Volume 205: 2019 Annual Summary

Background

The U.S. Army Corps of Engineers (USACE) 

monitors and forecasts the water levels of each of 

the Great Lakes. This report is primarily focused 

on summarizing the hydrologic conditions of the 

Great Lakes basin in 2019.

Official water levels are based on monthly lakewide means, and the period of record used for each 

of the lakes includes the years 1918 to 2019. These 

data have been coordinated between the United 

States and Canada. 

The elevations used are referenced to the 

International Great Lakes Datum of 1985. The 

water level of each lake is averaged from a 

network of individual gages around each lake. 

Also of note is that Lake Michigan and Lake 

Huron are hydraulically treated as one lake due to 

their connection at the Straits of Mackinac.

The Great Lakes are very large and behave 

differently from smaller, inland lakes. In general, 

Great Lakes water levels do not rise and fall with 

individual storms. Significant water level 

fluctuations require multiple months, seasons, or 

years of wet or dry conditions.

Seasonal changes in weather patterns typically 

cause an annual pattern of rising and falling of 

Great Lakes water levels. Each of the Great Lakes 

exhibits a seasonal rise in the spring primarily 

caused by an increase in liquid precipitation, 

increased runoff due to melting of accumulated 

snow, and low evaporation rates. The typical 

seasonal decline of the water levels in the fall and 

winter is primarily caused by an increase in 

evaporation, a decrease in precipitation, and the 

accumulation of snowpack on the land area.

The Net Basin Supply (NBS) is an important 

quantity for understanding the amount of water 

which arrives to the lake. USACE uses the 

residual method to compute NBS, shown below in 

the summarizing equations: 

Residual Method Net Basin Supply:

NBS = WL – I – D + O

WL: Water Level Change

I: Connecting Channel Inflow

O: Connecting Channel Outflow

D: Diversion into(+) or out(-) of lake

Altogether, NBS represents the combined effects 

of precipitation over the lake, runoff to the lake, 

and evaporation off of the lake. NBS is the main 

driver of water levels, and is also discussed in more 

detail in the following sections for each lake.

Record-High Waters Levels in 2019

All of the Great Lakes remained significantly 

above average in 2019. Lakes Superior, MichiganHuron, St. Clair and Erie have been above their 

monthly average levels since at least November 

2015. Lake Ontario’s level has been above average 

since January 2017 except for a three-month 

period of near average levels in 2018. Lakes 

Superior, St. Clair, Erie, and Ontario all matched 

or set record high monthly mean levels in 2019. In 

June and July, all four aforementioned lakes set 

record high monthly mean levels. 

Great Lakes

Update
Vol. 205 Great Lakes Update February 2020

Page 2

Lake Michigan-Huron was the only lake that did 

not break any record-high monthly level in 2019. 

Figure 1 below summarizes the months in which

record high levels were met or surpassed in 2019. 

Figure 2 shows the peak monthly level reached by 

each lake in 2019 and how they compare to the 

highest monthly mean level achieved by each lake 

since 1918, the beginning of their period of record.

Figure 1: Table indicating when record high 

levels were set on all the Great Lakes dating 

back to 1918.

Figure 2: Peak 2019 Monthly Level of each 

Lake and how they compare to each Lake's 

overall monthly record high since 1918

Lake Superior

Figure 3 shows the 2019 water levels of Lake 

Superior compared with the 2018 levels and the 

monthly long-term average (LTA) levels. A 

similar figure is shown for each lake in the 

following sections. Each lake’s data has been 

plotted relative to chart datum (a.k.a. low water 

datum). Chart datum for Lake Superior is 601.1 

feet. The dark line in Figure 3 represents the daily 

2019 water levels and the solid gray line shows the 

2018 levels. The LTA levels for each month are 

shown by the circles. Figure 4 shows monthly 

residual NBS, and the NBS shown is relative to the 

monthly LTA NBS. The lake’s annual NBS, which 

is the sum of the monthly NBS for all twelve 

months, was above average for the 7th year in a 

row. The lake’s 2019 annual NBS compared to 

recent annual NBS and its average annual NBS is 

provided in Figure 5.

