Great Lakes Article:

Lake levels rising
By Jack Storey
Soo Evening News
Published October 21, 2007

EASTERN UPPER PENINSULA - Above-average rainfall in September and local rains already well beyond the norm for October before Thursday's monsoon may promise an eventual change in Upper Great Lakes water levels.

On a month-to-date basis, the 3.05 inches of rain that fell on Sault Ste. Marie prior to Thursday's heavy rain rated nearly 1.25 inches above average for mid-October, the National Weather Service confirmed. Heavy fall rains stand in stark contrast to the many months of dry conditions that prevailed through the first half of 2007 and beyond.

After many months of drought and minimal snow pack last winter, Lake Superior struck a new monthly low level in August that continued, despite heavy rain, in September, the Corps of Engineers reported. While the Corps' most recent Monthly Bulletin of Lake Levels indicated another monthly low for the Big Lake is expected in October, that forecast was prepared before the heavy rains began over at least part of the Lake Superior watershed.

Lake levels on Lake Superior do not necessarily follow local rainfall patterns. Instead, they trend up or down based almost entirely on rainfall over the extended Lake Superior watershed.

In an accompanying report, the Corps of Engineers circulated a “Great Lakes Update” addressed exclusively to low water levels on Lake Superior. In it, the Corps indicated that before this year, all monthly record low water levels on the Big Lake were set in late 1925 and 1926. The all-time record low on Lake Superior was also set in March and April, 1926. That record was about one foot lower than the monthly record low set in August of this year.

The Corps report cited a number of factors that contributed to the record 1925-1926 low water records. They include:

-Rainfall. Lake Superior receives 96 percent of its water from rainfall, snowmelt and runoff. Several years of below average rainfall in the early 1920s contributed to the records set in 1925 and 1926. Rainfall at Marquette and Ispheming ran more that 10 inches below average in 1925. That year was the driest on record at Marquette.

-Snow pack. The winter of 1925-1926 was mild by Upper Peninsula standards. Only two major storms occurred that winter. Calumet, which averages more than 200 inches of snow each winter, received only 85 inches that 1925-'26 winter.

-Diversions. Although public officials and the general public frequently say the Chicago diversion of Lake Michigan water contributes to low water levels throughout the Upper Great Lakes, the facts do not support that claim.

Since the 1930s, the amount of water diverted at Chicago has been steadily reduced by action of the federal courts. For the past 40 years, the Chicago diversion has been limited to no mare that 3,000 cubic feet per second (cfs).

At the same time, the Long Lac and Ogoki diversions from Ontario into Lake Superior have added an average of 5,000 cfs of inflow to the Big Lake.

The net impact of the two diversions - one into the Great Lakes, the other out - is an additional 2,000 cfs more water coming in than going out.

-Recovery. Following the record low water levels of 1925 and 1926, Lake Superior rose rapidly with increased rainfall on its watershed. By 1928 and 1929, average water levels on Lake Superior rose from record lows to above-average levels.

Since Big Lake water levels are dependent almost entirely on rainfall, it is not possible to predict when lake levels will return to average or above.

As of early October, Lake Superior was 21 inches below its average for the time of year. Lakes Michigan and Huron were 23 inches below their average. Lake St. Clair was 10 inches below its average.

Lake Erie and Lake Ontario were also slightly lower than average at three and seven inches under the norm, respectively, the Corps report said.