MARCH 2018 BEACON

Information

Recorded water levels in this bulletin are derived from a representative network of water level gages on each lake (see cover map). Providers of these data are the U.S. Department of Commerce, NOAA, National Ocean Service, and Integrated Science Data Management, Department of Fisheries and Oceans, Canada. The Detroit District, Corps of Engineers and Environment Canada derive historic and projected lake levels under the auspices of the Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data. This bulletin is produced monthly as a public service. The Corps also, on a weekly basis publishes online the Great Lakes, Connecting Channels and St. Lawrence River Water Levels and Depths , which provides a forecast of depths in the connecting rivers between the Great Lakes and the International Section of the St. Lawrence River. This Monthly Bulletin of the Lake Levels for the Great Lake s may be obtained free of charge by writing to the address shown on the front cover, by calling (313) 226-6442 or emailing hhpm@usace.army.mil. Notices of change of address should include the name of the publication. This information is available on the internet at http://www.lre.usace.army.mil/Missions/GreatLakesInformation.aspx . According to preliminary estimates, basin-wide precipitation was near average for the basin as a whole during November, but Lake Michigan-Huron and Lake Ontario both received below average precipitation. Lake Erie received the most precipitation with estimates at 143% of its average November precipitation and Lake Michigan- Huron received the least rainfall at only 83% of its November average. Over the last 12 months, the total rainfall has been slightly above average for the Great Lakes basin. Net basin supply was above average for Lake Erie and Lake Ontario. Lake outflows in November were above average for all lakes. All of the lakes were above their November long-term average water levels. From October to November, all of the lakes experienced a decline of about an inch, except for Lake Ontario, which remained the same. This November’s levels were 7 to 15 inches above last year’s November level. All of the lakes are below their record high levels. Lake Superior is only 4 inches below its record high November level set in 1985. The other lakes are 13 to 21 inches below their record high November levels. All of the lakes remain above their long-term averages by 12 to 21 inches. Great Lakes Basin Hydrology November 2017

PRELIMINARY PRECIPITATION (INCHES)

November

12-Month Comparison

BASIN

Average

Average

% of Average

% of Average

Last 12 months

2017

Diff.

Diff.

(1900-2014)

(1900-2014)

Superior

2.55 2.30 4.10 2.98

2.48 2.77 2.86 3.16

0.07 -0.47

103

34.15 35.85 37.45 42.19

30.52 32.57 35.65 35.87

3.63 3.28 1.80 6.32

112 110 105 118

Michigan-Huron

83

Erie

1.24 143

Ontario

-0.18

94

Great Lakes

2.69

2.75

-0.06

98

36.38

32.76

3.62

111

November Net Basin Supplies 1 (cfs)

November Outflows 2 (cfs)

LAKE

Average 3 (1900-2008)

Average (1900-2008)

2017

2017

Superior

6,000

17,000

111,000

78,000

Michigan-Huron

14,000

40,000

216,000

190,000

Erie

19,000 58,000

-2,000

240,000 300,000

201,000 239,000

Ontario

20,000

Notes: Values (excluding averages) are based on preliminary computations; cfs denotes cubic feet per second. 1 Net basin supply is the net result of precipitation falling on the lake, runoff from precipitation falling on the land which flows to the lake, and evaporation from the lake. Negative net basin supply denotes evaporation exceeded runoff and precipitation. The net total supply can be found by adding the net basin supply and the outflow from the upstream lake. 2 Does not include diversions. 3 Lake Ontario average water supplies and average outflows are based on period of record 1900-2005