Figure 3: Lake Superior Water Levels

Figure 4: Lake Superior Residual Net Basin 

Supply, deviation from Long-Term Average

Figure 5: Lake Superior’s Annual NBS from 

2013-2019 compared its Average Annual NBS

Lake Superior hovered within an inch of its 2018 

monthly levels during the first 3 months of 2019. 

LAKE Peak Level (ft) Ranking

Superior 603.28 3rd highest

Mich-Huron 581.92 6th highest

St. Clair 577.56 Highest

Erie 574.61 Highest

Ontario 249.05 Highest

Year

Percent of Average Annual NBS 

(based on Coordinated Period of 

Record, 1900-2008)

2019 140%

2018 110%

2017 147%

2016 107%

2015 113%

2014 157%

2013 137%
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However, by June 2019, Lake Superior was 11 

inches above its level of a year ago, and 15 inches 

above its June LTA. The net basin supply to the 

lake was above average the first five months of 

2019. February’s NBS was buoyed by 

precipitation that was much above average. The 

lake’s April 2019 NBS, aided by above average

precipitation and melting of significant snowpack, 

was also well above average. 

Lake Superior’s 2019 seasonal rise of 12 inches

mirrored its 2018 seasonal rise and its average 

annual rise, but the lake’s seasonal decline prior to 

its 2019 rise was just 8 inches. Lake Superior’s 

seasonal rise took place from April to October,

when it reached its peak monthly average level of 

603.28 feet, its highest level since November 

1985, and its 3rd highest monthly level since 1918. 

Due to below average NBS during the summer 

months, the lake was at the same monthly mean 

level in July, August, and September, but rose in 

October by less than an inch. 

By the end of 2019, Lake Superior had been above 

its monthly LTA levels every month since May 

2014, a period of 68 months. Over the final 3 

months of 2019, Lake Superior monthly average 

levels were 13 to 15 inches above LTA and three

inches below its monthly record high water levels.

Lake Michigan-Huron

Lake Michigan-Huron’s 2019 levels are shown in 

Figure 6. Lake Michigan-Huron’s monthly mean

level in January was 20 inches above its monthly

LTA and 3 inches above its January 2018 level. 

Catapulted by NBS that was above average for 9

months in 2019, by December 2019, the lake’s 

level was 36 inches above LTA and 17 inches 

above its level of a year ago. Figure 6 also shows 

water levels from 2012 when the lake fell to a 

record low December level. Lake MichiganHuron’s mean level in December 2019 was 65 

inches higher than its record low in 2012. 

Figure 6: Lake Michigan-Huron Water Levels

The water level of Lake Michigan-Huron has been 

above average every month since November 2014, 

a streak of 62 consecutive months. Unlike all of the 

other Lakes, Michigan-Huron did not meet or 

exceed any record high levels in 2019, although 

the lake came within an inch of its record high 

monthly levels in June, July, and December. 

Lake Michigan-Huron’s seasonal rise of 22 inches 

in 2019 eclipsed its 2018 seasonal rise of 10 inches 

and its historical average seasonal rise of 12 

inches. The NBS to the lake in April, May, and 

June ranged from 50-75% above average, 

according to provisional statistics. The lake peaked 

in July at a monthly mean level of 581.92 feet. This 

level was its 2nd highest July level since 1918, its 

6th highest overall monthly level since 1918, and

its highest monthly level since November 1986.

The lake’s monthly mean levels from June through 

December were all their 2nd highest monthly 

means in their respective months.

Another notable occurrence was the modest 

seasonal decline after its 22 inch rise. The lake’s 

average water level decline from July to December 

is around 9 inches, but in 2019, the lake only fell 

only 5 inches. Within that timeframe, the lake’s 

monthly mean level rose slightly from September 

to October after falling from July to September.

This relatively short water level decline was due to

above average NBS over the final 4 months of the 

year. Contributing to that stretch of above average 

NBS was over 30% above average precipitation in 
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September and October, and substantially below 

average evaporation in September and December.

