2020-Nov-16
November 15 Water Levels Report
Temperatures this past week in the Great Lakes basin were unseasonably warm. For the upcoming week, temperatures will be more seasonable across the basin, and the next large system will move into the region Saturday night into Sunday, bringing widespread precipitation to the basin. Water levels continue to be well above average and near or above record high levels, but all the lakes are continuing their seasonal declines. 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 either the same as, or lower than, they were at this time last year.
From a month ago the water levels on Lakes Superior, Michigan-Huron, St Clair, Erie & Ontario are down 1, 2, 4, 2 & 4 inches respectively. Lakes Superior, Michigan-Huron, St. Clair, Erie & Ontario, are lower by 3, 3, 3, 1 & 18 inches, respectively, than they were at this time last year. Lakes Superior, Michigan-Huron, St Clair, Erie & Ontario are 10, 32, 28, 25 & 3 inches, respectively, above their long term November average. All the lakes are now well below their November record high.
In a month’s time, the levels of Lakes Superior, Michigan-Huron, St Clair, & Erie are expected to be lower by 2-3 inches, and Lake Ontario is expected to be unchanged. 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.
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.
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 continue to decline through the remainder of the year and into January 2021, with the normal seasonal increase commencing in March.
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.
** Average, Maximum and Minimum for period 1918-2019