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Great Lakes Water Level Outlook- July 2020 Edition - August Update

Outlook Summary:

This product is not an official forecast of Great Lakes water levels. Rather, this product is meant to illustrate outcomes that would occur under historical weather and water supply condition, with scenarios chosen based on similarities to recent conditions. For the official forecast, please see our Monthly Bulletin of Great Lakes Water Levels.

 

Near or above record high water levels continue on some of the Great Lakes. Water levels follow a seasonal cycle where water levels rise in the spring due to increased precipitation and enhanced runoff from snowmelt. In the fall, the lakes generally decline due to an increase in evaporation as temperatures decline and cold air moves over the relatively warm lake waters. We refer to the combined effect of precipitation over the lake, evaporation from the lake, and runoff to the lake as Net Basin Supply (NBS). This edition of the Water Level Outlook compares years that experienced very wet or very dry conditions over the next 3 months (July – Sept.). Two years that had significantly wetter than average conditions over the next 3 months were 1986 and 1977 (blue lines). Two years that had significantly drier than average conditions from July to September were 1930 and 1976 (brown lines). This publication of the Water Level Outlook incorporates the projection of water levels if the NBS over the next 12 months is similar to what occurred in 1986-87, 1977-78, 1930-31, and 1976-77. The most recent coordinated 6-month forecast is also shown for comparison.



Click on the individual graphics to view a larger, printer-friendly image (pdf).




 



 
 
* For the official 6-month forecast of all lakes, including Lake Ontario, see the Monthly Bulletin of Great Lakes Water Levels.
 

 

Click here to obtain the full Great Lakes Water Level Outlook document (pdf)

Great Lakes Water Level Outlook Data

 

To view the water level outlook data in tabular format, click on the links below.

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Lake Superior

Monthly Mean Water Level (meters IGLD)

  Aug-20 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21
1986-87 183.80 183.81 183.79 183.74 183.65 183.54 183.47 183.42 183.40 183.43 183.46 183.50
1977-78 183.82 183.91 183.94 183.87 183.81 183.73 183.63 183.57 183.55 183.60 183.69 183.75
1930-31 183.78 183.74 183.69 183.63 183.54 183.44 183.35 183.27 183.24 183.29 183.36 183.41
1976-77 183.77 183.68 183.57 183.46 183.35 183.27 183.22 183.25 183.32 183.37 183.41 183.47
Ensemble Median 183.81 183.80 183.76 183.72 183.64 183.55 183.49 183.46 183.48 183.58 183.66 183.72
Long Term Average 183.54 183.54 183.52 183.47 183.41 183.33 183.27 183.24 183.26 183.37 183.45 183.51
Long Term Maximum 183.86 183.86 183.91 183.89 183.81 183.70 183.63 183.61 183.68 183.77 183.84 183.86
Long Term Minimum 183.01 183.02 183.10 183.01 182.92 182.83 182.76 182.74 182.72 182.76 182.85 182.96

 

 

Lake Michigan-Huron

Monthly Mean Water Level (meters IGLD)

 

  Aug-20 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21
1986-87 177.39 177.42 177.48 177.39 177.28 177.20 177.12 177.08 177.08 177.08 177.07 177.04
1977-78 177.44 177.43 177.38 177.34 177.33 177.30 177.24 177.20 177.24 177.32 177.36 177.36
1930-31 177.39 177.27 177.13 177.00 176.89 176.79 176.71 176.66 176.64 176.66 176.68 176.66
1976-77 177.38 177.25 177.10 176.97 176.84 176.70 176.64 176.70 176.79 176.81 176.79 176.78
Ensemble Median 177.41 177.34 177.25 177.17 177.11 177.06 177.04 177.04 177.10 177.15 177.20 177.21
Long Term Average 176.57 176.52 176.45 176.39 176.35 176.30 176.29 176.31 176.39 176.49 176.56 176.59
Long Term Maximum 177.39 177.38 177.50 177.38 177.26 177.18 177.11 177.12 177.23 177.28 177.33 177.39
Long Term Minimum 175.77 175.76 175.70 175.65 175.61 175.57 175.59 175.58 175.61 175.74 175.76 175.78

