Vol. 191 Great Lakes Update August 2014 

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Volume 191: 2014 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 2014, and discusses 

the hydrologic conditions behind the recent 

significant water level rises on Lakes Superior 

and Michigan-Huron. 

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 2013 and this 

data has been coordinated between the United 

States and Canada. All 2014 water levels are 

considered provisional and will be officially 

coordinated in the spring of 2015. 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. 

2014 Overview: January - June 

In January 2014, the only Great Lake above its 

long-term average was Lake Ontario. Lakes 

Superior, Michigan-Huron, and St. Clair were 1, 

13, and 6 inches, respectively below their longterm averages (LTA), while Lake Erie was near 

its LTA. By June 2014, however, all of the Great 

Lakes, with the exception of Lake MichiganHuron, were above their LTAs. Although Lake 

Michigan-Huron was the only lake below LTA, it 

was only 6 inches lower than average, in contrast 

to its level in June 2013 when it was 19 inches 

below LTA. 

All of the Great Lakes were above their levels of 

a year ago in June 2014. In fact, Lakes Superior 

and Michigan-Huron were over a foot higher than 

they were in June 2013. Moreover, during the 

first 6 months of 2014, all of the Great Lakes 

were above their levels of a year ago, with the 

exception of Lake Ontario in March 2014. 

Great Lakes

Update 
Vol. 191 Great Lakes Update August 2014 

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These higher water levels were bolstered by 

above average NBS. All of the Great Lakes 

experienced above average Net Basin Supplies in 

April, May, and June 2014. Precipitation, a 

primary contributor to NBS, was also higher than 

average on all of the Great Lakes in April, May, 

and June, except for Lake Erie in May. 

These 3 months of above average precipitation 

were preceded by 5 consecutive months of 

average to below average precipitation on all of 

the Great Lakes, excluding Lake Michigan-Huron 

in November 2013, and Lake Erie in December 

2013 and February 2014. 

As there was record and near-record snowfall last 

winter in several cities within the Lakes 

Michigan-Huron basin, it is notable that the 

lake’s estimated precipitation was below average 

in the first 3 months of the year. Precipitation in 

the winter in cold weather regions is often underrecorded due to data collection limits. USACE 

Detroit uses measurements from a network of rain 

gauges around the Great Lakes to estimate lake 

basin-wide precipitation. These rain gauges are 

sometimes unable to collect all of the snowfall 

because winds can blow the falling snow away 

from the gauges. Because of this, the 

precipitation data from the winter months is not 

given much weight in this summary. 

Seasonal changes in the weather patterns 

typically cause an annual pattern of rising and 

falling water levels. In general, each of the Great 

Lakes exhibits a seasonal rise in the spring 

primarily caused by an increase in precipitation, 

the melting of accumulated snow, and an increase 

in runoff. The seasonal decline of the water level 

in the fall and winter is primarily caused by an 

increase in evaporation and the accumulation of 

snowpack on the land area. 

In table 1, the water level rise from January to 

June in 2014 is compared with each January to 

June rise in the historical record, which dates 

back to 1918. The January to June time period 

does not represent each lake’s total seasonal rise, 

because the timing of seasonal maximums and 

minimums varies from lake to lake. This analysis 

is simply highlighting what has happened so far 

in 2014. 

Water Level Rise (June monthly mean 

minus January monthly mean), inches 

Lake 2013 2014 

Historical 

Average Rise 

Superior 11 8 5 

Michigan-Huron 19 11 9 

St. Clair 18 13 13 

Erie 16 10 13 

Ontario 28 13 19 

Table 1: Great Lakes Water Level Changes 

from January to June (inches) 

For a second straight year, the rise in Lakes 

Superior and Michigan-Huron water levels were 

higher than their typical amounts, but not to the 

extent as they were in 2013. The 2014 rise of 

Lakes Superior and Michigan were 3 and 2 

inches, respectively, above their historical 

average rises. In addition, the rise in Lake St. 

Clair was equal to the historical average rise, but 

the rise on Lakes Erie and Ontario were actually 

lower than average, and much lower than they 

were in 2013. 

