Vol. 193 Great Lakes Update August 2015

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Volume 193: 2015 January through June Summary

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

monitors the water levels of each of the Great 

Lakes. This report provides a summary of the 

Great Lakes water levels and basin conditions 

from January through June 2015. 

The primary drivers of water level changes are 

precipitation falling on the lake surface, runoff 

draining to the lake, evaporation from the lake 

surface, diversions into or out of the lake, and 

connecting channel inflows and outflows. The 

combined effects of the first three hydrologic 

factors – precipitation, runoff, and evaporation –

are referred to as the Net Basin Supply (NBS) to 

the lake. The NBS is an important quantity for 

understanding the amount of water supplied to the 

lake. USACE uses the residual method to 

calculate NBS, which is equal to the water level 

change, minus the inflow from an upstream lake, 

plus the outflow, and plus any diversions out of 

(+) or into (-) the lake. Net Basin Supply is the 

most significant driver of water level change.

All water levels mentioned in this article are 

monthly mean surface elevations in feet 

referenced to the 1985 International Great Lakes 

Datum. The period of record used for each of the 

lakes includes the years 1918 to 2014 and these 

data have been coordinated between the United 

States and Canada. All 2015 water levels are 

considered provisional and will be officially 

coordinated in the spring of 2016. The water level 

of each lake is averaged from a network of 

individual water level 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.

2015 Overview: January - June

In January 2014, the only Great Lake above its 

long-term average was Lake Ontario. By January 

2015, however, Lake Ontario was the only lake 

whose water level was below its long term 

average. While Lake Ontario was 1 inch below its 

long term average January level in January 2015, 

Lakes Superior, Michigan-Huron, St. Clair, and 

Erie were 9, 8, 12, and 8 inches above their long 

term average January levels, respectively.

This dramatic change on the upper lakes resulted 

from a second consecutive year of significantly 

higher than average seasonal rises on those lakes.

This was not the case during 2015, however, as 

shown in Figure 1 and Table 1. Instead, seasonal 

rise (through June) was slightly less than average 

for Lakes Superior and Michigan-Huron, but 

significantly higher than normal for Lakes St. 

Clair, Erie, and Ontario. Figure 1 shows the 

difference between the observed lake level 

change during each month compared to that 

calendar month’s long term average lake level 

change. Table 1 provides the water level changes 

from the winter minimum level to the June level 

for each lake. 

Great Lakes

Update
Vol. 193 Great Lakes Update August 2015

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The notable rise on the lower lakes is largely a 

result of very high precipitation during the month 

of June (95% and 79% more precipitation than 

normal fell over Lakes Erie and Ontario, 

respectively, during June 2015). Lake Superior, 

on the other hand, received 91% of its long term 

average June precipitation. On the whole, the 

Great Lakes basin has transitioned from a drier 

than average fall and winter to a wetter than 

average late spring and early summer, and this 

has translated to a similar transition from lower 

than average NBS during winter to higher than 

average NBS in the summer.

Figure 1: Change in lake level, in inches, 

relative to the long term average change in 

lake level for each month.

As of June 2015, all of the Great Lakes were 

above their long term average monthly mean 

levels, and all lakes but Ontario were above their 

June 2014 levels.

Lake 2013 2014 2015 LTA

Superior 14 14 8 9

Michigan-Huron 19 17 8 11

St. Clair 18 24 27 15

Erie 16 18 21 13

Ontario 28 22 24 19

Table 1. Great Lakes Water Level Changes, in 

inches, from winter minima to June 

(calculated using monthly means)

Lake Superior Summary

In June 2015, Lake Superior’s water level was 1 

inch higher than it was a year before, and 7 inches 

higher than LTA. Figure 2 shows 2013, 2014, and 

2015 monthly mean water levels in comparison 

with the historical record and long term average 

monthly mean water levels.

Figure 2: 2013, 2014, and 2015 Lake Superior 

water levels overlaid with water levels from 

1918 to 2012 and the long term average (LTA) 

monthly mean water levels.

Figure 3 shows the deviation from long term 

average monthly precipitation since January 

2013. The Superior basin has, for the most part, 

experienced less than average precipitation since 

December 2014, with the exception of May 2015. 

Unlike the lower lakes, Lake Superior did not 

receive exceptionally high June precipitation. For 

the most part, this, in combination with higher 
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than average winter evaporation rates has resulted 

in slightly less-than-average NBS to Lake 

Superior. 

Figure 3: Deviation from long term average 

monthly precipitation.

Figure 4: Impacts of higher Lake Superior 

water levels at Havilland Bay, Ontario (top: 

2007; bottom: 2015). Credit: Lake Superior 

Board of Control.

Although Lake Superior levels have not reached 

record high values, two years of high levels 

following an extended period of very low water 

levels has resulted in noticable waterfront 

impacts. For example, beach area has been 

reduced, as in Figure 4.

