U.S. Department of the Interior

U.S. Geological Survey

Professional Paper 1778

National Water Availability and Use Pilot Program

Water Availability and Use Pilot: 

A Multiscale Assessment in the 

U.S. Great Lakes Basin
Front cover illustrations

Center: Block diagram of the Lake Michigan region showing, in section, aquifer layers; and in plan view, the 

Lake Michigan drainage boundary and major streams in the region. (Graphic by David C. Lampe, USGS Indiana 

Water Science Center)

Photo top: Center pivot irrigation. (Patrick C. Mills, USGS Illinois Water Science Center)

Photo second from top: Autumn trees along the Pentwater River, Mich. (James Nicholas, USGS Michigan 

Water Science Center)

Photo third from top: Water tower (Kimberly Shaffer, USGS Ohio Water Science Center)

Photo bottom: Thermoelectric powerplant (Kimberly Shaffer, USGS Ohio Water Science Center)

Back cover illustration

The National Water Availability and Use Pilot Program has conducted studies in the Great Lakes Basin 

(map inset) and the Southwest Alluvial Basins.
Water Availability and Use Pilot: 

A Multiscale Assessment in the 

U.S. Great Lakes Basin

By Howard W. Reeves

National Water Availability and Use Pilot Program

Professional Paper 1778

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Reeves, H.W., 2010, Water Availability and Use Pilot—A multiscale assessment in the U.S. Great Lakes Basin: 

U.S. Geological Survey Professional Paper 1778, 105 p.

Library of Congress Cataloging-in-Publication Data

Reeves, Howard W. (Howard William)

 Water availability and use pilot : a multiscale assessment in the U.S. Great Lakes Basin / by Howard W. Reeves.

 p. cm. -- (Professional paper ; 1778)

 Includes bibliographical references.

 ISBN 978-1-4113-2960-7

 1. Streamflow--Great Lakes Region (North America) 2. Groundwater--Great Lakes Region (North America) 3. Watersupply--Great Lakes Region (North America) I. Geological Survey (U.S.) II. Title. III. Series: U.S. Geological Survey 

professional paper ; 1778. 

 GB1207+.R44 2010

 551.480977--dc22 2010035207
iii

Foreword

Water is one of the most important natural resources of the United States and is essential to 

our health and economic well-being. Increasing competition for water to meet the needs of a 

growing population, municipalities, agriculture, industry, ecosystems, and recreation weighs 

on the sustainability of this resource. The sustained use of water resources is contingent 

on understanding the hydrologic implications of various alternative development strategies 

and properly evaluating their short- and long-term implications at scales that make sense. 

Compounding this complexity are unforeseen factors such as climate variability and change, 

which can further exacerbate an already challenging situation.

The question becomes, do we have sufficient supplies of freshwater in the United States to 

sustain human life and property as well as critical ecosystems? To address this concern, in 2002 

Congress directed the U.S. Geological Survey (USGS) to propose a national effort to assess 

the availability and use of freshwater resources throughout the United States. The first pilot 

assessment was initiated in 2005 in the U.S. portion of the Great Lakes Basin.

A major challenge in developing a sound approach for a National Assessment of Water 

Availability and Use has been to find effective means to deliver national-scale products while 

recognizing that these same water resources are commonly managed on a local scale. The 

USGS Great Lakes Basin pilot study focused on quantifying the source, movement, and dynamics 

of water resources in the Great Lakes region. New methods of hydrologic analysis and improved 

strategies for delivering water-related information were developed and tested in the process of 

assessing the region’s water availability. In this report we present the results of the pilot effort 

and examine the challenges and limitations for implementing a National Water Availability 

and Use Assessment. The collaboration of multiple partners from other Federal agencies, 

State agencies, nongovernmental organizations, industry, and academia has been valuable to 

the pilot effort and will continue to be important for refining the approach and methodologies 

used to determine the past, present, and future conditions of our Nation’s water resources. 

In short, our challenge is to characterize how much water is currently available, how water 

availability is changing, and how much water will be available in the future, and to do so at a 

scale that is relevant to local, State, Tribal, and Federal decision makers.

Matthew C. Larsen, Associate Director for Water

U.S. Geological Survey

v

Contents

Executive Summary.......................................................................................................................................1

Background and Major Issues ...........................................................................................................1

Regional Analysis..................................................................................................................................2

Subregional Analyses ..........................................................................................................................2

Lake Michigan Basin Groundwater-Flow Model....................................................................2

Estimation of Streamflows .........................................................................................................2

Water Withdrawals, Return Flows, and Consumption...........................................................2

Local Analyses ......................................................................................................................................3

Groundwater/Surface-Water Interaction................................................................................3

Assessment of Climate-Change Effects...................................................................................3

Assessment of Uncertainty of Flow, Water-Level, and 

Base-Flow Reduction Estimates..................................................................................3

Challenges and Lessons Learned ......................................................................................................4

Introduction.....................................................................................................................................................5

Purpose and Scope ..............................................................................................................................5

Previous Studies ...................................................................................................................................6

Approach to the Pilot ...........................................................................................................................7

Great Lakes Basin Water-Availability Issues............................................................................................7

Characteristics of the Great Lakes Basin..................................................................................................9

Regional Water Availability Analysis for the U.S. Great Lakes Basin.................................................12

Predevelopment Conditions..............................................................................................................12

Stocks (Storage) ........................................................................................................................12

Flows and Processes ................................................................................................................14

Postdevelopment Conditions ............................................................................................................17

Surface-Water Diversions Into and Out of the Great Lakes Basin....................................19

Regional Water Withdrawals and Water Use.......................................................................19

Regional Water Budgets Through Time .................................................................................27

Regional Indicators.............................................................................................................................32

Summary and Importance of Regional Analysis ...........................................................................35

Need for Subregional and Local Analyses.....................................................................................35

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin....................................35

Groundwater........................................................................................................................................35

Groundwater-Flow Model ........................................................................................................37

Groundwater Budget.................................................................................................................40

Groundwater-Availability Summary Indicators ....................................................................47

Groundwater-Flow Model and Groundwater Availability ...................................................55

Surface Water.....................................................................................................................................55

Water Withdrawals and Water Use.................................................................................................63

Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin ....................................73

Inset Groundwater-Flow Model Integrating Groundwater and 

Surface-Water Availability ..................................................................................................73

Groundwater/Surface-Water Interaction..............................................................................77
vi

Response to Climate Change...................................................................................................77

Monitoring and Network Analysis ...................................................................................................83

Example Bootstrap Analysis for Surface-Water Monitoring Network .............................83

Example Model-Uncertainty Analysis Using the Local Groundwater-Flow Model ........85

Summary of Pilot Study...............................................................................................................................90

Challenges for Future Water-Availability Studies ..................................................................................93

References ...................................................................................................................................................94

Acknowledgments.....................................................................................................................................103

Figures

1–3. Maps showing:

1. Study area for Great Lakes Basin Pilot............................................................................6

2. Level III ecoregions for the U.S. Great Lakes Basin....................................................10

3. Land use and cover for the U.S. Great Lakes Basin from the 

U.S. Geological Survey National Land Cover Database..............................................11

4. Hydrostratigraphy for the Lake Michigan Basin and adjacent region used in 

the groundwater-flow model developed in this project.......................................................13

5–11. Maps showing:

5. Summary of storage and flows for the Great Lakes ....................................................16

6. Shallow ground-water recharge estimated from 

base-flow-separation techniques...................................................................................17

7. Recharge distribution for the Lake Michigan Basin groundwater-flow 

model for the 1991–2000 simulation period ..................................................................18

8. Surface-water, groundwater, and total withdrawals in the 

Great Lakes Basin by source, hydrologic cataloging unit, 

Great Lakes watershed, and state area within Great Lakes Basin, 2005.................23

9. Public-supply withdrawals by source, hydrologic cataloging unit, 

Great Lakes watershed, and area of state within the 

Great Lakes Basin in 2005 ................................................................................................24

10. Self-supplied domestic water withdrawals by source, 

hydrologic cataloging unit, Great Lakes watershed, and area of state 

within the Great Lakes Basin in 2005..............................................................................25

11. Irrigation-water withdrawals by source, hydrologic cataloging unit, 

Great Lakes watershed, and state area within Great Lakes Basin in 2005..............26

12. Graphs showing A, Historical lake levels for the Great Lakes, 1860–2005........................28 

B, Late Holocene and historical level for Lake Michigan-Huron........................................29

13–14. Maps showing:

13. Changes in annual runoff at selected long-term streamgages. 

A, 1955–2004. B, 1935–2004 ..............................................................................................30

14. Changes in annual 7-day low runoff at selected long-term streamgages, 

1955–2004 ............................................................................................................................31

15–16. Graphs showing:

15. Trends in total water withdrawal by water-use sector in the 

Great Lakes Basin, 1985–2005 .........................................................................................32

16. Human water-use regimes defined by normalized human withdrawals, 

hout, and normalized human return flows, hin .................................................................34
vii

17. Diagram showing predevelopment and postdevelopment long-term average 

water budgets for the Great Lakes Basin...............................................................................36

18–19. Maps showing:

18. Model grid, Lake Michigan Basin drainage basin, and area where 

model cells are 5,000 feet by 5,000 feet..........................................................................38

19. Nearfield area of Lake Michigan Basin groundwater-flow model............................39

20. Graph showing recharge values assigned to stress periods for the 

Lake Michigan Basin groundwater-flow model with yearly and 5-year moving 

averages of recharge, as estimated by using the Soil-Water-Balance model ................41

21. Maps showing drawdown in Cambrian-Ordovician aquifer as simulated 

with the Lake Michigan Basin groundwater-flow model. 

A, 1950...........................................................................................................................................42

B, 1980...........................................................................................................................................43

C, 2005...........................................................................................................................................44

22–23. Graphs showing:

22. Simulated water-level hydrographs at pumping centers within 

water-budget zones of the Lake Michigan Basin groundwater-flow model ...........45

23. Water budget for the Lake Michigan Basin from groundwater-flow model

showing proportions of water-budget component for each modeled 

stress period.......................................................................................................................45

24–25. Maps showing:

24. Contributing areas to wells in principal aquifers .........................................................46

25. Water-budget zones of Lake Michigan Basin groundwater-flow model 

used to summarize groundwater-availability results...................................................48

26 Diagrams showing sources of water to wells by water-budget zone and 

aquifer system for 2005 from the Lake Michigan Basin groundwater-flow model. 

A, Shallow aquifer systems.......................................................................................................49

B, Deep aquifer systems............................................................................................................50

27–29. Graphs showing:

27. Demand-to-Supply Ratio and Base-flow-Reduction Ratio for 

the Lake Michigan Basin aquifer system as computed by use of 

the Lake Michigan Basin groundwater-flow model.....................................................52

28. Indictors computed for the water-budget zones for the Lake Michigan 

Basin groundwater-flow model. A, Base-flow-Reduction Ratio for shallow 

aquifers. B, Demand-to-Supply Ratio (DSR) for deep aquifers..................................53

29. Indicators computed at selected pumping areas within the Lake Michigan 

Basin groundwater-flow model. A, Base-flow-Reduction Ratio for shallow 

aquifers. B, Demand-to-Supply Ratio for deep aquifers .............................................54

30–31. Maps showing:

30. Staycast and forecast simulations for 2005–40 showing recovery and 

drawdown in the Quaternary aquifer system in response to continued 

pumping at 2005 rates (staycast) and projected pumping rates for 

2005–40 (forecast)..............................................................................................................56

31. Staycast and forecast simulations for 2005–40 showing recovery and 

drawdown in the Cambrian-Ordovician aquifer system in response to 

continued pumping at 2005 rates (staycast) and projected pumping rates 

for 2005–40 (forecast)........................................................................................................57

32. Schematic of AFINCH data sources and analysis results ...................................................58

33. Map showing NHDPlus stream reaches and USGS streamgage locations in 

hydrologic subregion 0405 used in AFINCH estimation .......................................................60
viii

34–36. Graphs showing:

34. Apparent incremental yield at streamgages within subregion 0405.........................61

35. Estimated monthly hydrograph for water years 1970–2000 generated with 

AFINCH for an ungaged stream in hydrologic subregion 0405 ..................................62

36. Monthly flow-duration curves for water years 1971–2000 with measured 

streamflows for water years 1971–75 and 1995–2000 at USGS streamgage 

04117000, Quaker Brook near Nashville, Mich. ............................................................63

37–38. Maps showing:

37. Constrained estimates of water yield for watersheds from the NHDPlus 

dataset for hydrologic subregion 0405 for May 2000, developed by 

using AFINCH .....................................................................................................................64

38. Constrained estimates of accumulated flows for stream segments in 

hydrologic subregion 0405 for October 2003, developed by using AFINCH.............65

39–40. Graphs showing:

39. Average monthly water withdrawals for water-use sectors for Ohio and 

Indiana, 1999–2005. 

A, All sectors ......................................................................................................................66

B, Withdrawals for thermoelectric power generation excluded...............................67

C, Withdrawal expressed as difference from annual average..................................68

D, Difference from annual average for each sector, excluding withdrawals 

for thermoelectric power .................................................................................................69

E, Difference from annual average, expressed as percent of 

annual average ..................................................................................................................70

F, Difference from annual average, expressed as percent of 

annual average excluding irrigation sectors ................................................................71

40. Monthly municipal water withdrawals for Lansing, Mich., during 2004–6 

and monthly mean flow from USGS streamgage 04113000, Grand River at 

Lansing, Mich. ....................................................................................................................72

41–43. Maps showing:

41. Inset-model overview showing subregional, intermediate, and 

local-scale model areas ...................................................................................................74

42. Surface-water network for subregional, intermediate, and 

local groundwater-flow models ......................................................................................76

43. Streams in local inset model with model gage, hypothetical well, 

and test watershed and stream indicated.....................................................................78

44–49. Grapsh showing:

44. Hydrographs and percent-change plots for the estimated streamflow 

at the gaged point showing streamflow depletion caused by pumping of 

hypothetical well from layers 1, 2, and 5 of the inset model.......................................79

45. Source of water to the hypothetical well in layers 1, 2, and 5 of the 

local inset model................................................................................................................80

46. Source of water to hypothetical well in layers 1, 2, or 5 of local inset 

model, with low-hydraulic-conductivity layer added to the model...........................81

47. Seasonal distribution of recharge values from the atmosphere-ocean 

coupled general circulation model (AOGCM) used for the inset-model 

climate-change scenario, by decade.............................................................................82
ix

48. Annual recharge for the inset-model climate-change scenario and 

base flow, by month, computed by the model for 1991–2000, 2013–22, 

and 2035–44 ........................................................................................................................84

49. Relation between censoring level and probability of estimating monthly 

flow within 10 percent of measured value, from bootstrap analysis of 

AFINCH-generated streamflows for hydrologic subregion 0405...............................86

50. Map showing head contours in layer 1 and layer 2 from the local inset model ..............88

51. Graphs showing relative contribution to prediction uncertainty from each 

parameter for A, head prediction and B, flow prediction within the local inset 

model at the locations specified in figure 50 .........................................................................89

52. Grid of candidate locations for additional head observations in prediction 

uncertainty analysis based on local inset model ..................................................................90

53–54. Graphs showing:

53. Observation uncertainty contribution for the head prediction at H115_259 

for layers 1 and 2 and three different parameterizations of the test area, 

based on the local inset model........................................................................................91

54. Observation uncertainty contribution for the flow prediction at the 

hypothetical streamgage for layers 1 and 2 and three different 

parameterizations of the test area, based on the local inset model.........................92

Tables

1. Great Lakes Basin Pilot reports (in U.S. Geological Survey publications series), 

focus topics, and predominant scale ........................................................................................8

2. Physical characteristics of the Great Lakes ..........................................................................10

3. Predevelopment generalized water budget...........................................................................14

4. Postdevelopment generalized water budget.........................................................................20

5. Consumptive-use-coefficient statistics for the Great Lakes Basin and 

climatically similar areas, by water-use category................................................................22
x

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) .3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) .003785 cubic meter (m3) 

million gallons (Mgal) 3,785 cubic meter (m3)

cubic foot (ft3) .02832 cubic meter (m3) 

Flow rate

foot per day (ft/d) 0.3048 meter per day (m/d)

cubic foot per second (ft3/s) .02832 cubic meter per second (m3/s)

cubic foot per second per square mile 

[(ft3/s)/mi2] .01093 cubic meter per second per square kilometer [(m3/s)/km2]

gallon per minute (gal/min) .06309 liter per second (L/s)

gallon per day (gal/d) .003785 cubic meter per day (m3/d)

million gallons per day (Mgal/d) .04381 cubic meter per second (m3/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the International Great Lakes Datum (IGLD) 

of 1985.

Altitude, as used in this report, refers to distance above the IGLD.
Water Availability and Use Pilot: 

A Multiscale Assessment in the 

U.S. Great Lakes Basin

By Howard W. Reeves

Background and Major Issues

The Great Lakes region has abundant water resources. 

The Great Lakes are the largest freshwater system on Earth, 

and groundwater resources are widespread and typically of 

high quality. The average discharge from the basin to the 

Atlantic Ocean through the St. Lawrence River makes it the 

second-largest drainage basin in the United States after the 

Mississippi River drainage. Diversions of water into and out 

of the basin are notable for galvanizing discussion of regional 

water resources, but such diversions actually play a small role 

in the overall water budget for the basin. Climate variations 

lead to variations in water delivery (through precipitation) 

and removal (through evaporation and transpiration). These 

variations, on seasonal, annual, decadal, and longer timeframes, are crucial in determining lake levels, groundwater 

levels, and streamflows within the basin. Human interactions 

with the hydrologic system, other than hydroelectric power 

generation, represent a small percentage of the overall flow 

through the system; but drawdown of groundwater levels in 

the Chicago/Milwaukee area has been as much as approximately 1,000 feet, and the areal extent of the drawdown area 

is very large (Alley and others, 1999; Reilly and others, 2008). 

Mapping water withdrawals and return flows by watershed 

within the basin helps highlight the spatial variation in water 

use by various economic and water-supply sectors across the 

basin and illustrates the importance of subregional or localscale analysis in quantifying the effect of water use on local 

water resources. 

Executive Summary 

Beginning in 2005, water availability and use were 

assessed for the U.S. part of the Great Lakes Basin through the 

Great Lakes Basin Pilot of a U.S. Geological Survey (USGS) 

national assessment of water availability and use. The goals 

of a national assessment of water availability and use are 

to clarify our understanding of water-availability status and 

trends and improve our ability to forecast the balance between 

water supply and demand for future economic and environmental uses. This report outlines possible approaches for 

full-scale implementation of such an assessment. As such, the 

focus of this study was on collecting, compiling, and analyzing a wide variety of data to define the storage and dynamics 

of water resources and quantify the human demands on water 

in the Great Lakes region.

The study focused on multiple spatial and temporal 

scales to highlight not only the abundant regional availability 

of water but also the potential for local shortages or conflicts 

over water. Regional studies provided a framework for understanding water resources in the basin. Subregional studies 

directed attention to varied aspects of the water-resources 

system that would have been difficult to assess for the whole 

region because of either data limitations or time limitations 

for the project. The study of local issues and concerns was 

motivated by regional discussions that led to recent legislative 

action between the Great Lakes States and regional cooperation with the Canadian Great Lakes Provinces. The multiscale 

nature of the study findings challenges water-resource managers and the public to think about regional water resources 

in an integrated way and to understand how future changes 

to the system—driven by human uses, climate variability, or 

land-use change—may be accommodated by informed waterresources management.
2 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Regional Analysis

Regional water budgets were assembled from existing 

information. The most notable feature of the regional water 

budgets is the large storage volume of the surface-water 

system that is unique to the Great Lakes region compared to 

most large basins in the United States. Groundwater storage 

in the U.S. Great Lakes Basin was estimated, and it exceeds 

the storage of Lake Erie and Ontario. The annual flow through 

the basin is approximately 1 percent of the volume in storage. Base-flow and recharge estimates were developed from 

streamgage data for the region and were found to vary according to climate, landscape, and geology. Temporal trends in 

precipitation, lake levels, and streamflow were investigated. 

Water-resources development and land-use change have 

altered the hydrology and hydraulics of the Great Lakes Basin, 

and control structures on the lakes and connecting channels 

have dampened some of the natural variability of the system. 

The large size of the basin, large natural storage of water 

in the system, and large annual flows through the system 

buffer the effects of most development, so development has 

had relatively little overall affect on water availability at the 

basin scale.

Subregional Analyses

Groundwater resources, surface-water flows, and water 

withdrawals and returns were studied on a subregional scale in 

the Great Lakes Basin Pilot.

Lake Michigan Basin Groundwater-Flow Model

A subregional groundwater-flow model for the Lake 

Michigan Basin was developed to quantify groundwater 

availability and to simulate system response to changes in 

anthropogenic and environmental stresses. This subregional 

model illustrates the source of water to wells and changes in 

the dynamics of the groundwater system during 1865–2004 

in response to development and climate-driven variations in 

recharge. The model also was used to show the changes in 

groundwater divides in response to pumping and to analyze 

the direct groundwater input to Lake Michigan, which is 

approximately 2 percent of the total groundwater discharge 

to surface water. The primary discharge of groundwater is to 

streams and other inland surface-water bodies. Pumping of 

groundwater produces changes in the estimates of discharge 

to streams but, because of the scale of the model, it does not 

distinguish the impact of wells on individual streams. 

Water-use projections were used to develop forecast 

scenarios to demonstrate the use of the subregional model 

in predicting changes to the groundwater system in response 

to projected uses. Changes in pumping in the CambrianOrdovician aquifer system on the west side of Lake Michigan 

produce the most dramatic changes in groundwater levels. 

Simulations indicate recovery in water levels of more than 

100 feet if current conditions are held through 2040; however, 

additional drawdown of more than 100 feet is indicated under 

forecast conditions of increased groundwater withdrawal in 

certain areas. 

Analysis of climate change was restricted to the local 

scale because at the subregional scale, effects of climate 

change cannot be adequately resolved by the groundwaterflow model. Shifts in long-term recharge rates are quickly 

compensated for by changes in the estimated base flow to 

streams such that the regional model response to climatechange scenarios is similar to its response to observed climate 

during 1864–2004.

Estimation of Streamflows

New methods were developed to improve estimates of 

surface-water delivery to the Great Lakes and streamflow in 

ungaged basins. Better estimates of streamflows in the basin 

are important because the primary discharge of groundwater 

in the basin is to the inland surface-water system, and surfacewater delivery to the Great Lakes from direct runoff and base 

flow is approximately half of the water supply to the Great 

Lakes. The effect of water withdrawals on streamflow—especially on the flow required to maintain ecosystem health, 

termed “ecosystem flows” or “ecological flows”—has gained 

great interest in the region, and estimates of ungaged flows are 

an essential part of establishing and understanding ecological flow requirements in any system. A regression-based 

approach that is constrained to route and conserve flow in the 

stream network, match observed mean flows at streamgages, 

and account for specified water withdrawals and transfers 

was developed into a computer application as part of the 

pilot. This application also provides the analyst with a suite 

of tools to interrogate streamflow data, identify anomalies 

perhaps due to unaccounted-for water use, develop regression models with selected independent landscape and climate 

variables, and analyze the resulting streamflow estimates. The 

method was applied to a hydrologic subregion within the Lake 

Michigan Basin and was shown to be effective in estimating 

ungaged flows and providing a framework for surface-water 

accounting.

Water Withdrawals, Return Flows, 

and Consumption

Water use also was examined at the subregional scale. 

Seasonal and monthly variations in water withdrawal, return 

flow, and consumption were documented by using data from 

Ohio, Indiana, and Wisconsin. This analysis revealed that 

for all major water-use sectors, water withdrawals increase 

during the summer months and are lower than the respective 

annual average during winter months. Peak use is often coincident with or just precedes the lowest summer streamflows, 
Executive Summary 3

implying that seasonal variation in withdrawals may be 

important when considerating ecological flows. The implication becomes stronger if ecological flows also have seasonal 

components; analysis of ecological flows in the region, 

however, was beyond the scope of this study. Understanding 

the current status and recognizing trends in water withdrawals, 

return flow, and consumption will help water managers evaluate ecological flows, instream use, and other constraints that 

may influence water availability.

Local Analyses

Local analyses focused on water-availability issues that 

are difficult to quantify on regional and subregional scales. 

Notably, analyzing groundwater/surface-water interaction and 

the potential to affect ecological flows in streams by pumping 

wells are inherently local-scale issues. The local-scale analysis 

also included examination of the effects of climate variability 

and methods to estimate uncertainty using surface-water and 

groundwater models.

Groundwater/Surface-Water Interaction

Understanding the interaction between pumping wells 

and local streams is a topic of growing interest and concern; 

however, studies on regional and subregional scales within 

the pilot project were not able to directly address questions 

at local spatial scales or short time periods. To illustrate the 

relation between regional-, subregional-, and local-scale studies, a local inset groundwater-flow model was built within 

the Lake Michigan Basin groundwater-flow model. The 

inset model covered a 20-square-mile area and examined the 

interaction between a single, hypothetical well and the stream 

network that can be accurately resolved at this local scale. 

The inset model enables the exploration of pumping-induced 

effects on streamflow given a set of pumping scenarios, such 

as withdrawal from different aquifer layers or variations in 

pumping schedules. For the case studied, streamflow depletion of the closest stream by the introduced pumping well was 

approximately half the pumping rate of the well. Capture of 

water from other streams was approximately 40 percent of 

the pumping rate, and the remaining water delivered to the 

well was from aquifer storage. The presence of a layer of low 

hydraulic conductivity between the aquifer being pumped and 

the stream shifted the distribution, increasing the capture from 

other streams in the surrounding area and decreasing capture 

from the closest stream. 

Assessment of Climate-Change Effects

The potential effects of climate change and variability were simulated by varying the recharge imposed on the 

subregional groundwater-flow model through the use of a soilwater-balance estimate. To demonstrate the technique, input to 

the soil-water-balance recharge estimate was from a scenario 

generated by an atmosphere-ocean coupled general circulation 

model, and base-flow changes in the system in response to a 

2000–40 scenario are presented. For the scenario tested, base 

flow increases for part of the scenario and then decreases after 

approximately 2015. The simulated base flow was zero for 

several years in the prediction scenario showing the sensitivity of the headwater stream to relatively modest changes in 

estimated recharge at the local scale.

Assessment of Uncertainty of Flow, Water-Level, 

and Base-Flow Reduction Estimates

Much of the analysis performed in the Great Lakes Basin 

Pilot relied upon USGS streamgage data. In addition, the 

groundwater-flow model relies on groundwater-level data. 

For the surface-water network, the importance of streamgage 

stations to the uncertainty in flow estimates was studied for 

a watershed in southwest Michigan/northwest Indiana. At a 

20-percent reduction of streamgage observations, the probability of the estimated flow being within 10 percent of measured 

flow at a gage was between 85 and 90 percent. This range of 

probability decreased dramatically to between 60 and 75 percent if half the streamgage observations were removed from 

the analysis. 

For the local groundwater-flow model, the most effective location for future data collection to reduce uncertainty in 

water level and base-flow reduction estimates for hypothetical pumping within the inset model area was studied. Use of 

numerical techniques that estimate prediction uncertainty and 

sensitivity to observations were very sensitive to the conceptual model used to develop the local-scale model. A highly 

parameterized approach was shown to be effective in identifying locations for additional observations that would decrease 

prediction uncertainty. Approaches with similar structure to 

the underlying aquifer characterization but with fewer parameters did not clearly identify locations where additional observations would be productive. These results indicate that local 

inset models should have a refined spatial distribution and be 

highly parameterized if these types of analyses are desired.
4 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Challenges and Lessons Learned

The Great Lakes Basin Pilot identified several challenges 

and lessons learned: 

• Studies summarizing water use highlight inconsistencies in water-use data collection and reporting across 

the region. Much of the reported water use in some 

sectors relies heavily on estimates, and the estimation procedures may vary from state to state. Resolving these inconsistencies and developing methods 

to improve estimates for the broad water-use sectors 

and for specific categories within the broader sectors 

remains a challenge. 

• Estimation of surface-water characteristics across the 

basin was hampered by the requirement that all streams 

in the geographic dataset used for the analysis be 

routed through the stream network. Existing datasets 

are quite well constructed in this respect, but there 

remains a small percentage of streams that are disconnected or improperly routed; correcting even these few 

problems is labor intensive and time consuming. 

• The tension between developing a regional groundwater-flow model capable of representing regional 

hydrologic dynamics and the desire to address problems of local interest is a challenge for regional wateravailability studies. Methods to allow regional models 

to be used to address local questions, such as the 

illustrative inset model discussed previously, provide 

insight into the potential local response in water levels 

and base flow to groundwater withdrawals. For sitespecific questions, more refinement of the hydrogeologic characteristics would be needed to better address 

local issues. 

One other issue that remains a challenge to both the 

subregional- and local-scale groundwater-flow models is 

that traditional models do not account for potential changes 

in recharge to the aquifer system in response to changes in 

pumping, return flow, or other specific changes to the environment. This separate treatment may be valid on the subregional 

scale; but as questions become more site specific, the potential 

for pumping to modify recharge to the local aquifer should be 

included in the simulation. For situations where recharge can 

be influenced by pumping, coupled groundwater-surface water 

models that generate recharge to the groundwater system as 

part of the simulation would be required.

Water availability is a function of water quantity and a 

range of other factors including water quality, physical infrastructure, water law and regulations, and economic considerations. Social decisions regarding desired instream flows for 

recreation, transportation, ecological support, or aesthetics 

may constrain water availability, and current societal decisions 

pertaining to water availability can be further complicated by 

changes in social norms with time. The legal framework for 

existing water use may override other considerations by granting primacy for use to senior water-rights holders or preventing any development near certain designated streams. These 

constraints were not studied as part of this effort. 

The underlying framework controlling water availability 

is the interplay between storage of water in the system, flux of 

water through the system, and human and ecological uses of 

water. Understanding this underlying framework is paramount 

to developing estimates of water availability given the constraints that are recognized today or that may be imposed in 

the future. This study summarizes regional estimates of water 

in storage and the fluxes of water through the system. Subregional and local analyses that were part of this study quantified various aspects of the water resources, demonstrated tools 

and techniques capable of assessing subregional and local 

issues, and helped provide the requisite information to inform 

regional, subregional, and local water-availability decisions.

Alley, W.M., Reilly, T.E., and Franke, O.L., 1999, Sustainability of ground-water resources: U.S. Geological Survey 

Circular 1186, 79 p. (Also available at http://pubs.usgs.gov/

circ/circ1186/.)