Figure 7 shows monthly residual net basin supply 

relative to its monthly LTA NBS. In 2019, Lake 

Michigan-Huron received a remarkable amount of 

water supplies. According to preliminary statistics,

the monthly NBS in April, May, September, and 

December were amongst the four highest NBS the 

lake has received in those months since 1900. 

Precipitation was over 30% above average in 3 of 

those 4 months, and was 8% above average for the 

year. Moreover, NBS was above average in 7 of 

the last 9 months of the year. Preliminary results 

show that the lake’s annual NBS, which is the sum 

of all of its monthly NBS in a year, was larger in 

2019 than in any year since 1900. Figure 8 shows 

a summary of the annual NBS over the past 7 

years.

Figure 7: Lake Michigan-Huron Residual Net 

Basin Supply, difference from Long-Term 

Average

Figure 8: Lake Michigan-Huron’s Annual 

NBS in 2019 compared to Annual NBS over 

the past 7 years and its Average Annual NBS

Lake St. Clair

Figure 9 shows the water levels of Lake St. Clair 

in 2019 compared to 2018 and the LTA levels. 

Lake St. Clair started the year 22 inches above 

LTA and was at least 30 inches above its LongTerm Monthly Average levels the final 7 months 

of 2019. In addition, the lake has been above its 

monthly LTA every month since March of 2015. 

Lake St. Clair was 15 inches below its record high 

water levels in January and February. However, 4 

consecutive months of above average NBS to start 

the year led to a February-to-July seasonal rise of 

25 inches, topping the prior year’s 19-inch rise and

its historical average rise of 16 inches, and notably

dwarfing the preceding 12-inch seasonal decline.

This 25-inch surge propelled the lake to eclipse its 

record high monthly mean water levels for five 

consecutive months in 2019 – May, June, July, 

August, and September – by a range of 1 to 4 

inches.

According to preliminary results, the lake reached 

a monthly mean level of 577.40 feet in June, the 

highest monthly mean level it had achieved for any 

month dating back to the start of its period of 

record (1918). This level was 3 inches above its 

previous June record high and an inch above the

previous record high monthly level set in October 

1986. This record high level was surpassed the 
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very next month when the lake’s mean level rose 2 

inches to its seasonal peak of 577.56 feet. 

Net basin supplies to Lake St. Clair were near 

average or below average the remaining eight 

months of the year. The lake’s monthly NBS is 

summarized in Figure 10. The lake’s decline from 

its July peak to December was 14 inches, slightly 

higher than its average July-to-December decline 

of 11 inches, resulting in Lake St. Clair being 4 to 

8 inches below record highs during the final 3 

months of the year. The lake's considerable inflow 

from the St. Clair River, driven by near-record 

Lake Michigan-Huron levels, sustained Lake St. 

Clair's elevated levels despite below average 

monthly NBS in the final 8 months of the year.

Figure 9: Lake St. Clair Water Levels

Figure 10: Lake St. Clair Net Basin Supplies

Lake Erie

Record breaking high water levels characterized

Lake Erie water levels in 2019, as displayed in 

Figure 11. The lake’s level has been above its 

monthly LTA since June 2015, a period of 55

consecutive months. According to preliminary 

data, Lake Erie surpassed its monthly mean level 

record high in May and continued to set monthly 

mean level record highs in June, July, August, and 

September. These new record high levels ranged 

from 2 to 4 inches above the previous record high 

levels reached in 1986. Lake Erie’s monthly mean 

level in June, 574.61 feet, is the lake’s highest

monthly level in its period of record dating back to 

1918.

The level of Lake Erie in January 2019 was about 

10 inches above its 2018 January level, 25 inches 

above LTA, and 9 inches below its record high 

January level. In March, the lake was even an inch 

below its March 2018 level. However, Lake Erie 

experienced a 21-inch seasonal rise in 2019, 

exceeding its historical average climb of 14 inches.

This seasonal rise resulted in the lake’s monthly 

mean level in July being 12 inches above its 2018 

levels, and 31 inches above LTA. 

