This document discusses changing water levels in the Great Lakes. It begins with an introduction and outline. It then covers historical water levels, including their seasonal and interannual variation. The main drivers of water level changes are described as the hydrologic cycle of precipitation, evaporation, runoff and flows between lakes. Projections are discussed for both seasonal and decadal timescales. The conclusions discuss challenges around quantifying data value, using models to replace observations, uncertainty quantification and the ability of projections to offer insights rather than firm predictions.

1. Introduction
Historical levels
Drivers
Forecasting
Changing Great Lakes Water Levels:
current conditions and future projections
Andrew Gronewold, Ph.D., P.E.
drew.gronewold@noaa.gov
Great Lakes Environmental Research Laboratory
National Oceanic and Atmospheric Administration
and
Department of Civil and Environmental Engineering
University of Michigan
May 2016
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2. Introduction
Historical levels
Drivers
Forecasting
Outline
1 Introduction
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3. Introduction
Historical levels
Drivers
Forecasting
Outline
1 Introduction
2 Historical water levels
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4. Introduction
Historical levels
Drivers
Forecasting
Outline
1 Introduction
2 Historical water levels
3 Drivers of water level change
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5. Introduction
Historical levels
Drivers
Forecasting
Outline
1 Introduction
2 Historical water levels
3 Drivers of water level change
4 Forecasting
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6. Introduction
Historical levels
Drivers
Forecasting
Outline
1 Introduction
2 Historical water levels
3 Drivers of water level change
4 Forecasting
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7. Introduction
Historical levels
Drivers
Forecasting
U.S. Great Lakes Coastline Comparison
Miles of
Lake Coastline
Lake Superior 1250
Lake Michigan 1640
Lake Huron 840
Lake Erie 470
Lake Ontario 330
TOTAL 4530
Source: The Coastline of the United States. U.S. Dept.
of Commerce, NOAA, NOAA/PA 71046 (Rev. 1975).
*All numbers rounded to the nearest 10 miles.
NATIONALOCEAN
IC
AND ATMOSPHERIC
ADMINISTRATION
U.S.
D
EPARTMENT OF COMM
E
R
CE
Great Lakes Environmental Research Laboratory
GLERL
ATLANTIC = 2170
GULF OF MEXICO = 1630
PACIFIC = 1300
ALASKA/HAWAII = 6330
From: Gronewold, Fortin, Lofgren, Clites, Stow, and Quinn (2013). Climatic Change.
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8. Introduction
Historical levels
Drivers
Forecasting
Name Country Surface area Volume
(km2) (mi2) (km3) (mi3)
Michigan–Huron U.S. and Canada 117,702 45,445 8,458 2,029
Superior U.S. and Canada 82,414 31,820 12,100 2,900
Victoria Multiple 69,485 26,828 2,750 660
Tanganyika Multiple 32,893 12,700 18,900 4,500
Baikal Russia 31,500 12,200 23,600 5,700
Great Bear Lake Canada 31,080 12,000 2,236 536
Malawi Multiple 30,044 11,600 8,400 2,000
Great Slave Lake Canada 28,930 11,170 2,090 500
Erie U.S. and Canada 25,719 9,930 489 117
Winnipeg Canada 23,553 9,094 283 68
Ontario U.S. and Canada 19,477 7,520 1,639 393
Table: Water volume and surface area of Earth’s largest (ranked by surface area) fresh surface waters.
From: Gronewold, Fortin, Lofgren, Clites, Stow, and Quinn (2013). Climatic Change.
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9. Introduction
Historical levels
Drivers
Forecasting
Name Country Surface area Volume
(km2) (mi2) (km3) (mi3)
Michigan–Huron U.S. and Canada 117,702 45,445 8,458 2,029
Superior U.S. and Canada 82,414 31,820 12,100 2,900
Victoria Multiple 69,485 26,828 2,750 660
Tanganyika Multiple 32,893 12,700 18,900 4,500
Baikal Russia 31,500 12,200 23,600 5,700
Great Bear Lake Canada 31,080 12,000 2,236 536
Malawi Multiple 30,044 11,600 8,400 2,000
Great Slave Lake Canada 28,930 11,170 2,090 500
Erie U.S. and Canada 25,719 9,930 489 117
Winnipeg Canada 23,553 9,094 283 68
Ontario U.S. and Canada 19,477 7,520 1,639 393
Table: Water volume and surface area of Earth’s largest (ranked by surface area) fresh surface waters.
From: Gronewold, Fortin, Lofgren, Clites, Stow, and Quinn (2013). Climatic Change.
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10. Introduction
Historical levels
Drivers
Forecasting
Outline
1 Introduction
2 Historical water levels
3 Drivers of water level change
4 Forecasting
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11. Introduction
Historical levels
Drivers
Forecasting
From: NOAA National Ocean Service (CO-OPs) and NOAA-GLERL.