 

 

Lake St. Clair

Monthly Mean Water Level (meters IGLD)

 

  Aug-20 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21
1986-87 175.86 175.85 175.92 175.84 175.83 175.75 175.65 175.67 175.69 175.66 175.64 175.61
1977-78 175.91 175.95 175.92 175.83 175.96 175.89 175.84 175.88 176.00 175.99 175.97 175.90
1930-31 175.85 175.71 175.61 175.44 175.36 175.29 175.24 175.24 175.29 175.28 175.30 175.28
1976-77 175.86 175.73 175.62 175.48 175.38 175.41 175.33 175.47 175.55 175.54 175.49 175.47
Ensemble Median 175.88 175.78 175.68 175.62 175.60 175.59 175.58 175.63 175.70 175.74 175.76 175.75
Long Term Average 175.17 175.10 175.01 174.93 174.93 174.85 174.80 174.92 175.06 175.14 175.19 175.21
Long Term Maximum 175.96 175.86 175.96 175.82 175.80 175.80 175.80 175.80 175.82 175.89 175.99 176.04
Long Term Minimum 174.41 174.34 174.27 174.18 174.24 173.88 173.89 174.05 174.32 174.42 174.45 174.50

 

 

Lake Erie

Monthly Mean Water Level (meters IGLD)

 

  Aug-20 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21
1986-87 174.94 174.89 174.90 174.88 174.90 174.88 174.80 174.78 174.83 174.83 174.80 174.77
1977-78 175.01 175.05 175.00 174.89 174.98 175.02 174.95 175.02 175.17 175.21 175.17 175.06
1930-31 174.92 174.77 174.62 174.50 174.43 174.39 174.36 174.38 174.45 174.48 174.47 174.44
1976-77 174.94 174.83 174.72 174.57 174.48 174.45 174.45 174.57 174.76 174.81 174.75 174.70
Ensemble Median 174.95 174.83 174.72 174.63 174.63 174.66 174.65 174.73 174.83 174.89 174.89 174.86
Long Term Average 174.27 174.18 174.08 174.01 174.01 174.01 174.00 174.09 174.24 174.32 174.35 174.34
Long Term Maximum 175.02 174.87 174.94 174.85 174.89 174.86 174.78 174.88 174.98 175.05 175.14 175.13
Long Term Minimum 173.43 173.38 173.30 173.20 173.19 173.21 173.18 173.20 173.38 173.44 173.45 173.45

 

Lake Superior

Monthly Mean Water Level (ft IGLD)

  Aug-20 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21
1986-87 603.03 603.05 602.99 602.81 602.51 602.18 601.93 601.77 601.71 601.79 601.91 602.05
1977-78 603.08 603.37 603.47 603.25 603.06 602.79 602.47 602.26 602.20 602.37 602.65 602.87
1930-31 602.95 602.82 602.67 602.47 602.18 601.84 601.54 601.27 601.18 601.34 601.56 601.75
1976-77 602.91 602.61 602.26 601.92 601.55 601.28 601.13 601.21 601.45 601.60 601.74 601.95
Ensemble Median 603.03 603.01 602.90 602.76 602.50 602.20 602.00 601.89 601.98 602.29 602.57 602.74
Long Term Average 602.17 602.17 602.10 601.94 601.74 601.48 601.28 601.18 601.25 601.61 601.87 602.07
Long Term Maximum 603.22 603.22 603.38 603.31 603.05 602.69 602.46 602.40 602.62 602.92 603.15 603.22
Long Term Minimum 600.43 600.46 600.72 600.43 600.13 599.84 599.61 599.54 599.48 599.61 599.90 600.26

 

 

Lake Michigan-Huron

Monthly Mean Water Level (ft IGLD)

 

