Volume 192: 2014 Annual Summary 

Background 

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

tracks 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 2014. 

Following a long period of much lower than 

average water levels, especially for Lakes 

Superior and Michigan-Huron, levels began to 

recover during 2013 and even surpassed long 

term average water levels in 2014. At the 

beginning of 2015, all of the Great Lakes are at a 

higher level than at the beginning of 2014, with 

the exception of Lake Ontario. A summary of 

2014 Great Lakes water levels is discussed below 

in the lake-by-lake sections. 

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 2013. 

These data have been coordinated between the 

United States and Canada. All 2014 water levels 

will be officially coordinated and added to the 

historical record in the spring of 2015. The 

elevations used are referenced to the 1985 

International Great Lakes Datum. 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, but rather 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 typically exhibits a seasonal rise in the 

spring primarily caused by an increase in 

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: 

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, runoff, and evaporation. NBS is 

far and away the main driver of water levels, and 

is also discussed in more detail in the following 

sections for each lake. 

Great Lakes

Update 
Vol. 190 Great Lakes Update February 2015 

Page 2 	 	

Figure 1: Lake Superior Water Levels 

Figure 2: Lake Superior Residual Net Basin Supply 

Lake Superior 

Figure 1 shows the 2014 water levels of Lake 

Superior compared with the 2013 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), which represents the horizontal line at a 

value of zero. Chart datum for Lake Superior is 
Vol. 190 Great Lakes Update February 2015 

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601.1 ft. The solid line in Figure 1 represents the 

2014 water levels and the dotted line shows the 

2013 levels. The LTA levels for each month are 

shown by the solid circles. 

By September of 2013, Lake Superior water 

levels had recovered to only 2 inches below LTA 

levels. This followed a nearly continuous period 

of low water levels that began in 1998. This 

recovery was largely due to a dramatic March to 

September rise of 23 inches (normal seasonal rise 

is 12 inches). A similarly dramatic rise occurred 

in 2014, when Lake Superior rose nearly 19 

inches from March to October. The seasonal rises 

of 2013 and 2014 were the second and tenth 

largest rises recorded from 1918 to 2014, 

respectively. As a result, Lake Superior levels 

have been above LTA levels since March of 

2014, and the January 2015 monthly mean water 

level was 9 inches above its LTA (10 inches 

higher than January 2014). 

The large seasonal rises during 2013 and 2014 

were caused by higher than average net basin 

supply (NBS), which incorporates the net effect 

of precipitation, runoff, and evaporation. Figure 2 

shows the Lake Superior NBS for each month in 

2014 compared to both the 2013 NBS and the 

historical average NBS. Large NBS values during 

May of 2013 and May of 2014 correspond to 

rapid lake level rise. May of 2013 and 2014 

ranked the second and third highest NBS in the 

period of record, which includes coordinated 

data from 1900 to 2008 and provisional data from 

2009 to 2014 . Precipitation was almost 10% 

above average during 2014, with up to 56% 

above average precipitation during the month of 

June and 25% to 38% above average precipitation 

during the months of October and November. 

Additionally, the colder than average winter 

resulted in very high ice coverage as well as 

increased snowpack, with the snowpack 

translating to high spring runoff to Lake Superior. 

NBS was consistently higher than normal from 

May 2013 throughout 2014. 

Lake Michigan-Huron 

Following historic low water levels in late 2012 

and early 2013, Lake Michigan-Huron had 

returned to near the low water datum by the end 

of 2013. By September 2014, water levels 

reached their long term average due to a 20 inch 

seasonal rise (average seasonal rise is 11 inches). 

Levels have remained above average since 

September, as shown in Figure 3. Water levels in 

Figure 3 are relative to the Lake Michigan-Huron 

chart datum level of 577.5 ft. 

The 2014 seasonal rise for Michigan-Huron was 

23 inches from January through November. 

Normally, the seasonal rise occurs from January 

through July. The 2014 seasonal rise ranked the 

fifth largest rise since 1918. Despite the dramatic 

rise of 2013 and 2014, Lake Michigan-Huron 

water levels in December were nearly 29 inches 

below their long term maximum December level. 

