systems 0.1 mile 20 miles Depth

15 Groundwater Stream Interaction Regional Flow Systems

16 Groundwater Stream Interaction Regional Flow Systems

17 Groundwater Stream Interaction Regional Flow Systems

18 Groundwater Stream Interaction Regional Flow Systems

19 Groundwater Flow Velocities Material Gravel Clean sand Clayey sand Clay Sandstone Highly fractured limestone Velocity 5-10 feet per day 1 5 feet per day feet per day < 0.1 feet per day < 0.5 feet per day s s feet per day

20 IL Geology glacial materials

21 Glacial depositional processes

22 Regional Bedrock Topography Green= higher elevations; Light violet= lower elevations

23 Major Sand & Gravel Aquifers

24 Withdrawals from Sand and Gravel Aquifers Total use ~ 350 mgd + ~200 mgd for irrigation

26 Aquifers of Northeastern Illinois West East DeKalb Chicago Unconsolidated Aquifer System Shallow Bedrock Aquifer Deep Bedrock Aquifer System Elmhurst-Mt. Simon Aquifer Cross-Section Modified from Bretz (1939)

27 Major Shallow Bedrock Aquifers

28 Withdrawals from Shallow Bedrock Aquifers Total use > 200 mgd

29 Major Deep Bedrock Aquifers

30 Withdrawals from Deep Bedrock Aquifers Total use ~ 100 mgd

31 Cone of Depression Well/Aquifer Interactions

32 Overlapping Cones of Depression Well/Aquifer Interactions

33 Overlapping Cones of Depression Well Interference Well/Aquifer Interactions

34 Overlapping Cones of Depression Well Interference A B Well/Aquifer Interactions

35 Overlapping Cones of Depression Well Interference A B Well/Aquifer Interactions

36 Overlapping Cones of Depression Well Interference A B Well/Aquifer Interactions

37 Overlapping Cones of Depression Well Interference A B Well/Aquifer Interactions

38 NE Illinois Deep Bedrock Withdrawals, mgd (1979) 140 Million Gallons per Day Estimated Practical Sustained Yield (Ideal Well Distribution)= 65 mgd 71.9 mgd (2000) Year Estimated Practical Sustained Yield (1958 Well Distribution)= 46 mgd

39 Distribution Of Deep Bedrock Aquifer Pumpage Source: Jaffe

40 Potentiometric Surface of the Deep Bedrock Aquifer System, Fall 2000

41 Potentiometric Surface Across NE Illinois WEST Elevation (ft) 1000 DeKalb Elburn EAST Elevation (ft) Geneva Elmhurst Bellwood Industrial site in Chicago St. Peter Ss Ironton-Galesville Ss

42 Deep Well Water Levels, Cook County

43 Oswego #3 (Kendall County) Elevation above Sea Level (feet)

45 Groundwater Flow Modeling: NE Illinois Regional Model Grid 226 rows 174 columns 18 layers 707,832 nodes Minimum grid spacing of 2500 Maximum grid spacing of 80,000

46 Modeled Heads in upper Galena-Platteville

47 Modeled Heads in lower Galena-Platteville

48 Modeled Heads in Ancell (St. Peter)

49 Modeled Heads in Ironton-Galesville

50 Thanks! Look for more information and updates: me with questions:

Groundwater Occurrence & Movement:

Groundwater Occurrence & Movement: An Introductory Discussion with Application to East-Central Illinois East-Central Illinois Regional Water Supply Planning Committee July 27, 2007 Allen Wehrmann, P.E.,