The water level of Lake Superior is forecast to 

begin is seasonal decline between August and 

September. Levels are anticipated to be below 

last year’s levels from September to January, but 

remain several inches above LTA levels over the 

next 6 months.

Lake Michigan-Huron Summary

In June 2015, Lake Michigan-Huron’s water level 

was 12 inches higher than it was a year before, 

and 6 inches higher than LTA. Figure 5 shows 

2013, 2014, and 2015 monthly mean water levels 

in comparison with the historical record and long 

term average monthly mean water levels. 

Figure 6 shows the deviation from long term 

average monthly precipitation since January 

2013. Greater than normal precipitation during 

May and June followed a 5-month period of 

below average precipitation. For the most part, 

this has resulted in less-than-average NBS to 

Lake Michigan-Huron, except in December and 

in June. 

June 2015 water levels were 26 inches below 

record high June water levels (1986). However, 

two years of high levels following an extended 

period of very low water levels has resulted in 

noticable waterfront impacts, similar to those 

seen on Lake Superior. Figure 7 shows one 

location where water levels have encroached on 

property and eroded a sandy beach to expose 

rocks and pebbles.

Lake Michigan-Huron is predicted to begin its 

seasonal decline in August, but will remain above 

last year’s levels until December. By January, the 

level is forecast to be 1 inch below last year’s 
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level. Levels will remain 7 to 8 inches above 

LTA over the next 6 months.

Figure 5: 2013, 2014, and 2015 Lake MichiganHuron water levels overlaid with water levels 

from 1918 to 2012 and the long term average 

(LTA) monthly mean water levels.

Figure 6: Deviation from long term average 

monthly precipitation.

Figure 7: Impacts of changes in Lake 

Michigan-Huron water levels at one location in 

Two Rivers, Wisconsin (top: December 2013; 

bottom: July 2015). Credit: the Sacket Family,

Two Rivers, WI.

Lake St. Clair Summary

The water level of Lake St. Clair in June 2015 

was 8 inches above the level of one year ago and 

10 inches above the LTA. Figure 8 shows 2013, 

2014, and 2015 monthly mean water levels in 

comparison with the historical record and long 

term average monthly mean water levels.

Lake St. Clair’s mean water level in December 

2014 was 9 inches above its LTA December 

level. Due to dry conditions and constriction of 

flow in the St. Clair River during the very cold 

winter months, however, the level dropped to 2 

inches below LTA by February. The subsequent 

breakup of ice followed by very high 
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precipitation in June then resulted in a rise of 15 

inches bringing the lake to June’s high level. 

Figure 8: 2013, 2014, and 2015 Lake St. Clair 

water levels overlaid with water levels from 

1918 to 2012 and the long term average (LTA) 

monthly mean water levels.

Lake St. Clair is expected to continue its seasonal 

decline, but is forecast to remain above last year’s 

levels for the next 6 months. Levels are 

anticipated to be 9 to 13 inches above LTA 

levels.

Lake Erie Summary

In June 2015, Lake Erie was 7 inches above its 

June LTA level and 5 inches above its level in 

June 2014. Figure 14 shows 2013, 2014, and 

2015 monthly mean water levels in comparison 

with the historical record and long term average 

monthly mean water levels.

Figure 10 shows the deviation from long term 

average monthly precipitation since January 

2013. Greater than normal precipitation during 

May and nearly double the normal June 

precipitation followed a 7-month period of below 

average precipitation. This has resulted in lessthan-average NBS to Lake Erie from October 

2014 to March 2015 transitioning to NBS values 

much higher than average by June (the June NBS 

was more than 3.5 times its LTA June NBS). 

This very large NBS, combined with higher than 

average Detroit River flows, was responsible for 

a very large rise on Lake Erie.

Figure 9: 2013, 2014, and 2015 Lake Erie 

water levels overlaid with water levels from 

1918 to 2012 and the long term average (LTA) 

monthly mean water levels.

Figure 10: Deviation from long term average 

monthly precipitation.

The lake’s seasonal rise until June was 21 inches, 

which is 8 inches more than the normal March to 

June rise. The lake began the year 7 inches above 
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LTA, but returned to its LTA level in March. The 

subsequent very wet late spring and early summer 

then resulted in Lake Erie returning to above 

average levels by June. 

Lake Erie is expected to continue its seasonal 

decline, but remain above levels seen last year 

over the next 6 months. The latest 6-month 

forecast shows Lake Erie levels ranging from 10 

to 16 inches above LTA.

Lake Ontario Summary

Despite dropping to 11 inches below LTA levels 

by March, Lake Ontario returned to just 2 inches 

below LTA by June. The water level of Lake 

Ontario in June 2015 was 6 inches below the 

level of one year ago. Figure 11 shows 2013, 

2014, and 2015 monthly mean water levels in 

comparison with the historical record and long 

term average monthly mean water levels.