Reilly, T.E., Dennehy, K.F., Alley, W.M., and Cunningham, 

W.L., 2008, Ground-water availability in the United States: 

U.S. Geological Survey Circular 1323, 70 p. (Also available 

at http://pubs.usgs.gov/circ/1323/.)
Introduction 5

Introduction

Water availability for the U.S. Great Lakes Basin is 

characterized by abundance at the regional scale but potential 

scarcity at local scales. Scarcity may arise from the interplay 

between local hydrology and hydrogeology, local demand, 

local water quality, and societal decisions regarding local 

instream use or desired ecological flows (minimum or varied 

flows necessary for the well-being of aquatic life). Wateravailability assessment is crucial for proper resource management under complex, uncertain, and changing environmental 

and social conditions. Such assessments are paramount to 

address two issues of global concern: sustainable development 

and adaptation in response to climate change. Water-availability assessment also provides context for understanding 

how water demands interact with water resources. Population growth, increases in industrial or agricultural water use, 

and diversions from a basin may increase demand for water 

resources within a basin. Because water is a finite, open-access 

resource, these increased demands increase the potential for 

conflict over and degradation of water resources (Dietz and 

others, 2002). Regardless of the issue, development, climate 

change, or conflict, “Environmental governance1 depends 

on good, trustworthy information about stocks, flows, and 

processes within the resource system being governed, as well 

as about the human-environment interactions affecting those 

systems” (Dietz and others, 2003). 

The Great Lakes Basin Pilot of a U.S. Geological Survey 

(USGS) national assessment of water availability and use was 

prompted by the need for an increased understanding of water 

availability and, as Dietz and others (2003) suggest, “good, 

trustworthy information.” Some of the water-resources issues 

identified in recent years by the Great Lakes Commission 

(2003) were addressed in this project. The project was framed 

by USGS Circular 1223 (U.S. Geological Survey, 2002) and 

the Presidential National Science and Technology Council 

Report on Fresh Water Availability (National Science and 

Technology Council, 2004). In these reports, “water-availability assessment” refers to a water-resources analysis that considers status and trends of the volume of water in storage, flow 

rates, and water use. These assessments also should include 

consideration of instream flow, water quality, data consistency, 

future projection analysis, and development of consistent indicators for water availability (U.S. Geological Survey, 2002). 

Major tasks addressed in the Great Lakes Basin Pilot 

and described herein were (1) analysis of surface-water flows 

and storage, (2) analysis of groundwater flows and storage, 

and (3) analysis of water-use data in the context of assessing 

water availability. Constraints on use are important in the final 

assessment of water availability; however, this project did not 

1

Dietz and others (2003) state: “We refer to adaptive governance rather than 

adaptive management because the idea of governance conveys the difficulty 

of control, the need to proceed in the face of substantial uncertainty, and the 

importance of dealing with diversity and reconciling conflict among people 

and groups who differ in values, interests, perspectives, power and kinds of 

information they bring to situations.”

inventory or research any of the various potential constraints 

on the system. Water quality can be an important factor in 

determining water availability for an area (Hirsch and others, 

2008); other USGS programs focus on water quality, however, 

so water-quality limitations were not explicitly considered in 

the Great Lakes Basin Pilot.

This project built on past studies to quantify regional 

water availability in the U.S. Great Lakes Basin, summarized 

the status and trends for regional water resources, and laid 

the groundwork for both quantifying and monitoring stocks, 

flows, and processes governing regional water resources. 

Because local constraints are the only limitations to water 

availability foreseen in the near future in the Great Lakes 

Basin, methods to quantify subregional- and local-scale water 

availability were applied. Ways to build upon the regional 

study to address local issues were analyzed. As a pilot project, 

this study provided techniques and methods for both regionaland subregional-scale water-availability assessments that may 

be applied across the Nation. 

Purpose and Scope

This report highlights and summarizes studies conducted 

within the Great Lakes Basin Pilot. The importance of spatial 

and temporal scale in the analysis of water availability is 

emphasized. The report is structured to provide, first, a summary of issues confronting water availability in the U.S. Great 

Lakes Basin and a summary of the physical conditions of the 

basin. Regional water budgets highlighting the regional abundance of freshwater resources in the Great Lakes Basin and 

the response of the system to water use and manmade controls 

are then presented. Next, results of more detailed studies of 

the processes governing water availability in the Great Lakes 

Basin relative to regional-, subregional-, and local-scale water 

availability questions are presented. These studies included 

(1) a subregional-scale groundwater-flow model of the Lake 

Michigan Basin and associated local-scale inset model 

focusing on headwater streams and analysis of groundwater/

surface-water interaction, (2) an improved spatial regression 

model to estimate surface-water flows constrained by the 

stream geometry and streamgage data applied at the subregional scale, and (3) a subregional analysis of seasonal trends 

in consumptive water use illustrating the variation in water 

withdrawals that may influence water availability. The importance of monitoring data and key features of network analysis 

also are discussed through local-scale example applications.

For this project and report, the U.S. Great Lakes Basin 

is defined as the area where surface water drains to the Great 

Lakes and to the St. Lawrence River upstream from the Richelieu River drainage boundary and is designated as Hydrologic 

Region 04 by the USGS (Seaber and others, 1987) (fig. 1). 

Because of the vastness of the U.S. Great Lakes Basin, many 

of the detailed studies within this project focused on local 

areas within the basin. Other applications—groundwater and 

water-use studies in particular—required extension beyond 
WISCONSIN

ILLINOIS

INDIANA OHIO

PENNSYLVANIA

NEW

YORK

ONTARIO

QUEBEC

MINNESOTA

M I C H I G A N

IOWA

90°W 80°W

42°N

48°N

EXPLANATION

United States portion

of the Great Lakes Basin

KILOMETERS

0 100 200 MILES

0 100 200

Great Lakes Basin boundary

Base from ESRI, 2001; U.S. Army Corps of Engineers, 1998; and Environment Canada, 1995.

CANADA

U.S.A

CANADA

U.S.A

Lake

Huron

Lake

Erie

Lake

Ontario

Lake Superior

Lake Michigan

6 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 1. Study area for Great Lakes Basin Pilot.

the surface-water drainage divide. For the groundwater studies, the extension was necessary to capture the groundwater 

divides of the system that lie beyond the surface-water divides. 

For the water-use studies, data availability and the desire to 

more fully analyze consumptive use and within-year variations 

in water withdrawals required the extension. The spatial scope 

for each application discussed in the report is given with each 

specific application. 

Previous Studies

Water resources in the Great Lakes region have been 

studied at various scales by many researchers and entities. 

One comprehensive, although dated, report series by the 

Great Lakes Commission (1976) is an extensive overview of 

the natural features, economics, population, and resources of 

the basin, and it presents the commission’s recommendations 

regarding multiple issues and concerns. An atlas of the Great 

Lakes region summarizing many features of the basin was produced by the Government of Canada and U.S. Environmental 

Protection Agency (1995). Previous USGS regional studies 

included three Regional Aquifer-System Analysis (RASA) 

studies: Michigan Basin, Midwestern Basins and Arches, and 

Northern Midwest (Sun and others, 1997). Regional water 

quality has been studied by USGS through local studies and 

the National Water Quality Assessment (NAWQA) Program, 

especially NAWQA’s Lake Erie-Lake Saint Clair Drainages, 

Upper Illinois River Basin, and Western Lake Michigan Drainages study units (see, for example, Myers and others, 2000; 

Groschen and others, 2004; Peters and others, 1998); the Great 

Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy Major 

River Basin Assessment (Lorenz and others, 2009); and the 

Glacial Principal Aquifer Regional Assessment (Arnold and 

others, 2008).

In addition to these regional reports, water-availability 

assessments and the importance of regional water budgets 

are discussed by U.S. Geological Survey (2002), Anderson 

and Woosley (2005), Healy and others (2007), and Reilly and 

others (2008). Hirsch and others (2008) summarize the links 

between water quality and water availability. Reports quantifying water availability in the Central Valley of California 

that include a regional groundwater-flow model were recently 

published (Faunt, 2009; Faunt and others, 2009). 
Great Lakes Basin Water-Availability Issues 7

Approach to the Pilot 

The Great Lakes Basin Pilot comprised several individual 

studies focusing on various aspects of water availability over 

a range of spatial and temporal time scales. As mentioned 

previously, some of the studies examined the entire Great 

Lakes Basin, almost 300,000 mi2, and others examined smaller 

parts of the basin, the smallest focusing on groundwater/surface water interaction for a 20-mi2

 area. A study summarizing 

research on Great Lake water levels examined lake-level variations over a timespan of approximately 4,500 years, whereas 

another study on water use examined monthly and seasonal 

variations. A team of researchers, listed in the acknowledgments section, worked on studies within the pilot to address 

issues of groundwater, surface water, and water use. Much of 

this work is detailed in a series of individual reports (table 1). 

This final report summarizes and highlights work from these 

component studies of the Great Lakes Basin Pilot. In addition 

to results of the individual analysis, the reports listed in table 

1 discuss previous work in detail and refer to major sources of 

data used in the Great Lakes Basin Pilot.

Great Lakes Basin 

Water-Availability Issues

The U.S. Great Lakes States and Canadian Great Lakes 

Provinces are concerned with many water issues, including 

(1) water management in response to increased demand and 

potential conflict because of population growth, land-use 

change, or changes in agricultural practices; (2) diversion of 

water outside the basin; (3) increased societal recognition of 

and desire to protect environmental flows; (4) adaptation to 

changes and timing in supply arising from climate change; and 

(5) water-quality challenges from natural and human sources, 

both point and nonpoint. Response to these issues has led to 

debates and new legislation regarding water rights and governance in the region. 

Among these water-availability issues, the management 

of Great Lakes water—in particular, control and regulation of diversions of water outside the basin—has received 

much attention over the past decade. Decisions regarding regional water management by representatives of the 

Great Lakes States and Provinces are embodied in the Great 

Lakes-St. Lawrence River Basin Water Resources Compact 

(Council of Great Lakes Governors, 2005b) and the Great 

Lakes-St. Lawrence River Basin Sustainable Water Resources 

Agreement (Council of Great Lakes Governors, 2005a). In 

2008, the interstate compact between the eight Great Lakes 

States received consent and approval by Congress and was 

signed into law (U.S. Congress, 2008). The Sustainable Water 

Resources Agreement is a good-faith agreement among the 

eight Great Lakes U.S. States and two Great Lakes Canadian Provinces. This compact and agreement build upon 

the Great Lakes Charter Annex of 2001 (Council of Great 

Lakes Governors, 2001), which seeks to “protect, conserve, 

restore, improve and effectively manage the Waters and Water 

Dependent Natural Resources of the Basin.” Key features that 

have gained significant attention in the region are regulation 

of diversions of water outside of the basin and development 

of water-management goals and policies for the states and 

provinces within the basin. 

This legislation is important for future water-availability 

decisions in the region. Diversions of water outside the basin 

are prohibited except for limited cases. New or increased 

consumptive use within the basin greater than 5 Mgal/d for a 

90-day period is subject to review by the Great Lakes States 

and Provinces and requires unanimous approval. Smaller 

withdrawals, those less than 5 Mgal/d for a 90-day period but 

greater than 100,000 gal/d for a 90-day period, also are covered in the compact and agreement. These smaller withdrawals 

are to be managed by the individual states and provinces to a 

standard that is protective of the waters of the Great Lakes and 

water-dependent natural features of the basin. 

One type of potential diversion, water bottling, has 

received a great deal of scrutiny in the region (for example, 

Granholm, 2005; Lydersen, 2008). In the compact and agreement, water shipped in containers larger than 5.7 gal is treated 

as any other diversion. Water shipped in smaller containers 

may be regulated by individual states and provinces—but 

water shipped in these smaller containers is not explicitly 

governed. Other special cases in the compact and agreement 

include exemptions from diversion regulation for water used 

to supply vessels and aircraft or for water used for short-term 

noncommercial purposes such as firefighting, humanitarian 

need, or emergency response. 

In addition to limiting diversions, the compact and 

agreement sets forth regional goals for water efficiency and 

conservation. In adopting the compact and agreement, the 

Great Lakes States and Provinces commit to science goals 

(section 1.4, Council of Great Lakes Governors, 2005a) aimed 

at “development of a collaborative strategy with other regional 

partners to strengthen the scientific basis for sound water management decision making under this Compact.” The compact 

also seeks to prevent adverse ecological impacts by withdrawals or losses within the basin. This regional decision to prevent 

adverse ecological impact on all watersheds or groundwaterdependent natural resources within the Great Lakes Basin may 

become the limiting factor determining water availability in 

the region, rather than lack of water or conflict with others’ 

water rights. 

Other issues also have gained attention in the region, 

including priority issues outlined in a 2005 U.S. federal strategy to restore and protect the Great Lakes: aquatic invasive 

species, coastal health, areas of concern, toxic pollutants, 

habitat and species, nonpoint-source pollution, indicators and 

information, and sustainability (Great Lakes Regional Collaboration, 2005). In February 2008, a letter from regional 

representatives emphasizing these priorities was sent to each 

member of Congress (Council of Great Lakes Governors, 
8 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Table 1. Great Lakes Basin Pilot reports (in U.S. Geological Survey publications series), focus topics, and predominant scale.

Report Focus topic(s) Scale

Great Lakes Basin Water Availability and Use: A study of the National Water 

Availability and Water Use Program (Grannemann and Reeves, 2005)

Overview of project Regional.

Estimate of ground water in storage in the Great Lakes Basin, United States, 

2006 (Coon and Sheets, 2006)

Groundwater Regional.

Estimation of shallow ground-water recharge in the Great Lakes Basin (Neff and 

others, 2006)

Groundwater, surface water Regional.

Historical changes in precipitation and streamflow in the U.S. Great Lakes 

Basin, 1915–2004 (Hodgkins and others, 2007)

Surface water Regional.

Compilation of regional ground-water divides for principal aquifers 

corresponding to the Great Lakes basin, United States (Sheets and 

Simonson, 2006)

Groundwater, 

hydrogeology

Regional.

Consumptive water-use coefficients for the Great Lakes Basin and climatically 

similar areas (Shaffer and Runkle, 2007)

Water use Regional.

Consumptive water use in the Great Lakes Basin (Shaffer, 2008) Water use (fact sheet) Regional.

Estimated withdrawals and other elements of water use in the Great Lakes Basin 

of the United States in 2005 (Mills and Sharpe, 2010)

Water use Regional.

Lake-level variability and water availability in the Great Lakes (Wilcox and 

others, 2007)

Surface water Subregional.

Processing, analysis, and general evaluation of well-driller logs for estimating 

hydrogeologic parameters of the glacial sediments in a ground-water flow 

model of the Lake Michigan Basin (Arihood, 2009)

Groundwater, 

hydrogeology

Subregional.

Application guide for AFINCH (Analysis of Flows in Networks of Channels) 

described by NHDPlus (Holtschlag, 2009)

Surface water Subregional, local, 

methods development.

Hydrostratigraphy and salinity distribution for Lake Michigan Basin 

groundwater-flow model (Lampe, 2009)

Groundwater, 

hydrogeology

Subregional.

Variations in withdrawal, return flow, and consumptive use of water in Ohio and 

Indiana, with selected data from Wisconsin, 1999–2004 (Shaffer, 2009)

Water use Subregional.

SWB—A modified Thornthwaite-Mather Soil-Water Balance code for 

estimating groundwater recharge (Westenbroek and others, 2009) 

(partially funded by Great Lakes Basin Pilot)

Groundwater recharge Regional, subregional, local 

methods development.

Estimation of groundwater use for a groundwater-flow model of the Lake 

Michigan Basin and adjacent areas, 1864–2005 (Buchwald and others, 2010)

Water use, groundwater 

model

Subregional, local.

Regional groundwater-flow model of the Lake Michigan Basin in support 

of Great Lakes Basin water availability and use studies (Feinstein and 

others, 2010)

Groundwater Subregional.

Application of AFINCH as a tool for evaluating the effects of streamflowgaging-network size and composition on the accuracy and precision of 

streamflow estimates at ungaged locations in the Southeast Lake Michigan 

Hydrologic Subregion (Koltun and Holtschlag, 2010)

Surface water Subregional, local, 

methods development.

Implementation of local grid refinement in MODFLOW for the Lake Michigan 

Basin regional groundwater-flow model (Hoard, 2010)

Groundwater Local.

Using prediction uncertainty analysis to design hydrologic monitoring networks: 

Example applications from the Great Lakes Water Availability Pilot Project 

(Fienen and others, 2010)

Groundwater Local.
Characteristics of the Great Lakes Basin 9

2008), and a report was published describing legislative 

priories for fiscal year 2009 (Great Lakes Commission, 2008). 

The four near-term priorities highlighted in the Great Lakes 

Commission report are consistent with those described by the 

Regional Collaboration: stopping invasive species, cleanup 

of toxic sediments, restoration of Great Lakes wetlands, and 

protection of water quality. There also are treaty obligations 

for the United States and Canada under the Great Lakes Water 

Quality Agreement that was signed in 1972 and subsequently 

renewed and amended in 1978 and 1987. This agreement is 

administered by the International Joint Commission, which 

was formed under the 1909 Boundary Waters Treaty (International Joint Commission, 2008). In 2006, the International 

Joint Commission published a report reviewing and making 

recommendations for revisions to this agreement (International 

Joint Commission, 2006). 

Great Lakes levels, flows in the connecting channels, and 

regulation of levels and flows also have been important topics 

in the region. Recent, (2000–2008) low levels of the Upper 

Great Lakes (Lakes Michigan, Huron, and Superior) have led 

to much interest and debate on this issue. In 2005, a report 

was published stating that dredging in the St. Clair River in 

the 1960s for a shipping channel had permanently lowered 

levels in Lakes Michigan and Huron (W.F. Baird Associates, 

2005). Lake levels and flows are crucial factors for navigation, recreational boating, lakefront property, hydropower 

generation, and interaction of the St. Lawrence River with the 

Atlantic Ocean. The 2005 report, along with low lake levels, 

has motivated additional investigations in the region, among 

which was a study of the Upper Great Lakes coordinated by 

the International Joint Commission (International Upper Great 

Lakes Study, 2009).

Characteristics of the 

Great Lakes Basin

The Great Lakes Basin is approximately 575 mi from 

north to south and 900 mi from east to west (fig. 1). The 

approximate land drainage area of the basin is 201,460 mi2; 

water area is 94,250 mi2, and total area of the basin is 

296,000 mi2 (Government of Canada and U.S. Environmental 

Protection Agency, 1995). It is the second-largest drainage 

basin in the United States after the Mississippi River drainage in terms of average discharge, the third largest in terms 

of area, and fourth largest in terms of length from source to 

mouth (Kammerer, 1987). Characteristics for each of the Great 

Lakes are summarized in table 2. In addition to the large area 

of the basin, the abrupt change in altitude of the lakes between 

Lake Erie and Lake Ontario (Niagara Falls) is notable. 

The Great Lakes Basin was formed through series of 

geological events and did not appear in its present form until 

relatively recently, after continental glaciers retreated from the 

region approximately 10,000 years ago. (See Hough, 1958, 

and Dorr and Eshman, 1970, for discussion of the geological history of the region.) Important geological features of 

the Great Lakes Basin influencing water-resources stocks and 

flows include the Michigan Basin and the regional bedrock 

arches that define this structural basin, bedrock aquifers and 

confining units, and the veneer of glacial deposits that overlies 

older bedrock. Precambrian bedrock of the Canadian Shield, 

approximately 3.5 billion years old, crops out on the northern 

boundary of the Great Lakes Basin. Bedrock aquifers in the 

basin are formed primarily in layered Paleozoic rocks. Notable 

in this sequence are Middle Silurian (Niagaran) dolomite formations, which are an important structural control of the Great 

Lakes Basin (Hough, 1958). Glacial deposits overlie the bedrock over almost all of the Great Lakes Basin. These deposits 

are thickest—as thick as 1,500 ft—in the northern part of the 

Lower Peninsula of Michigan. The deposits include a range 

of materials from fine clay to gravel and can be well sorted in 

some areas and highly heterogeneous in others. In some parts 

of the basin, the glacial deposits serve as important aquifers, 

but in others they do not. 

The Great Lakes Basin is part of the extensive Great 

Interior, Southern Plains, and Lowlands generalized physical 

climatic region that dominates the continental United States. 

Although, the overall climate classification for the basin is 

Continental (Baldwin, 1973), the large size of the basin leads 

to different climate characteristics across the basin. Summer 

mean daily air temperature ranges from 53 to 73°F, winter 

mean daily air temperature ranges from −4 to 28°F, and annual 

precipitation ranges from 25 to 50 in/yr. The Great Lakes tend 

to buffer changes in temperature; this buffering leads to areas, 

particularly to the east of each lake, that have cooler summer 

temperatures, warmer winter temperatures, and increased 

precipitation. The climate in the region is characteristically 

changeable because of the interaction between the buffering effects of the lakes and two competing air masses: warm, 

moist air from the Gulf of Mexico and cool, dry air from the 

Arctic (Government of Canada and U.S. Environmental Protection Agency, 1995). 

Climate interacts with surficial geology, soils, and 

other features of the landscape to form ecoregions (fig. 2). 

Twelve Level-III Ecoregions have been defined for the U.S. 

Great Lakes Basin. These ecoregion definitions highlight differences in terms of natural productivity, land use, and human 

alteration of the landscape (Commission for Environmental 

Cooperation, 1997; U.S. Environmental Protection Agency, 

2002, 2007). This diversity is important because it implies 

that local conditions across the region may differ greatly from 

the regional average condition. Dominant water use and the 

importance of local flows help shape the water-availability 

issues for a particular location. 

Land use and land cover is varied across the region, 

from predominantly forest to agricultural and urban (fig. 3). 

The largest urban areas in the U.S. and Canadian parts of the 

basin tend to be near or on the Great Lakes. Use of the lakes 

for shipping and water supply helped shape this development. 

Forests across the basin were very important historically. 
Great Lakes Basin boundary

Central Corn Belt Plains

Eastern Corn Belt Plains

Eastern Great Lakes and Hudson Lowlands

Erie Drift Plain

Huron/Erie Lake Plains

North Central Appalachians

Ecoregions North Central Hardwoods

Northeastern Highlands

Northern Appalachian Plateau and Uplands

Northern Lakes and Forests

Southeastern Wisconsin Till Plains

Southern Michigan/Northern Indiana Drift Plains

90°W

80°W

42°N

48°N

KILOMETERS

0 100 200 MILES

0 100 200

EXPLANATION

Omernik level III ecoregions (1987)

Lake

Huron

Lake

Erie

Lake

Ontario

Lake Superior

Lake Michigan

10 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 2. Level III ecoregions for the U.S. Great Lakes Basin (U.S. Environmental Protection Agency, 2007).

Table 2. Physical characteristics of the Great Lakes.

[From Government of Canada and U.S. Environmental Protection Agency, 1995]

Property Lake Superior Lake Michigan Lake Huron Lake Erie Lake Ontario

Altitude, in feet at low-water datum1 600 577 577 569 243

Length, in miles 350 307 206 241 193

Breadth, in miles 160 118 183 57 53

Average depth, in feet at low-water datum 483 279 195 62 283

Maximum depth, in feet at low-water datum 1,332 925 750 210 802

Water area, in square miles 31,700 22,300 23,000 9,910 7,340

Land drainage area, in square miles 49,300 45,600 51,700 30,140 24,720

1

Low-water datum, also known as chart datum, is a reference point for water-level elevation where 95 percent of recorded/historical elevations are above the 

datum. It is referenced to the International Great Lakes Datum (IGLD) of 1985.
Landcover

Barren

Agriculture

Forest

Urban

Wetland

Grassland

Water

Shrub scrub

Great Lakes Basin boundary

90°W

80°W

42°N

48°N

KILOMETERS

0 100 200 MILES

0 100 200

EXPLANATION

U.S. Geological Survey National Land Cover Database (2003)

Lake

Huron

Lake Erie

Lake

Ontario

Lake Superior

Lake Michigan

Characteristics of the Great Lakes Basin 11

Between 1870 and 1890 most of the forests in Michigan were 

cut, and lumber was shipped on the Great Lakes eastward 

to the northeast United States or through Chicago to the 

U.S. Plains States. Similar logging occurred in other Great 

Lakes States, and this logging affected water resources by 

changing both rainfall/runoff characteristics and sediment 

loads in the watersheds. These changes influenced, and continue to influence, the morphology of streams and the amount 

of sediment delivered to the Great Lakes (see for example, 

Fitzpatrick and others, 1999).

The population of the Great Lakes Basin in 2000 was 

greater than 34 million people, and approximately 10 percent 

of the U.S. population and 30 percent of the Canadian population live in the Great Lakes Basin (Government of Canada and 

U.S. Environmental Protection Agency, 1995; Great Lakes 

Commission, 2006b). Accounting for the population in the 

Chicago and Milwaukee metropolitan areas, however, complicates the population estimate for the basin. The surface-water 

divide in this part of the basin is quite close to Lake Michigan, and many of the millions of people in the Chicago and 

Milwaukee metropolitan areas actually reside outside of the 

basin. Many of these people, however, rely on water from 

Lake Michigan, or water tributary to Lake Michigan, for their 

water supply, and the reported population estimates may either 

underestimate the number of people getting water from the 

Great Lakes Basin or overestimate the number of people living 

in the basin (Great Lakes Information Network, 2006).

The surface-water network of streams tributary to the 

Great Lakes is extensive, and the stream density across the 

region varies with local geological and geomorphic conditions. 

Typically, areas with poorly draining soils have denser stream 

networks than areas with more freely draining soils. USGS 

uses Hydrologic Unit Codes (HUCs) to classify hydrologic 

systems. The number of digits in the HUC code indicates 

drainage basins of progressively smaller areas that are embedded within larger drainage basins. Hydrologic Region 04 has 

Figure 3. Land use and cover for the U.S. Great Lakes Basin from the U.S. Geological Survey National Land 

Cover Database.
12 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

been subdivided by USGS (Seaber and others, 1987) into 

15 subregions (4-digit HUCs), 27 accounting units (6-digit 

HUCs), and 111 cataloging units (8-digit HUCs). Inland 

surface water is important as potable water supply, irrigation 

and industrial water supply, thermoelectric-generation cooling 

water, and receiving water for municipal and industrial waste 

disposal. Recreational use of inland surface water for fishing, 

boating, and swimming is important to the region economically and for the residents’ quality of life.

Groundwater also is an important source of water for 

potable water supply, irrigation, and industrial use. Aquifers 

are found in parts of the highly heterogeneous glacial deposits 

that cover most of the region and also are formed in, primarily, 

Paleozoic bedrock. The USGS (Miller, 2000; U.S. Geological 

Survey, 2003) designates nine principal aquifers in the region: 

(1) localized sand and gravel aquifers in glacial deposits 

(Cenozoic), also called the surficial aquifer system, (2) New 

York sandstone aquifers, (3) Pennsylvanian aquifers, (4) Mississippian aquifer of Michigan, (5) Mississippian sandstone 

and carbonate-rock aquifers, (6) Silurian-Devonian aquifers, 

(7) New York and New England carbonate-rock aquifers, 

(8) Cambrian-Ordovician aquifer system, and (9) Jacobsville 

aquifer (Precambrian). Terminology used for the bedrock aquifer units varies across the region. The regional hydrostratigraphy used to develop a groundwater-flow model for the Lake 

Michigan Basin for this project (fig. 4) shows this variation 

and summarizes the hydrogeology in part of the overall study 

area. (Note that the Lake Michigan Basin model does not 

include three of the principal aquifers in the region: New York 

sandstone aquifers, Mississippian sandstone and carbonaterock aquifers, or New York and New England carbonaterock aquifers.)

Water quality generally does not limit water availability 

in the region. In some areas, however, poor water quality is 

an important issue. Poor water quality in the region may be a 

result of natural processes leading, for example, to unacceptable levels of arsenic, radon, or other potentially hazardous 

constituents (see for example, Thomas, 2007; Ayotte and others, 2007; Arnold and others, 2008). It also may be the result 

of point-source or nonpoint-source contamination. Gilbertson 

(2001) offers a sobering history of chemical contamination in 

the Great Lakes. Concerns and scientific challenges posed by 

these water-quality issues are raised in the priority areas listed 

by the Council of Great Lakes Governors, the Great Lakes 

Commission, and the Great Lakes Regional Collaboration, 

and by Lakewide Management Plans for the Great Lakes (for 

example, Lake Michigan Technical Committee, 2006).

Regional Water Availability Analysis 

for the U.S. Great Lakes Basin

The Great Lakes Basin contains a vast amount of 

freshwater: it is the largest system of fresh surface water on 

the Earth (Government of Canada and U.S. Environmental 

Protection Agency, 1995). In this section, predevelopment and 

postdevelopment regional water budget are described, and the 

relations between stocks, flows, and water use are discussed. 

In this report, “predevelopment” refers to conditions before 

approximately 1864; “postdevelopment” refers to conditions 

after 1864, but it is especially used to refer to conditions since 

approximately 1990. The stock and flows values presented in 

this section are long-term temporal averages because interannual, decadal, and long-term variations in climate are the 

major drivers changing stocks and flows in the system. The 

importance of different spatial and temporal scales is discussed in this section because short-term or local-scale water 

shortages or conflicts regarding water resources are quite 

possible even in a system that has, on average, an abundance 

of freshwater. 

Predevelopment Conditions

Predevelopment conditions are difficult to quantify 

because reported direct observations of predevelopment conditions are few. Estimates of predevelopment stocks, flows, and 

processes, however, set the baseline and reveal the context for 

regional analysis of the impacts of water use and diversion on 

the regional water balance. Analysis of trends since predevelopment helps to illustrate changes in the system in response 

to human influences and variations in climate over the last 

century. The components of the water budget are discussed 

below and summarized in table 3, and their spatial distribution 

is shown in figure 5.

Stocks (Storage)

The largest reservoirs of freshwater in the Great Lakes 

Basin are the five Great Lakes. Together they contain approximately 8.0 × 1014 ft3

 of freshwater. This volume, which is 

estimated to be approximately 84 percent of the fresh surface 

water in North America (U.S. Environmental Protection 

Agency, 2006; 2008), could cover the continents of North 

America, South America, and Africa to a depth of more than 

1 ft (Neff and Nicholas, 2005). The volume of fresh groundwater in storage represents, in a sense, another Great Lake. 

For the U.S. part of the basin, it is approximately 1.4 × 1014 ft3

(Coon and Sheets, 2006), which is greater than the volume 

of either Lake Erie or Lake Huron. Additional water is held 

in the basin in (1) aquifers in the Canadian part of the basin, 

(2) smaller lakes and streams, (3) snowpack, and (4) soil 

moisture. The largest and most stable of these other reservoirs 
Regional Water Availability Analysis for the U.S. Great Lakes Basin 13

Figure 4. Hydrostratigraphy for the Lake Michigan Basin and adjacent region used in the groundwater-flow model developed in 

this project (from Lampe, 2008).