Lake Superior Summary 

In June 2014, Lake Superior’s water level was 13 

inches higher than it was a year before, and 6 

inches higher than LTA. Lake Superior reached 

its long-term average in March which ended a 15 

- consecutive year period in which the lake was 

below LTA, the longest stretch of below average 

levels in Lake Superior’s period of record dating 

back to 1918. Below is a graph of the Lake 

Superior water levels from January to June for 

2013 and 2014. 
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Figure 1: 2013 and 2014 Lake Superior Water 

Levels 

Figure 1 shows the considerable water level 

increase on Lake Superior since last year and its 

rise above LTA in the spring and early summer of 

2014. In fact, these recent relatively higher levels 

are indicative of a longer trend in which the level 

of Lake Superior has generally been rising 

relative to its LTA since the low water levels of 

2012. Figure 2 demonstrates this trend. 

Figure 2: Rise in Lake Superior Level relative 

to LTA since January 2013 

The 14-month time period in which the monthly 

mean levels rose relative to the LTA (May 2013 

to June 2014), closely coincides with the time 

period in which the Net Basin Supply of water to 

Lake Superior was above average in 13 of those 

months. Figure 3 below illustrates this trend in 

above average NBS. 

Figure 3: Lake Superior Monthly Net Basin 

Supply 

The 2013 and 2014 NBS values are preliminary. 

Based on the coordinated NBS data record, which 

includes data from 1900 to 2008, the NBS 

received by Lake Superior in May 2013 and May 

2014, were the 2nd and 3rd highest NBS ever 

received by the lake in May. 

As stated earlier, the precipitation on Lake 

Superior was above average in April, May, and 

June, but near or below average the first 3 months 

of the year. Figure 4 shows the recent trend in 

the above average precipitation. Given the 

difficulty of accurately measuring snowfall, we 

are skeptical of the basin-wide precipitation 

estimates for the winter months. 

Figure 4: Lake Superior Precipitation in 2014 

The precipitation in April was only minimally 

above average by 0.04 inches; however, the 
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precipitation that fell in June was almost 2 inches 

above average. 

The water level of Lake Superior will continue its 

seasonal rise until August and then begin its 

seasonal decline. The lake is forecasted to range 

from 3 to 6 inches above LTA from August 

through January. 

The historic ice cover of the winter 2013-2014 

may affect the water levels in the fall. The ice 

coverage on Lake Superior peaked at nearly 96% 

in March, and was still over 40% at the beginning 

of May. The longer ice cover has had a cooling 

effect on the lake’s surface water temperature. 

Figure 4 is a plot created by NOAA’s Great 

Lakes Environmental Research Laboratory that 

shows Lake Superior’s surface temperature has 

been below average all year. 

Figure 5: Lake Superior’s surface temperature 

in 2014 compared to average (NOAA) 

The water surface temperature was 10 degrees 

below average temperatures from 1992-2013 at 

the time of this printing. Evaporation from the 

lake surface is directly related to the difference in 

temperature between the air and lake surface. If 

these cooler temperatures persist into fall, the 

lake surface will be closer in temperature to 

fall/winter air that is already predicted to be 

milder due to El Nino. This smaller temperature 

difference may lead to lower than usual 

evaporation this fall and winter. 

Lake Michigan-Huron Summary 

From January to June 2014, Lake MichiganHuron continued a 15 consecutive year stretch of 

below average levels, the longest in its period of 

record. However, by June 2014, Lake MichiganHuron’s water level was only 6 inches lower than 

its LTA. In contrast, the lake was 13 inches below 

LTA in January 2014, and 19 inches below LTA 

in June 2013. In addition, the lake’s level from 

January to June 2014 was consistently more than 

a foot above its level of a year ago. Figure 6 

demonstrates these trends. 

Figure 6: Lake Michigan-Huron Water Levels 

Figure 6 shows that Lake Michigan-Huron’s level 

was flat during the first 3 months before it began 

rising in April. In addition, the above figure 

shows the gap between Lake Michigan-Huron’s 

level and its LTA decreased from January to June 

2014. This is part of a longer trend of Lake 

Michigan-Huron inching closer to its LTA ever 

since the lake dropped to its record low level in 

January of 2013. See Figure 7 below. 
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Figure 7: Rise in Lake Michigan-Huron Level 

relative to LTA since January 2013 

This remarkable rise in Lake Michigan-Huron 

was buoyed by a trend of generally above average 

NBS to Lake Michigan-Huron in the past year 

and a half since the historic low water levels. 