Lake Erie’s 21-inch rise can be attributed to net 

basin supplies to the lake that were above average 

in 4 of the 5 months from February to June. Its 

NBS in June was 2.5 times the average for that 

month. Contributing to the NBS were runoff and 

precipitation that were above average in April, 

May, and June, according to preliminary estimates. 

In fact, Lake Erie was the only Great Lake in 2019 

to experience above average precipitation in 4 

consecutive months, April to July. 

The lake’s monthly NBS in 2019 is shown in 

Figure 12. In the second half of the year, –

November was the only month Lake Erie 

experienced above average NBS. Lake Erie’s 

monthly mean levels remained 3 to 7 inches above 

the previous year’s levels, and 7 to 8 inches below 

record high levels, over the final 3 months of 2019.
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Figure 11: Lake Erie Water Levels

Figure 12: Lake Erie Residual Net Basin 

Supply, deviation from Long-Term Average

Lake Ontario

Figure 13 shows Lake Ontario water levels relative 

to the chart datum of 243.3 feet. The lake began 

2019 as it began 2018 – 11 inches above LTA and 

13 inches below its record high January level. 

Unlike the other Great Lakes, which have been 

above average in every month since at least late 

2015, Lake Ontario’s current streak of above 

average water levels began in October 2018. 

The lake’s seasonal rise in 2019, was 51 inches, 

substantially more than the lake’s 2018 seasonal 

rise of 19 inches, and its average seasonal rise of 

21 inches. Lake Ontario’s monthly Net Basin 

Supply, shown in Figure 14, was above average for 

every single month of 2019. In fact, its May and 

June net basin supplies were around 70% above 

normal. Preliminary results suggest precipitation 

and runoff were well above average those 2 

months.

While in January 2019, Lake Ontario was at the 

same level it was in January 2018, by July, Lake 

Ontario’s mean level was 29 inches above what it 

was 12 months before, and 31 inches above 

average. In addition, the lake’s meteoric rise of 51 

inches resulted in surpassing the record high water 

levels in June and July that had been set just two 

years earlier in 2017. Lake Ontario peaked in June 

at 249.05 feet, 4 inches above its record high June 

mean level. This level, which was 33 inches above 

LTA, is also the highest monthly mean level 

recorded on Lake Ontario since the lake’s period 

of record began in 1918. 

The lake’s 2019 seasonal decline of 36 inches 

occurred from June to December. This is much 

larger than the lake’s average June-to-December 

decline of 21 inches and brought Lake Ontario

down to 11 inches above its 2018 monthly mean 

level, and 19 inches above LTA, in December.

According to provisional statistics, record and 

near-record high monthly Lake Ontario outflows 

through the St. Lawrence River occurred from 

June through December, contributing to the lake’s 

above average decline. In 2019, the lake’s annual 

NBS - the sum of all of its monthly NBS in a 

calendar year - was the lake’s 5th highest since 

1900, according to provisional data.

Figure 13: Lake Ontario Water Levels
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Figure 14: Lake Ontario Residual Net Basin 

Supply, deviation from Long-Term Average

Emergency Management Rises to the Occasion

The U.S. Army Corps of Engineers (USACE) 

Emergency Management is authorized by Public 

Law 84-99 to support local, county, and state 

efforts during flood emergencies. USACE support 

comes in two forms, Technical Assistance and 

Direct Assistance. Technical Assistance allows 

USACE to provide data, recommendations and 

solutions to the community’s flooding concerns. 

Additionally, under Technical Assistance, USACE 

can deploy a skilled flood fight team during a flood 

event in order to bring expertise into a community, 

and train local communities how to properly fill 

and place sandbags and other temporary flood 

protection measures. Under Direct Assistance, 

USACE can provide materials and equipment to 

communities during a flooding event. These 

materials include sandbags, plastic sheeting, and 

HESCO barriers. All materials provided must be 

returned if not used or reimbursed back to USACE, 

unless a Presidential Disaster is declared. 

Additionally, flood fight supplies provided under 

Direct Assistance are solely for the protection of 

critical public infrastructure. USACE cannot 

directly assist individual homeowners or 

commercial interests.