Time-stratigraphic

unit

System Series

References

Quaternary

Jurassic

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

Precambrian

Upper

Glacial deposits Glacial deposits Glacial deposits Glacial deposits Glacial deposits

Wisconsin Illinois Indiana Ohio Michigan

Ionia Fm

Upper

Lower

Upper

Middle

Lower

Upper

Middle

Lower

Grand River Fm

Saginaw Fm

Parma Sandstone

Bayport Ls

Michigan Fm

Marshall Sandstone

Coldwater Shale

Sunbury Shale

Ellsworth Shale

Antrim Shale

Traverse Group

Detroit River Group

Bass Islands Group 

Salina Group

Niagara Group

Manistique Group

Burnt Bluff Group

Cataract Group

Upper Richmond Group

Middle

Trenton Fm

Black River Fm

Glenwood Fm

St. Peter Sandstone

Prairie du Chien Gr

Trempealeau Fm

Lower

Franconia Fm

Galesville

Sandstone

Eau Claire Fm

Mount Simon

Sandstone

Middle

Upper

Lower Absent

Catacosinos

and others, 2001

Gray and others,

1985

Jacobsville Sandstone

Crystalline Basement

Complex

Coldwater Shale

Sunbury Shale

Ellsworth Shale

Antrim Shale

Muscatatuck

Group

Salina Group

Salamonie Dolomite

Brassfield Limestone

Absent

Maquoketa Group

Trenton Limestone

Black River Limestone

Ancell Group

Prairie du Chien Gr

Potosi Dolomite

Franconia Sandstone

Ironton Sandstone

Galesville Sandstone

Eau Claire Sandstone

Mount Simon

Sandstone of 

Dresbach Group

Crystalline Basement

Complex

Absent

Coldwater Shale

Sunbury Shale

Bedford Shale

Antrim Shale

Traverse Group

Dundee Formation

Detroit River Group

Absent

Salina Group

Lockport Group

Cataract Group

Rochester Shale

Dayton Formation

Cincinnati group

Trenton Limestone

Black River Group

Wells Creek Fm

Absent

Knox Dolomite

Kerbel Fm

Eau Claire Fm

Mount Simon

Sandstone

Crystalline Basement

Complex

Hull, 1990

Antrim Shale

Milwaukee Fm

Thiensville Fm

Absent

Waubakee Fm

Racine Fm

Manistique Fm

Hendricks Fm

Byron Fm

Mayville Fm

Neda Fm

Maquoketa Fm

Sinnipee Group

Prairie du Chien Gr

Glenwood Fm

St. Peter Fm

Trempealeau Group

Tunnel City Group

Eau Claire Fm

Mount Simon

Formation

Wonewoc Fm

Absent

Keweenawan

Supergroup

Wisconsin 

Geological

and Natural History

Survey, 2006

Buschbach, 1964

Kolata and Graese, 1983

Kolata, 1990

Mikulic and others, 1985

Willman and others, 1975

Young and Siegel, 1992

Maquoketa Group

Galena Group

Platteville Group

Ancell Group

Prairie du Chien Gr

Potosi Dolomite

Franconia Fm

Ironton Sandstone

Galesville Sandstone

Eau Claire Fm

Mount Simon

Sandstone

Crystalline Basement

Complex

New Albany Shale

Group

Cedar Valley Limestone

Wapsipinicon Limestone

Racine Dolomite

Sugar Run Dolomite

Joliet Dolomite

Kankakee Dolomite

Wilhelmi Fm

Absent

Mississippian System

(Undifferentiated)

Absent

Hydrogeologic unit

(model layer)

Quaternary

(1-3)

Jurassic (4)

Upper

Pennsylvanian

(5)

Lower

Pennsylvanian

(6)

Michigan (7)

Marshall (8)

DevonianMississippian

(9)

Silurian-Devonian

(11-12)

Maquoketa (13)

Sinnipee

(14)

St. Peter

(15)

Prairie du ChienFranconia

(16)

IrontonGalesville

(17)

Eau Claire (18)

Mount Simon 

(19-20)

EXPLANATION

Absent

Pennsylvanian System

(Undifferentiated)

USGS 

principal 

aquifer

Surficial aquifer

system

Pennsylvanian

Mississippian

SilurianDevonian

CambrianOrdovician

Silurian-Devonian

(10)

1

1

Rocks of the Pennsylvanian System were grouped with 

the Mississippian-Devonian hydrogeologic unit for Illinois 

Saginaw Fm (Shale)

Jacobsville

Aquifer

Aquifer/confining unit

Confining unit

Erosional surface

Depositional surface Gr, Group

Fm, Formation

Ls, Limestone
14 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

is aquifers on the Canadian part of the basin; however, the 

storage in these aquifers is not known (Riveria, 2005). One 

example from a Canadian system that has been the focus of 

much study is that of the Oak Ridges Moraine, an important 

aquifer system north of Toronto: storage in those deposits is 

estimated to be 0.05 × 1014 ft3 (Riveria, 2005). Estimates of 

groundwater storage require assumptions regarding the depth 

of freshwater available in aquifers basinwide; geometries, 

storage coefficients, and specific yields of aquifer materials; 

and approximate heads (water levels) in the major aquifers. 

Therefore, storage estimate can vary widely depending on 

the values used in these estimates; for example, Weist (1978) 

cites an unpublished report for an estimate for storage in the 

entire basin of 0.35 x 1014 ft3. The Great Lakes Commission 

(1976) preferred not to make an estimate of groundwater in 

storage and used annual base-flow estimates as an indicator for 

groundwater availability.

Flows and Processes

Under predevelopment conditions, the only inputs to 

the basin were precipitation driven: direct precipitation to the 

lakes and direct precipitation to the land surface. The latter 

becomes either direct runoff to the lakes, direct groundwater discharge to the lakes, indirect groundwater discharge to 

the lakes, or runoff to streams and stream input to the lakes. 

Historically, the only outputs from the basin were the St. Lawrence River, direct evaporation from the lakes, and evaporation and transpiration from the land area of the basin. Direct 

Table 3. Predevelopment generalized water budget.—Continued

[Numbers in brackets are either alternate values reported in the literature or component values already included in other table entries and not included in the 

reported total flows. ft3/s, cubic feet per second]

Volume, in cubic feet Source Comments

Surface-water 

storage 

(Great Lakes)

8.0 × 1014 Government of Canada and U.S. 

Environmental Protection Agency, 1995

Groundwater 

storage

1.4 × 1014 Coon and Sheets, 2006 U.S. side of the basin only.

Flows in

Rate, in thousand cubic 

feet per second Source Comments

Direct precipitation 

to Great Lakes

229

[223]

Croley, 2003;

Neff and Nicholas, 2005

1950–99 simulation.

Precipitation to 

land area

505 Croley, 2003 1950–99 simulation.

Surface-water 

runoff

[220] Croley, 2003 Surface runoff is equal to precipitation 

minus evapotranspiration; it is internal to 

regional budget and not included in “total 

in” calculation.

Base flow to 

streams 

(approximately 

aquifer recharge)

[151] Neff and others, 2005 Average of several base-flow-separation 

techniques and included in surface-water 

runoff. This value is internal to the budget 

and not included in “total in” calculation.

Surface water 

diverted into 

basin

0

Groundwater from 

outside basin

Unknown The Lake Michigan Basin groundwaterflow-model estimate for the Lake 

Michigan Basin is 400 ft3/s, which 

is less than 2 percent of total flow to 

groundwater system.

Total in 734
Regional Water Availability Analysis for the U.S. Great Lakes Basin 15

Table 3. Predevelopment generalized water budget.—Continued

[Numbers in brackets are either alternate values reported in the literature or component values already included in other table entries and not included in the 

reported total flows. ft3/s, cubic feet per second]

Flows out

Rate, in thousand cubic 

feet per second Source Comments

Groundwater out of 

the basin

0

Surface water out 

the St. Lawrence 

River

271

[251]

[246]

Government of Canada and 

U.S. Environmental Protection 

Agency, 1995; Croley, 2003; 

Neff and Nicholas, 2005

Flow out of 251,000 ft3/s given 

by Government of Canada and 

U.S. Environmental Protection Agency, 

1995; flow of 246,000 ft3/s given by Neff 

and Nicholas, 2005; 271,000 ft3/s from 

Croley, 2003, balances the net-basinsupply estimate.

Surface water 

diverted outside 

basin

0

Groundwater 

transferred 

outside basin

0 Assumed; groundwater divides and relation 

to surface-water divides not well known 

for the entire basin.

Direct evaporation 

from Great Lakes

178 Croley, 2003 1950–99 simulation.

Evapotranspiration 

from land area of 

basin

284 Croley, 2003 1950–99 simulation.

Total out 733

precipitation to the lakes and evaporation from the lakes are 

major factors and are difficult to quantify. Neff and Nicholas 

(2005) report that these quantities are currently estimated from 

data at land-based stations, and they cite the lack of direct 

over-lake weather monitoring as the greatest data gap contributing to the uncertainty in estimates of the Great Lakes water 

balance and accounting of water in the system.

Streamflow input to the lakes is generated from surface 

runoff to streams and groundwater discharge to streams, 

and it is generally dominated by groundwater discharge to 

streams. Holtschlag and Nicholas (1998) estimate that the 

average groundwater component of streamflow for streams 

in the Great Lakes basin ranges from 25 to 96 percent, and 

the resulting “indirect” groundwater discharge to the Great 

Lakes ranges from 22 and 42 percent of the supply to the 

lakes. (Indirect groundwater discharge is the volume of water 

that moves through the groundwater system at some point 

in its travel, is discharged to a stream, and is subsequently 

discharged to a Great Lake: it is the base-flow component 

of streamflow discharged to the lakes.) Thus, although 

direct groundwater discharge to the Great Lakes is generally neglected in water-balance estimates for the lakes (Neff 

and Nicholas, 2005), groundwater plays an important role in 

moving water from precipitation on the land surface to the 

Great Lakes.

The Great Lakes form the headwaters of the St. Lawrence 

River, and quantification of the groundwater flows into the 

system depends on the definition of the basin used in the analysis. If the basin is defined by the surface-water divide, then 

there is potential for groundwater input from outside the basin 
90°W

80°W

42°N

48°N

KILOMETERS

0 100 200 MILES

0 100 200

Ground Water

Surface-water

divide

St. Mary's River

78

Straits of 

Mackinac

52

Chicago

Diversion

3

St. Clair & 

Detroit Rivers

187

Welland

Canal

7

Niagra

River

205

St. Lawrence

River 251

Ogoki

Diversion

2.5

Long Lac

Diversion

2.5

NOTE: Numbers beside rivers and diversions represent flow in thousands of cubic feet per second

-200 -100 100

Flow (thousand cubic feet per second)

0

Storage, in cubic feet x 1014

Connecting channel in

Connecting channel out

Direct precipitation

Runoff

Evaporation

Diversion

Flow positive or negative 

in cubic feet per second

0 1

Storage, in cubic feet x 1014

EXPLANATION

Lake Michigan and Huron

3.0

-200 -100 100 200

Flow (thousand cubic feet per second)

0

Storage, in cubic feet x 1014

Lake Erie

0.2

Storage, in cubic feet x 1014

1.4

-300 -200 -100 100 200

Flow (thousand cubic feet per second)

0

Storage, in cubic feet x 1014

Lake Ontario

0.6

-100 100

Flow (thousand cubic feet per second)

0

Storage, in cubic feet x 1014

Lake Superior

4.3

Lake

Huron

Lake rErie

Lake

Ontario

Lake Superior

Lake Michigan

16 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

in areas where the groundwater divide extends beyond the 

surface-water divide away from the Great Lakes. The location 

of groundwater divides, the response of divides to changes in 

stresses, and the flux of water through aquifer into the surfacewater basin, however, are not well known (Sheets and Simonson, 2006). Regional groundwater-flow modeling of the entire 

basin would be required to generate an estimate of this flux, 

but it is expected to be only a minor input to the lakes (Neff 

and Nicholas, 2005). For example, in the groundwater-flow 

model of the Lake Michigan Basin developed for this project, 

the net groundwater import across the surface-water divide 

under predevelopment conditions is approximately 440 ft3/s, 

which less than 2 percent of the total input to the groundwater 

system (Feinstein and others, 2010).

Recharge to the groundwater system balances the discharge to streams (indirect discharge to the lakes), direct discharge to the lakes, and loss of groundwater within the basin; 

for example, via transpiration by vegetation that taps groundwater. A variety of methods may be used to estimate recharge 

at different scales (Delin and Risser, 2007). Neff and others 

(2006) provide a regional estimate for recharge in the Great 

Lakes Basin based on base-flow estimates at streamgages and 

Figure 5. Summary of storage, in cubic feet, and flows, in thousands of cubic feet per second, for the Great Lakes 

(data from Government of Canada and U.S. Environmental Protection Agency, 1995; Neff and Nicholas, 2005; Coon and 

Sheets, 2006).
EXPLANATION

CANADA

U.S.A.

CANADA

U.S.A.

Recharge, in inches per year

Lake

Nipigon

M I C H I G A N

Less than 4 

4.0–7.9

8.0–11.9

12.0–15.9

Greater than 16

for 8-digit Hydrologic Unit Code (U.S.) or 

Tertiary (Canada) watersheds

Lake

Huron

Lake

Erie

Lake

Ontario

Lake Superior

Lake Michigan

Regional Water Availability Analysis for the U.S. Great Lakes Basin 17

the assumption that long-term recharge is equal to average 

base flow (fig. 6). These estimates were computed on a fairly 

coarse spatial scale but reveal variation in recharge rates 

across the region, from less than 4 in/yr to more than 16 in/yr. 

To estimate recharge at a more resolved spatial scale and to 

account for the mechanisms generating recharge from precipitation, a soil-water-balance approach (Westenbroek and others, 

2010) was used to estimate recharge for the Lake Michigan 

Basin groundwater-flow model (fig. 7). Because these estimates were calibrated by using a subset of streamgage data, 

the average estimate of regional recharge generated by the 

methods is expected to be similar. The advantages of the soilwater-balance approach are that it calculates components of 

the water balance on a daily basis, it can be scaled to produce 

estimates on a spatial scale consistent with the application, 

its data requirements include commonly available tabular and 

gridded types, and its data and formats are designed to work 

with widely available geographic information system (GIS) 

datasets and file structures (Westenbroek and others, 2010).

Postdevelopment Conditions

The water budget in the Great Lakes Basin has changed 

from predevelopment conditions because of diversions of 

water into and out of the Great Lakes Basin and because 

of humans’ use of water within the basin (table 4). Water 

withdrawals and return flows have changed flow paths, timing, and, potentially, quality of water moving through the 

basin. Consumptive water use removes water from the basin, 

although the amount of water lost through consumptive use 

is difficult to quantify (Shaffer and Runkle, 2007). Consumptive water use is the amount of water evaporated, transpired, 

incorporated into products or crops, consumed by humans or 

livestock, or otherwise removed from the immediate water 

environment. Consumptive use is estimated in relation to 

human activities; evaporation and transpiration from the 

system that occurs without human intervention is not typically included in the estimate. For example, the water used by 

rain-fed agriculture is not included as a consumptive use: this 

Figure 6. Shallow ground-water recharge estimated from base-flow-separation techniques (Neff and others, 2005).
41°

46°

45°

89° 87° 85° 83°

44°

43°

42°

Base from U.S. Geological Survey digital data

1:100,000 1983. Universal Transverse Mercator projection

Zone 16, Standard Parallel 0° (Equator), Central Meridian 87° W,

North American Datum 1983

EXPLANATION

16

10

14

6

4

0

Model nearfield Recharge, in inches per year

Lake Michigan boundary

Lake Michigan 

Basin boundary 12

8

2

0 50 100 KILOMETERS

0 50 100 MILES

L

A

K

E

MIC

H

I

GA

N

18 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 7. Recharge distribution for the Lake Michigan Basin 

groundwater-flow model for the 1991–2000 simulation period 

(from Feinstein and others, 2010).
Regional Water Availability Analysis for the U.S. Great Lakes Basin 19

water is accounted for in the estimates of evapotranspiration 

from the land surface. The distinction is important in wateruse accounting: water withdrawn by humans is either returned 

to the basin or lost as consumptive use. Land-use changes 

may have altered the distribution of precipitation on the land 

surface and runoff characteristics from the land surface. 

Part of this water moves through the groundwater system 

as recharge to the aquifer and discharge to streams (as base 

flow). These changes, however, are internal to the basin and 

do not affect the overall budget. Change in storage of water 

in the Great Lakes in response to annual and decadal variations in climate is less under developed conditions than under 

predevelopment conditions because control structures have 

dampened variations in lake levels (Wilcox and others, 2007). 

Temporal variations in the regional water budget are discussed 

in subsequent paragraphs, following presentation of a timeaveraged budget.

Surface-Water Diversions Into and Out of 

the Great Lakes Basin

The major diversions are the Ogoki and Long Lac diversions (into the basin) and the Chicago diversion (out of the 

basin). (For more discussion on these diversions, see International Joint Commission, 1985; Neff and Killian, 2003; and 

Neff and Nicholas, 2005.) Major intrabasin diversions are the 

Welland Canal and the New York State Barge Canal. Both 

of these intrabasin diversions transfer water from Lake Erie 

to Lake Ontario to allow shipping between these lakes that 

otherwise would be blocked by Niagara Falls in the natural connecting channel, the Niagara River, between the two 

Great Lakes.

Regional Water Withdrawals and Water Use

Understanding water withdrawals, transfers, and consumptive uses is important in the context of water availability 

because one potential constraint on future development is 

adverse impacts on current users. Examining the effects of 

withdrawals, transfers, and consumptive uses on the system 

also provides information required to predict the potential 

effect of new or expanded uses. By including water-use analysis, water-availability studies can illustrate to decisionmakers 

that there “is no unused water”: new or expanded water 

withdrawals, transfers, and consumptive uses have effects on 

surface-water and groundwater system dynamics (Hunt, 2003). 

The water-use-related activities within the Great Lakes Basin 

Pilot included four main tasks: assessment of methods to estimate consumptive use and review of typical consumptive-use 

coefficients for the region (Shaffer and Runkle, 2007; Shaffer, 

2008), assessment of seasonal and monthly variation in water 

withdrawals and consumptive use (Shaffer, 2009), historical 

water-withdrawal estimates for a groundwater-flow model 

of the Lake Michigan Basin (Buchwald and others, 2010), 

and compilation of water withdrawals by watershed in the 

U.S. Great Lakes Basin (Mills and Sharpe, 2010). 

The Great Lakes-St. Lawrence River Basin Water 

Resources Compact (Council of Great Lakes Governors, 

2005b) sets water-withdrawal limits in terms of consumptive 

use, so estimates of consumptive use for various water-use 

sectors are required for proper implementation of the compact 

and envisioned water-resource management. Theoretically, 

consumptive water use could be determined by measuring 

water supplied and water returned for each user. In practice, 

however, direct determination of consumptive water use is 

complicated by unknown basin transfers, water returned to the 

basin through loss in distribution systems, and—most significantly—lack of data regarding the volume of water supplied 

and the volume of water returned by most sectors. For these 

reasons, consumptive use is usually estimated by multiplying 

the volume of water supplied, or withdrawn by self-supplied 

users, by a consumptive-use coefficient that varies by wateruse sector (table 5) or, rarely, by the specific use within a sector (Shaffer and Runkle, 2007; Horn and others, 2008). 

 Use of simple coefficients to estimate consumptive 

water use can be problematic because more accurate water use 

accounting is desired for either water management or future 

water-withdrawal projections (Horn and others, 2008). For 

example, the median consumptive-use coefficient for irrigation for the region is 90 percent; but many crops and delivery 

systems are used across the region. Irrigated crops include 

corn and soybeans, and Michigan ranked third in the nation 

(in sales value) in floriculture and nursery products as of 2008 

(Kleweno, 2009). Although high consumptive-use coefficients, 

90–100 percent, are both the target for efficient irrigation and 

the most conservative value for water managers, little data 

are available demonstrating that irrigation reaches this level 

of efficiency for all sectors across the region. In more arid 

regions of the county, irrigation by imported surface water 

represents a major source of groundwater recharge through 

irrigation return flow and loss of water during distribution 

through unlined canals and irrigation ditches (Dickinson and 

others, 2006). For systems that lack data on water delivery 

and estimated evapotranspiration, an estimated consumptive use coefficient of 70 percent has been used for irrigated 

cropland (Hanson and others, 2003; Dickenson and others, 

2006). In the same way, variation is expected in the commercial and industrial sectors in the Great Lakes region, as 

was described for a smaller area in New Hampshire (Horn 

and others, 2008). Techniques to account for water by using 

more detailed census data, as demonstrated by Horn and others (2008), may be necessary at the regional scale for more 

accurate water-use accounting. Additionally, because wateruse reporting and accounting has traditionally been done by 

each state or province independently, different sector definitions, estimation methods, and consumptive-use coefficients 

have been used among the various jurisdictions. As a result of 

the Great Lakes-St. Lawrence River Basin Water Resources 

Compact and the Great Lakes-St. Lawrence River Basin Sustainable Water Resources Agreement, increased consistency 
20 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

in water-use reporting has been proposed (Council of Great 

Lakes Governors, 2009).

The USGS has published summaries of water use for 

the United States every 5 years since 1950 (U.S. Geological Survey, 2009). Until 2000, these reports included summaries of water use by hydrologic region (2-digit HUC). For 

the 2000 and subsequent reports, aggregation of water-use 

data collected from the states by hydrologic cataloging unit 

(8-digit HUC) became optional, and the 5-year reports have 

not included summaries by watershed (Kenny, 2004). Because 

presenting water-use data by watershed may be useful for 

water managers and may improve the analysis of water availability, the 2005 water-use data from the Great Lakes Basin 

was aggregated by 8-digit HUC for the Great Lakes Basin 

Pilot. Mills and Sharpe (2010) discuss the methods used to 

generate this compilation and limitations of the analysis. The 

data from 2005 used in the report were compiled from state 

and local agencies with assistance from other Federal agencies and nongovernmental entities. Water-use estimates for 

each state are stored in the USGS Aggregate Water Use Data 

System (AWUDS), and, after final approval of data from all 

the states, these data will be accessible at http://water.usgs.

gov/watuse/. In addition to compiling the data by cataloging 

unit, the data also are summarized by state area included in the 

Great Lakes Basin and by the drainage area to each of the five 

Great Lakes (Mills and Sharpe, 2010) (fig. 8). 

Basinwide and across all types or sectors of water use, 

use of surface water dominates, especially surface water 

directly from the Great Lakes (fig. 8). Great Lake surface 

water is the dominant supply because the sector with the largest water use in the Great Lakes Basin is thermoelectric power 

generation, and nearly all water is used for once-through 

Table 4. Postdevelopment generalized water budget.—Continued

[Numbers in brackets are either alternate values reported in the literature or component values already included in other table entries and are included in the 

tabulated total flows. ft3/s, cubic feet per second]

Volume, in cubic feet Source Comments

Surface-water 

storage 

(Great Lakes)

8.0 × 1014 Government of Canada and U.S. 

Environmental Protection Agency, 1995

See discussion on temporal variability. 

Groundwater 

storage

1.4 × 1014 Coon and Sheets, 2006 U.S. Great Lakes Basin only; also see 

discussion on temporal variability.

Flows in

Rate, in thousand cubic 

feet per second Source Comments

Direct precipitation 

to Great Lakes

229

[223]

Croley, 2003;

Neff and Nicholas, 2005

1950–99 simulation.

Precipitation to 

land area

505 Croley, 2003 1950–99 simulation.

Surface-water 

runoff

[220] Croley, 2003 Surface runoff is equal to precipitation 

minus evapotranspiration; it is internal to 

regional budget and not included in “total 

in” calculation.

Base flow to 

streams 

(approximately 

aquifer recharge)

[151] Neff and others, 2005 Average of several base-flow separation 

techniques and included in surface-water 

runoff. This value is internal to the budget 

and not included in “total in” calculation.

Surface water 

diverted into 

basin

5.0

[5.4]

Government of Canada and 

U.S. Environmental Protection Agency, 

1995; Neff and Nicholas, 2005

Groundwater from 

outside basin

Unknown The Lake Michigan Basin groundwaterflow-model estimate for the Lake 

Michigan Basin is 500 ft3/s, which 

is less than 2 percent of total flow to 

groundwater system.

Total in 739
Regional Water Availability Analysis for the U.S. Great Lakes Basin 21

cooling of powerplants. An estimated 72 percent of all withdrawals in the basin in 2005 were for power generation. The 

Lake Michigan and Lake Erie Basins supply most of the water 

for U.S. water withdrawals. The distribution of withdrawals 

by state follows the expected pattern based on land area within 

the basin, although withdrawal for Illinois is large compared 

to its very small area in the basin because of the use associated with the Chicago metropolitan region. Note that water 

used for hydroelectric power generation was only reported as 

an instream use in USGS water-use reports prior to 2000, and 

it is not included in the estimates herein or in the report by 

Mills and Sharpe (2010). 

The spatial pattern of source for public supply, selfsupplied domestic, and irrigation sectors reveal reliance on 

groundwater and the importance of sources other than the 

Great Lakes. Most large municipal water systems rely on 

surface water from one of the Great Lakes, and, as a result, 

88 percent of withdrawals for public supply are from surface 

water (fig. 9). Conversely, self-supplied groundwater is the 

source for almost all the domestic water for the population 

in the U.S. Great Lakes Basin outside of municipal areas 

(fig. 10). Overall, most people in the Great Lakes Basin live 

in municipal areas served by public supply, whereas most of 

the area of the basin relies on groundwater for water supply. 

The source for irrigation water is almost equally split between 

surface water and groundwater (fig. 11) but, unlike for public 

water supply, the surface-water sources for irrigation tend to 

be inland surface water rather than surface water directly from 

a Great Lake.

Table 4. Postdevelopment generalized water budget.—Continued

[Numbers in brackets are either alternate values reported in the literature or component values already included in other table entries and are included in the 

tabulated total flows. ft3/s, cubic feet per second]

Flows out

Rate, in thousand cubic 

feet per second Source Comments

Groundwater out of 

the basin

0

Surface water out 

the St. Lawrence 

River

271

[251]

[246]

Government of Canada and U.S. 

Environmental Protection Agency, 1995; 

Croley, 2003; Neff and Nicholas, 2005

Flow out of 251,000 ft3/s given by 

Government of Canada and U.S. 

Environmental Protection Agency, 

1995; flow of 246,000 ft3/s given by 

Neff and Nicholas, 2005; 271, 000 ft3/s 

from Croley, 2003, balances the net-basinsupply estimate.

Surface water 

diverted outside 

basin

3.

[3.2]

Government of Canada and U.S. 

Environmental Protection Agency, 1995;

Neff and Nicholas, 2005

Direct evaporation 

from Great Lakes

178 Croley, 2003 1950–99 simulation.

Evapotranspiration 

from land area of 

basin

284 Croley, 2003 1950–99 simulation.

Surface-water 

withdrawal 

[63] Great Lakes Commission, 2006a Great Lakes and inland surface waters, 2004 

withdrawals. Only consumptive use is 

used in the “total out” estimate.

Groundwater 

withdrawal

[2.3] Great Lakes Commission, 2006a 2004 withdrawals, only consumptive use is 

used in the “total out” estimate.

Consumptive water 

use

3

[3.4]

Great Lakes Commission, 2002, 2006 3,000 ft3/s from 2004 data, 3,400 ft3/s from 

1998 data. Destination of return flow is 

not specified.

Total out 739
22 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Table 5. Consumptive-use-coefficient statistics for the Great Lakes Basin and climatically similar areas, by water-use category 

(from Shaffer and Runkle, 2007; Shaffer, 2008).

[Minimum (min), median, and maximum (max), 25th percentile, and 75th percentile are in percent and rounded to the nearest whole number. N is the number of 

references used in the statistical analysis. References are only from publications after either 1975 (mining and commercial), 1980 (industrial, irrigation, thermoelectric, livestock) or 1985 (domestic and public water supply)]

Geographical area

Summary statistics of consumptive-use coefficients, by indicated water-use category

Min 25th Median 75th Max N

Domestic and Public Supply

Great Lakes Basin 0 10 12 15 74 161

Climatically similar areas 6 10 15 20 70 68

Industrial

Great Lakes Basin 0 7 10 14 35 122

Climatically similar areas 0 4 10 13 34 97

Thermoelectric

Great Lakes Basin 0 1 2 2 21 141

Climatically similar areas 0 0 2 4 75 75

Irrigation

Great Lakes Basin 70 90 90 96 100 95

Climatically similar areas 37 90 100 100 100 75

Livestock

Great Lakes Basin 10 80 83 90 100 85

Climatically similar areas 210 86 100 100 100 73

Commercial

Great Lakes Basin 4 8 10 15 26 29

Climatically similar areas 3 8 10 13 33 61

Mining

Great Lakes Basin 0 7 10 25 58 58

Climatically similar areas 0 10 14 20 86 83

1

The livestock low coefficient minimum (0 percent) is from the Great Lakes Commission (2002), in which Minnesota reported 0.25 Mgal/d total withdrawn in 

1998 and 0 Mgal/d consumptive use. The next lowest coefficient for the Great Lakes Basin was 66 percent.