  Aug-20 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21
1986-87 582.00 582.07 582.27 582.00 581.62 581.35 581.11 580.98 580.97 580.97 580.95 580.83
1977-78 582.14 582.11 581.96 581.84 581.80 581.68 581.51 581.37 581.49 581.76 581.89 581.88
1930-31 581.98 581.58 581.13 580.70 580.34 580.03 579.75 579.58 579.54 579.59 579.66 579.59
1976-77 581.96 581.54 581.04 580.61 580.18 579.72 579.54 579.73 580.02 580.08 580.02 579.98
Ensemble Median 582.06 581.83 581.53 581.28 581.07 580.91 580.82 580.84 581.03 581.21 581.37 581.41
Long Term Average 579.30 579.13 578.90 578.71 578.58 578.41 578.38 578.44 578.71 579.04 579.27 579.36
Long Term Maximum 581.99 581.96 582.35 581.96 581.56 581.30 581.07 581.10 581.46 581.63 581.79 581.99
Long Term Minimum 576.67 576.64 576.44 576.28 576.15 576.02 576.08 576.05 576.15 576.57 576.64 576.71

 

 

Lake St. Clair

Monthly Mean Water Level (ft IGLD)

 

  Aug-20 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21
1986-87 576.98 576.95 577.16 576.91 576.86 576.61 576.28 576.36 576.41 576.33 576.25 576.15
1977-78 577.12 577.26 577.16 576.88 577.28 577.05 576.89 577.04 577.42 577.39 577.33 577.10
1930-31 576.95 576.47 576.14 575.60 575.34 575.11 574.92 574.93 575.10 575.07 575.12 575.06
1976-77 576.98 576.56 576.17 575.73 575.40 575.50 575.23 575.69 575.95 575.93 575.76 575.70
Ensemble Median 577.03 576.69 576.39 576.17 576.11 576.07 576.05 576.21 576.44 576.58 576.63 576.60
Long Term Average 574.70 574.48 574.18 573.92 573.92 573.65 573.49 573.88 574.34 574.61 574.77 574.84
Long Term Maximum 577.30 576.97 577.30 576.84 576.77 576.77 576.77 576.77 576.84 577.07 577.40 577.56
Long Term Minimum 572.21 571.98 571.75 571.46 571.65 570.47 570.51 571.03 571.92 572.24 572.34 572.51

 

 

Lake Erie

Monthly Mean Water Level (ft IGLD)

 

  Aug-20 Sep-20 Oct-20 Nov-20 Dec-20 Jan-21 Feb-21 Mar-21 Apr-21 May-21 Jun-21 Jul-21
1986-87 573.96 573.77 573.83 573.77 573.81 573.77 573.49 573.42 573.58 573.59 573.49 573.39
1977-78 574.18 574.32 574.13 573.80 574.07 574.22 573.97 574.22 574.71 574.85 574.69 574.34
1930-31 573.90 573.38 572.91 572.50 572.26 572.14 572.04 572.12 572.35 572.44 572.41 572.32
1976-77 573.95 573.57 573.22 572.73 572.43 572.33 572.33 572.75 573.37 573.51 573.32 573.16
Ensemble Median 573.98 573.58 573.22 572.95 572.92 573.03 573.01 573.28 573.58 573.78 573.80 573.68
Long Term Average 571.75 571.46 571.13 570.90 570.90 570.90 570.87 571.16 571.65 571.92 572.01 571.98
Long Term Maximum 574.21 573.72 573.95 573.65 573.79 573.69 573.43 573.75 574.08 574.31 574.61 574.57
Long Term Minimum 569.00 568.83 568.57 568.24 568.21 568.27 568.18 568.24 568.83 569.03 569.06 569.06

 

Detroit District Disclaimer

NOTICE: All data contained herein is preliminary in nature and therefore subject to change. The data is for general information purposes ONLY and SHALL NOT be used in technical applications such as, but not limited to, studies or designs. All critical data should be obtained from and verified by the United States Army Corps of Engineers, Detroit District, Engineering and Technical Services, Great Lakes Hydraulics and Hydrology Office, 477 Michigan Ave., Detroit, MI 48226. The United States of America assumes no liability for the completeness or accuracy of the data contained herein and any use of such data inconsistent with this disclaimer shall be solely at the risk of the user.