Figure 8 highlights this trend. 

Figure 8: Lake Michigan Net Basin Supply by 

month since January 2013 

Figure 8 shows that in the 18 month period 

beginning January 2013, the NBS to Lake 

Michigan-Huron was above average in 12 of 

those months. The 2013 and 2014 NBS values are 

preliminary. Based on the coordinated NBS data 

record (1900-2008) the NBS received by Lake 

Michigan-Huron in April 2013 and April 2014 

were the 3rd and 8th highest NBS ever received by 

the lake in April. 

The considerable differences between estimated 

NBS and Historical mean NBS in April through 

June 2014 can largely be explained by the above 

average precipitation during those 3 months. In 

the first 3 months of 2014, however, the 

precipitation was below average. Figure 9 shows 

the precipitation trend of the last 6 months. 

Figure 9: Lake Michigan-Huron Precipitation 

It is somewhat surprising that the estimated 

precipitation was not above average in the first 3 

months of 2014. During the 2013-2014 winter 

season, Chicago, IL received the third-highest 

snowfall in its history, and the cities of Grand 

Rapids, MI; Milwaukee, WI; Green Bay, WI; and 

Saginaw, MI experienced snowfall that was 55%, 

35%, 40%, and 45%, respectively, above average. 

As alluded to earlier in this article, the accuracy 

of the basin-wide precipitation values is 

questionable, and we suspect near average or 

above average precipitation on Lake MichiganHuron during the winter months. 

The historically high snowfall of winter 2013-

2014, however, is reflected in the Snow Water 

Equivalent (SWE) computed for the Lake 

Michigan and Huron basins. SWE is the depth of 

liquid precipitation that would result if the 

snowpack melted instantaneously. Figures 10a 

and 10b shows this past winter’s peak SWE 

estimates on the Lakes Michigan and Huron subbasins compared to the peaks of recent winters. 

Figure 10a: Lake Michigan sub-basin Peak SWE 
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Figure 10b: Lake Huron sub-basin Peak SWE 

Figure 10 shows the peak SWE in the Lake 

Michigan sub-basin was 37% higher than the 

peak SWE in any of the previous ten winters, 

while the Lake Huron peak SWE was over 10% 

higher than the peak SWE of the previous 3 

years. The Lake Huron analysis is only 4 years 

long, because only 4 years of SWE data for the 

Canadian side of the Lake Huron sub-basin exist. 

Another factor which has contributed to Lake 

Michigan-Huron’s considerable water level rise is 

the above average inflow from the St. Mary’s 

River. The St. Mary’s river flow, regulated by 

the International Lake Superior Board of Control 

in accordance with Regulation Plan 1977-A, was 

above average every month from January to June 

2014 as shown in Figure 9, and has been above 

average since July 2013. This trend is shown in 

Figure 11 below. 

Figure 11: Lake Michigan-Huron inflow 

through the St. Mary’s River 

The difference between the observed outflow and 

historical average significantly increased in May 

and June 2014, which is due to higher outflow 

being released from Lake Superior due to the rise 

in water level on that Lake. 

While inflow through the St. Mary’s River was 

above average during the first six months of 

2014, Lake Michigan-Huron’s outflow through 

the St. Clair River was below average in four of 

the 6 months. Figure 12 illustrates these 

conditions. 

Figure 12: Lake Michigan-Huron outflow 

through the St. Mary’s River 

Figure 12 shows the outflows through the St. 

Clair River were near average in February and 

June, and that the historical monthly average 

outflows were not exceeded from January to June 

2014. Lake Michigan-Huron outflows were 

generally below average in part due to the lake 

remaining below LTA. 

Lake Michigan-Huron is predicted to begin its 

seasonal decline in September. The lake level is 

forecasted to continue to get closer to LTA, and 

reach LTA by November 2014. 