2

The livestock low minimum coefficients are from Solley and others (1988) and may be the result of their adding animal specialties, including fish farming, 

into the livestock water-use category. In previous and subsequent USGS reports, fish farming was in different water-use categories.
MINNESOTA

MINNESOTA

MINNESOTA

WISCONSIN

WISCONSIN

WISCONSIN

ILLINOIS

ILLINOIS

ILLINOIS

INDIANA

INDIANA

INDIANA

OHIO

OHIO

OHIO

PENNSYLVANIA

PENNSYLVANIA

NEW

YORK

NEW

YORK

Lake

Superior

680

Lake

Superior

681

Lake

Superior

0.10

Lake

Michigan

12,300

Lake

Michigan

12,300

Lake

Michigan

0.40

Lake

Huron

1,060

Lake

Huron

1,060

Lake

Huron

0.47

Lake Ontario

2,100

Lake Ontario

2,100

< 1

< 1

1 to 10

1 to 10

10 to 100

10 to 100

100 to 500

100 to 500

500 to 1,000

500 to 1,000

Lake Erie

7,860

Lake Erie

7,870

Lake E

7.35

Surface water

95%

Groundwater

5%

TOTAL WITHDRAWALS,

IN MILLION GALLONS PER DAY

TOTAL WITHDRAWALS,

IN MILLION GALLONS PER DAY

20,000

20,000

15,000

15,000

10,000

10,000

5,000

5,000

0

0

EXPLANATION

EXPLANATION

Surface-water withdrawals,

in million gallons per day

Total water withdrawals,

in million gallons per day

Superior Michigan Huron 

IL IN MI MN NY 

Areas are 8-digit hydrologic

cataloging unit (HUC) watersheds

Figure 8. Surface-water, groundwater, and total withdrawals in the Great Lakes Basin by source, hydrologic cataloging unit (8-digit HUC watershed)and state area within Great Lakes Basin, 2005 (from Mills and Sharpe, 2010).
MINNESOTA

MINNESOTA

MINNESOTA

WISCONSIN

WISCONSIN

WISCONSIN

ILLINOIS

ILLINOIS

ILLINOIS

INDIANA

INDIANA

INDIANA

OHIO

OHIO

OHIO

PENNSYLVANIA

PENNSYLVANIA

NEW

YORK

NEW

YORK

Lake

Superior

37.3

Lake

Superior

37.3

Lake

Superior

0.00

Lake

Michigan

1,460

Lake

Michigan

1,460

Lake

Michigan

0.00

Lake

Huron

225

Lake

Huron

225

Lake

Huron

0.00

Lake Ontario

70.1

Lake Ontario

70.1

EXPLANARTION

EXPLANATION

Lake Erie

1,120

Lake Erie

1,120

Lake E

0.01

Surface-water withdrawals,

in million gallons per day

Total water withdrawals,

in million gallons per day

TOTAL WITHDRAWALS,

IN MILLION GALLONS PER DAY

TOTAL WITHDRAWALS,

IN MILLION GALLONS PER DAY

2,000

2,000

1,500

1,500

1,000

1,000

500

500

0

0

Groundwater

12%

Surface water

88%

< 1

< 1

1 to 10

1 to 10

10 to 50

10 to 50

50 to 100

50 to 100

100 to 200

100 to 200

Superior Michigan Huron 

IL IN MI MN NY 

Areas are 8-digit hydrologic

cataloging unit (HUC) watersheds

Figure 9. Public-supply withdrawals by source, hydrologic cataloging unit (8-digit HUC watershed), Great Lakes watershed, and area of state within 2005 (from Mills and Sharpe, 2010).
MINNESOTA

MINNESOTA

MINNESOTA

WISCONSIN

WISCONSIN

WISCONSIN

ILLINOIS

ILLINOIS

ILLINOIS

INDIANA

INDIANA

INDIANA

OHIO

OHIO

OHIO

PENNSYLVANIA

PENNSYLVANIA

NEW

YORK

NEW

YORK

Lake

Superior

1.38

Lake

Superior

0.10

Lake

Superior

0.00

Lake

Michigan

0.56

Lake

Michigan

0.05

Lake

Michigan

0.30

Lake

Huron

2.27

Lake

Huron

0.20

Lake

Huron

0.00

Lake Ontario

0.00

Lake Ontario

0.00

La

EXPLANATIOM

EXPLANATION

Lake Erie

1.07

Lake Erie

0.09

Lake E

0.01

Self-supplied domestic

population, in thousands

Total water withdrawals,

in million gallons per day

TOTAL WITHDRAWALS,

IN MILLION GALLONS PER DAY

TOTAL WITHDRAWALS,

IN MILLION GALLONS PER DAY

300

225

300

150

225

75

150

75

0

0

Groundwater

> 99%

Surface water

< 1%

< 1

1 to 10

10 to 50

50 to 100

100 to 500

< 0.1

0.1 to 1

1 to 10

10 to 25

25 to 50

Superior Michigan Huron 

IL IN MI MN NY 

Areas are 8-digit hydrologic

cataloging unit (HUC) watersheds

Figure 10. Self-supplied domestic water withdrawals by source, hydrologic cataloging unit (8-digit HUC watershed), Great Lakes watershed, and arGreat Lakes Basin in 2005 (from Mills and Sharpe, 2010).
MINNESOTA

MINNESOTA

MINNESOTA

WISCONSIN

WISCONSIN

WISCONSIN

ILLINOIS

ILLINOIS

ILLINOIS

INDIANA

INDIANA

INDIANA

OHIO

OHIO

OHIO

PENNSYLVANIA

PENNSYLVANIA

NEW

YORK

NEW

YORK

Lake

Superior

0.01

Lake

Superior

0.01

Lake

Superior

0.00

Lake

Michigan

2.47

Lake

Michigan

2.47

Lake

Michigan

0.00

Lake

Huron

3.06

Lake

Huron

3.06

Lake

Huron

0.00

Lake Ontario

0.03

Lake Ontario

0.04

EXPLANATION

EXPLANATION

Lake Erie

0.63

Lake Erie

0.64

Lake E

0.01

Surface-water withdrawals,

in million gallons per day

Total water withdrawals,

in million gallons per day

Groundwater

70%

Surface water

30%

TOTAL WITHDRAWALS,

IN MILLION GALLONS PER DAY

TOTAL WITHDRAWALS,

IN MILLION GALLONS PER DAY

500

375

500

250

375

125

250

125

0

0

< 0.1

0.1 to 1

1 to 10

10 to 50

50 to 100

< 0.1

0.1 to 1

1 to 10

10 to 100

100 to 200

Superior Michigan Huron 

IL IN MI MN NY 

Areas are 8-digit hydrologic

cataloging unit (HUC) watersheds

Figure 11. Irrigation-water withdrawals by source, hydrologic cataloging unit (8-digit HUC watershed), Great Lakes watershed, and state area within 2005 (from Mills and Sharpe, 2010).
Regional Water Availability Analysis for the U.S. Great Lakes Basin 27

Regional Water Budgets Through Time

The water budget in the Great Lakes Basin changes with 

time primarily because of climate variations. Periods of higher 

precipitation or lower evaporation lead to increases in lake 

levels, and periods of lower precipitation or increased evaporation can lead to decreased lake levels (Assel and others, 

2004). Climate also has affected streamflow, and trends in 

precipitation and streamflow are both discussed in this section. 

Groundwater levels appear to be less influenced by short-term 

climate variability, but longer droughts are evident in waterlevel records. Groundwater pumping has led to large drawdowns in some areas of the Great Lakes region. 

Water storage in the Great Lakes Basin is dominated 

by the Great Lakes; therefore, storage in the system is much 

more variable seasonally, and over longer time periods, than 

storage for groundwater-dominated systems. The average 

annual variation in storage for the lakes, from summertime 

high to wintertime low, is 2.2 × 1012 ft3 (Wilcox and others, 2007). Expressed as a rate (2.2 × 1012 ft3

 in 6 months = 

1.4 × 105 ft3/s), this change is approximately two orders of 

magnitude greater than the estimated consumptive-use rate 

in the basin (3.0 × 103 ft3/s, table 4). The annual variation is 

driven by cycles of precipitation, which delivers more water 

to the basin in the spring and early summer, and evaporation, 

which removes more water from the lakes in fall and early 

winter. Winter evaporation from the lakes is critical to lake 

levels. Lack of ice cover on the lakes can lead to increased 

winter evaporation and lowering of Great Lake water levels 

(Wang and others, 2010). Wilcox and others (2007) discuss 

long-term lake level variations and the mechanisms that have 

controlled lake levels in the past 4,500 years. These authors 

show that more variation in lake levels has been observed 

directly in the past 150 years, and inferred from other indicators for the past 4,500 years, than has been typical from year 

to year since postdevelopment (fig. 12). The difference in the 

volume of water in storage from relatively high to relatively 

low lake levels is several times greater than the average annual 

change in volume. 

In addition to lake-level records, precipitation and 

streamgage records exhibit both interannual variation and 

trends over the past 50 to 90 years (Hodgkins and others, 

2007). Precipitation and runoff both appear to have increased 

with time for most monitoring stations within the U.S. Great 

Lakes Basin, and Hodgkins and others (2007) detail these 

changes in terms of monthly and annual averages. In summary, mean annual runoff increased during 1955–2004 by 

2.6 in. based on the average of records from 43 streamgages; 

however, there was significant variability in both time and 

space. Runoff was lower higher from 1970 until 2004 than it 

was from 1955 to 1970. Some increase in runoff was evident 

at most stations, exceptions being a few gages near and in the 

Upper Peninsula of Michigan (fig. 13A). Fewer gages were 

available with streamflow records extending from 1935 to 

2004; but trends at these 16 gages were similar to those in 

the set available for 1955–2004 (fig. 13B). The analysis also 

showed increases in mean monthly runoff for most months 

based on records from 28 streamgages; groups of gages 

showed decreases in March, April, and May, with an evident 

decrease in mean monthly runoff values in April at most gages 

(Hodgkins and others, 2007). Overall, low flows in the basin 

increased over much of the basin, as illustrated by widespread 

general increase in the mean annual 7-day low runoff (the lowest annual average of 7 consecutive days of runoff) (fig. 14). 

The average increase in the mean annual 7-day low runoff 

from 1955 to 2004 was 0.048 (ft3/s)/mi2 based on the average 

of records at 27 gages.

Estimation of the change in groundwater storage in the 

system in response to development is complicated by two 

factors: (1) natural variations in groundwater storage are 

estimated to be larger than the change in storage resulting 

from pumping, and (2) groundwater divides have moved in 

response to pumping. On the regional scale, at averaged or 

long-term temporal conditions, water moves into and out of 

storage in response to climate variations. In dry years, or for 

several years during dry periods, average groundwater levels 

decline and water is released from storage. Conversely, during 

wet years, or for several years during wet periods, average 

water levels rise and water is returned to storage. The large 

cone of depression in the deep bedrock aquifer in southeast 

Wisconsin and northern Illinois near Chicago resulting from 

extensive pumping in the region does not release enough water 

from storage compared to the regional behavior of the system 

to significantly affect the regional water budget.

The effect of the movement of groundwater divides in 

response to pumping on groundwater in storage is more difficult to quantify. Quantification depends on the conceptual 

model used to define the system. In one view, the groundwater 

basin is defined by the existing groundwater-flow divides so 

that pumping may essentially enlarge the basin at the same 

time that water is removed from storage (Coon and Sheets, 

2006). For the Great Lakes groundwater basin, the increase in 

storage resulting from the westward shift of the groundwater 

divide in southeast Wisconsin since predevelopment was estimated to be approximately 3 percent of the total groundwater 

in storage in the basin. Despite the very large cone of depression caused by groundwater pumping in southeast Wisconsin and near Chicago, the estimated decrease in volume of 

water from storage in the system is relatively small, less than 

0.1 percent. This apparent contradiction is because of the relatively low specific storage coefficient for the confined bedrock 

aquifers used for water supply. An alternate viewpoint would 

be to fix the groundwater basin to its predevelopment boundaries. Changes in groundwater divides, such as the westward 

shift of the divide in southeast Wisconsin, would be represented by changes in the lateral flux across the fixed predevelopment boundary. By this second viewpoint, pumping does 

not change the size of the groundwater basin, and, therefore, it 

cannot change the volume of aquifer material contributing to 

groundwater in storage. 
175.5

176.0

176.5

177.0

177.5

178.0

173.0

173.5

174.0

174.5

175.0

175.5

73.5

1860

1870

1880

1890

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

74.0

74.5

75.0

75.5

76.0

LAKE LEVEL, IN METERS (IGLD 1985)

TIME, IN YEARS

182.0

182.5

183.0

183.5

184.0

184.5 Lake Superior

Lake Michigan-Huron

Lake Erie

Lake Ontario

LAKE LEVEL, IN FEET (IGLD 1985)

598

600

602

604

576

578

580

582

568

570

572

574

242

244

246

248

584

28 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 12. A, Historical lake levels for the Great Lakes, 1860–2005. 

For the generalized regional water budgets, no change 

in groundwater storage is given; these issues are explored in 

more detail through the subregional groundwater-flow model 

developed for the Great Lakes Basin Pilot (Feinstein and others, 2010) and discussed later in this report.

Water withdrawals in the region have changed as population has increased in the basin. The total withdrawals tend to 

reflect the national trend that, despite increasing population, 

total water withdrawals either decreased or increased only 

slightly from 1980 to 2005 (Hutson and others, 2004). In 

the Great Lakes Basin, water withdrawals for thermoelectric 

power decreased by 4 percent and public-supply withdrawals 

decreased by 14 percent from 1985 to 2005. These decreases 

were offset somewhat by increased withdrawal for self-supplied domestic use, 16 percent, and irrigation, 57 percent, over 

this same time period (fig. 15). The net decrease in withdrawals in the U.S. Great Lakes Basin during 1995–2005 is estimated to have been 2.2 billion gallons per day, about a 7-percent decrease over this time period (Mills and Sharpe, 2010).

One of the more interesting trends in the water-use data 

is that withdrawals for public water supply have decreased 

despite an increase in population in the region. As discussed 
5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

CALENDAR YEAR BEFORE 1950

175

176

177

178

179

180

181

574

576

578

580

582

584

586

588

590

592

594

Measured upper limit

Inferred lower limit

Historical

record

Historical average

(1819−2005)

(1950)

3000 2500 2000 1500 1000 500 BC 0 AD 500 1000 1500

YEAR

Nipissing II

Phase

2000

LAKE LEVEL, IN METERS (IGLD 1985)

LAKE LEVEL, IN FEET (IGLD 1985)

178

1500

178

177

2000 1800

≈160-year fluctuation

≈30-year fluctuation

Regional Water Availability Analysis for the U.S. Great Lakes Basin 29

Figure 12. B, Late Holocene and historical level for Lake Michigan-Huron; red line is interpreted from beach-ridge studies, and 

lower black line is an inferred lower limit based on the range of historical record (from Wilcox and others, 2007).

by Mills and Sharpe (2010), this trend may be caused by 

increased efficiency or conservation, reductions in delivery of 

water from public-supply systems to industrial users, or shifts 

in overall domestic water use away from public supply to 

self-supplied domestic sources as population increases in areas 

outside those served by public supply. Uncertainty in estimation, changes in reporting, and changes in water accounting 

over the time period also may explain some of the observed 

trends (Mills and Sharpe, 2010).

In the context of water availability, natural variation 

in the system dominates changes in storage and flows, and 

effective water-resources planning must recognize the natural 

variability in the system. The importance of natural variability, however, does not discount human impact on the water 

resources at the Great Lakes Basin scale. As mentioned, dredging in the 1960s has been suggested as a mechanism leading to permanently lowered lake levels for Lakes Michigan 

and Huron (W.F. Baird Associates, 2005). Wilcox and others 

(2007) discuss how regulation of the levels of Lakes Superior 

and Ontario has affected the ecological and beach-building 

effects of natural variation in levels. 

These trends and the temporal variability of the system 

are important for water management because long-term averages often are used to base decisions. If the hydrologic system 

does not vary about a constant long-term average, then the 

nature of the trend and its implications on future development 

should be studied (Milly and others, 2008). Water-management decisions need to be tempered by an understanding of 

the natural variability of the system and long-term trends in 

the region. Development may have occurred in areas during 

times when the lakes were naturally lower or higher than average, and the impact of changing lake levels on this development may not be feasibly mitigated because natural variation 

appears to be much greater than human-influenced variation. 

Use of models developed for subregional and local spatial 

scales within the Great Lakes Basin as part of the Pilot project 

to evaluate potential effects of climate change are presented in 

this report. 
30 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 13. Changes in annual runoff at selected long-term streamgages. A, 1955–2004. 

B, 1935–2004. Circle sizes are proportional to increases or decreases (from Hodgkins and 

others, 2007).
Regional Water Availability Analysis for the U.S. Great Lakes Basin 31

Figure 14. Changes in annual 7-day low runoff at selected long-term streamgages, 1955–2004. 

Circle sizes are proportional to increases or decreases (from Hodgkins and others, 2007).
NO DATA

WITHDRAWALS, IN BILLION GALLONS PER DAY

TOTAL WITHDRAWALS, IN BILLION GALLONS PER DAY

POPULATION, IN MILLIONS

30

31

32

33

34

35

24.5

23.5

22.5

21.5

20.5

10

15

20

25

0

5

1985 1990 1995 2000 2005

EXPLANATION

Public supply

Domestic

Thermoelectric power

Industrial

Mining

Irrigation

Aquaculture and Livestock

Total withdrawals

Population

32 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Regional Indicators

The basic indicators of water availability include streamflows, lake levels, groundwater levels, water quality, and 

water withdrawals. These data may be combined and distilled 

to yield a smaller set of indicators that may be helpful for 

decisionmakers and the public because they condense a great 

deal of information into a few values. Trends in time or spatial 

comparisons can be made clearer by way of these more refined 

indicators. Application of refined indicators at the Great Lakes 

regional scale emphasizes both the large storage volume 

and the large flux of water through the system. The indicators proposed by Vörösmarty and others (2000, 2005) and 

Weiskel and others (2007) are straightforward to apply for the 

Great Lakes Basin.

The index of relative water demand, RWD (Vörösmarty 

and others, 2000, 2005), is defined as the ratio of water use 

for the domestic sector (D), the industrial sector (I), and the 

agricultural sector (A) relative to the flux of water through the 

system. This flux may be quantified by the estimated predevelopment mean annual streamflow, Q, from the basin. The 

denominator also may be interpreted as the net water available 

for use, and it may be adjusted for required instream flow or 

for streamflow that is otherwise inaccessible (see for example, 

Postel and others, 1996). The RWD may be expressed as

(1)

Scale of application is important to recognize in interpreting the meaning of a computed indicator. Indicators may be 

estimated for regional basins, smaller watersheds, or arbitrary 

areas of any size. For example, in order to map relative water 

stress for Africa, Vörösmarty and others (2005) computed a 

local relative water demand for 8-km (26,000-ft) grid cells 

across Africa by estimating local water use and local flux 

through each grid cell,

(2)

Figure 15. Trends in total water withdrawal by water-use sector in the Great Lakes Basin, 1985–2005 (from Mills and Sharpe, 2010).
Regional Water Availability Analysis for the U.S. Great Lakes Basin 33

where

RWDn is the index of local relative water demand for 

grid cell n, dimensionless,

(D+I+A)n is the water demand in grid cell n for 

domestic, industrial and agricultural 

sectors, as volume per time, and

QCn is the river-corridor discharge entering cell n

from upstream cells, as volume per time.

On a regional scale for the Great Lakes Basin, a relative water demand may be determined by combining the total 

freshwater-withdrawal information for 2005 presented by 

Mills and Sharpe (2010) with an estimated mean annual flow 

of the St. Lawrence River: 

Total freshwater withdrawal in 2005 = 30,305 Mgal/d = 

47,000 ft3/s

Mean annual outflow of the St. Lawrence River (tables 3 

and 4) = 271,000 ft3/s

(3)

Of this, the major withdrawal is for thermoelectric power 

generation, and the withdrawn water is largely returned to the 

basin. The estimated consumptive use in the basin in 2004 was 

approximately 1,900 Mgal/d (2,950 ft3/s) (Great Lakes Commission, 2006).

(4)

High stress on water resources of an area are indicated by 

index values greater than 0.4 (Vörösmarty and others, 2000; 

Vörösmarty and others, 2005), and the Great Lakes Basin 

is well below this threshold, especially if the RWD is computed with consumptive use. This computation was done on 

the highest estimate of mean annual flow out of the basin in 

table 3. Use of a lower estimate or adjustment to account for 

instream flow requirements would increase the estimated RWD

indicators, but the RWD for the Great Lakes Basin would still 

be quite small.

Weiskel and others (2007), who built on the work by 

Vörösmarty and others (2000, 2005) to develop indicators 

of human impact on hydrologic systems, state that the RWD

does not fully capture the full range of human impacts because 

it does not incorporate return flow or water imports. Return 

flow and imports can lead to a system that is dominated by 

human activity while having a relatively low RWD. Weiskel 

and others (2007) propose examining the net flux for a basin 

that includes estimates of return flow and water import to the 

basin. Normalizing the human-induced inflows and outflows 

(shown below) by the net flow of water through the system 

produces two new indices, hin and hout , that can be graphed 

to illustrate the dominant water-use regime for a basin. 

Endpoints on such a plot can be used to classify the regimes 

into four types: (1) natural-flow dominated, (2) withdrawal 

dominated, (3) return-flow dominated, and (4) human-flow 

dominated (fig. 16). 

The normalized flows, hin and hout, also were combined 

to form two additional indices: (1) the human water balance 

index, HWB, and (2) the water-use intensity index, WUI 

(Weiskel and others, 2007). These two new indices may be 

written as

HWB = hin – hout , (5)

WUI = (hin + hout)/2 , (6)

where 

hin normalized human-induced return flows into a 

basin, Hin /NetFlux,

hout normalized human-induced withdrawals out of a 

basin, Hout /NetFlux,

Hin human-induced flux into a basin (returns), and

Hout human-induced flux out of a basin (withdrawals).

The NetFlux normalizing human return flows and withdrawals may be defined for the whole basin or for just the aquifer, 

depending on the system of interest. These basin and aquifer 

expressions for net flux can be written as follows (Weiskel and 

others, 2007):

NetFluxbasin = (P – ET ) + (GWin + SWin ) + Hin – ∆S/∆t

= (GWout + SWout) + Hout

NetFluxaquifer = Rnet + (RGW +RSW ) + Hin – ∆S/∆t

= (DGW + DSW ) + Hout

The flux components are the following.

Flows into the basin:

P precipitation,

GWin groundwater inflow from adjacent basins,

SWin surface-water inflow from adjacent basins,

Rnet net aquifer recharge (RP − DET ), 

RP aquifer recharge from precipitation,

DET water lost from aquifer by evapotranspiration,

RGW aquifer recharge by leakage from adjacent aquifers, 

and

RSW aquifer recharge by leakage of surface water.

Flows out of the basin:

ET evapotranspiration,

GWout groundwater outflow to adjacent basins,

SWout surface-water outflow to adjacent basins,

DGW aquifer discharge to adjacent aquifers, and

DSW aquifer discharge to surface water.

Change in storage:

∆S/∆t net rate of change of storage in the basin or aquifer.

The HWB ranges from −1 to 1, and the WUI ranges from 

0 to 1. The HWB indicates the type and magnitude of human 

alteration of the water-resources system. Positive values of 

HWB indicate that the human impacts result in a net import of 

water to the system, and negative values of HWB indicate net 
0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

NORMALIZED WITHDRAWALS, IN h out 

NORMALIZED RETURN FLOWS, IN h in

Return-flow

dominated

Widthdrawal

dominated

Natural-flow 

dominated

Water-use Intensity (WUI) Increases

Human Water Balance 

(HWB) Positive

HWB Negative

Human-flow 

dominated

34 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

withdrawals from the system. The magnitude of the HWB indicates the relative magnitude of the net import or withdrawal 

from the basin, but low values of HWB may be caused by a 

balance between human-induced imports and exports. The 

WUI also indicates the relative importance of human-induced 

flows to natural flows; however, its magnitude includes both 

import and withdrawal. As WUI approaches 1, the system 

becomes entirely dominated by human-induced flows (fig. 16).

Estimating these summary indicators for the Great Lakes 

Basin confirms that the overall basin has low values for both 

the HWB and the WUI and is classified as natural-flow dominated. The reason for this classification is because the large 

natural flow that divides the values of hin and hout, yielding 

low values. 

hin = 0.02

hout = 0.02

HWB = −0.003

WUI = 0.023

The values are computed without taking into account the 

amount of water used for hydroelectric power generation, 

which was 809,120 Mgal/d for 2004 (Great Lakes Commission, 2006). If this volume is included in the calculation, the 

system is dominated by human use because hydroelectricpower-generation volumes exceed the natural flow rate from 

the system by approximately a factor of 5. Another confounding issue is importation of groundwater from outside the 

surface-water basin, either because the natural groundwater 

divide is, in some places, outside the surface-water divide 

used for the calculation or because pumping near the basin 

divide has, in some places, captured water from beyond the 

divide that is returned to the Great Lakes Basin. This volume 

is unknown, but it is thought to be small relative to other 

fluxes in the system, and it is not included in the estimates of 

the indices. 

Figure 16. Human water-use regimes defined by normalized human withdrawals, hout, and 

normalized human return flows, hin.
Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 35

HWB and WUI for the Great Lakes Basin (−0.003, 0.023) 

are lower than any of those reported for selected stream basins 

by Weiskel and others (2007) and are substantially lower than 

for developed basins such as the South Platte River Basin in 

Colorado, Nebraska, and Wyoming, which drains approximately 24,300 mi2

 (−0.30, 0.76), or the Yellow River in China, 

which drains 334,000 mi2 (−0.73, 0.52).

Other indicators that may help illustrate the storage and 

flow in the Great Lakes Basin and relate flux through the 

system to storage within the basin. For the entire basin, the 

ratio of storage volume to flow through the system serves as 

an average retention time in the basin and is approximately 

100 years (Government of Canada and U.S. Environmental 

Protection Agency, 1995). This ratio often is inverted and cited 

as a water-renewal rate in the basin of 1 percent. This low 

renewal rate is used to illustrate the vulnerability of the system 

to pollution or to changes in climate (for example, Williamson and others, 2009). If each lake is examined individually, 

then the retention time ranges from 2.6 years for Lake Erie, 

because of its relatively small volume and its more downstream location in system resulting in large flow through it, 

to 191 years for Lake Superior, because of its large storage 

volume and relatively lower flow (Government of Canada and 

U.S. Environmental Protection Agency, 1995). These indicators imply that the lakes are relatively resistant to short-term 

changes or stresses because of their storage. The long retention 

time and large storage also imply that once adverse conditions 

are observed in the system, many years may be required for 

corrective action to produce desired results.

Summary and Importance of Regional Analysis

Generalized predevelopment and postdevelopment 

water budgets presented in tables 3 and 4 may be summarized schematically (fig. 17). These summaries emphasize 

the importance of surface-water storage in the Great Lakes 

Basin. This situation is unique, especially on the large scale of 

the basin, in that surface-water storage exceeds groundwater 

storage. In most large areas, groundwater storage is dominant. Also notable are the large storage volumes compared 

to the flow rates through the basin and the large volumes and 

flows compared to water withdrawal and return in the system. Figure 17 and related summary tables 3 and 4 include 

fluxes that are not quantified very well: direct groundwater 

discharge to the lakes, groundwater flow to or from adjacent 

basins (outside the surface-water divide), and consumptive 

use. The proportion and location of return flows have not 

been well documented for many uses. Overlake precipitation 

and evaporation, which are major contributors to the water 

budget, have not been directly measured (Neff and Nicholas, 

2005). Important temporal variability in the system also is not 

reflected in these summaries. On the whole, water in storage 

and water flux through the system are very large compared to 

observed and estimated water withdrawals.

Need for Subregional and Local Analyses

The Great Lakes Basin hydrologic setting contains 

such a great deal of freshwater that the overall water availability of the system may not be in question. The appropriate 

question for this system may be, “Is water available in the 

basin for human and ecological needs where it is needed and 

when it is needed?” Answering this question, and managing 

resources in light of this question, requires information and 

analysis at more local scales than that of the whole basin and 

at timeframes shorter than historical long-term annual averages. Closer examination of hydrologic processes and water 

use in the system also is required. The Great Lake Basin Pilot 

stressed the analyses at various spatial and temporal scales, 

and results of these multiscale analyses are summarized in the 

remainder of this report.

Subregional Water-Availability 

Analysis Within the 

U.S. Great Lakes Basin

Water-availability results from individual subregional 

studies within the Great Lakes Basin Pilot are summarized 

in this section. These studies included examinations of 

groundwater availability, surface-water availability, and water 

withdrawal in different subregions within the U.S. Great Lakes 

Basin. In keeping with the pilot nature of the project, studies 

included water-availability assessments, methods development, and methods testing. The results are presented by topic 

rather than subregion to help clarify the presentation.

Groundwater

The need for hydraulic analysis to evaluate of the effect 

of new or increased withdrawals on groundwater has been 

clearly articulated by Bredehoeft and others (1982), Bredehoeft (1997, 2002), and Alley and others (1999). The overall 

water budget for the groundwater system, expressed in terms 

of long-term recharge, for example, provides little information 

regarding the response of the system to increased pumping. 

The pumping will initially remove water from storage and 

will lower the hydraulic head in the aquifer. At some time, 

however, the increased pumping will be balanced by either 

an increase in recharge to the pumped aquifer or a decrease in 

discharge from the pumped aquifer. Groundwater availability 

depends on the response of the aquifer to pumping. Groundwater-availability constraints may arise either from undesired 

lowering of the hydraulic head in the aquifer (excessive 

removal from storage) or from undesired reduction in streamflow or other surface-water capture, which in turn may lead 
Great Lakes Storage

Groundwater Storage1

8.0 x 1014 ft3

1.4 x 1014 ft3

1U.S. part of the Great Lakes Basin

271 x 103 ft3/s

Flow out St. Lawrence River

Direct precipitation to lakes 

Direct evaporation from lakes

178 x 103 ft3/s

Predevelopment Regional Water Budget

229 x 103 ft3/s

151 x 103 ft3/s

505 x 10 3 ft3/s

Precipitation to land area of basin

Direct runoff and streamflow 

Baseflow to streams

(≈ aquifer recharge)

220 x 103 ft3/s

Direct groundwater discharge

Flow in from adjacent basins

Evapotranspiration from land area of basin 

284 x 103 ft3/s

5 x 10 3

ft3/s

Developed Regional Water Bud

Great Lakes Storage

Direct groundwater discharge 

8.0 x 1014 ft3

Direct precipitation to lakes

Direct evaporafrom lakes 

178 x 103 ft3 229 x 10 /s 3 ft3/s

151 x 103 ft3/s

Direct runoff and streamflow

220 x 103 ft3/s

Return flow

Withd

2 x 10

 62 x 103 ft3/s

Baseflow to streams(≈ aquifer recharge)

5 x 103 ft3/s

Precipitation and evapotranspiration 

Diversion in

5 x 103 ft3/s 

Groundwater Storage1 

1.4 x 1014 ft3

Figure 17. Predevelopment and postdevelopment long-term average water budgets for the Great Lakes Basin.
Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 37

to ecological impact or conflict over surface-water resources 

(excessive capture of discharge). Given that groundwater is 

such a large component of streamflow in the U.S. Great Lakes 

Basin (Holtschlag and Nicholas, 1998) and given the difficulty 

in increasing recharge to the aquifer by groundwater pumping 

(Bredehoeft and others, 1982; Bredehoeft, 1997), the dominant 

process in the Great Lakes Basin is likely to be reduction in 

discharge of groundwater to surface water. The rate at which 

the system transitions from removal of storage to capture of 

streamflow or other surface water is important in understanding the effect of groundwater withdrawals. Local analysis to 

assess the source of water to wells and the transient behavior 

of the system is required to understand the dynamics of the 

groundwater system. Therefore, a groundwater-flow model for 

the Lake Michigan Basin was developed to examine subregional groundwater availability.