Figure 11: 2013, 2014, and 2015 Lake Ontario 

water levels overlaid with water levels from 

1918 to 2012 and the long term average (LTA) 

monthly mean water levels.

The NBS to Lake Ontario was above average in 

April and June 2015, but below average during 

the remainder of the 6 month period. The June 

NBS was more than twice its normal June value, 

a result of the very large amount of June 

precipitation, demonstrated in Figure 12.

Lake Ontario will continue its seasonal decline, 

but is forecast to remain 1 to 6 inches above last 

year’s levels over the next 6 months. The 6-

month forecast predicts levels ranging from 9 

inches above LTA in August to 2 inches below 

LTA in December.

Figure 12: Deviation from long term average 

monthly precipitation.

2015 Winter Conditions

The winter of 2014-2015 was somewhat drier 

than the previous winter (see Figure 3, Figure 6, 

Figure 10, and Figure 12). However, despite a 

warmer-than-average start in December 2014, the 

winter of 2015 was very cold, especially during 

the month of February. The extremely cold 

February meant that although the overall 

precipitation was low for the winter, snow that 

did fall remained on the ground. Ultimately, the 

snow water equivalent (the amount of liquid 

water contained within the snowpack, SWE) was 

relatively high throughout the winter in the Lake 

Erie and Lake Ontario basins, despite low 

precipitation (Figure 14 shows the Lake Erie 

SWE alongside the monthly departure from 

average precipitation).
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SWE has a strong impact on runoff to the lakes in 

the early spring months, and according to maps 

produced by the U.S. Geological Survey, runoff 

in the Lake Erie basin was at or above normal in 

March and April, and runoff in the Lake Ontario 

basin was above normal in April. The above 

average April runoff was likely responsible for 

the higher than average increase in Lake Erie and 

Lake Ontario lake levels during April (Figure 1).

Figure 13: Preliminary monthly temperature 

deviation from average (overland). 

2015 Spring Conditions

During May and June, much of the Great Lakes 

basin experienced a transition from drier than 

average conditions to wetter than average 

conditions. During June, several frontal systems 

passed through the Great Lakes region and stalled

just north of the Ohio River. Additionally, the 

remnants of Tropical Storm Bill brought tropical 

moisture to the Erie Basin. According to 

preliminary precipitation estimates, the June 2015 

precipitation was the highest June precipitation 

ever recorded for Lake Erie, and the third highest 

June precipitation on record for Lake Ontario. 

Overlake precipitation directly contributes to the 

lakes’ water budgets, and overland precipitation 

contributes indirectly through the translation of 

precipitation to runoff to the lakes. Throughout 

the month of June, many streamgages in the Lake 

Erie and Lake Ontario basins were recording 

flows at or above the 90th percentile discharge 

values for that time of year. The dramatic lake 

level rise seen on Lakes Erie and Ontario (Figure 

1) was a result of this direct and indirect 

contribution from extremely high June 

precipitation. The change from dry to wet 

conditions is reflected in the USGS maps of 

monthly streamflow in Figure 15.

Figure 14: Top: Deviation in monthly 

precipitation (inches). Bottom: snow water 

equivalent (SWE) for Lake Erie. Deviation 

from monthly precipitation is estimated from 

preliminary monthly precipitation amounts,

and SWE data are aggregated from the 

National Weather Service’s SNOw Data 

Assimilation System (SNODAS).
Vol. 193 Great Lakes Update August 2015

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Figure 15: Monthly streamflow for Great 

Lakes hydrologic units for February (top) and 

June (bottom) of 2015. Source: 

waterwatch.usgs.gov.

Request for Photos

The recent lake level rise has resulted in dramatic 

changes on shoreline properties. Images showing 

shoreline properties under low and high water

level conditions, such as those shown in Figure 4

and Figure 7 provide valuable documentation of 

the impacts these lake level changes have on 

individuals and communities. If you have images 

that show impacts of lake level change, be they

positive or negative, please consider sharing them 

with the Detroit District. To send images, please 

email hhpm@usace.army.mil or send hard copies 

to the address listed at the end of this document. 

Include your name, contact information, and a 

short description of the photos, including the 

location, year, and season in which they were 

taken. Credit will be given when using these 

images in publications (as in Figure 4 and Figure 

7).

More Information

The Detroit District’s Monthly Bulletin of Great 

Lakes Water Levels provides 1- to 6-month lake 

level forecasts and a summary of recent basin 

hydrological conditions. Additionally, the Detroit 

District issues an updated 1-month forecast each 

week. The bulletin and weekly forecasts can be 

found online at:

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

kesInformation/GreatLakesWaterLevels/WaterLe

velForecast.aspx

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