2021-Apr-12
April 11 Water Levels Report
The Great Lakes basin experienced much higher than average temperatures over the past week. Water levels continue to be well above average and near record high levels. 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 2, 0, 1, 2 and 4 inches respectively. Lakes Superior, Michigan-Huron, St Clair, Erie & Ontario, are lower by 7, 13, 15, 17 & 28 inches, respectively, than they were at this time last year. Lakes Superior, Michigan-Huron, St Clair & Erie are 7, 22, 19, & 15 inches, respectively, above their long term April average, whereas Lake Ontario is 12 inches below. All the lakes are now well below their April record highs.
In a month’s time, the levels for Lakes Superior, St Clair, Erie & Ontario are expected to be up 2-7 inches with Lake Michigan expected to be up 2 inches. High water levels and potentially record high water levels are expected to persist for at least the next six months, so flood prone areas are expected to remain vulnerable.
Outflows from Lake Superior into the St. Mary’s River and Lake Michigan-Huron’s outflow into the St. Clair River are 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 commence their normal seasonal increase through June. Levels are then expected to commence their seasonal decline in July.
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.
The satellite image below from earlier today shows that the Bay is now completely clear of ice.