Groundwater-Flow Model

A groundwater-flow model was developed for the 

Lake Michigan Basin to analyze subregional groundwater availability. The size of the entire basin, lack of data or 

previous modeling efforts in eastern parts of the basin, and 

challenges posed by modeling an international groundwater 

system precluded development of a regional model for the 

entire Great Lakes Basin. The subregional scale of the Lake 

Michigan Basin model is commensurate in size with other 

regional groundwater-availability studies being done by USGS 

(Reilly and others, 2008); the subregional scale also yielded 

important water-availability information for much of the Great 

Lakes Basin and allowed for methods development and testing 

within the pilot project for use in other projects nationwide. 

The groundwater-flow model for the Lake Michigan Basin is 

described in a series of reports (Arihood, 2009; Lampe, 2009; 

Buchwald and others, 2010; Feinstein and others, 2010).

Feinstein and others (2010) summarize the Lake Michigan Basin groundwater-flow model as

• a simulator providing an opportunity for refining 

quantitative methods in support of groundwater 

modeling, developing indicators of sustainability of 

water resources in the Lake Michigan Basin, illustrating groundwater-system response to pumping, and 

quantifying current groundwater availability in the 

Lake Michigan Basin;

• a platform for development of embedded, refined 

models needed to address water-management issues at 

the local scale;

• an integrator of data from numerous sources at a 

variety of scales regarding hydrogeology, hydrologic 

observations, and water use for future water-availability studies; and

• a forecasting tool that can be used to address the effects 

of future changes in water use and in climate for the 

western part of the Great Lakes Basin and adjacent 

areas.

Model results also help frame the analysis for issues that 

have high uncertainty and are difficult to describe, such as 

(1) the location and movement of aquifer divides (Sheets and 

Simonson, 2006), (2) groundwater storage and the change in 

storage in response to changing conditions (Coon and Sheets, 

2006), and (3) direct and indirect groundwater discharge to 

Lake Michigan (Holtschlag and Nicholas, 1998; Neff and 

Nicholas, 2005). 

The groundwater-flow model was developed by using 

the computer programs MODFLOW-2000 (Harbaugh and 

others, 2000) and SEAWAT-2000 (Langevin and others, 2003). 

It is a finite-difference model with 391 rows oriented west to 

east and 261 columns oriented north to south. The rows and 

columns are both nonuniform, but the area of greatest interest 

of the model has the smallest cells, with uniform cell sizes of 

5,000 ft by 5,000 ft. This area of uniform cell sizes is centered on Lake Michigan and extends from row 10 to row 381 

and from column 12 to column 248. The area of the model 

domain is 180,963 mi2. Less than half of this area falls within 

the Lake Michigan Basin, and Lake Michigan itself has an 

area of approximately 22,000 mi2 (Government of Canada and 

U.S. Environmental Protection Agency, 1995). Twenty numerical layers were used to discretize the subsurface from the 

land surface to Precambrian bedrock. The three upper layers 

of the model represent glacial deposits over most of the land 

area, and the model extends vertically through several bedrock 

aquifers that form the Wisconsin Arch and structural Michigan 

Basin (figs. 4 and 18). To aid in presentation of model results, 

the area of the model with uniform cell spacing of 5,000 by 

5,000 ft and some nonuniform cells within the Lake Michigan 

Basin are referred to as the model nearfield (fig. 19). Model 

results are reported for the nearfield. In order to simulate 

groundwater conditions in the area, boundary conditions and 

stresses are applied to both the nearfield and remaining part of 

the model (farfield).

Feinstein and others (2010) described in detail the 

boundary conditions and stresses imposed on the numerical 

model, and they analyzed the sensitivity of model results to 

changes in these boundary conditions and stresses. The farfield 

boundary conditions include no-flow boundaries along the 

outer edges of the model area. Two zones of model cells in the 

northwest and northeast corners of the model where thin glacial materials overlie Precambrian bedrock also are assigned 

as no-flow boundaries. Head-dependent flux boundaries are 

applied to cells that represent areas under the major lakes in 

the farfield of the model domain: Lake Superior, Lake Huron, 

Lake Erie, and Lake St. Clair. For these lakes, the lake stage 

and lakebed conductance is specified. The flux between the 

model and each lake varies in accordance with the difference between estimated head in the finite-difference cell with 

the boundary condition imposed and the lake stage assigned 
0 

0 50 

Base from U.S. Geological Survey digital data 1:100,000 1983.Universal Transverse Mercator projection Zone 16, Standard Parallel 0° (Equator), Central Meridian 87° W, North American Datum 1983

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

EX

LakLakAre5,00Mo

Figure 18. Model grid, Lake Michigan Basin drainage basin, and area where model cells are 5,000 feet by 5,000 feet (from Fein
Lake

Winnebago

90°W 88°W 86°W 84°W 82°W

46°N

44°N

42°N

WISCONSIN

ILLINOIS

INDIANA OHIO

ONTARIO

M I C H

I G

A

N

0 50 100 Miles

0 50 100 Kilometers

Base from ESRI, 2001 EXPLANATION

Model domain boundary

Lake Michigan Basin

Lake

St. Clair

Nearfield

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 39

Figure 19. Nearfield area of Lake Michigan Basin groundwater-flow model.
40 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

to the cell. Specified-flux boundary conditions are applied 

in the southwest corner of the farfield to allow the model to 

account for water that moves across the boundaries in the 

southwest part of the model farfield in response to pumping within the model. The fluxes specified were estimated by 

using results from a numerical model of northeastern Illinois 

(Meyer and others, 2009). Constant-head boundary conditions 

were assigned to the topmost active layer of the farfield of the 

model to fix the water table in these cells to an approximation 

of the observed water table; doing so fixes the recharge to the 

system in the farfield and allows model calibration focus on 

the behavior in the nearfield of the model domain. 

Surface water in the nearfield is represented as imposed 

boundary conditions on the model. These boundary conditions 

represent major lakes (Lake Michigan and Lake Winnebago), 

smaller lakes, wetlands, and streams. Lake Michigan and 

Lake Winnebago are represented by using head-dependentflux boundary conditions in a similar fashion to the farfield 

Great Lakes. For farfield lakes, the conductance values used to 

simulate the lakebeds were quite high so that the lakebed itself 

offers little resistance to flow. The upper layers of the model 

under Lake Michigan, however, were designed to represent 

the sediments under the lake and more accurately reflect the 

exchange of water between the two lakes and the groundwater 

system (Feinstein and others, 2010). Smaller lakes, wetlands, 

and streams were represented in the model, and approximately 

60 percent of the nearfield cells had some surface-water feature imposed as a boundary condition. 

The model simulates groundwater conditions from 1864 

through 2005. This timespan was subdivided into 13 stress 

periods: a stress period is an interval of time during which the 

conditions imposed on the model are held constant, and five 

time steps are used within the simulation of each stress period 

except the first. The first stress period produced a steady-state 

approximation to conditions prior to 1864 and required only 

one time step. Pumping, boundary conditions, and recharge 

were held constant for each stress period. The withdrawals 

by pumping are summarized by Feinstein and others (2010) 

and detailed by Buchwald and others (2010). Recharge to 

the model was estimated by developing computer code for a 

modified Thornthwaite-Mather soil-water-balance approach 

(Westenbroek and others, 2010). The Soil-Water-Balance 

(SWB) model performs an accounting of water in the soil zone 

by using daily time steps to estimate water delivered through 

the soil zone to the water table, which is recharge to the aquifer. Climate variables, including temperature and precipitation, and landscape and soil characteristics are required inputs 

for the SWB model (Westenbroek and others, 2010). Water 

is added to the soil zone through precipitation and snowmelt 

and is removed through evapotranspiration and recharge to 

the aquifer. The daily estimates of recharge produced by the 

model were aggregated to produce long-term average recharge 

values that were applied to the 13 stress periods (fig. 20). 

Recharge imposed on the model varies with stress period and 

is generally higher after 1970, which is consistent with general 

increases in precipitation and changes in land-use practices, 

particularly improvement in land-conserving agricultural 

practices, in the region (Gebert and Krug, 1996; Hodgkins and 

others, 2007; Juckem and others, 2008). Juckem and others 

(2008) state that climate variation appears to control the overall trends in base flow (which is tied to groundwater recharge), 

and agricultural-practice changes have magnified the recharge 

changes in part of Wisconsin outside of the Great Lakes Basin.

Indicators of the condition of the groundwater system and 

its response to development included the simulated hydraulic 

head in the system and associated change in head (drawdown). A major cone of depression, one of the largest in the 

United States, is adjacent to and extends into the Great Lakes 

Basin. The importance of the Cambrian-Ordovician aquifer to 

the region and the observed drawdowns in this aquifer have 

motivated many studies, including those by Young and others 

(1989), Mandle and Kontis (1992), and Feinstein and others 

(2005). Because these earlier results indicated that the cone 

of depression could extend into saline parts of the Michigan 

Basin (data sources for the saline-water input are detailed by 

Lampe, 2009), the effect of salinity and density-dependent 

flow was included in the Lake Michigan Basin model through 

the use of the SEAWAT-2000 computer program (Feinstein 

and others, 2010). The drawdown is caused by pumping in 

the Chicago and Milwaukee metropolitan regions, and the 

observed behavior is reproduced by the flow model (fig. 21; 

see also Feinstein and others, 2010). 

Observations and analysis of model results reveal that the 

maximum drawdown in the system occurred in approximately 

1985 and was approximately 1,000 ft. In the 1980s, Chicago, 

Milwaukee, and other communities near Lake Michigan 

shifted from wells to Lake Michigan water for public supply. 

This shift decreased the demand on the groundwater system and led to a recovery of approximately 400 ft (fig. 22). 

Between 1970 and 1990, the locus of the cone of depression 

moved westward in response to decreased demand from wells 

near the lake and increased development in western suburbs 

of Chicago and Milwaukee. Between 2000 and 2005, the 

drawdown stabilized, primarily because new development has 

focused on shallower wells or wells in the Cambrian-Ordovician aquifer outside the major cone of depression because of 

water-quality concerns associated with radium in the Cambrian-Ordovician aquifer (Kay, 1999). 

Groundwater Budget

Simulation results from the model can be analyzed to 

show the water budget through time for the Lake Michigan 

Basin (fig. 23A,B). This analysis shows that despite large 

drawdowns due to pumping in the Chicago and Milwaukee 

metropolitan areas, the overall effect of development on the 

groundwater system is small compared to fluctuations caused 

by climate variation. The major components of the groundwater budget are recharge into the system and discharge to local 

surface-water features (streams out) (fig. 23A). The next most 

important fluxes are input from losing surface-water features 
2

3

4

5

6

7

8

9

1 0

1 1

1 2

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

6.96 7.26

7.26

7.25 7.00 6.80 8.73 7.12 8.84 7.45 7.47

3 4 5 6 7 8 9 10 11 12

NEARFIELD RECHARGE, IN INCHES PER YEAR

DATE

EXPLANATION

Yearly average nearfield recharge

Five-year moving average of yearly recharge

5 Model stress period

Average nearfield recharge for stress period

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 41

Figure 20. Recharge values assigned to stress periods for the Lake Michigan Basin groundwater-flow model with 

yearly and 5-year moving averages of recharge, as estimated by using the Soil-Water-Balance model (from Feinstein 

and others, 2010).

and flow out to inland lakes. Least important to the budget, but 

perhaps most visible and of interest to users in the area, are the 

fluxes out of the system to wells and directly to Lake Michigan, and the fluxes into and out of storage as heads in the aquifers change in response to pumping and changes in recharge. 

The role of pumping and storage changes can be noted in this 

type of figure only if changes in time are emphasized by highlighting the changes in budget components. Even when the 

changes in the budgets are emphasized, the major components 

are (1) changes in recharge arising from climate variability and 

(2) associated responses of outflow to inland surface water and 

groundwater levels determining water in storage. This pattern 

is especially true for the four stress periods during 1970–90 

(stress periods 8–11; see also fig. 20); the changes in imposed 

recharge because of climatic changes from one period to the 

next cause water to move in and out of storage as the system 

responds to the change from the lowest imposed recharge in 

stress period 7 (1960–70) to high recharge in stress period 

8 (1970–75) followed by lower recharge in stress period 9 

(1975–80) (fig. 23B).

An alternative analysis that illustrates the source of water 

to wells is generated by using particle tracking to identify the 

potential pathways water moves through the system (Feinstein 

and others, 2010). Through this analysis, the starting point for 

particles that are discharged to wells within principal aquifers 

in the system are identified (fig. 24). These starting points 

represent locations where water that eventually is removed by 

a well originates in the shallow aquifer system. The purpose 

of this analysis is twofold: first, it reinforces and illustrates the 

notion of capture discussed by Bredehoeft (2002) and, second, 

it shows interaction between major pumping centers and 

Lake Michigan, which is of interest in the area (see, for example, Cherkauer and others, 2006). Wells pumping water from 

the bedrock aquifer capture water from the surface-water system and interact with Lake Michigan on very long time scales. 

A large area within Lake Michigan is simulated to supply 

water to wells, but most of the particles that begin in the lake 

travel longer than 10,000 years to reach the pumping wells. 

The discharge of groundwater to Lake Michigan should 

be recognized as occurring either as direct discharge from 

the groundwater system to the lake or indirect discharge of 

groundwater to streams that then discharge into the lake. 

Regionally, indirect discharge is far more important to the 

water budget of the lake (Holtschlag and Nicholas, 1998; 

Neff and Nicholas, 2005). Groundwater-budget results for the 

Lake Michigan Basin (fig. 23) indicate that direct discharge 

to the lake (“Lake Michigan out”) under predevelopment 

conditions was 1.2 percent of the total input to the groundwater system and that indirect discharge to the lake (“Streams 

out”) under predevelopment conditions was 98.8 percent. 

Simulation results from the end of the 2000–2005 stress period 

indicate that 96.9 percent of the inflow to the groundwater 
41°

46°

45°

89° 87° 85° 83°

44°

43°

42°

EXPLANATION Base from U.S. Geological Survey digital data 1:100,000 1983.

Universal Transverse Mercator projection, Zone 16, Standard Parallel 0° (Equator), 

Central Meridian 87° W, North American Datum 1983 Drawdown, in feet Model nearfield

Lake Michigan boundary

Lake Michigan 

Basin boundary

1010

610

810

410

210

10

0 50 100 KILOMETERS

0 50 100 MILES

42 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 21. Drawdown in Cambrian-Ordovician aquifer as 

simulated with the Lake Michigan Basin groundwater-flow 

model (Feinstein and others, 2010). A, 1950.
41°

46°

89° 87° 85° 83°

44°

43°

42°

Base from U.S. Geological Survey digital data 1:100,000 1983. 

Universal Transverse Mercator projection, Zone 16, Standard Parallel 0° (Equator), 

Central Meridian 87° W, North American Datum 1983

EXPLANATION

Drawdown, in feet Model nearfield

Lake Michigan boundary

Lake Michigan 

Basin boundary

1010

610

810

410

210

10

0 50 100 KILOMETERS

0 50 100 MILES

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 43

Figure 21. Drawdown in Cambrian-Ordovician aquifer as 

simulated with the Lake Michigan Basin groundwater-flow 

model (Feinstein and others, 2010). B, 1980. 
41°

46°

45°

89° 87° 85° 83°

44°

43°

42°

Base from U.S. Geological Survey digital data 1:100,000 1983. 

Universal Transverse Mercator projection, Zone 16, Standard Parallel 0° (Equator), 

Central Meridian 87° W, North American Datum 1983

EXPLANATION

Drawdown, in feet Model nearfield

Lake Michigan boundary

Lake Michigan 

Basin boundary

1010

610

810

410

210

10

0 50 100 KILOMETERS

0 50 100 MILES

44 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 21. Drawdown in Cambrian-Ordovician aquifer as 

simulated with the Lake Michigan Basin groundwater-flow 

model (Feinstein and others, 2010). C, 2005.
-400

-200

0

200

400

600

800

1000

1860 1880 1900 1920 1940 1960 1980 2000

SE_WI (Waukesha area, C-O aquifer system)

NE_IL (Elgin area, C-O aquifer system)

NE_WI (Green Bay area, C-O aquifer system)

SLP_MI (Lansing area, MSHL aquifer system)

YEAR

WATER-LEVEL ALTITUDE, IN FEET

-25,000

-20,000

-15,000

-10,000

-5,000

0

5,000

10,000

15,000

20,000

25,000

Lateral flow in (net)

Storage source

Surface water in

Recharge in

Streams out

Inland lakes out

Storage sink

Lake Michigan out

Wells out

Predevelopment

2001–05

STRESS PERIOD

FLUX, IN MILLION GALLONS PER D

AY

1901–20

1921–40 

1941–50

1951–60

1961–70

1971–75

1976–80 

1981–85

1986–90

1991–2000

1864–1900

EXPLANATION

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 45

Figure 23. Water budget for the Lake Michigan Basin from groundwater-flow model showing proportions of water-budget components 

for each modeled stress period (from Feinstein and others, 2010).

Figure 22. Simulated water-level hydrographs at pumping centers within water-budget zones of the Lake Michigan 

Basin groundwater-flow model (from Feinstein and others, 2010).
LAKE SUPERIOR LAKE MICHIGAN

LAKE

HURON

LAKE

WINNEBAGO

LAKE

St. CLAIR

LAKE

ERIE

90°W 88°W 86°W 84°W 82°W

46°N

44°N

42°N

ILLINOIS

INDIANA

OHIO

M I C H I G

A

N

0 50 100 MILES

0 50 100 KILOMETERS

Base from ESRI, 2001

EXPLANATION

Major contributing area to aquifer systems Model or hydrologic boundary

Traveltime greater than 10,000 years

Flow particles start in sink cell (RIV, GHB, WEL)

Flow particles discharge to QRNR sink

Flow particles discharge to PENN sink

Flow particles discharge to MSHL sink

Flow particles discharge to SLDV sink

Flow particles discharge to C-O sink

Model domain 

Lake Michigan Basin

Model nearfield

WISCONSIN

ONTARIO

46 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 24. Contributing areas to wells in principal aquifers (from Feinstein and others, 2010).
Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 47

system was delivered to Lake Michigan through indirect 

discharge (“Streams out”), 3.1 percent of the inflow to the 

groundwater system was removed by pumping (“Wells out”), 

and 1.1 percent of the inflow to the groundwater system was 

discharged directly to Lake Michigan (“Lake Michigan out”). 

The rate of direct discharge estimated with the Lake Michigan 

Basin model ranged from approximately 0.08 to 8 ft3/s per 

5,000 ft of shoreline. The overall average direct discharge rate 

was an average of 0.33 ft3/s per 5,000 ft of shoreline. More 

detailed analysis and grid refinement of the model near the 

lake suggested that these estimates slightly underestimated the 

direct discharge (Feinstein and others, 2010). Refinements to 

the subregional model, however, yield an estimated value of 

0.5 ft3/s per mile of shoreline, with a corresponding increase 

in the fraction of input to the system discharged directly to the 

lake such that the direct discharge is approximately 2 percent of the overall water budget for the Lake Michigan Basin 

(Feinstein and others, 2010). These values are consistent with 

estimates reported by Neff and Nicholas (2005).

To analyze the water budget in more detail and to contrast 

different locations within the model, the domain was divided 

into seven water-budget zones, and the groundwater budget 

for 1864–2005 was estimated for each zone from the model 

simulation results (figs. 25 and 26). Additional refinement of 

the analysis identified shallow and deep aquifer systems. In 

this context, shallow aquifer systems refer to those above the 

first major and relatively continuous confining unit, and deep 

aquifer systems are those below the first relatively continuous 

bedrock confining unit. Shallow groundwater flow is either 

unconfined (for example, flow that occurs in coarse-grained 

glacial deposits or in bedrock that is overlain by coarsegrained glacial deposits) or semiconfined (for example, flow 

in zones where fine-grained glacial deposits overlie a bedrock 

aquifer without an intervening bedrock confining unit). Deep 

groundwater flow is by definition always in bedrock, and it 

is always either confined or semiconfined as in the example 

given above. Pumping wells and withdrawals can be described 

as shallow or deep depending on the open interval of the well 

and its relation to the uppermost bedrock confining unit. 

Examination of the sources of water to shallow and deep 

aquifer systems for the seven water-budget zones reveals 

some similarities but also some major differences in behavior 

between the east and west parts of the study area (fig. 26A, B). 

For all the water-budget zones, downward leakage from inland 

surface water is the major source of water to wells for the 

subregional groundwater-flow model. Storage release, which 

is the result of changes in hydraulic heads in the aquifers, is 

more important for aquifers west of Lake Michigan. For 2005 

(results in the figure are shown for the end of the 2000–2005 

stress period), storage release is less important for shallow 

pumping than for pumping from deep systems.

Shallow pumping in the Northeast Wisconsin (NE_WI) 

water-budget zone decreased groundwater levels, and approximately 9 percent of the water produced by wells came from 

this release in storage. Six percent of the water pumped was 

from lateral flow into the water-budget zone either from 

Lake Michigan (1 percent) or outside of the zone (5 percent). 

The remaining 85 percent of pumping was captured inland 

surface water, and it may have been either diversion of water 

that would have been discharged to streams or induction of 

inland surface water to the shallow aquifer. To the east of 

Lake Michigan, the Northern Lower Peninsula of Michigan 

zone (NLP_MI) behaved much the same for shallow pumping except that lateral flow was not a significant source of 

water to wells. For this shallow water-budget zone, 9 percent 

of the water came from storage release, and 91 percent came 

from captured inland surface water. A decrease in pumping 

in the Northeast Illinois (NE_ILL) water-budget zone for the 

2000–2005 stress period lead to recovery of water levels, and 

water returned to storage in this water-budget zone. Because 

water levels recovered from earlier drawdown by pumping, 

the analysis indicates that the source to water to wells from 

captured inland surface water is greater than 100 percent. 

All the water produced by the wells is captured from inland 

surface water, and the excess (9 percent of the pumping rate 

in this case) represents the water that is returning to storage 

in the shallow system. The remaining shallow mass-balance 

zones all were dominated by capture of inland surface water.

For the deep aquifer system, changes in storage and 

lateral flow were more important for the Southeast Wisconsin 

(SE_WI), Northeast Illinois (NE_ILL), and Northern Lower 

Peninsula of Michigan (NLP_MI) water-budget zones than 

these sources were for the shallow system. Again, water 

returned to storage in the NE_ILL water-budget zone, amounting to 18 percent of the pumping rate; sources of water to the 

wells and to storage were leakage from the overlying aquifers 

that ultimately is captured inland surface water (68 percent), 

lateral flow from Lake Michigan (8 percent), and lateral flow 

from outside the water-budget zone (42 percent). Captured 

water from Lake Michigan was more important for the deep 

SW_WI zone (11 percent of pumping) and deep NLP_MI 

zone (56 percent of pumping). The deep NE_WI and SLP_MI 

water-budget zones were dominated by leakage from overlying aquifers capturing inland surface water (greater than 

95 percent of the pumping rate in both cases).

Groundwater-Availability Summary Indicators

Water-budget information from the groundwater-flow 

model may be used to calculate summary indicators for the 

Great Lakes Basin region. To contrast the different budget 

zones, summary indicators for the deep and shallow aquifer 

systems in each of the budget zones were computed. Slightly 

different summary indicators were developed for analysis of 

model results than were used for the regional water-budget 

analysis. The normalized water-use components of the HWB

and WUI indicators discussed previously are bounded by 1 

(Weiskel and others, 2007). Use of a groundwater-flow model 

to compute these indicators, however, allows for climatedriven variations in the water budget to be separated from 

other changes in the system, therefore making it possible to 
LAKE SUPERIOR LAKE MICHIGAN

LAKE

HURON

LAKE

ERIE

LAKE

WINNEBAGO

90°W 88°W 86°W 84°W 82°W

46°N

44°N

42°N

ILLINOIS

INDIANA OHIO

M I C H I G

A

N

0 50 100 MILES

0 50 100 KILOMETERS

Northeastern

Wisconsin

Southeastern

Wisconsin

Northeastern

Illinois

Northern

Indiana

Southern

Lower Peninsula,

Michigan

Northern

Lower Peninsula,

Michigan

Upper Peninsula,

Michigan

Base from ESRI, 2001

EXPLANATION

LAKE

St. CLAIR

Model domain boundary 

Lake Michigan Basin

WISCONSIN

ONTARIO

48 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 25. Water-budget zones of Lake Michigan Basin groundwater-flow model used to summarize groundwateravailability results (from Feinstein and others, 2010).
93%

4%1% 2%

SE_WI: Pumpage =

37.1 mgd from QRNR + SLDV

91%

9%

NLP_MI: Pumpage =

32.1 mgd from QRNR

100%

1% -1%

SLP_MI: Pumpage =

212.1 mgd from QRNR

2%

99%

-2% 1%

UP_MI: Pumpage = 5.4 mgd from QRNR + SLDV

1%

85%

9% 5%

NE_WI: Pumpage = 57.3 mgd from QRNR +SLDV

98%

2%

N_IND: Pumpage = 116.2 mgd from QRNR

109%

-9%

NE_ILL: Pumpage =

82.3 mgd from QRNR + SLDV

Lateral flow under Lake 

Michigan coast

Lateral flow across inland 

boundary

Diverted or induced from 

streams and inland lakes

Storage release

EXPLANATION

Shallow well locations

Model nearfield

Lake Michigan boundary

Lake Michigan drainage

basin boundary

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 49

Figure 26. Sources of water to wells by water-budget zone and aquifer system for 2005 from the Lake Michigan Basin 

groundwater-flow model. A, Shallow aquifer systems.

define indicators that further emphasize withdrawal-related 

differences between areas. 

The major source of water to wells is captured surface 

water from inland sources (fig. 26). Observations and analysis 

presented by Hodgkins and others (2007), however, suggest 

that groundwater discharge (base flow to streams), as indicated 

by the mean annual 7-day low flow, increased during 1970–

2005 (fig. 14). This apparent contradiction is reconciled by 

examination of the imposed recharge on the model (fig. 20). 

The recharge increase for 1970–2005 delivers more water to 

the groundwater system than is removed by pumping over this 

time period (fig. 23). To estimate the effect of pumping on 

streamflow and to eliminate the effects of climate variability, 

the model was run without any pumping stress imposed. The 

model results with pumping were then subtracted from the 

model results without pumping to isolate the effect pumping 

has on the system. Because the recharge to the groundwater 

system is fixed for each time period and because recharge does 

not depend on the pumping rate in the simulations, subtracting the results removes the effects of climate variability from 

the analysis. 

Summary indicators were developed in which the water 

withdrawals and returns were normalized to the estimated 

net flux through the system in the absence of pumping. The 

new indicator, HWB', is similar to the Demand-to-Supply 

Ratio (DSR) discussed by Cherkauer (2009). The difference 
SE_WI: Pumpage = 37.1 Mgal/d from C-O

SLP_MI: Pumpage = 

81.9 Mgal/d from PENN + MSHL

NLP_MI: Pumpage = 11.6 Mgal/d from SLDV

UP_MI: only 1.0 Mgal/d of deep 

pumping from C-O 

 N_IND: only 1.2 Mgal/d of deep 

pumping from MSDV and SLDV

NE_WI: Pumpage = 56.9 Mgal/d from C-O

NE_ILL: Pumpage = 

80.2 Mgal/d from C-O

1% 1%

69%

42%

-18% 8%

74%

-2% 11% 17%

99%

3% -2%

98%

2%

48% 56%

-6%

Lateral flow under Lake 

Michigan coast

Lateral flow across inland 

boundary

Downward leakage from 

(inland) surface water

Storage release

EXPLANATION

Shallow well locations

Model nearfield

Lake Michigan boundary

Lake Michigan 

Basin boundary

50 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 26. Sources of water to wells by water-budget zone and aquifer system for 2005 from the Lake Michigan Basin groundwaterflow model. B, Deep aquifer systems (from Feinstein and others, 2010).

between the new indicator, denoted by either HWB' or DSR',

and the DSR used by Cherkauer (2009) is that in the latter net 

withdrawal is normalized by predevelopment flows. The DSR

summary indicator is sensitive to climate variability; and, if 

climate variability is significant compared to withdrawals, then 

it will mask the effects of pumping on the analysis. 

A modified the water-use intensity index, WUI', also 

could be defined where human-induced inflows and outflows are normalized by estimated fluxes computed by 

using the groundwater-flow model without pumping; for the 

Great Lakes Basin, however, areas are generally not characterized by low HWB and high WUI indicators representative of a 

human-dominated system (fig. 16), so a modified WUI is not 

considered in this section.

A Base-flow-Reduction Ratio (BRR') defined by the 

decrease in estimated net base flow to streams for each massbalance region was estimated by using the difference between 

the pumping and no-pumping simulations. Because pumping 

may induce the capture of surface water from streams to the 

aquifer, the net base flow may become negative and the ratio 

may exceed 1. In the same way as the Demand-to-Supply 

Ratio, BRR' differs from the Base-flow Reduction Index BRI

used by Cherkauer (2009) because the latter normalizes with 

respect to predevelopment conditions (it also is expressed as 

a percentage), and in this section the normalization is with 

respect to a no-pumping condition.

The indicators used in this section are

DSR' = HWB' = h'in – h'out

= (net withdrawal)(net flux without pumping) ,

BRR'= (bfnopumping – bfpumping ) / bfnopumping

= (change in net base flow due to pumping)/

(net flow without pumping) 

.
Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 51

where 

h'in normalized human return flows into a basin, 

Hin /NetFlux',

h'out normalized human withdrawals out of a basin, 

Hout /NetFlux',

Hin human-induced flux into a basin (returns), 

Hout human-induced flux out of a basin (withdrawals), 

bfpumping net base flow (base flow to streams – flux from 

streams to aquifers) under pumping conditions, 

and

bfnopumping net base flow (base flow to streams – flux from 

streams to aquifers) under no-pumping 

conditions.

The NetFlux’ normalizing human return flows and withdrawals is computed by using the calibrated groundwater-flow 

model with no human withdrawals imposed on the simulation.

NetFlux' = Rnet + (RGW + RSW ) + ∆S'in /∆t

= (DGW + DSW ) + ∆S'out /∆

All terms in these equations were defined previously except 

∆S'in , which is volume of water released from storage for 

the time interval computed by the model in the absence of 

withdrawals by pumping, and ∆S'out , which is the volume of 

water added to storage for the time interval computed by the 

model in the absence of withdrawals by pumping. Water is 

released from storage if water levels in the aquifer decrease, 

and water is taken into storage if water levels increase.

Water-budget results indicate that withdrawals by pumping are only a small fraction of the overall groundwater budget 

for the Lake Michigan Basin (fig. 23). The Demand-to-Supply 

Ratio and Base-flow-Reduction Ratio calculated for the 

Lake Michigan Basin by using the entire aquifer system also 

show this result (fig. 27). The DSR' indicator maximum value 

was approximately 0.03 for the Lake Michigan Basin, and the 

BRR' was approximately 0.033. These results echo the important theme describing water availability in the region: there 

is regional abundance of groundwater resources compared 

to regional demand. By examining the indicators for smaller 

areas, however, the potential for local conflicts, limitations, or 

storages can be seen.

