2021-Jul-19
July 18 Water Levels Report
Precipitation throughout July has been above normal for the Great Lakes basin except for Lake Superior. This month predicted outflows from Lake Superior into the St. Mary’s River are predicted to be only average, not above average as they have been for at least 2 years. This shows that, under Plan 2012 balancing, the flow into Lake Michigan-Huron continues to be reduced. Lake Michigan-Huron continues to be below the level it was at this time last year – see first graph below. All the lakes are now lower than they were at this time last year.
From a month ago the water levels on Lakes Superior, Michigan-Huron, St Clair, Erie and Ontario are up 0, 3, 4, 3 & 4 inches respectively. Lakes Superior, Michigan-Huron, St Clair, Erie & Ontario, are lower by 8, 18, 13, 11 & 15 inches, respectively, than they were at this time last year. Lakes Superior, Michigan-Huron, St Clair & Erie are 1, 16, 19 & 15 inches, respectively, above their long term July average, whereas Lake Ontario is 8 inches below. All the lakes are now well below their July record highs.
In a month’s time, the levels for Lakes Superior is expected to be up 1 inch and Lakes Michigan-Huron, St Clair, Erie & Ontario are expected to be down 1, 3, 4 & 3 inches, respectively.
Outflows from Lake Superior into the St. Mary’s River is predicted to be average for this month and Lake Michigan-Huron’s outflow into the St. Clair River is predicted to be above average for this month. Lake St. Clair’s outflow through the Detroit River and Lake Erie’s outflow through the Niagara River are also forecasted to be above average in this month. In addition, Lake Ontario’s outflow through the St. Lawrence River is projected to be above average for this month.
This report below shows the most recent month of precipitation and outflows published by Level News:
With regard to the forecast graph below, and the more recently updated first graph in this report, the USACE is predicting that the most likely outcome is that levels will now remain flat through July. The usual seasonal March to June increase has not occurred due to reduced precipitation, even with the significant recent rainfall. Levels are then expected to commence their seasonal decline in August through November.
Monthly mean water levels for the previous year and the current year to date are shown as a solid line on the hydrographs. A projection for the next six months is given as a dashed line. This projection is based on the present condition of the lake basin and anticipated future weather. The shaded area shows a range of possible levels over the next six months dependent upon weather variations. Current and projected levels (solid and dashed lines) can be compared with the 1918-2019 average levels (dotted line) and extreme levels (shown as bars with their year of occurrence). The legend below further identifies the information on the hydrographs.
