Kenneth R. Bradbury Wisconsin Geological and Natural History Survey, University of Wisconsin-Extension Daniel Feinstein

1. Wisconsin Geological and Natural History Survey Regional Hydrogeology and Groundwater Flow Modeling in Southeastern WisconsinWisconsin Legislative Council, Special Committee on the Great LakesWater Resources CompactOct 4, 2006 Kenneth R. Bradbury Wisconsin Geological and Natural History Survey, University of Wisconsin-Extension Daniel Feinstein U S Geological Survey, Wisconsin Water Science Center

2. Wisconsin Geological and Natural History Survey The Southeastern Wisconsin Regional Planning Commission (SEWRPC) area

3. 20 miles Sand-and gravel aquifer Silurian aquifer Sandstone aquifer Maquoketa aquitard Wisconsin Geological and Natural History Survey General hydrogeology of southeast Wisconsin Maquoketa subcrop Lake Michigan Milwaukee 2200 feet

4. “Sandstone” aquifer: -sandstone, dolomite -regionally extensive -excellent aquifer -porous flow -most high-capacity wells -occurs beneath shale in east Exposure of sandstone in the Wisconsin Dells

5. Wisconsin Geological and Natural History Survey “Dolomite” aquifer: -Silurian dolomite -fracture-dominated flow -only present in east -important for municipal and domestic wells

6. Relative well depths domestic wells: 100-300 ft deep most municipal wells: ~200-800 ft deep deepest wells: ~2200 ft deep (municipal wells in SE WI) Wisconsin Geological and Natural History Survey tallest buildings: ~600 ft high dolomite shale sandstone granite

7. Wisconsin Geological and Natural History Survey What is a groundwater flow model? • Computers are used to solve mathematical equations describing groundwater flow • Complex geology, wells, and surface water features are simulated using a three-dimensional grid • Such models are powerful tools for interpreting the past and predicting future conditions

8. One view of the groundwater flow model of SE Wisconsin

9. Wisconsin Geological and Natural History Survey What does a model give us? Simulations of… • groundwater levels (heads); changes in water levels through time • directions and velocities of flow in three dimensions • volumes or rates of water movement toward or away from surface water features

10. Water-level decline by county

11. Shallow Deep The following series of slides shows the simulated history of groundwater pumping and groundwater levels in southeast Wisconsin from the late 1800s through the present Water Levels in the Sandstone Aquifer (feet above sea level) Well Locations and Pumping Rates 1864-1880

12. Shallow Deep Water Levels in the Sandstone Aquifer (feet above sea level) Well Locations and Pumping Rates 1910-1920

13. Shallow Deep Water Levels in the Sandstone Aquifer (feet above sea level) Well Locations and Pumping Rates 1940-1945

14. Shallow Deep Water Levels in the Sandstone Aquifer (feet above sea level) Well Locations and Pumping Rates 1965-1970

15. Shallow Deep Water Levels in the Sandstone Aquifer (feet above sea level) Well Locations and Pumping Rates 1970-1980

16. Shallow Deep Water Levels in the Sandstone Aquifer (feet above sea level) Well Locations and Pumping Rates 1990-2000

17. Shallow Deep Water Levels in the Sandstone Aquifer (feet above sea level) Well Locations and Pumping Rates 2000-2010

18. Shallow Deep The Milwaukee/Chicago cone of depression is one of the largest areas of groundwater drawdown in North America Water Levels in the Sandstone Aquifer (feet above sea level) Well Locations and Pumping Rates 2010-2020

19. Consequences of development… • Downward flow to sandstone aquifer from above (lakes, streams, and recharge) has increased by 19.7 mgd just within the 7-county SE Wisconsin region • Flow toward Lake Michigan has reversed in the deep part of the flow system; 2.8 mgd once flowed under the coastline toward the Lake, now 3.7 mgd flows the other way, a change of 6.5 mgd • Due to pumping Wisconsin loses to N. Illinois about 2.4 mgd through the deep part of the flow system

20. Wisconsin Geological and Natural History Survey Summary and implications • Onshore pumping has significantly lowered deep groundwater levels adjacent to Lake Michigan • In some areas, historical groundwater flow directions have reversed • But…the impact on Lake Michigan itself is vanishingly small • More significant impacts occur as flow reductions in onshore streams

21. 4 OCT 2006 Groundwater and the Great Lakes Compact: How do the wells in southeastern Wisconsin interact with Lake Michigan?

22. The groundwater system is complicated – it changes with depth and with time….. With a mathematical model, we can not only simulate this complicated flow system but answer questions such as: what are the sources of water that goes to pumping centers in SE Wisconsin?

23. resistant shale About half the high-capacity pumpage in SE Wisconsin is from shallow wells, half from deep wells.

24. resistant shale The sources of water to shallow wells is mostly local. Shallow wells in the Lake Michigan Basin capture water that originates as precipitation in the Lake Michigan Basin. Shallow wells in the Mississippi River Basin capture water that originates as precipitation in the Mississippi River Basin.

25. resistant shale But the sources of water to deep wells are regional – it can originate from ancient precipitation far from pumping centers. We want to know what is the relation of those sources to Lake Michigan and the Lake Michigan Basin.