For shallow aquifers, the Base-flow-Reduction Ratio 

is more illustrative of the behavior of the system than the 

Demand-to-Supply Ratio in the water-budget zones because 

the natural flux through the shallow system is high compared 

with the demands on the system. The BRR' increases from 

zero at predevelopment conditions to maximum values near 

19 for in 1985, after which it stabilizes or decreases slightly 

(fig. 28A). The water-budget zones with the greatest groundwater withdrawals, NE_ILL and SW_WI, have the largest 

BRR'. On the scale of this model, the base-flow reduction is 

diffuse and cannot be attributed to significant impacts on certain streams. Local-scale modeling is required to quantify the 

interaction of wells with individual surface-water features, as 

shown in a later section of this report. The BRR' is computed 

only for the shallow aquifers because these aquifers account 

for almost all of the base flow to streams in the model. The 

pumping in these water-budget zones, however, is from both 

the deep and shallow systems. Shallow pumping dominates 

local base-flow reduction, but pumping in the deep part of the 

flow system may increase leakage from the overlying shallow 

system and thereby cause local base-flow reduction.

The DSR' indicator is less than 0.12 for all water-budget 

zones for both shallow and deep parts of the flow system 

except the southeast Wisconsin (SE_WI) and northeast Illinois 

(NE_ILL) water-budget zones. All the water-budgets zones 

other than SE_WI and NE_ILL, like the Great Lakes Basin, 

would be considered within the natural-flow-dominated wateruse regime. The two exceptions indicate withdrawals are an 

important part of the water budget of the respective zone. 

Exploring the data used to create the indices reveals that, in 

the absence of pumping, the flux of groundwater in the deep 

part of the flow systems in SE_WI and NE_ILL is low and 

that pumping increases the flow through the system as more 

water is induced into the system and discharged through wells. 

Examining the DSR' indicator through time indicates that for 

the deep parts of the SE_WI and NE_ILL flow systems, the 

pumping flux exceeds the natural flux through the deep aquifer 

system. In both of these mass-balance areas, pumping has 

caused large drawdowns (fig. 22) and has induced both lateral 

and vertical flow through the aquifer system to the pumping 

centers. For NE_ILL the Demand-to-Supply ratio peaked at 

approximately 7.5, and for SE_WI it peaked at approximately 

3.5 (fig. 28B). The time histories of DSR' also reveal changes 

in the pumping history for the two zones and emphasize the 

peak in pumping in the 1980s. These results imply that different management schemes might be necessary in the SE_WI 

and NE_ILL zones than in the rest of the region and that 

groundwater availability may be limited by different factors in 

these zones than in the rest of the region.

Drawdown from four pumping centers within the 

Lake Michigan Basin was examined in fig. 22. Three of these 

centers are reexamined here with respect to the Base-flowReduction Ratio and Demand-to-Supply Ratio to further 

illustrate the importance of spatial scale on groundwateravailability analysis. The BRR' for the Green Bay pumping 

area, Waukesha pumping area, and Lansing pumping area are 

consistent with the values computed for the larger water-budget zones. The maximum BRR' is for the Green Bay area, at 14 

(fig. 29A). The Demand-to-Supply Ratio, however, was much 

higher for these pumping centers than the larger mass-balance 

zones, peaking at greater than 12 for the Waukesha pumping 

area (fig. 29B). High values of DSR' may motivate stakeholders to examine local water-budget components and sources of 

water to wells in order to learn the dynamics of the groundwater system. Such understanding could lead to improved 

groundwater-availability planning in the region. 

One potential problem with the use of these indicators, 

especially at local spatial scales, is that self-supplied domestic 

use is not included in the subregional model. Water use in the 

groundwater-flow model focuses on high-capacity publicsupply, irrigation, and industrial wells. High-capacity wells are 
0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

1900 1920 1940 1960 1980 2000

DEMAND-TO-SUPPLY RATIO

Baseflow Reduction Ratio

Demand-to-Supply Ratio

TIME, IN YEARS

52 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

defined as those that extract on average more than 70 gal/min 

(100,000 gal/d) over a pumping period. Domestic wells are 

typically not included in regional models of this scale because 

they represent a poorly known, diffuse demand on the model 

and because much of the water removed by domestic wells is 

returned to the system through onsite septic systems or similar 

wastewater disposal methods. Because the accounting for 

these withdrawals and return flow to the groundwater system 

is not in place, Hin and h'in cannot be estimated very well. The 

indicators also should be used with caution. Low values of 

these indicators do not necessarily mean that there are not 

groundwater-availability issues. For example, the DSR' for the 

Lansing pumping area is quite low for the entire simulation 

time, but the Lansing area did experience excessive drawdown leading to degradation of water quality in the 1960s. To 

mitigate this drawdown, the demands in the area were spread 

out by the use of additional wells, and system recovered. 

This episode is not shown through the indicators. Conversely, 

high values of DSR' may not mean that the pumping is not 

sustainable. Pumping can induce flow from both the broader 

region and adjacent aquifers. The aquifers in the Great Lakes 

Basin appear to be able to capture enough water to stabilize 

drawdown fairly quickly, and, although the drawdowns are 

quite large, they might not pose a major constraint on groundwater availability. The indicator might highlight potential 

areas of groundwater availability limitations, but the actual 

dynamics of the system and local effects of withdrawals must 

be determined.

Despite these caveats, these summary indicators may be 

useful in contrasting different locations within the modeled 

area, thereby highlighting differences in the region that might 

warrant attention for more detailed water-availability analysis. 

The indicators may reveal areas at risk for water competition, 

conflict, or shortages from relatively small decreases in the 

supply of water to the area, increases in use, or changes in how 

local communities value instream flows or make decisions 

regarding development and water resources. The indicators 

also may be more intuitive to decisionmakers or stakeholders 

than maps showing drawdown or source of water to wellwater budgets.

Figure 27. Demand-to-Supply Ratio and Base-flow-Reduction Ratio for the Lake Michigan Basin aquifer 

system as computed by use of the Lake Michigan Basin groundwater-flow model.
0

1

2

3

4

5

6

7

8

1900 1920 1940 1960 1980 2000

DEMAND-TO-SUPPLY RATIO

Northeast Illinois

Southeast Wisconsin

Maximum value for other deep and 

all shallow Demand-to-Supply Ratio (DSR)

Scale of Lake Michigan Basin DSR

TIME, IN YEARS

0

2

4

6

8

10

12

14

16

18

20

1900 1920 1940 1960 1980 2000

BASEFLOW-REDUCTION RATIO

A

B

TIME, IN YEARS

Northeastern Illinois

Southeastern Wisconsin

Northern Indiana

Southern Lower Peninsula of Michigan

Northeastern Wisconsin

Northern Lower Peninsula of Michigan

Upper Peninsula of Michigan

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 53

Figure 28. Indictors computed for the water-budget zones for the Lake Michigan Basin groundwater-flow 

model. A, Base-flow-Reduction Ratio for shallow aquifers. B, Demand-to-Supply Ratio (DSR) for deep aquifers.
TIME, IN YEARS

TIME, IN YEARS

0

2

4

6

8

10

12

14

1900 1920 1940 1960 1980 2000

DEMAND-TO-SUPPLY RATIO

Waukesha area

Green Bay area

Lansing area

0

2

4

6

8

10

12

14

16

1900 1920 1940 1960 1980 2000

BASEFLOW-REDUCTION RATIO

Green Bay area

Waukesha area

Lansing area

A

B

54 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 29. Indicators computed at selected pumping areas within the Lake Michigan Basin 

groundwater-flow model. A, Base-flow-Reduction Ratio for shallow aquifers. B, Demand-to-Supply 

Ratio for deep aquifers.
Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 55

Groundwater-Flow Model and 

Groundwater Availability

Analysis of groundwater-flow model results has illustrated the two major responses of the system that may constrain groundwater availability: drawdown and base-flow 

reduction. Once identified through field observations and 

described by applied groundwater-flow modeling, management decisions may be made to mitigate potential negative 

impacts of these responses. Drawdown can lead to increased 

energy costs, excessive consolidation of aquifer material 

leading to undesired land subsidence, interference between 

high-capacity wells and other users, and migration of poorquality water into the aquifer (Freeze and Cherry, 1979). Large 

base-flow reductions can adversely impact ecosystems or other 

riparian users and may raise issues of sustainability. Drawdown may be shown through maps of model results and field 

observations or indicated by high values of DSR'. Base-flow 

reduction may be shown through mass-balance results and 

the BRR'. Indicators may be helpful in summarizing technical 

information for stakeholders. 

From a management perspective, focusing the analysis on 

local watersheds within the modeled region to identify those 

that might have water-availability issues is often necessary. 

The scale of the modeling, however, precludes such an analysis on local scales. The fluxes estimated for a small number of 

grid cells will not accurately portray the hydraulic or hydrologic conditions for individual watersheds and, as discussed 

previously, many local removals and returns are not included 

in the subregional model. To address this limitation, methods to extend the subregional analysis to the local scale were 

tested within the Great Lakes Basin Pilot, and these methods 

and the results of application of the methods are discussed 

later in this report. The local-scale application also integrates 

local groundwater analysis with the surface-water analysis 

discussed in the next section.

A final use of the Lake Michigan Basin groundwater-flow 

model is as a forecasting tool to examine the potential effects 

of future changes in water use and climate. The SWB method 

was used to estimate recharge under a climate-change scenario 

generated by using an atmosphere-ocean coupled general circulation model (AOGCM) (Maurer and others, 2002; Hayhoe 

and others, 2008). The particular AOGCM used provided 

potential temperature and precipitation realizations on a daily 

basis from 1960 to 2099. The data output from the AOGCM 

reflects potential conditions under an assumed scenario of high 

global greenhouse gas emissions (A1fi scenario) (Hayhoe and 

others, 2008). For the long stress periods relevant to this subregional model, the changes in recharge are not very large, and 

changes to the system would be akin to the changes observed 

in the original 13-stress-period simulation. If recharge is 

varied slightly, the stream base flow received from the aquifer 

responds fairly quickly, and there is a slight adjustment in 

the source of water to wells. Climate-change simulations 

appear to be more relevant in the model domain when local 

stream response on shorter time scales is considered. Such 

simulations are presented later in this report where local-scale 

issues are discussed.

Two different projections were simulated. The first is a 

“no future growth scenario,” and it is referred to as a “staycast.” This scenario is used to simulate how the system will 

continue to change if 2005 conditions stay constant, and it 

serves as a useful baseline because accurate predictions of 

future water use are quite difficult. The staycast shows the 

potential for the delay in response of the aquifer to pumping 

as the system shifts from change in storage to capture, and 

it illustrates how long it could take for the system to reach 

equilibrium with current imposed conditions. Future water-use 

projections, referred to as “forecasts”, were developed for the 

model region independent of effects of climate variability or 

change. These projections were assembled by using information from local and regional planning agencies (Buchwald and 

others, 2010). The water-use projections were used to develop 

two new stress periods, 2006–20 and 2021–40, and the model 

was used to forecast the response of the groundwater system 

to the projected water use. The recharge used in the both the 

staycast and forecast simulations was the same as used for 

the models for the last two model stress periods (1991–2005), 

thereby omitting climate change as a driver on the system.

Model results for both the staycast and the forecast 

indicate recovery in parts of the different aquifer systems 

but additional drawdown elsewhere. Changes in the shallow 

system are fairly small, 10 ft or less, for the whole model 

domain (fig. 30). Changes in the deep bedrock aquifer system 

are greater and more coherent compared to the changes in the 

shallow, Quaternary system (fig. 31). In the staycast simulations, water levels in the deep bedrock aquifer system are 

predicted to recover in the Chicago/Milwaukee area of the 

model because 2005 pumping stress in this area of the model 

is less than the maximum withdrawals imposed before 2000. 

Some drawdown is predicted in the deep bedrock aquifer 

system on the eastern side of Lake Michigan in the staycast. 

In the forecast, however, future use in Wisconsin from the 

deep bedrock aquifer system was predicted to decrease or stay 

at 2005 conditions, but use in Illinois southwest of Chicago 

was predicted to increase from 2005 levels. These water-use 

projections lead to forecasted water levels that recover in Wisconsin and decrease in both Illinois and Michigan. In the deep 

bedrock aquifer system, the predicted recovery or drawdown 

is much larger than for the Quaternary system, and forecasted 

changes for this system exceed 100 ft on the western side of 

Lake Michigan.

Surface Water

The surface-water characteristic of primary interest in 

the Great Lakes Basin pilot study was streamflow, which is 

a major component of regional water budgets for the Great 

Lakes (tables 3 and 4; fig. 17) and a critical factor in assessing 

water availability on subregional or local scales. Streamflow 

is commonly characterized by use of a streamflow statistic, 
N_IND

SLP_M

NLP_M

UP_M

NE_W

SE_WI

NE_ILL

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

0 50 100 KILOMETERS

0 50 100 MILES

EXPLANATION

Base from U.S. Geological Survey digital data 1:100,000 1983. 

Universal Transverse Mercator projection Zone 16, Standard Parallel 0° (Equator), 

Central Meridian 87° W, North American Datum 1983

Model nearfield

Lake Michigan boundary

Lake Michigan drainage

basin boundary

Drawup (ft)

Layer 1 QRNR

1,000.0

100.0

10.0

1.0

STAYCAST

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

Drawdown (ft)

Layer 1 QRNR

1,000.0

100.0

10.0

1.0

STAYCAST

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

Drawup (ft)

Layer 1 QRNR

1,000.0

100.0

10.0

1.0

FORECAST

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

Drawdown (ft)

Layer 1 QRNR

1,000.0

100.0

10.0

1.0

FORECAST

N_IND

SLP_M

NLP_M

UP_M

NE_W

SE_WI

NE_ILL

N_IND

SLP_M

NLP_M

UP_M

NE_W

SE_WI

NE_ILL

N_IND

SLP_M

NLP_M

UP_M

NE_W

SE_WI

NE_ILL

LAKE MICHIGAN

LAKE MICHIGAN

LAKE MICHIGAN

LAKE MICHIGAN

56 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 30. Staycast and forecast simulations for 2005–40 showing recovery and drawdown in the Quaternary aquifer system, 

in feet, in response to continued pumping at 2005 rates (staycast) and projected pumping rates for 2005–40 (forecast) (from 

Buchwald and others, 2010).
N_IND

SLP_M

NLP_M

UP_M

NE_W

SE_WI

NE_ILL

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

0 50 100 KILOMETERS

0 50 100 MILES

EXPLANATION

Base from U.S. Geological Survey digital data 1:100,000 1983. 

Universal Transverse Mercator projection Zone 16, Standard Parallel 0° (Equator), 

Central Meridian 87° W, North American Datum 1983

Model nearfield

Lake Michigan boundary

Lake Michigan drainage

basin boundary

Drawup (ft)

Layer 17 IRGA

1,000.0

100.0

10.0

1.0

STAYCAST

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

Drawdown (ft)

Layer 17 IRGA

1,000.0

100.0

10.0

1.0

STAYCAST

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

Drawup (ft)

Layer 17 IRGA

1,000.0

100.0

10.0

1.0

FORECAST

41°

46°

89° 87° 85° 83°

 45°

44°

43°

42°

Drawdown (ft)

Layer 17 IRGA

1,000.0

100.0

10.0

1.0

FORECAST

N_IND

SLP_M

NLP_M

UP_M

NE_W

SE_WI

NE_ILL

N_IND

SLP_M

NLP_M

UP_M

NE_W

SE_WI

NE_ILL

N_IND

SLP_M

NLP_M

UP_M

NE_W

SE_WI

NE_ILL

LAKE MICHIGAN

LAKE MICHIGAN

LAKE MICHIGAN

LAKE MICHIGAN

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 57

Figure 31. Staycast and forecast simulations for 2005–40 showing recovery and drawdown in the Cambrian-Ordovician aquifer 

system, in feet, in response to continued pumping at 2005 rates (staycast) and projected pumping rates for 2005–40 (forecast) 

(from Buchwald and others, 2010).
AFINCH Design

Varies Annually

Varies Monthly

National Land

Cover Dataset

PRISM

Climatic Data

Gaging Station

Streamflow Data

AFINCH Climate Change

by Regression

Indicators

Monthly runoff

in catchments

USGS

WaterWatch

Monthly flows

in reaches

Trends and 

flow duration

Water Use Data

NHDPlus and

Gaging Station

Network Design

58 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

such as monthly mean flow. The difficulty with a streamflow 

statistic for this study, however, is that a summary statistic 

fails to characterize the temporal variability in the streamflow 

resource. In this analysis, therefore, streamflow is characterized by a time series of monthly flow estimates rather than a 

summary statistic. For water-availability studies, flow estimates are needed to define not only the desired ecological 

flows at all reaches but also the quantity of water available to 

attain these ecological flows (Poff and others, 1997; Arthington and others, 2006; The Nature Conservancy, 2008).

Under the Great Lakes Basin Pilot, a new method was 

developed to estimate monthly streamflow and water yields. 

The new method, Analysis of Flows In Networks of CHannels 

(AFINCH; Holtschlag, 2009) produces estimates of monthly 

flows in reach segments and water yields from catchments 

defined by the National Hydrography Dataset (NHD) with 

value-added attributes through the NHDPlus suite of data 

(Bondelid and others, 2006). NHDPlus reach segments average about 1 mi in length, and catchment areas average about 

1 mi2. Water yield is defined as the incremental flow in a 

reach segment divided by the local drainage area. Yields are 

used because drainage area explains much of the variation in 

streamflow: streams with larger drainage areas tend to have 

higher flows. To explain more of the variability in streamflow 

in the region and to link landscape characteristics such as land 

use, land cover, slope or soils to flows, the observed flow in a 

reach segment is divided by its drainage area and the resulting 

yield is correlated to landscape characteristics. 

In AFINCH, water yields are estimated by user-defined 

multiple-regression equations on the basis of measured 

flows at streamgages and monthly climatic data and land-use 

characteristics. One important feature of AFINCH is that the 

measured flows may be adjusted for water use if detailed 

water-use data are available for the area of interest. Estimated 

water yields are multiplied by corresponding catchment areas 

to compute estimated streamflows, and these streamflows are 

accumulated downstream through the NHDPlus network. Estimated flows at streamgages are constrained to match measured 

flows by adjusting upstream estimates of water yields. Flows 

are conserved within AFINCH, and AFINCH also automatically adapts to annual changes in the active streamgage 

network. AFINCH integrates monthly streamflow, water-use, 

and climatic data with land-use data. Annual changes in the 

set of active streamgages and the subsequent alterations in 

the incremental areas and land-use characteristics assigned 

to each gage and land are incorporated (fig. 32). In the initial 

development of AFINCH, monthly streamflow data were 

obtained from USGS streamgages, and monthly climatic data 

were obtained from PRISM (Parameter-elevation Regressions 

on Independent Slopes Model) dataset (Daly and others, 2002; 

Figure 32. Schematic of AFINCH data sources and analysis results.
Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 59

see also http://www.prism.oregonstate.edu/). Land-use characteristics, based on the 1992 National Land Cover Database 

(NLCD), were used for development and initial testing (Vogelmann and others, 2001; see also http://landcover.usgs.gov). 

Limited water-use data were available for the area of study. 

Streamgages in a monitoring network commonly measure flows that have been measured previously at one or more 

upstream gages. This remeasurement creates a spatial correlation structure that is not consistent with the independence 

among response variables that is assumed in multiple-regression analysis. To reduce this dependence among monthly 

flows at streamgages, incremental flows and drainage areas 

are computed. Incremental flows represent the change in flow 

that occurred since it was last measured at upstream gages. 

Incremental flows at the most upstream gage in a monitoring 

network equals the total measured flow. Similarly, incremental drainage areas represent the total drainage area minus the 

drainage areas of any upstream gages. 

Within AFINCH, measured monthly flows at streamgages 

may be adjusted by specified monthly water-use information at 

upstream reach segments before the monthly regression equations are developed. Specified monthly water withdrawals are 

added to measured flows at downstream gages to better reflect 

natural flows. Similarly, specified flow augmentations, such 

as interbasin transfers to a stream or wastewater discharges, 

are subtracted from measured flows at downstream gages. 

Measured monthly flows at streamgages are termed “apparent 

flows” in AFINCH; measured flows that have been adjusted on 

the basis of specified water-use data to better represent natural 

flow conditions are referred to as “adjusted flows.” 

Monthly water yields, derived from streamflow data, 

were related to monthly climatic and land-use data through 

a set of annual multiple-regression equations to produce 

estimates of monthly water yields from NHDPlus catchments. 

The time series of annual regression parameter estimates 

provides a basis for assessing possible changes in responses 

between individual explanatory variables and water yields, 

which may be associated with climate change or variability. 

Monthly water-yield estimates are computed for each catchment on the basis of the annual regression equations and then 

multiplied by the corresponding drainage areas to estimate 

monthly flows. Flows are accumulated downstream from 

catchments to estimate streamflow in all stream segments 

defined within NHDPlus. At stream segments with active 

streamgages, upstream estimated water yields are adjusted so 

that resultant flows match measured flows. 

In addition to estimation of water yields and flows during 

periods of streamflow measurement, AFINCH can be used for 

prediction. Monthly water yields can be predicted by use of 

predicted climate variables that are specified in the regression 

equations by assuming that the water-yield response to land 

use, and land-use characteristics themselves, are invariant with 

time. This assumption, however, is difficult to substantiate, 

so the resulting predicted yields and flows may have limited 

utility as predicted climatic variables diverge from observed 

climatic conditions. 

The methods developed were applied only to a subregion 

of the Great Lakes Basin because AFINCH requires that the 

NHDPlus datasets accurately route flow through the stream 

network. A small percentage of the network required editing; 

however, complete editing of the entire basin was beyond the 

scope of the project. Application development, rather than 

implementation, was stressed in this aspect of the Great Lakes 

Basin Pilot. The hydrologic subregion used in the example 

application was 0405 (fig. 33), and results from this subregion 

are used to illustrate use of AFINCH.

The AFINCH computer program includes visualization 

tools to help the analyst identify anomalies in water yields 

(for details, see Holtschlag, 2009). In particular, apparent 

incremental monthly water yields are plotted by year for each 

month and streamgage in the analysis to help the user identify 

anomalies that might be related to unspecified water-use or 

streamflow data error. In figure 34, the atypically low water 

yields at streamgage 04106400 (West Fork Portage Creek at 

Kalamazoo, Mich.) in 2000 shown by the solid white color for 

the months of March through June indicates that the stream is 

either losing water or not gaining water at nearly the same rate 

at other parts of the basin. Because streams do not commonly 

lose water in Michigan from natural causes, and because this 

gage data pattern does not match the seasonal patterns for the 

other gages shown in the figure, this anomaly may indicate 

unspecified water withdrawals in the area gaged by 04106400. 

AFINCH provides an interactive environment for 

specifying explanatory variables in regression equations for 

estimating adjusted monthly water yields. When the analyst is 

satisfied with the form of the regression, AFINCH computes 

constrained and unconstrained estimates of water yields for 

all catchments and flows in all reach segments defined within 

NHDPlus within the specified period of analysis. The results 

of these analyses are written to output files, which can be analyzed further within AFINCH or with other applications. 

Estimated hydrographs based on monthly median values 

can be generated for any NHDPlus reach segment (fig. 35). 

For the segment identified by reachcode 04050001000590, 

low flows are noted in water years 1984, 1988, 1996, and 

1999, and high flows noted for water years 1985 and 1986. 

The length of the hydrograph is determined by the period of 

analysis specified by the AFINCH user. These hydrographs 

may be used directly in assessing flow in the selected reach 

segment, or the time series of monthly data may be further 

evaluated within AFINCH to examine the statistical characteristics of the hydrograph.

Monthly flow-duration curves show the likelihood that 

flows of various magnitudes will be equaled or exceeded 

(fig. 36). Monthly flow-duration curves have a similar shape as 

daily flow-duration curves, which are commonly used in flowduration analyses, except near the upper and lower limits of 

the flow-duration curve. In this case, AFINCH estimates fill in 

the duration curve for a streamgage that operated during only 

part of the analysis period of water years 1971–2000.

AFINCH-estimated water yield may be mapped to visualize the distribution of water yields for the area of interest 
04119000

04118500

04117500

04117000

04116000

04115265

04115000

04114000

04113000

04112500

04112000

04111500

04111000

04109000

04108800

04108600

04106400

04106320

04105700

04105000

04104945

04103010

04102776

04102700

04102500

04101800

04101500

04101000

04100500

04100377 04100295

04100252

04100222

04099850

04099510

04099000

04097540

04097500

04096515

04096405

Location of reachcode

04050001000590

EXPLANATION

USGS streamgage

Streamgages Identified in other figures

04106400

04117000

Stream reaches used in estimation

Hydrologic subregion 0405 boundaries

86°

86°

85°

85°

84°

84°

43°

42°

0 25 50 MILES

0 25 50 KILOMETERS

Lake Michigan

60 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 33. NHDPlus stream reaches and USGS streamgage locations in hydrologic subregion 0405 used in AFINCH estimation. 

Locations of streamgages and ungaged stream segment referenced in examples are noted.
MONTH, IN WATER YEAR SEQUENCE

USGS STREAMGAGING STATION NUMBER, IN DOWNSTREAM ORDER

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sep

04096405

04096515

04097500

04097540

04099000

04099510

04099750

04099808

04099850

04100222

04100252

04100295

04100377

04100500

04101000

04101500

04101800

04102500

04102700

04102776

04103010

04104945

04105000

04105500

04105700

04106000

04106320

04106400

04108600

04108800

04109000

04111000

04111500

04112000

04112500

04113000

04114000

04115000

04115265

04116000

04117000

04117500

04118500

04119000

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

WATER YIELD, IN AREA INCHES

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 61

Figure 34. Apparent incremental yield at streamgages within subregion 0405 (graph allows AFINCH user to identify potential 

anomalies in the regression and focus analysis to discover the reason for the anomalies; from Holtschlag, 2009).
1000

900

800

700

600

500

ESTIMATED MEDIAN MONTHLY FLOW, IN CUBIC FEET PER SECOND

400

300

200

100

1975 1980 1985

TIME, IN YEARS

1990 1995

reachcode = 04050001000590

2000

62 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 35. Estimated monthly hydrograph for water years 1970–2000 generated with AFINCH for an ungaged stream in 

hydrologic subregion 0405; reachcode = 0405001000590, flow in cubic feet per second.

(Holtschlag, 2009). As an example, constrained water yields in 

May 2000 in southern catchments tend to be lower than yields 

in the northern part of the hydrologic subregion (fig. 37). This 

yield map shows where streamflow is generated, so areas of 

high yield would be expected to have higher streamflows. 

Higher streamflows may be associated with lower stream temperatures in the summer and warmer stream temperatures in 

the winter due to the moderating effect of groundwater input 

on the stream. Water-availability decisions may depend on the 

impact of water withdrawals on ecological flows; therefore, 

knowledge of the distribution of flows in a watershed may be 

important for sound management decisions.

Accumulated monthly flows also may be mapped 

(Holtschlag, 2009). The accumulated flows for October 2003 

(fig. 38), highlight the variation of flow in the hydrologic 

subregion and the density of the stream network used in the 

estimation. Headwaters and small streams with flows less than 

5 ft3/s are common, and larger river systems, including the 

St. Joseph River, Grand River, and Kalamazoo River in the 

western part of the subregion being tested are clearly visible. 

The estimated flows for each reach discharging to a Great 

Lake may be used to compute the monthly surface-water 

runoff to the Great Lakes. Surface-water runoff to the Great 

Lakes is a major component of the regional water budget (fig. 

17; tables 3 and 4), and generating more accurate estimates of 

this part of the water budget will improve lake-level forecasting and understanding of the system. AFINCH has the 

potential to greatly improve these estimates because of the 

mass-balance constraints inherent in the approach and because 

it produces both estimates and uncertainties. Knowledge of 

estimated uncertainties in monthly flows can be incorporated 

in subsequent analysis to understand the overall uncertainty in 

the monthly mass balance for the Great Lakes. Current work 

with AFINCH is focused on editing the NHDPlus datasets for 

the Great Lakes Basin to allow for 

• application of the modeling tools, 

• study of water-use data to define data requirements and 

availability, 

• evaluation of options to incorporate miscellaneous 

measurements into the set of tools available to the user, 

and 
1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 October

STREAMFLOW, IN CUBIC FEET PER SECOND

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 November

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 December

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 January

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 February

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 March

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 April

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 May

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 June

1 5 10 25 50 75 90 95 99

10 0

10 1 July

1 5 10 25 50 75 90 95 99

10 0

10 1

10 2 August

PERCENTAGE OF TIME STREAMFLOW WAS EQUALLED OR EXCEEDED

1 5 10 25 50 75 90 95 99

10 0

10 1 September

EXPLANATION

Estimated streamflow

Measured streamflow

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 63

Figure 36. Monthly flow-duration curves for water years 1971–2000 with measured streamflows for water years 1971–75 and 

1995–2000 at USGS streamgage 04117000, Quaker Brook near Nashville, Mich. (from Holtschlag, 2009).

• refinement of temporal aspects of the regression methods to allow the system to consider information gained 

by gages that are active at times other than the current 

month of interest.

Water Withdrawals and Water Use

Just as the use of general consumptive-use coefficients 

for broad sectors may not yield accurate estimates of consumptive water use, the practice of considering only annual 

average use or water withdrawals may not be adequate to 

support water-resources management decisions. Data were 

available from various sectors for monthly water withdrawals 

and return flows three states that are partly in the Great Lakes 

Basin—Ohio, Indiana, and Wisconsin. These data were evaluated to determine the monthly variation in water withdrawal 

and consumptive use. In addition to monthly variation, the 

water-withdrawal trends were compared between sectors and 

between states (Shaffer, 2009). 