Lake St. Clair Summary 

The water level of Lake St. Clair in June 2014 

was 9 inches above the level of one year ago and 

2 inches above the LTA. The lake’s rise from 

January to June 2014 was 13 inches, equaling its 

historical average rise. Lake St. Clair started its 

seasonal rise in February. Figure 13 shows the 

Lake St. Clair water levels thus far in 2014 

compared to average and last year. 
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Figure 13: Lake St. Clair Water Levels 

Lake St. Clair ranged from 2 to 4 inches below 

LTA before reaching the LTA in May. In 

addition, Lake St. Clair was consistently above its 

level of year ago during the first 6 months of 

2014 – ranging from 3 to 11 inches above. The 

Lake began its seasonal rise in March, as it 

typically does. 

Lake St. Clair experienced above average NBS 

from March to June 2014. Above average 

precipitation occurred from April to June 2014, 

preceded by 3 months of below average 

precipitation. 

Lake St. Clair is expected to follow the typical 

seasonal decline for the remainder of 2014. From 

July’s mean water level to January, the lake is 

predicted to fall 12 inches. 

Lake Erie Summary 

In June 2014, Lake Erie was 3 inches above LTA 

and 7 inches above its level in June 2013. 

Figure 14 shows the water levels through the first 

six months of 2014. 

Figure 14: Lake Erie Water Levels 

The lake’s January to June rise in 2014 was 10 

inches, three inches less than normal. Also, the 

Lake Erie’s level began rising in February. The 

Lake has ranged from 3 to 10 inches above last 

year’s levels in the first half of 2014. It was near 

its LTA in January, below LTA in February and 

March, regained its LTA in April, and exceeded 

LTA in May and June. 

Inflow from the Detroit River was near average 

from March to June 2014, and outflow through 

the Niagara River was near average from 

February to June. Since inflow and outflow to 

Lake Erie were generally near average, they 

probably did not influence the seasonal rise 

substantially. 

There has been no trend in the NBS to Lake Erie 

during the first half of 2014. The NBS has been 

above average in 3 different months, near average 

in two non-consecutive months, and below 

average in March. Several cities in the Lake Erie 

basin received record high snowfall in the winter 

of 2013-2014. Detroit, MI, and Toledo, OH, 

experienced their highest snowfall on record, 

while Fort Wayne, IN saw its 2nd highest 

snowfall. 

The level of Lake Erie has plateaued for the year. 

The latest six month forecast shows Lake Erie’s 

beginning its seasonal decline in August and will 

fall 11 inches during the next 6 months. 

Lake Ontario Summary 

Typically, Lake Ontario begins rising in January. 

However, the lake began 2014 by dropping the 

first two months, before beginning its seasonal 

climb in April. The lake rose just 13 inches from 

January to June 2014, far below the 19-inch 

average. Figure 15 shows the lake’s water levels 

from January to June 2014. 
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Figure 15: Lake Ontario Water Levels 

The water level of Lake Ontario was 3 inches 

above the level of one year ago and 5 inches 

above LTA in June 2014. Lake Ontario hovered 

within 5 inches of its LTA through the first 6 

months of 2014. Also, besides February, it was 

above its levels of a year ago in every other 

month. 

The NBS to Lake Ontario was above average 

from April to June 2014. The NBS was certainly 

boosted by precipitation that was also above 

average during those 3 months as well. 

Lake Ontario began its seasonal decline in July. 

The latest 6 month forecast shows Lake Ontario 

continuing to fall into December. Its December 

mean level will be 26 inches lower than its mean 

level was in July. 

More Information 

Detroit District recently changed the links to the 

PDF documents for its Monthly Bulletin of Great 

Lakes Water Levels. Below is a list of the new 

links for the Bulletin PDFs: 

Combined Bulletin and Backpage 

http://w3.lre.usace.army.mil/hh/ForecastData/MB

OGLWL-combined_bulletin_and_backpage.pdf

Superior Bulletin 

http://w3.lre.usace.army.mil/hh/ForecastData/MB

OGLWL-superior.pdf

Michigan-Huron Bulletin 

http://w3.lre.usace.army.mil/hh/ForecastData/MB

OGLWL-mich_hrn.pdf

St. Clair Bulletin 

http://w3.lre.usace.army.mil/hh/ForecastData/MB

OGLWL-stclair.pdf

Erie Bulletin 

http://w3.lre.usace.army.mil/hh/ForecastData/MB

OGLWL-erie.pdf

Ontario Bulletin 

http://w3.lre.usace.army.mil/hh/ForecastData/MB

OGLWL-ontario.pdf

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