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15. Introduction
Historical levels
Drivers
Forecasting
Historical water levels:
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16. Introduction
Historical levels
Drivers
Forecasting
Historical water levels: seasonal and interannual
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20. Suite of Software Analyzes
Data on the Sphere
Dawn Spacecraft Orbits
Dwarf Planet Ceres
The Social Contract
Between Science and Society
VOL. 96 • NO. 6 • 1 APR 2015
Earth & Space Science News
GREAT LAKES
WATER LEVELS
SURGE
See also: Gronewold et al (In Press) Water Resources Research

24. Introduction
Historical levels
Drivers
Forecasting
Outline
1 Introduction
2 Historical water levels
3 Drivers of water level change
4 Forecasting
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25. Introduction
Historical levels
Drivers
Forecasting
Drivers of water level change:
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26. Introduction
Historical levels
Drivers
Forecasting
Drivers of water level change: hydrologic cycle
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27. Introduction
Historical levels
Drivers
Forecasting
Drivers of water level change: hydrologic cycle
1.6
2.0
1.4
Lake Superior
2.7
3.1
1.9
Lake
Michigan-Huron
0.2<0.1
<0.1
Lake St. Clair
0.7 0.7
0.8
Lake Erie
1.1
0.5
0.4
Lake Ontario
Runoff Overlake Precipitation Overlake Evaporation
Budgets Within Lakes
From: Hunter et al. (2015), Journal of Great Lakes Research; Satellite Imagery: NOAA CoastWatch
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28. Introduction
Historical levels
Drivers
Forecasting
Drivers of water level change: hydrologic cycle
1.6
2.0
1.4
Lake Superior
2.7
3.1
1.9
Lake
Michigan-Huron
0.2<0.1
<0.1
Lake St. Clair
0.7 0.7
0.8
Lake Erie
1.1
0.5
0.4
Lake Ontario
St.
Lawrence
River
7.0
Niagara River
(& Welland Canal)
6.3
Detroit River
5.5
St. Clair River
5.4
St. Marys River
2.2
The Ogoki and
Long Lac
diversions bring
water from the
Hudson Bay
watershed into
Lake Superior.
0.2
The Chicago
diversion sends
water from Lake
Michigan into the
Mississippi River
Basin.
0.1
A very small amount
of water is sent
through the Erie
Canal from Lake Erie
to the Hudson River.
Runoff Overlake Precipitation Overlake Evaporation Flow Between Lakes Diversions
<0.1
Flow Between Lakes and DiversionsBudgets Within Lakes
From: Hunter et al. (2015), Journal of Great Lakes Research; Satellite Imagery: NOAA CoastWatch
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29. Introduction
Historical levels
Drivers
Forecasting
Great Lakes, December 1999
Credit: NASA
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30. Introduction
Historical levels
Drivers
Forecasting
Outline
1 Introduction
2 Historical water levels
3 Drivers of water level change
4 Forecasting
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31. Introduction
Historical levels
Drivers
Forecasting
Water level projections: seasonal
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35. Introduction
Historical levels
Drivers
Forecasting
Water level projections: decadal
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39. Introduction
Historical levels
Drivers
Forecasting
Concluding remarks
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40. Introduction
Historical levels
Drivers
Forecasting
Concluding remarks
How do we quantify value of data?
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41. Introduction
Historical levels
Drivers
Forecasting
Concluding remarks
How do we quantify value of data?
Can models replace observations?
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42. Introduction
Historical levels
Drivers
Forecasting
Concluding remarks
How do we quantify value of data?
Can models replace observations?
Uncertainty quantification: simple or complex models?
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43. Introduction
Historical levels
Drivers
Forecasting
Concluding remarks
How do we quantify value of data?
Can models replace observations?
Uncertainty quantification: simple or complex models?
Projections and simulations: “predict” or offer insight?
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44. Introduction
Historical levels
Drivers
Forecasting
Acknowledgements
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45. Introduction
Historical levels
Drivers
Forecasting
Acknowledgements
Kaye LaFond, Joe Smith, Anne Clites, Tim Hunter
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46. Introduction
Historical levels
Drivers
Forecasting
Acknowledgements
Kaye LaFond, Joe Smith, Anne Clites, Tim Hunter
NOAA, USACE, USGS, Environment Canada, and IJC
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47. Introduction
Historical levels
Drivers
Forecasting
Changing Great Lakes Water Levels:
current conditions and future projections
Andrew Gronewold, Ph.D., P.E.
drew.gronewold@noaa.gov
Great Lakes Environmental Research Laboratory
National Oceanic and Atmospheric Administration
and
Department of Civil and Environmental Engineering
University of Michigan
May 2016
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48. Introduction
Historical levels
Drivers
Forecasting
White Shoal Lighthouse: Lake Michigan
Photo courtesy Dick Moehl
(Lighthouse Keepers Association)
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49. Introduction
Historical levels
Drivers
Forecasting
Drivers of water level change:
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50. Introduction
Historical levels
Drivers
Forecasting
Drivers of water level change: atmospheric circulation and climate patterns
10
6
2
Watertemperature
(degC)
300
550
800
Overlakeevaporation
(mm)
1950 1960 1970 1980 1990 2000 2010
-1
0
1
Waterlevel
(departurefrommean,m)
A
B
From: Gronewold & Stow (2014), Science.
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51. Introduction
Historical levels
Drivers
Forecasting
Glacial isostatic rebound
From: Mainville and Craymer (2005), GSA Bulletin.
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