26. We use the phrase “sources of water to wells” in two ways: • The sources of water currently discharged by pumping wells • The sources of water replenishingthe water discharged by wells

27. Let’s rephrase our questions in the context of the Great Lakes Charter….

28. Discharge • How much of the water pumped today from SE Wisconsin deep wellsis actually Lake Michigan water? • 2.How much of the water pumped today from SE Wisconsin deep wellswould have flowed toward Lake Michigan if there were no wells?

29. Discharge • How much of the water pumped today from SE Wisconsin deep wells is actually Lake Michigan water? • 2. How much of the water pumped today from SE Wisconsin deep wells would have flowed toward Lake Michigan if there were no wells? • Replenishment • How much of the water that flows toward pumping • centers to replenish water captured by deep wells is flowing out of Lake Michigan itself? • 2. How much of the water that flows towards pumping centers to replenish water captured by deep • wells originates anywhere in the Lake Michigan Basin,as opposed to the Mississippi River Basin?

30. One more preliminary: • In the year 2000, deep wells in Southeast Wisconsin pumped about 33 mgd. • Waukesha city wells pumped a large fraction of that amount – about a quarter of the total.

31. 1) How much of the water discharged today from SE Wisconsin deep wells is actually Lake Michigan water? Answer: None Simulated contributing areas for deep wells for year 2000 conditions.

32. Interesting fact about Southeast Wisconsin: the deep groundwater divide has always been situated far to the west of the subcontinental surface-water divide…..

33. 2) How much of the water discharged today from SE Wisconsin deep wells would have flowed toward Lake Michigan if there were no wells? Answer: Probably all of it * *…. But it would have taken 100s or 1000s of years to reach the Lake Simulated deep flow lines for year 2000 entering Waukesha County from Lake Michigan side

34. 2) How much of the water discharged today from SE Wisconsin deep wells would have flowed toward Lake Michigan if there were no wells? Answer: Probably all of it * *…. But it would have taken 100s or 1000s of years to reach the Lake Simulated deep flow lines for year 2000 entering Waukesha County from Lake Michigan side

35. Now let’s turn to – Sources of water replenishing pumping by deep wells……

36. Key points: Under pre-pumping conditions (pre-1900) the model shows that only about 3 mgd of deep groundwater flowed from west to east under the Lake Michigan coastline of Ozaukee, Milwaukee, Racine, and Kenosha Counties.

37. Key points: Under pre-pumping conditions (pre-1900) the model shows that only about 3 mgd of deep groundwater flowed from west to east under the Lake Michigan coastline of Ozaukee, Milwaukee, Racine, and Kenosha Counties. But the pumping from SEWI deep wells is 33 mgd, over 10 times as much as the original deep flow.

38. Key points: Under pre-pumping conditions (pre-1900) the model shows that only about 3 mgd of deep groundwater flowed from west to east under the Lake Michigan coastline of Ozaukee, Milwaukee, Racine, and Kenosha Counties. But the pumping from SEWI deep wells is 33 mgd, over 10 times as much as the original deep flow. So it is not enough to talk about ancient tributary water to Lake Michigan. It is also necessary to talk about all the new water that is flowing toward the deep wells. Where is it coming from?

39. 1) How much of the water that flows into the cone of depression to replenish water discharged by deep regional pumping (including discharge from Waukesha’s deep wells) is flowing out of Lake Michigan itself?

40. Answer: the model shows that only 4% of the water flowing toward pumping centers in SE Wisconsin originates from Lake Michigan

41. If so little water is coming from Lake Michigan, where is most of it coming from? Most of it is derived from streams and inland lakes. That is, groundwater that once flowed toward these streams and lakes is now “diverted” downward to the deep aquifer.

42. According to the model, ALMOST ALL groundwater flow diverted toward deep wells is captured from streams within theMississippi River Basin … and there is a reason for that:

43. With the model we can answer the question: • 2) How much of the water that flows into the cone of depression to replenish water discharged by deep regional pumping originates anywhere in the Lake Michigan Basin, as opposed to the Mississippi River Basin? ~70% of the water that flows toward deep wells to replenish water discharged by regional pumping originates in the Mississippi River Basin….mostly as diverted streamflow. … the remaining ~30% originates in the Lake Michigan Basin, from storage, or from diversions from streams and inland lakes and from Lake Michigan itself.

44. Summary of model findings…..

45. 1) How much of the water pumped today from SEWI deep wells is actually Lake Michigan water?  None 2) How much of the water pumped today from SEWI deep wells would have flowed toward Lake Michigan if there were no wells?  All But wait: pre-1900, only about 3 mgd was flowing toward the Lake, just 1/10th of the 33 mgd pumped today! 3) How much of the water that flows into the deep aquifer to replenish 33 mgd of pumped water is flowing out of Lake Michigan itself?  4% 4) How much of the water that flows into the deep aquifer to replenish 33 mgd of pumped water originates anywhere in the Lake Michigan Basin, as opposed to the Mississippi River Basin?  30%

46. Or to say it another way: • When deep wells in SE Wisconsin turn on, they capture water that wason its way, slowly, toward Lake Michigan and now is curling back and moving much more quickly towards the deep wells. • But those wells are just taking the water that is at the “head of the line”. • Very little of the water “joining the back of the line” is or will be from Lake Michigan – because of the thick, resistant shalebetween it and the deep aquifer. • Most of the water “joining the line” is redirected from streams in the Mississippi River Basin where the shale is absent.

47. http://wi.water.usgs.gov/glpf/