All water-withdrawal sectors examined by Shaffer (2009) 

exhibited variations in monthly withdrawals and consumptive 

use (fig. 39A–F ). As expected, the largest percentage change 

in withdrawal during the year was for irrigation, with most 

withdrawals occurring in the summer and very little for the 

rest of the year (fig. 39A–E ). The consistency of the trend of 
04108800

#

# # #

#

#

#

#

#

#

#

#

#

#

#

#

#

#

# ##

#

#

#

##

#

#

#

#

#

#

# #

#

# #

#

# #

#

#

#

#

Active

streamgage

86°W 85°W 84°W

43°N

42°N

41°N

EXPLANATION

0.00−0.50

0.51−1.00

1.01−1.50

1.51−2.00

2.01−2.50

2.51−3.00

3.01−3.50

3.51−4.00

4.01−4.50

4.51−5.00

5.01−5.50

5.51−6.00

0 12.5 25 50 MILES

0 25 50 KILOMETERS

Water yield, in inches

64 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 37. Constrained estimates of water yield for watersheds from the NHDPlus dataset for hydrologic 

subregion 0405 for May 2000, developed by using AFINCH (from Holtschlag, 2009).
#

# # #

#

#

#

#

#

#

#

#

#

# #

#

#

#

# ##

#

#

#

##

#

#

#

#

#

#

# #

#

# #

#

# #

#

#

#

#

86°W 85°W 84°W

43°N

42°N

41°N

0 12.5 25 50 MILES

0 25 50 KILOMETERS

0.00−0.10

0.10−0.25

0.25−1.00

1.0−2.5

2.5−10.0

10.0−25.0

25−100

100−250

250−1,000

1,000−2,500

2,500−10,000

10,000−25,000

EXPLANATION

Streamgage

Streamflow, in cubic feet per second

Subregional Water-Availability Analysis Within the U.S. Great Lakes Basin 65

Figure 38. Constrained estimates of accumulated flows for stream segments in hydrologic subregion 0405 for 

October 2003, developed by using AFINCH (from Holtschlag, 2009).
0

2,000

4,0006,0008,000

10,00012,00014,00016,00018,00020,000

Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec.

WATER WITHDRAWAL IN MGAL/D FOR OHIO AND INDIANA 

TIME, IN MONTHS 

Figure 39. Average monthly water withdrawals for water-use sectors for Ohio and Indiana, 1999–2005, in million gallons per day. A, All se
TIME, IN MONTHS 

0

500

1,0001,500

2,0002,5003,0003,5004,000

Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec.

WATER WITHDRAWAL IN MGAL/D FOR OHIO AND INDIANA

Figure 39. Average monthly water withdrawals for water-use sectors for Ohio and Indiana, 1999–2005, in million gallons per day. B, Withdrapower generation excluded.
TIME, IN MONTHS 

-2,000-1,500-1,000

-500

0

500

1,0001,5002,0002,5003,000

Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec.

CHANGE FROM ANNUAL AVERAGE IN MGAL/D

CHANGE FROM ANNUAL AVERAGE IN MGAL/D

Figure 39. Average monthly water withdrawals for water-use sectors for Ohio and Indiana, 1999–2005, in million gallons per day. C, Withdra

difference from annual average, in million gallons per day. 
TIME, IN MONTHS 

-300-200-100

0

100200300400500

Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec

CHANGE FROM ANNUAL AVERAGE IN MGAL/D

Figure 39. Average monthly water withdrawals for water-use sectors for Ohio and Indiana, 1999–2005, in million gallons per day. D, Differfor each sector, excluding withdrawals for thermoelectric power. 
TIME, IN MONTHS 

-150.0-100.0

-50.0

0.0

50.0

100.0150.0200.0250.0300.0350.0

Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec

PERCENTCHANGEFROMANNUALAVERAGE

Figure 39. Average monthly water withdrawals for water-use sectors for Ohio and Indiana, 1999–2005, in million gallons per day. E, Difference fexpressed as percent of annual average.
TIME, IN MONTHS 

-50.0-40.0-30.0-20.0-10.0

0.0

10.020.030.040.0

Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec.

PERCENT CHANGE FROM ANNUAL AVERAGE

Figure 39. Average monthly water withdrawals for water-use sectors for Ohio and Indiana, 1999–2005, in million gallons per day. F, Difference frexpressed as percent of annual average excluding irrigation sectors.
60

55

50

45

40

35

TOTAL WITHDRAWALS, IN CUBIC FEET PER SECOND

MONTHLY MEAN FLOW, IN CUBIC FEET PER SECOND

TIME, IN YEARS

Aug 2004 Aug 2005 Aug 2006

0 500 1500

AUG

SEP

AUG

APR

JULY

JULY

JUNE

JAN

JULY MAY

APR

JAN

JUNE

MAR

MAR

MAR MAY

JAN

MAY

FEB FEB

DEC

DEC

APR

NOV

FEB DEC

NOV NOV

OCT

OCT

OCT

SEP

SEP

AUG

JUNE

1000 2000 2500 3000

TOTAL WITHDRAWALS, IN CUBIC FEET PER SECOND/

MEAN FLOW, IN CUBIC FEET PER SECOND

30

0.10

0.05

0.00

0.25

0.20

0.15

72 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 40. Monthly municipal water withdrawals for Lansing, Mich., during 2004–6 (expressed as an average rate in cubic feet per 

second) and monthly mean flow from USGS streamgage 04113000, Grand River at Lansing, Mich. (in cubic feet per second).

increased withdrawal in summer and decreased withdrawals for the rest of the year, however, is much stronger than 

expected across all sectors (fig. 39C, D, F ). The only sector 

that does not show this strong yearly variation is aquaculture, which is a small contributor to the total withdrawals 

(fig. 39B, D). Water withdrawals for thermoelectric power 

generation increased the most in terms of withdrawal rate 

among all categories during the summer months, but, because 

this is the largest water withdrawal, the corresponding percentage increase was less than 20 percent (fig. 39E). In absolute 

terms, the amount of increase of public-supply and industrial 

water withdrawals were close to the increase for irrigation 

supply (fig. 39B). Because of the large amount of withdrawals, however, the percentage change for these sectors was 

smaller (fig. 39E, F): public-supply withdrawals increased 

by 10–12 percent from the annual average during the summer months, and industrial water withdrawals increased by as 

much as 10 percent of the annual average. 

Higher water withdrawals shown in figure 39 typically 

occur during periods when natural streamflows are below 

the annual average. This pattern is illustrated by examining monthly municipal water withdrawals for 2004–6 for 

Lansing, Mich. (Carol Luukkonen, U.S. Geological Survey, 

written commun., 2010), and the flow measured at the USGS 
Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin 73

streamgage on the Grand River at Lansing (station 04113000) 

(fig. 40). Monthly withdrawal, expressed as an average rate, 

varied by less than 30 ft3/s, whereas monthly flow at the 

Grand River streamgage varied more than 2,000 ft3/s during 

the 3-year period—an indication that increased withdrawals are not causing the observed decrease in flow. At this 

streamgage, and for most streamgages in the region, flows 

tend to be low and withdrawals tend to be high during late 

summer and early fall. If the impact of withdrawals on 

streamflow at a particular gage was potentially significant, 

considering only annual averages in both streamflow and use 

could greatly underestimate the effect of water withdrawals 

on streams. Because the effect of withdrawals on streamflow 

or stream ecosystems may be a water-availability constraint, 

the dynamics of the system should be well quantified. Ideally, 

water withdrawal and return information would be incorporated into water-resources analysis with tools such as AFINCH 

to analyze the human-affected hydrology of the system; that 

is, the flows through pipes, reservoirs, irrigation-distribution 

systems, and water and wastewater-treatment plants could be 

considered in the analysis of the hydrology of an area. These 

flows could be treated more like parts of the local hydrologic 

system to achieve a more comprehensive view of the hydrology and the role of humans in the hydrologic system.

Local-Scale Water Availability 

Analysis Within the 

U.S. Great Lakes Basin

In this section of the report, aspects of water-availability 

studies are combined to illustrate a more comprehensive 

water-availability analysis at the local scale. At this local 

scale, the potential effect of new groundwater withdrawal on 

streamflow is analyzed. This analysis combines groundwater 

and surface-water aspects of the pilot study. Using the same 

local-scale example, the sensitivity of the water resources to 

climate change within the Great Lakes Basin is analyzed by 

use of the models developed in this project and one potential 

scenario generated by a global climate models (GCM). Techniques for network analysis based on the groundwater-flow 

and surface-water-characteristics models developed in this 

project also are presented.

Inset Groundwater-Flow Model Integrating 

Groundwater and Surface-Water Availability

Regional officials and the public are interested in groundwater/surface-water interaction and the potential interaction 

between pumping wells and streamflow depletion (Reeves 

and others, 2009). To illustrate how regional or subregional 

groundwater-flow models may be used to help gain insight on 

this question, a refined, or inset, groundwater-flow model was 

developed for part of the Lake Michigan Basin groundwaterflow model. This inset model allows for simulation of groundwater flow at much finer spatial and temporal scales. Several 

factors motivated the development of the inset model: (1) the 

smallest cell size of the Lake Michigan Basin groundwaterflow model, 5,000 ft on a side, is too large to resolve individual streams that may be affected by groundwater withdrawals, 

(2) the large cell size of the subregional model also prevents 

resolution of the position of individual wells, and (3) the cell 

size is much larger than would be required to accurately model 

the flow between groundwater and surface-water features 

(Haitjema and others, 2001; Feinstein and others, 2010). 

The appropriate cell size within MODFLOW to accurately simulate flow between groundwater and surface-water 

systems was investigated by Haitjema and others (2001). The 

authors developed a “characteristic length” that can be used 

to relate aquifer and streambed properties and also to serve as 

a guidance for cell size (Haitjema and others, 2001; Hunt and 

others, 2003). For accurate representation of the flow between 

a surface-water body and the aquifer where gradients in head 

may be large, the cell size for a finite-difference model for 

groundwater flow should be about one-tenth of the characteristic length; and in areas of less variation, the cell size should 

be approximately one characteristic length. The characteristic 

length may be written as

λ = Tc (7)

Here,

λ is the characteristic length, L,

T is the transmissivity of the aquifer, L2/T,

c is a characteristic stream resistance, T, given by 

d/K, where

d is the streambed thickness, L, and

K is the hydraulic conductivity of the streambed 

materials, L/T.

Evaluating a representative characteristic length for the 

subregional groundwater-flow model yields values on the 

order of 1,000 ft, and for accurate representation of streamflow depletion caused by groundwater pumping, the inset 

model was designed to have cell sizes on the order of 0.1λ. 

Cells of this size also help resolve geometry issues and allow 

simulation of wells within hundreds of feet from streams 

(see Feinstein and others, 2010, appendix 2).

The inset model is located in the Lower Peninsula of 

Michigan, in a headwater region near the Lake Michigan 

Basin surface-water divide (fig. 41). The inset model was 

constructed in two steps. First, an intermediate model approximately 450 mi2

 was extracted from the Lake Michigan Basin 

groundwater-flow model. The cell size for the intermediate 

model is 500 ft by 500 ft, and it was extracted by applying 

Telescopic Mesh Refinement (Leake and Claar, 1999) to a 

23-cell by 22-cell part of the subregional MODFLOW model 
Wisconsin

Illinois

Michigan

Indiana Ohio

Lake Superior

Lake Huron

Lake St. Clair

Lake Michigan

LakeErie

Michigan

90° 87° 84°

48°45°42°

0 100 200 MILES0 100 200 KILOMETERS

Stream networkLake Michigan BasinReginal model extentIntermediate model extentLocal model extentPumping center

EXPLANATION

0 5 

0 5 

Figure 41. Inset-model overview showing subregional, intermediate, and local-scale model areas.
Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin 75

discussed previously (Hoard, 2010; Feinstein and others, 

2010; Hoard, 2010). In the second step, a local model with 

an area of approximately 21 mi2 discretized into 71 ft by 71 ft 

cells was developed within the intermediate model. Sharednode Local Grid Refinement (LGR) (Mehl and Hill, 2005) on 

a 50-cell by 50-cell intermediate-model grid, equivalent to 

5-cell by 5-cell grid from the original subregional model, was 

used to construct the local model (Hoard, 2010).

The geometry and characteristics of the surface-water 

network and topography of the land surface were the major 

changes in input for the intermediate and local models. Details 

of how these models were extracted from the subregional 

model are presented by Hoard (2010). Briefly, for the intermediate model, the top and bottom elevations of the finitedifference cells were smoothed to eliminate blocky transitions 

at the original cell boundaries within the intermediate model 

domain. The top elevation of layer 1, which represents the 

land surface, was recomputed by averaging values from the 

30-m digital elevation model (DEM) (U.S. Geological Survey, 

2001). The surface elevations and stream topography were 

checked and smoothed to ensure that the streams stayed in the 

topographic channels in the 30-m DEM. A similar process was 

used for cell tops and bottoms, top elevation of layer 1, and 

stream geometry when the local model was extracted from the 

intermediate model (except in this case, the cell size was less 

than the 30-m DEM, and, therefore, the nearest elevation value 

from the DEM was assigned to each finite-difference cell). 

The representation of the stream geometry improves 

dramatically from the subregional model to the local mode 

(fig. 42), and this more accurate representation allows for 

simulation of groundwater/surface-water interaction for a 

single well and stream. The refinement of the streams also 

improved the simulation of the shallow groundwater system 

in the local model compared to the subregional model. In the 

subregional model, many cells in layer 1 include a surfacewater feature. This limits the ability of the subregional model 

to simulate the shallow groundwater system because groundwater levels in the uppermost active layer will be strongly 

tied to the boundary conditions imposed by the surface-water 

features. (For more discussion of this limitation, see Feinstein 

and others, 2010.) In the subregional model, approximately 

64 percent of the cells have surface-water features within the 

area of the local model; in the intermediate model, for this 

same area, approximately 14 percent of the cells are surfacewater features; and for the local model, only 2.3 percent of the 

cells represent surface water-features. 

In addition to refined geometry, a more detailed algorithm, the Stream-Flow Routing package (SFR1) (Prudic and 

others, 2004), was used to simulate the streams within the 

intermediate and local models compared to the algorithm used 

in the subregional model (River package). The SFR1 package 

was chosen because it routes flow through the streams and 

therefore explicitly simulates stream/groundwater interaction. The inputs required to use this package are an ordered 

stream network, streambed conductance, streambed elevation, 

and stream geometry. An ordered stream network provides 

an accounting of the connections between individual stream 

segments, which are assigned by the user, so that flow may 

be routed through the system. Streamflow routing between 

the intermediate and local models was accomplished with a 

beta version of LGR (Steffen Mehl, U.S. Geological Survey, 

written commun., 2008). To implement this version of the 

LGR, stream segments that cross the boundary between the 

intermediate and the local model had to be split at the local 

model boundary. An additional challenge in using the SFR1 

package for this application, beyond resolving the topography 

and stream geometry, was that flow in the stream had to be 

assigned for any stream flowing into the intermediate model 

from the subregional model.

To determine the flow in the streams crossing into the 

intermediate model, the AFINCH application discussed previously was used. The flow for gaged and ungaged streams in 

the network was computed by using AFINCH, and monthly 

flows for each simulation were assigned as inflows for the 

crossing streams to the intermediate model. Because the same 

base datasets were used to develop the constrained regression within AFINCH and the input to the intermediate and 

local models, the estimated flows from AFINCH did not have 

to be extensively processed to be used for the SFR1 input. 

The procedure for generating the SFR1 package for the local 

model was the same as that for the intermediate model except 

that starting flows were not assigned to streams that originate 

outside the local model boundary because that flow was being 

routed from the intermediate model to the local model through 

LGR (Hoard, 2010). 

Monthly simulation periods or “stress periods,” as 

defined previously, were used for the inset-model simulations 

to better illustrate temporal dynamics of the system compared 

to stress periods in the subregional model on the order of 

5 years or more. The Soil-Water-Balance (SWB) (Westenbroek and others, 2010) approach used to estimate recharge 

for the subregional model was applied to the intermediate and 

local grids, and the daily values from the SWB were averaged to produce average monthly recharge values that are held 

constant for each stress period. To ensure consistency between 

streamflow and groundwater recharge, the same monthly 

precipitation values used in the SWB computation of recharge 

were used in the estimate of streamflow with the AFINCH 

program. Details on estimates of recharge to the intermediate 

and local models are given by Hoard (2010).

The local and intermediate models were used to illustrate 

three capabilities: assessment of groundwater/surface-water 

interaction, assessment of changes to the local groundwater 

system in response to climate variability, and use of local models to guide data collection in order to reduce uncertainty in 

model predictions (network analysis). The network analysis is 

discussed in the next section, after an examination of groundwater/surface-water interaction and climate change results. 
42 ̊55’30”

42 ̊58’30”

42 ̊57’00”

84 ̊52’30” 84 ̊51’00” 84 ̊49’30”

0 1 2 Miles

0 1 2 Kilometers

42 ̊55’30”

42 ̊58’30”

42 ̊57’00”

84 ̊52’30” 84 ̊51’00” 84 ̊49’30”

0 1 2 Miles

0 1 2 Kilometers

42 ̊55’30”

42 ̊58’30”

42 ̊57’00”

84 ̊52’30” 84 ̊51’00” 84 ̊49’30”

0 1 2 Miles

0 1 2 Kilometers

Intermediate model 

Local model 

Regional model 

76 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 42. Surface-water network for subregional, intermediate, and local groundwater-flow models.
Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin 77

Groundwater/Surface-Water Interaction

The local model was used to evaluate streamflow 

depletion by a high-capacity pumping well. To illustrate this 

interaction, the effect of the well on a test stream and local 

watershed to this stream is reported. The well is hypothetical, and the local model was not recalibrated to site-specific 

data after extraction from the subregional model. In practice, 

site-specific calibration of the local model is important in 

order to obtain reliable simulation results. Four test cases were 

simulated: (1) a control (or base) case where no new well is 

added, (2) placement of a high-capacity well in the glacial 

deposits simulated in layer 1 of the model, (3) placement of 

a high-capacity well in the glacial deposits simulated in layer 

2 of the model, and (4) placement of a high-capacity well in 

the bedrock aquifer simulated as layer 5 in the model. In each 

case, the well was placed 430 ft from the stream, the pumping rate assigned to the well was 71.4 gal/min, and the Gage 

package (documented in Prudic and others, 2004) was used 

to record the flow in the stream near the well (fig. 43). The 

simulation period was 1991–99, with monthly stress periods 

as noted above. The pumping in cases 2–4 started in 1991 and 

was held constant for the entire simulation; the only changes 

from one stress period to the next were the imposed recharge 

to the system and the inflows to the SFR1 streams as computed by using SWB and AFINCH.

The effect of this rather modest amount of pumping on 

streamflow is illustrated in hydrographs of base flow. Withdrawing water from layers 1, 2, or 5 lowers the estimated base 

flow, especially during low-flow period, in all cases (fig. 44). 

By subtracting the base-case computed from the other cases, 

the difference caused by the introduced well in cases 2–4 is 

produced (figs. 44–45). The well typically removes between 

10 and 100 percent of the base flow depending on the recharge 

conditions imposed during each stress period. In this case, 

well depth did not strongly change the capture of streamflow 

by the well. This type of simulation result could be used to 

evaluate effects on environmental flows by comparing them to 

the ecological requirements of the stream, including changes 

in these requirements through the year to estimated base flow 

(Richter, 2009). Further coupling with rainfall-runoff models 

(for example, Markstrom and others, 2008) could be used to 

estimate total streamflow through the year.

Streamflow depletion by the introduced pumping well 

is the important feature of the analysis, and this depletion 

also may be evaluated by examining the source of water to 

the pumping well in a similar fashion as done for the subregional model. Water budgets echo the results evident in the 

hydrographs: the well placed in either layer 1, 2, or 5 affects 

local streamflow (fig. 45). As the well is placed deeper in the 

system, the effect of the well is spread to neighboring watershed slightly because capture of water that would have entered 

the nearby stream is reduced as capture of water from lateral 

sources is increased. Water from lateral sources is water crossing the boundary of the local watershed shaded in figure 43; 

this water is primarily captured from surface-water features in 

nearby watersheds.

To illustrate the importance of local site conditions on 

streamflow capture by a pumping well, the series of simulations were repeated with a layer of low hydraulic conductivity 

introduced to the system. For this second set of simulations, 

the hydraulic conductivity of layer 4 was reduced approximately 4 orders of magnitude to 2.8 × 10–5 ft/d. The effects 

of this low-hydraulic-conductivity layer are to increase the 

proportion of water captured from the stream when the well is 

placed in the shallow system (layers 1 and 2) and to decrease 

the proportion of the water captured from the stream when 

the well is placed in layer 5 (fig. 46). The low-conductivity 

layer was added to reduce the hydraulic connection between 

the bedrock aquifer (layer 5) and the shallow aquifer system and headwater stream. At the scale of the subregional 

model, such a thin low-conductivity layer would be hard to 

identify, calibrate, or justify; but, on the local scale, this low 

layer is important to the assessment of the potential impact of 

the water withdrawal on ecological flows in this headwater 

stream. The subregional model serves as a good platform to 

build the local-scale models, but, these results indicate that the 

local-scale models require site-specific calibration and may 

require refinement of local aquifer properties. This observation 

is revisited in the results of the network analysis.

Response to Climate Change

Similar to the climate-change analysis at the subregional 

scale, temperature and precipitation data from an atmosphereocean coupled general circulation model (AOGCM) (Maurer 

and others, 2002; Hayhoe and others, 2008) were used to 

generate a climate-change scenario to illustrate the use of the 

inset model to study the potential effects of climate change 

on the shallow groundwater system. As before, this particular 

AOGCM provided daily temperature and precipitation realizations from 1960 to 2099 and reflected an assumed scenario of 

high global greenhouse gas emissions (A1fi scenario) (Hayhoe 

and others, 2008). 

Use of the climatic data derived from the AOGCM as 

the input to the SWB model provided a means to estimate 

future recharge and the effects global climate change may 

have on recharge (see Hoard, 2010). The SWB results were 

again averaged to produce monthly estimates of recharge 

for the local model (fig. 47). These recharge values exhibit a 

great deal of interannual variability, resulting in wide ranges 

of values for each month. Typically, there is no recharge to 

the system in the summer months in any of the three periods: 

1991–2000, 2013–22, or 2035–44. As noted in figure 47, the 

annual average recharge value increased slightly from 1991 

to 2016 and then decreased gradually. From 2024 to 2044, the 

average annual recharge computed by the SWB program with 

temperature and precipitation from the AOGCM was less than 

the annual average recharge for the set of scenarios from 1991 

through 1999.
Streamgage

Well

Test watershed

Test stream

Streams

EXPLANATION

0 0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

78 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 43. Streams in local inset model with model gage, hypothetical well, and test watershed and stream 

indicated (from Hoard, 2010).
Jan91 Jan92 Jan93 Jan94 Jan95 Jan96 Jan97 Jan98 Jan99 Jan00 0

0.5

1

1.5

2

FLOW, IN CUBIC 

FEET PER SECOND

Pumping in layer 1

StreamflowStreamflow with pumping

Jan91 Jan92 Jan93 Jan94 Jan95 Jan96 Jan97 Jan98 Jan99 Jan00

DATE

REDUCTION OF FLOW, 

IN CUBIC FEET PER SECOND

Jan91 Jan92 Jan93 Jan94 Jan95 Jan96 J

0

0.5

1

1.5

2

FLOW, IN CUBIC 

FEET PER SECOND

Pumping in layer 2

Jan91 Jan92 Jan93 Jan94 Jan95 Jan96 J

DATE

StreamflowStreamflow with pumping

Jan91 Jan92 Jan93 Jan94 Jan95 Jan96 Jan97 Jan98 Jan99 Jan00 0

0.5

1

1.5

2

FLOW, IN CUBIC 

FEET PER SECOND

Pumping in layer 5

Jan91 Jan92 Jan93 Jan94 Jan95 Jan96 Jan97 Jan98 Jan99 Jan00

DATE

StreamflowStreamflow with pumping

0

0.05

0.1

0.15

0.2

0

0.05

0.1

0.15

0.2

REDUCTION OF FLOW, 

IN CUBIC FEET PER SECOND

0.05

0.1

0.15

0.2

0 REDUCTION OF FLOW, 

IN CUBIC FEET PER SECOND

Figure 44. Hydrographs and percent-change plots fat the gaged point showing streamflow depletion cauhypothetical well from layers 1, 2, and 5 of the inset m
Well pumps 71.4 gallons per minute from layer 1

Stream source

Storage source

Lateral-flow source

Sum sources

Well pumps 71.4 gallons per minute from layer 2

-28

-14

0

14

28

42

56

69

83

1991 1992 1993 1994 1995 1996 1997 1998 1999

1991 1992 1993 1994 1995 1996 1997 1998 1999

GALLONS PER MINUTE GALLONS PER MINUTE GALLONS PER MINUTE

1991 1992 1993 1994 1995 1996 1997 1998 1999

59.11%

53.26%

50.12%

7.65%

6.51%

6.73%

43.37%

33.23%

40.01%

Well pumps 71.4 gallons per minute from layer 5

NET SOURCE OF WATER TO WELL 1991−99

EXPLANATION

ANNUAL SOURCE OF WATER TO WELL 1991−99

- 28

-14

0

14

28

42

56

69

83

- 28

-14

0

14

28

42

56

69

83

80 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 45. Source of water to the hypothetical well in layers 1, 2, and 5 of the local inset model (from Hoard, 2010; 

Mgal/d, million gallons per day).
Well pumps 71.4 gallons per minute from layer 5

Well pumps 71.4 gallons per minute from layer 1

Well pumps 71.4 gallons per minute from layer 2

NET SOURCE OF WATER TO WELL 1991−99

65%

7%

28%

60%

6%

34%

40%

5%

55%

Stream source

Storage source

Lateral-flow source

Sum sources

EXPLANATION

-20

-10

0

10

20

30

40

50

60

70

80

GALLONS PER MINUTE GALLONS PER MINUTE

1991 1992 1993 1994 1995 1996 1997 1998 1999

ANNUAL SOURCE OF WATER TO WELL 1991−99

-20

-10

0

10

20

30

40

50

60

70

80

1991 1992 1993 1994 1995 1996 1997 1998 1999

1991 1992 1993 1994 1995 1996 1997 1998 1999

GALLONS PER MINUTE

-10

0

10

20

30

40

50

60

70

80

Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin 81

Figure 46. Source of water to hypothetical well in layers 1, 2, or 5 of local inset model, with low-hydraulic-conductivity 

layer added to the model (Mgal/d, million gallons per day).
x

x

x

oo

oo

oo o o o o o

o

oo

xx

o

o

01234567

10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

x

o

10 

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

TIME, IN MONTHS

Figure 47. Seasonal distribution of recharge values from the atmosphere-ocean coupled general circulation model (AOGCM) used for the inset-scenario, by decade.
Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin 83

Monthly base-flow values computed by the inset model at 

the gage (fig. 43) mirrored the variability noted in the estimated recharge values, although base flow tends to vary less 

and have a smoother distribution across the year (fig. 48). The 

predicted increase in recharge during 2013–22 produces more 

base flow to the stream. The base flow for March approximately doubles from the 1991–99 period to the 2013–22 

period, and peak streamflow for all three time periods tends 

to occur in April. For the third time period, 2035–44, the base 

flow is much less than for either of the other two time periods, 

and, on average, the stream is dry for much of the year. These 

simulations driven by the AOGCM illustrate the sensitivity of 

the headwater stream to rather small changes in recharge. In 

periods when the long-term average recharge is higher, simulations show that base flow is maintained during dry seasons 

by release of groundwater from storage. As the long-term 

average recharge decreases, groundwater storage is depleted, 

and the aquifer cannot maintain the same base-flow levels during dry seasons.

Full analysis of the effects of climate change would 

require simulation of a suite of potential climate-change 

scenarios and consideration of potential land- and water-use 

changes. Land use and water use, however, are held constant 

for this example simulation. Potential feedback or other nonlinear effects within the system also should be considered. For 

example, under conditions of higher atmospheric CO2, plants 

may use water more efficiently and have lower water demand 

(Kamps and others, 2008; Kruijt and others, 2008). This 

secondary effect would have to be included in the SWB algorithms used to estimate recharge to the system. Longer growing seasons may allow different crops or different crop schedules. Changes in agricultural practice in response to changes 

in climate could change the timing and amount of irrigation 

demands on the groundwater system. The purpose of the simulation shown in this section was to illustrate the ability of the 

inset model to respond to small changes in recharge amounts 

and timing that would allow for more thorough analysis.

Monitoring and Network Analysis

Water-availability analysis is not possible without basic 

data on flows, storage, and processes within the system. Longterm monitoring supported every part of every aspect of the 

Great Lakes Basin Pilot: groundwater monitoring was required 

to calibrate the Lake Michigan Basin groundwater-flow 

model (Feinstein and others, 2010), surface-water monitoring 

was crucial to the development and application of AFINCH 

(Holtschlag, 2009) and the analysis of regional trends (Hodgkins and others, 2007), and water-use data were used in the 

analysis of monthly and seasonal variation (Shaffer, 2009) and 

form the basis for both actual and estimated withdrawals from 

1865 to 2005 used in the groundwater-flow model (Buchwald 

and others, 2010). The importance of long-term data is discussed by, for example, Taylor and Alley (2001) and Feinstein 

and others (2004). Water-use data collection and water-use 

estimation techniques are discussed by the National Research 

Council (2002). 

Given the importance of long-term monitoring, how 

should monitoring networks be planned and evaluated? 

“Network analysis” is used to evaluate monitoring networks, 

but this generic term may refer to many different activities. 

Most importantly, specific networks must be designed to 

answer specific questions. Likewise, specific network analyses 

must be designed to answer specific questions. For example, 

monitoring designed to measure flows in headwater streams 

and effects of development on these flows might require many 

streamgages in headwater systems, but monitoring to improve 

the estimate of water flux and contaminant loading to the 

Great Lakes might require streamgages at the river mouths 

where major streams enter the Great Lakes. When the network 

is analyzed, the purpose will have to be specified: development effects on headwaters or loading to the Great Lakes. 

Groundwater monitoring designed to observe the effects of 

climate would be quite different from groundwater monitoring 

designed to document the effects of a large pumping center. 

For more background on network-design issues—specifically, 

network design for the USGS National Streamflow Information Program, including an overview of methods and evaluation of different factors influencing network design—see the 

detailed discussion by the National Research Council (2004). 

The surface-water-characteristics model and groundwater-flow models may be used to help evaluate monitoring 

networks, quantify prediction uncertainty, and target areas 

where additional data should be collected to improve model 

estimates. Two techniques are discussed in the following 

paragraphs: a resampling bootstrap analysis using AFINCH 

to explore the design of a surface-water monitoring network 

(Koltun and Holtschlag, 2010) and a prediction-uncertainty 

based approach using the local-scale groundwater-flow model 

in which the uncertainty of model estimates are evaluated 

and the value of new observations or additional information regarding model parameters is assessed (Fienen and 

others, 2010).

Example Bootstrap Analysis for 

Surface-Water Monitoring Network

Bootstrap analysis is a type of resampling technique in 

which the same dataset used to estimate a characteristic of a 

system also is used to estimate its uncertainty. The uncertainty 

analysis involves repeated computations of the characteristic 

with subsets of the original data. The major advantage of this 

technique is that additional datasets are not required; moreover, the existing model used for the original estimate can 

be used for the bootstrap analysis without major modification. The bootstrap approach is especially good at identifying 

important components of uncertainty in the existing system. 