Figure 4 shows the 2014 NBS for Lake 

Michigan-Huron compared to the 2013 NBS and 

the historical averages. The year began with 

lower than average NBS due to lower than 

average precipitation and increased storage of 

that precipitation in snowpack. However, the 

basin experienced very high NBS in April and 

May (ninth and eleventh highest in the period of 

1900 to 2014) due to higher than average 

precipitation and runoff from melting snow. The 

higher than normal NBS during August to 

September are also responsible for the lack of 

seasonal decline in lake levels normally occurring 

during the late summer and autumn. 
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Figure 3: Lake Michigan-Huron Water Levels 

Figure 4: Lake Michigan-Huron Residual Net Basin Supply 

Lake St. Clair 

As seen in Figure 5 Lake St. Clair water levels 

exhibit more short-term fluctuation than lakes 

Superior, Michigan-Huron, Erie, or Ontario 

because of the smaller size of Lake St. Clair. The 

smaller size causes the connecting channels (the 

St. Clair River upstream and the Detroit River 

downstream) to have a large influence on the 

Lake St. Clair water levels. Wind, ice, and other 

climate variations can cause fluctuations in the 

hydraulic behavior through the St. Clair River, 
Vol. 190 Great Lakes Update February 2015 

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Lake St. Clair, and Detroit River system. The 

Lake St. Clair water level is starting 2015 much 

higher than 2014 due to the nearly 26 inch rise 

from February 2014 to August 2014 followed by 

only a 5 inch fall from September to December. 

Lake St. Clair water levels have been above 

average since June 2014. 

Figure 5: Lake St. Clair Water Levels 

Lake Erie 

Figure 6 shows the Lake Erie water levels relative 

to the chart datum of 569.2 ft. Following low 

water levels during 2012, Lake Erie levels 

recovered to normal conditions by the end of 

2013 and remained at or slightly below average 

levels until April of 2014. Since May 2014, water 

levels have been above their long term average 

monthly levels. The seasonal rise resulted in 

water levels increasing by about 18 inches from 

February to July 2014. By December 2014 Lake 

Erie water levels were 9 inches higher than 

December 2013 and 7 inches above LTA. 

Precipitation was greater than average from April 

2014 to September 2014, resulting in higher than 

average NBS, as shown in Figure 7. Large April 

and May NBS values in 2014 are a result of the 

combined impacts of above average precipitation 

during those months and increased runoff 

resulting from snow accumulation during the 

colder and wetter than average early winter 

months. 
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Figure 6: Lake Erie Water Levels 

Figure 7: Lake Erie Residual Net Basin Supply 

Lake Ontario 

Figure 8 shows Lake Ontario water levels relative 

to the chart datum of 243.3 ft. Lake Ontario is the 

only Great Lake whose water levels began 

January 2015 lower than January 2014. During 

2014, the Lake Ontario monthly mean water 

levels remained 5 inches below to 5 inches above 

LTA. 

Figure 9 shows the 2014, 2013 and LTA NBS for 

Lake Ontario. Below average NBS in February 
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and March of 2014 followed by well above 

average NBS in April resulted in a rise of about 

13 inches from March to May. Higher than 

average NBS persisted from April to August due 

to monthly precipitation that was from 7 to 47% 

above LTA, and this corresponds to a period of 

higher than average water levels. Precipitation 

was 70% and 56% of LTA during the months of 

November and December, respectively, however, 

bringing water levels back below LTA. Lake 

Ontario ended the year at 2 inches below LTA.

Figure 8: Lake Ontario Water Levels 

Figure 9: Lake Ontario Residual Net Basin Supply 
Vol. 190 Great Lakes Update February 2015 

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Winter Conditions of 2013-2014 

During the winter of 2013-2014, the Great Lakes 

basin experienced very cold temperatures and 

record setting snowfall. The December to 

February season in the Great Lakes region was 

the coldest winter in 20 years. The amount of 

water contained in the snowpack was 125% to 

300% of average, resulting in very large spring 

runoff to the lakes. The increased runoff was the 

primary cause of extremely high seasonal rise 

seen especially on the upper lakes. 

Ice cover began early in the season and reached 

the second highest percentage since 1973 (Figure 

10). Maximum ice coverage (92.5%) occurred on 

March 6, 2014. Winters with high ice cover are 

often followed by cooler summer water 

temperatures and lower evaporation rates, but 

high evaporation rates can occur during the 

autumn and early winter preceding high ice 

periods. 

Figure 10: Ice cover for years 1973 to 2014. 

More Information 

Update articles are included in the February and 

August Monthly Bulletins highlighting topics and 

explanations relevant to Great Lakes water levels. 

February’s Monthly Bulletin will typically include 

an annual summary from the year before and each 

August Monthly Bulletin will typically include a 

summary of the first six months of the year. 

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 each Thursday and can 

be 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/pages/Detroit-District-USArmy-Corps-of-Engineers/144354390916

The Detroit District welcomes comments on all of 

our forecast products. 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-HH-W 

477 Michigan Avenue 

Detroit, MI 48226