2019-2020 Great Lakes High Water 

Due to the rising water level on the Great Lakes, 

USACE Detroit District activated their Emergency 

Operations Center (EOC) in early May 2019. This 

Great Lakes high water event has persisted since 

then and Emergency Management is currently 

providing Technical Assistance to six counties in 

Wisconsin, twelve counties in Michigan, and one 

tribe in Michigan. Typical Technical Assistance 

for this event has included reviewing areas of 

concern and providing flood fighting 

recommendations, and educating/training in 

proper sandbag filling and placement. In addition 

to Technical Assistance, USACE Detroit District 

has provided over 290,000 sandbags to 

communities.

Preparedness is a key principle in Emergency 

Management, and USACE Detroit District 

Emergency Management has been engaged with 

many communities in Michigan and Wisconsin to 

provide outreach regarding the ongoing threat 

from the Great Lakes high water levels. These 

engagements range from one-on-one meetings 

with local/county government agencies, to public 

meetings/presentations on Great Lakes water 

levels, USACE Emergency Management 

authorities, and the Detroit District response to the 

Great Lake high water level event. 

Case Study: City of Detroit Flood Fight

Figure 15: Flood Fighting Staging Area in 

Jefferson-Chalmers community, Detroit, MI, 

May 2019
Vol. 205 Great Lakes Update February 2020

Page 8

Figure 16: Sandbagged property in JeffersonChalmers community, Detroit, MI, May 2019

During the spring and summer of 2019, the City of 

Detroit experienced substantial flooding along the 

shore of Lake St. Clair. Flooding caused damage 

to numerous homes, streets to become impassible, 

and evacuation routes to be blocked. During this 

event, the USACE Detroit District Flood Fight 

Team (FFT) was deployed to support the 

Jefferson-Chalmers community. The FFT’s first 

initiative was to establish a flood fighting staging 

area in that neighborhood. Then, the FFT helped 

train the community in sandbag filling and 

placement techniques. In addition, the FFT 

evaluated areas of concern throughout the 

community that were vulnerable to flooding and 

provided recommendations to mitigate the 

flooding. This flooding was a community-wide 

issue, and was tackled with a community-wide 

effort. 

Who Can You Contact?

If you are in need of assistance in your community, 

please contact your local or county emergency 

management agency. USACE support is 

supplemental to local efforts and it is important 

that the county and state are aware of the need in 

their area of responsibility. If you have any 

questions for USACE Detroit District, please 

contact Emergency Management at CELREEOC@usace.army.mil or visit our dedicated Great 

Lakes High Water webpage at 

https://www.lre.usace.army.mil/About/GreatLakes-High-Water/

More Information

Update articles are included periodically in the 

Monthly Bulletins highlighting topics and 

explanations relevant to Great Lakes water levels. 

Nearly all past Update Articles dating back to 1985 

can be accessed here:

https://www.lre.usace.army.mil/Missions/Great-LakesInformation/News-and-Information/Great-Lakes-UpdateArticles/

The Monthly Bulletin is sent by postal mail. To be 

added to the postal mailing list, please send an 

email to hhpm@usace.army.mil or call 1-888-694-

8313 and select option 1. Alternatively, the 

Monthly Bulletin can be viewed on our website. 

The home page is: http://www.lre.usace.army.mil. 

In addition to the Monthly Bulletin, the Detroit 

District issues the Weekly Great Lakes Water Level 

Update and the Weekly Great Lakes Connecting 

Channels Water Levels and Depths. Both products 

are updated at the end of each week. Additionally, 

a one year Great Lakes Water Level Outlook is

produced once every three months. All forecast 

products are located here:

http://www.lre.usace.army.mil/Missions/GreatLakesInform

ation/GreatLakesWaterLevels/WaterLevelForecast.aspx

The Detroit District also has a Facebook page 

which can be found here:

https://www.facebook.com/USACEDetroitDistrict/

Please email questions and comments to 

hhpm@usace.army.mil. To contact the District by 

phone call toll free 1-888-694-8313 and select 

option 1. The Detroit District’s mailing address is:

Department of the Army

Detroit District Corps of Engineers

ATTN: CELRE-EHW

477 Michigan Avenue

Detroit, MI 48226