Its major disadvantage is that causes of uncertainty other than 

due to sample size and composition are not explored.
x

xxxx

xxx

oooo

x

xx

xxx

xxx xxxx x

xx

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

50 50 50 50 51 50 50 50 50 49 50 50

1991−2000

DISCHARGE, IN CUBIC FEET PER SECOND

xxx

Jan

Feb

Mar

Apr

May

Jun

Jul

2.01.51.00.5

0

2.5

2.01.51.00.5

0

2.5

2.01.51.00.5

0

2.5

50 50 50 50 50 50 50 

2013−202

DISCHARGE, IN CUBIC FEET PER SECOND

x

Jan

Feb

Mar

Apr

May

Jun

Jul

50 50 50 50 50 50 5

2035−2

DISCHARGE, IN CUBIC FEET PER SECOND

EXPLANATION

x

o

75th percentile

median

25th percentile

Data value between 1.5times the interquartile range and the last quartile 

Outlier data value greater than 3 times the interquartile range 

Data value between 1.5 and 3 times the interquartile range 

50 Number of samples

1991 2001 2011 2021 2031 2041

YEAR

05

1015

ANNUAL RECHARGE, IN INCHES

Annual recharge for inset model 1991−2044

Annual rechargeLOESS fit

Figure 48. Annual recharge for the inset-model climate-change scenario and base flow, by month, computed by the model for 1991–2000, 201(from Hoard, 2010).
Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin 85

A bootstrap analysis was applied to streamflow estimates developed for hydrologic subregion 0405 (Southeast 

Lake Michigan) by use of the AFINCH model (Koltun and 

Holtschlag, 2010). In the analysis, AFINCH was first run to 

compute monthly flow estimates for water years 1971–2003 

with the full set of 75 streamgages that were active for one or 

more years during this time period. To examine the effects of 

sample size and composition on estimate uncertainty, subsets 

of the gages were created by randomly censoring (removing) 

approximately 10, 20, 30, 40, 50, and 75 percent of the gages 

from the full 75-gage data set. Thirty subsets were created for 

each of the 6 censoring levels and each of those subsets was 

used to estimate monthly flows. The resulting estimates were 

used to evaluate estimate precision and accuracy as a function 

of the size and composition of the gage network operated in 

the subregion. 

Streamflow estimates for each of six flow lines (representations of stream reaches) were aggregated by censoring 

level, and results were analyzed to assess (a) how the size and 

composition of the streamflow-gaging network affected the 

average apparent errors and variability of the estimated flows 

and (b) whether results for certain months were more variable 

than for others. The six flow lines were categorized into one of 

three types depending upon their network topology and position relative to operating streamflow-gaging stations. 

Statistical analysis of the model results indicates that 

(1) less precise (that is, more variable) estimates resulted from 

smaller streamflow-gaging networks as compared to larger 

streamflow-gaging networks, (2) precision of AFINCH flow 

estimates at an ungaged flow line is improved by operation of 

one or more streamflow gages upstream and (or) downstream 

in the enclosing basin, (3) no consistent seasonal trend in estimate variability was evident, and (4) flow lines from ungaged 

basins appeared to exhibit the smallest absolute apparent percent errors (APEs) and smallest changes in average APE as a 

function of increasing censoring level. Koltun and Holtschlag 

(2010) attributed the counterintuitive results described in 

item (4) to using the estimate from the full-gage network as 

the base for comparisons and also to an insensitivity in the 

average model-derived estimates to changes in the streamflow-gaging-network size and composition. Another analysis 

demonstrated that errors for flow lines in ungaged basins have 

the potential to be much larger than indicated by their APEs if 

measured relative to their true (but unknown) flows.

“Missing gage” analyses, based on examination of 

censoring subset results where the streamflow gage of interest 

was omitted from the calibration data set, were done to better 

understand the true error characteristics for ungaged flow 

lines as a function of network size. Figure 49 shows results 

examined for 2 water years, indicating that the probability of 

computing a monthly streamflow estimate within 10 percent 

of the true value with AFINCH decreased from greater than 

0.9 at about a 10-percent network-censoring level to less than 

0.6 as the censoring level approached 75 percent. In addition, 

estimates for typically dry months tended to be characterized 

by larger percent errors than typically wetter months.

Example Model-Uncertainty Analysis Using the 

Local Groundwater-Flow Model

Estimates of uncertainty in model-prediction results are 

derived by using first-order second-moment techniques that 

combine model sensitivity and input uncertainty. (For discussion of underlying mathematics of these techniques, see 

Fienen and others, 2010.) Three approaches can be used for 

uncertainty analysis of a calibrated model: (1) observations 

can be added to the calibration dataset, (2) observations can 

be excluded from the calibration dataset, or (3) better information on model parameters can be obtained. In an analysis of 

the local-scale (inset) model (Hoard, 2010), Fienen and others 

(2010) focused on approaches 1 and 3 to examine uncertainty 

in predictions of groundwater levels and base flow to a stream. 

Base-flow prediction is especially relevant because of the 

interest in streamflow depletion by wells; further, uncertainty 

analysis can indicate where in the modeled area additional 

observations should be made or what parameters should be 

measured to reduce prediction uncertainty.

Two suites of software were examined in this study: 

OPR/PPR (Tonkin and others, 2007; 2008), which is typically 

used in conjunction with UCODE (Poeter and others, 2005), 

and PREDUNC/PREDVAR, which are part of the suite of 

PEST tools (Doherty, 2010a,b). Although different philosophical and numerical approaches characterize the two software 

suites, both can be used to estimate prediction uncertainty as 

a function of model sensitivity, sensitivity of the prediction 

to changes in the parameters and sensitivity of each observation to each parameter, and some measure of uncertainty of 

parameters and observations. 

The PEST tools were designed to facilitate inverse 

analysis if the number of parameters is larger—and often 

much larger—than the number of observations; such situations 

are sometimes referred to as “underdetermined problems.” 

Regularization is imposed for the underdetermined problems 

to allow for solution. Conversely, UCODE is designed for 

“overdetermined problems,” where the number of parameters 

is kept small, typically less than the number of observations. 

Fienen and others (2010) show that PREDUNC and OPR/PPR 

are equivalent under certain assumptions and that numerical 

efficiency may indicate the use of one or the other, depending 

upon the number of parameters and the number of observations. For either suite of tools, the analyst must specify the 

prediction of interest. For OPR or PREDUNC, potential locations for additional observations must be specified if analysis 

of the addition of observations is desired.

The subregional Lake Michigan Basin groundwater-flow 

model was developed with PEST tools but with a combination 

of approaches (Feinstein and others, 2010). Parameters were 

minimized and large zones were used for most of the model 

(overdetermined approach); however, pilot points and regularization were adopted for one geologic unit (underdetermined 

approach) (Feinstein and others, 2010). 

PREDUNC and PREDVAR were applied to three different parameterizations of the local inset groundwater-flow 
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86 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 49. Relation between censoring level and probability of estimating monthly flow within 

10 percent of measured value, from bootstrap analysis of AFINCH-generated streamflows for 

hydrologic subregion 0405 (from Koltun and Holtschlag, 2010).
Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin 87

model to illustrate use of these utilities for network analysis 

and to investigate the influence of the underlying subregional 

model structure on analysis of the local model: 

1. The simplest parameterization of the local model was to 

adopt the inset-model structure and apply simple multipliers to eight inset-model parameters: horizontal hydraulic 

conductivities of layers 1, 2, and 3; vertical hydraulic 

conductivities of layers 1, 2, and 3; recharge array; and 

streambed leakance for all streams. These multipliers 

acted on values for the entire inset model. 

2. In the second parameterization, the 25 underlying cells 

from the subregional model were treated as zones. The 

hydraulic conductivities within each zone were uniform, but a multiplier was assigned to each zone so that 

each could, potentially, be calibrated. The zones also 

individually contributed to prediction uncertainty, and 

more resolution of contribution to prediction uncertainty 

from the individual hydraulic-conductivity values was 

expected. The second approach resulted in 300 hydraulicconductivity parameters—25 horizontal and 25 vertical 

hydraulic conductivities for each of the 6 layers in the 

inset model. Stream leakance and recharge were treated 

with single multipliers in the same way as for the first 

parameterization. 

3. The final parameterization used 400 pilot points regularized by kriging for both horizontal and vertical hydraulic 

conductivity in each of the 6 layers of the inset model. 

Recharge and streambed leakage also were parameterized 

by using pilot points in the third case.

The local inset model was used to generate the test case. 

A well was placed in the second layer of the model, the extraction rate was set to 500 gal/min, and uncertainty was analyzed 

for two predictions: head in layer 1 near the well and flow 

at a streamgage on a nearby headwater stream (H115_259 

and gage 17 in fig. 50). The contribution of the parameters to 

prediction uncertainty was analyzed for the first parameterization, and the location of additional head observations to reduce 

either head or flow prediction uncertainty was explored for all 

three parameterizations.

Assessing the parameter contributions to prediction 

uncertainty allows the analyst to identify the most important 

parameters in terms of the specified prediction. Measurement 

of these parameters should reduce both parameter uncertainty 

and prediction uncertainty. In the simplest parameterization, 

multipliers on the eight parameters were considered. The 

relative pattern for each parameter remained the same, but the 

multiplier could be used to uniformly vary the parameter values. For the two predictions of interest, recharge and streambed leakance contributed the most to the prediction uncertainty 

(fig. 51). In the case of the uncertainty in the head prediction, 

recharge is the most important parameter. Estimated uncertainty depends on the uncertainty of the input parameters. In 

this case, the estimate of input-parameter uncertainty indicates 

a 90-percent confidence that the input value is within one 

order of magnitude. This is quantified by specifying a standard deviation of the log-transform value of the parameter 

to 0.25. If the uncertainty in the estimate of input recharge is 

reduced (perhaps through measurement) such that the standard 

deviation for this parameter becomes 0.0625, then the vertical 

hydraulic conductivity of layer 1 and the horizontal hydraulic 

conductivity of layer 2 become the most important parameters 

(fig. 51, right panel). These results are consistent with expectations, because the pumping well is placed in layer 2 and the 

observation of interest is in layer 1. In the case of uncertainty 

in the flow estimate at the streamgage, streambed leakance is 

the most important parameter contributing to the uncertainty 

of the flow estimate. Reduction of uncertainty in recharge does 

little to affect this observation.

An alternative to measuring a parameter, which may be 

expensive or difficult, is collection of additional head observations. Those head observations that would decrease prediction uncertainty the most can be identified by mapping the 

contribution of each potential observation to the prediction 

uncertainty (Fienen and others, 2010). For the inset-model 

analysis, candidate locations for such head observations were 

sought by using PREDUNC in combination with two grids 

of points: a coarse, 10 × 10 grid of points was used to test 

the entire local inset-model area, and a refined, 35 × 28 grid 

surrounding the pumping well and predictions of interest 

was used to focus analysis where the most benefit from head 

observations was expected (fig. 52). The effect of adding a 

new observation in either layer 1 or layer 2 was analyzed. The 

spacing of the refined grid of points could not be used across 

the entire local inset-model domain because the computations 

became intractable. 

The decrease in head and flow prediction uncertainty 

at the specified locations was computed for each candidate 

location, and the resulting values were mapped for the three 

parameterizations and for potential observations from layer 1 

or 2 (figs. 53 and 54). The most important finding of this 

analysis is the profound effect of the chosen parameterization scheme on the results obtained. For head predictions, 

the pilot-point parameterization depicted in the rightmost 

panel of figure 53 is the only one that obviously matches the 

expected outcome. The figure shows clear structure in the 

potential reduction in uncertainty, with the greatest reduction 

near the point of interest although biased slightly away from 

the stream. The bias away from the stream is more evident for 

observations in layer 2. The potential observation point with 

the highest value would be selected as a monitoring location to 

decrease the prediction uncertainty as observations were collected and incorporated through recalibration of the numerical model. The same method used with the simple-multiplier 

(“KLM”) parameterization does not clearly identify a point 

or points for additional observation: when normalized by the 

reduction in uncertainty from the pilot-point test, the reduction in uncertainty in the KLM test is small, and the locations 

are not very well isolated. The lack of spatial coherence arises 
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EXPLANATION

Flow prediction location (Layer 1)

Head prediction location (Layer 1)

Proposed pumping well location (Layer 2)

MODFLOW stream cells

Groundwater head contours, in 1.5 foot intervals

LAYER 1 LAYER 2

0 5 10 Kilometers

0 2.5 5 10 Miles

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Pumping well

Streamgage 17

H115_259

N

88 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 50. Head contours in layer 1 (left panel) and layer 2 (right panel) from the local inset model. The contour interval is 1.5 feet, 

and the locations of the pumping well (black symbol), uncertainty in head prediction (blue symbol, H115_259), and uncertainty in flow 

prediction (red symbol, Gage 17) are indicated. The pumping well is in layer 2, and the uncertainty locations are evaluated for layer 1 

(from Fienen and others, 2010).
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Local-Scale Water Availability Analysis Within the U.S. Great Lakes Basin 89

Figure 51. Relative contribution to prediction uncertainty from each parameter for A, head prediction 

and B, flow prediction within the local inset model at the locations specified in figure 50. The left-hand 

panels were computed with initial uncertainty set to 0.25 for each parameter, and the right-hand panels were 

computed with uncertainty set to 0.25 for all parameters except recharge. A reduced uncertainty for recharge 

of 0.0625 was used in the right-hand panels (from Fienen and others, 2010).

from the use of a single multiplier for hydraulic conductivity 

for the whole layer. Observations anywhere will potentially 

influence the estimates of hydraulic conductivity. The parameterization involving the 300 hydraulic-conductivity parameters 

(“300K”) is more challenging to evaluate. Unlike the KLM 

approach, the 300K parameterization allows for hydraulic 

conductivity across the domain to vary independently for the 

25 zones. Yet, the normalized plots show that the predicted 

decrease in head uncertainty in the 300K test is, again, very 

small compared to the pilot-point test. More testing would be 

required to determine the spatial-parameterization “tipping 

point” required to yield coherent results; but on the basis of 

these results, it lies somewhere between the 25-zone density 

of the 300K case and the 400-point density of the pilotpoint case.

Reduction in the flow-prediction uncertainty resulting from additional observation at the candidate locations is 

similar to that for head-prediction uncertainty (fig. 54). The 

pilot-point parameterization shows clear structure in the potential reduction and greatest reduction near the point of interest 

but, again, biased slightly away from the stream. The potential 

observation point with the highest value would be selected as 
EXPLANATION

Streamgage 17

Head prediction location (H115_259)

Pumping well

Potential observation

MODFLOW stream cells

0 5 10 KILOMETERS

0 2.5 5 10 MILES

2.5

90 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 52. Grid of candidate locations for additional head observations in prediction 

uncertainty analysis based on local inset model (from Fienen and others, 2010).

a monitoring location to decrease the flow-prediction uncertainty as observations were collected and incorporated through 

recalibration of the numerical model. The KLM and 300K 

parameterizations show the same behavior as seen previously 

for reduction of head-prediction uncertainty. And, as with the 

head-prediction analysis, more testing would be required to 

find the spatial-parameterization tipping point yielding coherent results for reduction in flow-prediction uncertainty.

Summary of Pilot Study

Beginning in 2005, water availability and use were 

assessed for the U.S. part of the Great Lakes Basin through 

the Great Lakes Basin Pilot of a USGS national assessment 

of water availability and use. The focus of this study was on 

defining the storage and dynamics of water resources and 

the human demands on water in the Great Lakes region. The 

study focused on several spatial and temporal scales, and 

highlighting the importance of scale is a key outcome of the 

project. To illustrate both the abundant regional availability 

of water and the potential for local shortages of water, the 

U.S. Geological Survey provided scientific information, data, 

and analysis to help define water resources in the region and 

quantify demands on the resources. The multiscale nature of 

the study challenges water-resource managers and the public 

to think about regional water resources in an integrated way 

and to understand how future changes to the system driven 

by water withdrawals and returns, climate variability, or 

land-use change may be accommodated by informed waterresources management. Major features of the study include 

the following:

• The regional water budget, compiled from many 

sources, was summarized and discussed to highlight 

the overall abundance of water in the Great Lakes 

region. Subregional and local studies within the pilot 

demonstrated, however, that water-availability limitations may arise in the region because of variations in 

water supply and demand in both space and time.

• Results from a groundwater-flow model of the 

Lake Michigan Basin (Feinstein and others, 2010) 

show that groundwater budgets west of Lake Michigan 

are quite different from those east of Lake Michigan. 

Pumping of the deep bedrock aquifer west of Lake 

Michigan has resulted in a large drawdown in water 

levels, has induced flow from outside the predevelopment groundwater basin into the Great Lakes Basin, 

and has captured groundwater that would have naturally discharged to Lake Michigan. The groundwaterflow system east of Lake Michigan is dominated by 

pumping wells capturing water that would have been 

discharged to inland surface water or, in places, by 

pumping wells inducing flow from inland surface 

water. Water levels have declined in areas of pumping 

east of Lake Michigan, but these declines are much 

less than those west of the lake. 
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Summary of Pilot Study 91

Figure 53. Observation uncertainty contribution for the head prediction at H115_259 for layers 1 and 2 and three different 

parameterizations of the test area, based on the local inset model (from Fienen and others, 2010).

• Local-scale analysis combining groundwater and 

surface-water modeling shows that a single pumping well can affect a nearby stream, even to the point 

of drying the stream during some of the year (Hoard, 

2010). Regional approaches cannot represent this 

level of detail, and use of streamflow estimates alone 

to quantify water availability neglects the dynamics 

of the groundwater system and its response to new 

pumping stresses. A combined approach quantifying 

both groundwater and surface-water resources, coupled 

with detailed information regarding the dynamics of 

existing water withdrawals and returns, would yield 

the most information for water-availability decisions at 

the local scale.

• Temporal trends in Great Lakes water levels (Wilcox 

and others, 2007) and streamflow and precipitation in 

the basin (Hodgkins and others, 2007) were quantified, 

revealing the dynamic nature of the regional water 

budget and the need to understand temporal changes 
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92 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

Figure 54. Observation uncertainty contribution for the flow prediction at the hypothetical streamgage for layers 1 and 2 and 

three different parameterizations of the test area, based on the local inset model (from Fienen and others, 2010).

for water-availability analysis. Variations in water 

withdrawals and flows during the year and over many 

years show that water-management decisions may have 

to be based on more than long-term annual average 

flows or withdrawals. Large withdrawals during times 

of naturally low flows may be constrained by a lack of 

water to supply the demand or by societal decisions to 

maintain flows at target values to protect the ecological 

function of a stream.

• Water withdrawals for 2005 were compiled by watershed (Mills and Sharpe, 2010) and, for much of the 

area, major groundwater withdrawals were compiled 

and estimated from 1865 through 2005 (Buchwald 

and others, 2010) for input to a groundwater-flow 

model of the Lake Michigan Basin (Feinstein and 

others, 2010). In response to questions regarding 

estimation of consumptive water use in the region, 

consumptive-use coefficients and monthly variation 

in consumptive use were explored and quantified 
Challenges for Future Water-Availability Studies 93

(Shaffer and Runkle, 2007; Shaffer, 2008; 2009). Water 

withdrawals from all water-use sectors were shown 

to vary seasonally, the greatest withdrawals occurring 

in summer.

• Groundwater is a major source for water in the region 

(Mills and Sharpe, 2010). Groundwater provides 

hundreds of cubic miles of regional storage (Coon and 

Sheets, 2006; Sheets and Simonson, 2006), and the 

groundwater system plays an important role in routing 

water from precipitation to streams as base flow (Neff 

and others, 2006). The groundwater contribution to 

water availability is best quantified through use of 

a groundwater-flow model because of the interplay 

between the hydrogeology of the system, natural 

boundaries, and imposed withdrawals. The groundwater-flow model that was developed for the Lake 

Michigan Basin was used to illustrate the response of 

the groundwater budget to development in the region 

from predevelopment to present (Feinstein and others, 

2010). This model also serves to integrate and synthesize information regarding the hydrogeology and 

groundwater use in the region (Arihood, 2009; Lampe, 

2009; Buchwald and others, 2010). From a methodological perspective, several alternative models were 

tested and presented, and this use of alternative models 

may serve as a example for future groundwater-availability studies (Feinstein and others, 2010).

• Summary indicators were introduced in this report to 

condense the water-budget information produced by 

the groundwater-flow model. These indicators revealed 

the contrast in groundwater dynamics and response to 

development between the eastern and western sides of 

the Lake Michigan Basin.

• Methods development and application were important 

in the Great Lakes Basin Pilot. 

• The AFINCH modeling system was developed to 

produce estimates of streamflow characteristics for 

ungaged basins; these estimates are constrained to 

match observations at streamgages if such observations are available (Holtschlag, 2009). The system 

also is useful for water-use accounting. AFINCH 

could be used to develop, for example, time series 

of flows for ungaged basins that could be related to 

stream ecology and used to define ecological flows.

• The Lake Michigan Basin groundwater-flow model 

relied on methods development and application to 

account for glacial hydrogeology (Arihood, 2009) 

and for calibration of the extensive model with many 

parameters and observations (detailed in Feinstein 

and others, 2010). 

• Recently developed methods to use the regional 

model to address local groundwater issues were 

applied and their use demonstrated (Hoard, 2010). 

• Finally, surface-water and groundwater models 

were applied to demonstrate analysis of data worth 

and ways to estimate where additional observations should be collected to decrease prediction 

uncertainty in the models (Fienen and others, 2010; 

Koltun and Holtschlag, 2010).

Challenges for Future 

Water-Availability Studies

The Great Lakes Basin Pilot was a true pilot project, 

designed to identify opportunities and challenges for a potential nationwide program. In addition, several new methods to 

estimate aspects of water availability were developed, applied, 

or tested. The focus of this study was on the storage of water 

in the system, flux of water through the system, and water use 

relating to human activity. Understanding these features of 

the water budgets of the region is paramount to developing 

estimates of water availability given constraints that are recognized today or that may be imposed in the future. 

Studies summarizing consumptive water use and seasonal 

variations in water use highlight inconsistencies in water-use 

data collection and reporting across the region. Much of the 

reported water use in some sectors relies heavily on estimates, 

and the estimation procedures have been inconsistent among 

states in the region and, for some categories of use, inconsistent over time. Further, classification of specific water uses 

into broad sectors has not consistent between states or between 

state and Federal agencies. Resolving these inconsistencies 

and developing methods to improve estimates for the broad 

sectors and different categories within those sectors remains 

a challenge. 

Estimation of surface-water characteristics across the 

basin with the AFINCH modeling system developed in the 

pilot was hampered by the requirement that all streams in 

the geographic dataset used to develop and report the analysis be routed through the stream network. Existing datasets 

are closely representative of actual physical conditions, 

but a small percentage of streams in the system during the 

pilot project were found to be disconnected or improperly 

routed. Correcting these problems is labor intensive and 

time consuming. 

The AFINCH system for analysis of streamflows offers 

capabilities to account for water use and, in this way, it may be 

used as a streamflow-accounting tool. Site-specific water-withdrawal information, however, is often not available throughout the Great Lakes Basin, and accounting for more diffuse 
94 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

withdrawals such as domestic use or agricultural irrigation to 

examine their effects on streamflow is difficult. One advantage 

of using AFINCH for estimation of streamflow characteristics 

is that anomalous results will be produced if major water uses 

are not included in the analysis, signaling the analyst of the 

potential missing information.

The tension between developing a regional groundwaterflow model capable of representing regional hydrologic-system behavior and the desire to address problems of local interest is a challenge for regional groundwater-availability studies. 

Regional models often cannot represent local behavior well 

enough to address local questions. Therefore, the pilot project 

tested methods to allow regional models to be extended and 

used as a base for additional analysis addressing local questions (such as the illustrative inset model discussed in this 

report). These methods were indeed found to clarify the potential local response in water levels and base flow to groundwater withdrawals. For site-specific questions, more refinement 

of the hydrogeologic characteristics of the inset model would 

be needed to produce a more reliable model. One other issue 

that remains a challenge to both the subregional and localscale groundwater-flow models is that traditional models treat 

recharge as separate from the imposed pumping on the system. 

This separate treatment may be valid on the subregional scale; 

but as questions become more site specific, the potential for 

pumping to modify recharge to the local aquifer should be 

included in the simulation. For situations where recharge can 

be influenced by pumping, coupled groundwater/surface-water 

models that generate recharge to the groundwater system as 

part of the simulation would be desired. (See, for example, 

Markstrom and others, 2008.)

Indicators that combine various components of the water 

budget with water withdrawals (and potentially return flows) 

help condense these data, but such combined indicators may 

be difficult to explain and understand. Simple indicators 

including groundwater levels or streamflows are straightforward and easily understood. These simple indicators, 

however, vary across the region and may not properly serve 

as an integrated metric capable of summarizing a mass of 

diverse information. Combined indictors summarize data more 

appropriately, but they may be more difficult to understand. 

Comparison of several combined indicators to values from 

the literature underscores the nature of water resources in the 

Great Lakes Basin and the dominance of flow in the system 

over human uses. The combined indicators also help highlight 

differences in groundwater budgets between different areas of 

the Lake Michigan Basin. This same information, however, 

may be communicated without the combined indicators. The 

effectiveness of different indicators for making informed 

water-resources decisions should be evaluated when selecting a set of indicators to summarize water availability on a 

national scale.

References 

Alley, W.M., Reilly, T.E., and Franke, O.L., 1999, Sustainability of ground-water resources: U.S. Geological Survey 

Circular 1186, 79 p. (Also available at http://pubs.usgs.gov/

circ/circ1186/.)

Anderson, M.T., and Woosley, L.H., Jr., 2005, Water availability for the western United States—Key scientific challenges: 

U.S. Geological Survey Circular 1261, 85 p. (Also available 

at http://pubs.usgs.gov/circ/2005/circ1261/.)

Arihood, L.D., 2009, Processing, analysis, and general evaluation of well-driller logs for estimating hydrogeologic 

parameters of the glacial sediments in a ground-water 

flow model of the Lake Michigan Basin: U.S. Geological 

Survey Scientific Investigations Report 2008–5184, 26 p. 

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Acknowledgments 103

Acknowledgments

This project required the efforts of many USGS scientists, support staff, and administrative staff. USGS Enterprise Publishing Network staff provided expert assistance with editing, 

formatting, posting of online publications, and publishing the entire series of reports produced 

by the project. The scientists who worked on this project included the following:

USGS Illinois Water Science Center, 1201 West University Avenue, Suite 100, Urbana, IL, 61801 

Patrick C. Mills, Hydrologist

Task Leader for report on water use by Hydrologic Unit Code 

Jennifer B. Sharpe, Geographer

Water-use team

USGS Indiana Water Science Center, 5957 Lakeside Boulevard, Indianapolis, IN, 46278

Leslie D. Arihood, Hydrologist

Lake Michigan Basin groundwater-flow-model team

Donald V. Arvin, Hydrologist

Water-use team

Randall Bayless, Research Hydrologist

Lake Michigan Basin groundwater-flow-model team

David C. Lampe, Hydrologist

Lake Michigan Basin groundwater-flow-model team

USGS Maine Water Science Center, 196 Whitten Road, Augusta, ME 04330

Glenn A. Hodgkins, Hydrologist

Task leader for surface-water trends report

Robert W. Dudley, Hydrologist

Surface-water trends report

USGS Michigan Water Science Center, 6520 Mercantile Way, Suite 5, Lansing, MI 48823

Lori M. Fuller, Geographer

GIS support

Christopher J. Hoard

Lake Michigan Basin groundwater-flow-model team

David J. Holtschlag, Hydrologist

Surface-water-characteristics team

Carol L. Luukkonen

Water-use and Lake Michigan Basin groundwater-flow-model teams

Brian P. Neff, Hydrologist

Recharge team

Howard W. Reeves, Research Hydrologist

Project Chief and Lake Michigan Basin groundwater-flow-model team

Cynthia M. Rachol, Hydrologist

Water-use team
104 Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin

USGS Minnesota Water Science Center, 2280 Woodale Drive, Mounds View, MN 55112

Allan Arntson, Hydrologist

Water-use team

USGS New York Water Science Center, 425 Jordan Road, Troy, NY 12180

William F. Coon, Hydrologist

30 Brown Road, Ithaca, NY 14850

Storage team

Kristin S. Linsey, Hydrologist 

Water-use team

USGS Ohio Water Science Center, 6480 Doubletree Avenue, Columbus, OH 43229

Robert A. Darner, Hydrologist

 Storage team

Greg F. Koltun, Hydrologist

Project oversight and assistance, surface water, network analysis

Kimberly H. Shaffer, Hydrologist

Task Leader, water use

Laura A. Simonson, Biologist

Divides report team

USGS Pennsylvania Water Science Center, 215 Limekiln Road, New Cumberland, PA 17070

Russell A. Ludlow, Hydrologic Technician

Water-use team 

USGS Wisconsin Water Science Center, 8505 Research Way, Middleton, WI 53562

Cheryl A. Buchwald, Hydrologist

Water-use and Lake Michigan Basin groundwater-flow-model teams

Daniel T. Feinstein, Hydrologist

Milwaukee Project Office, Geosciences Department, University of Wisconsin Milwaukee,

3209 North Maryland Aveneu, Milwaukee, WI 53211

Task Leader, Lake Michigan Basin groundwater-flow-model model

Michael N. Fienen, Research Hydrologist

Lake Michigan Basin groundwater-flow-model team, network analysis

Warren A. Gebert, Scientist Emeritus

Recharge team

Randall J. Hunt, Research Hydrologist

Task Leader, recharge team, and technical assistance with groundwater-flow modeling

John F. Walker, Research Hydrologist

Recharge team

Stephen M. Westenbroek, Hydrologist

Recharge team
Acknowledgments 105

USGS Eastern Region NSDI Partnership, 6520 Mercantile Way, Suite 5, Lansing, MI 48911 

Stephen S. Aichele, Geographer, Great Lakes Liaison

GIS and hydrogeography support, surface-water trends report

USGS technical steering and technical assistance:

Office of Groundwater: William M. Alley, Kevin F. Dennehy, Arlen W. Harbaugh, Thomas E. Reilly, William L. Cunningham

Office of Surface Water: Robert R. Mason

Eric J. Evenson, Eastern Region, Program Officer for the Northeast

Norman G. Grannemann, Northeastern Region, Great Lakes Focus Area Coordinator

James R. Nicholas, USGS Michigan Water Science Center, Director

Geoffrey N. Delin, Central Region Groundwater Specialist

Rodney A. Sheets, Eastern Region Groundwater Specialist, Northeast and Midwest Areas
Prepared by the USGS Enterprise Publishing Network

Columbus Publishing Service Center

Mike Eberle, editor; Rosemary Stenback, illustrator; Elizabeth Ciganovich, layout

Printed on recycled paper

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CANADA U.S.A

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United States portion

of the Great Lakes Basin

Reeves— Water Availability and Use Pilot: A Multiscale Assessment in the U.S. Great Lakes Basin—Professional Paper 1778