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January 14, 2014

Great Lakes see sizable gains in water levels over 2013

By Kevin Bunch
C & G Staff Writer

MACOMB COUNTY — The Great Lakes have come closer than they have in years to returning to their long-term average water levels, thanks to 2013’s wet weather, according to hydrologists with the U.S. Army Corps of Engineers and the National Oceanic and Atmospheric Administration.

Lake Erie rose 4 inches from December 2012 to December 2013, the Lake Michigan-Huron system rose 11 inches, and Lake St. Clair was up 8 inches, according to Jim Lewis, hydraulic engineer with the Corps of Engineers.

“It was a really wet year in 2013,” Lewis said. “For example, the Michigan-Huron level stayed steady from October to November this fall, and that time of year is when it’s at its deepest decline.”

NOAA Great Lakes Environmental Research Lab Hydrologist Drew Gronewald said the lake levels in Erie, Superior and Michigan-Huron — which is counted as one lake system — dropped around 1998, and did not change much for the ensuing decade.

“The water levels on all the Great Lakes go up and down over a variety of different timescales,” he said. “For example, the natural range on Michigan and Huron is around 2 meters, or six feet.”

That stability ended in 2012, however, due to a dry winter and ensuing drought, he said. The aftermath saw lake levels drop to record lows. The long-term data showed the last time they had dropped that low was in the 1960s, Gronewald said.

“Water temperatures were very high and we had above-average evaporation rates, which led to precipitous drop in water levels,” Gronewald said of 2012. “It was unprecedented. Lake Erie has never failed to rise in the spring, but it did that year because of drought.”

Lewis said the standard lake cycle sees water levels decline in the fall and winter before getting boosted back up in the spring and summer from precipitation and the snowpack melting. The snowfall in early 2013, coupled with the rest of the year seeing above-average rainfall even into the typically drier October and November seasons, brought water levels close to where they should be.

Gronewald said that January tends to be the point where the lakes are at their lowest in the entire year, but they have recovered to the point they were all at two years ago, before the drought.

Additionally, Lewis said that while it is difficult to guess what will happen down the line, the Corps is forecasting that the lakes will, at the least, likely stay where they currently are through June, in terms of water levels.

Lewis said that if precipitation is reasonably strong, it is possible that Lake St. Clair and Lake Erie could hit or exceed their long-term average amounts of water within that six-month span, as both are near that point already. The Lake Michigan-Huron system is 14 inches below its long-term average, however, and will take more time and precipitation to return.

Precipitation is only one factor in the water levels in the lakes, Lewis said. Evaporation is an issue that the lakes face throughout the year, but the temperature difference between the water and air can help slow it down or exacerbate it.

Evaporation occurs in the winter when colder air moves across warmer water, he said, but if a layer of ice develops, it will slow down evaporation.

“In a given winter, you may have a bunch of evaporation from the cold air, but you also may develop a lot of ice, so it’s not always easy to identify,” Lewis said. “If we do have a lot of ice as it gets into spring and early summer, the water temperature stays cooler. That can influence the next fall, as the water stays the lower temperature and doesn’t evaporate as much.”

Gronewald said the water levels in the Great Lakes have a very limited impact on inland rivers and lakes, though those can see their own water levels impacted by the same meteorological trends.

“The regional climate factors that draw the flow in the tributaries of the lakes and the inland lakes are similar across certain special scales, but the lakes themselves don’t have that much of an effect, in terms of near-shore hydrology into the rivers and lakes,” Gronewald said. “But they do have impact on the climate of the region, in terms of how moisture leaves the lake into the air and into the rest of the system — like the lake-effect snow.”

He said smaller lakes could have a different material as a lakebed, such as a bed of clay, which impacts how water gets out of the lake and into the ground, as well.

“Not necessarily everything is different, but there is a lot of variability on what can affect smaller lakes,” Gronewald said.