ALPENA - Water levels in the Great Lakes are approaching record lows, forcing commercial shippers in Lake Huron and elsewhere to carry less freight and sailors to watch their depth measurements.
In Lakes Huron and Michigan, the monthly mean for September's water levels was about 26 inches lower than the monthly average, John Allis SAID. The chief of the Great Lakes Hydraulics and Hydrology Office for the United States Army Corps of Engineers said this is four inches above the record low, and lake levels in November and December could beat the previous record low set in 1964.
Lakes Huron and Michigan are considered to be one lake by certain government agencies because the two share such a large connection through the Straits of Mackinac, Allis said.
According to preliminary data from the National Oceanic and Atmospheric Agency, Lake Huron measured 12.8 inches below low water datum near Alpena.
Lake levels are measured by averaging measurements from stations all around Michigan, Allis said. They're compared to the international Great Lakes datum of 1985, a figure used as a benchmark for monitoring the Great Lakes. It's similar to measuring water levels in terms of feet above sea level.
While it's typical for lake levels to decline during the fall, this year's drop is faster than normal, Allis said. A mild 2011-12 winter and low amounts of rainfall in the summer are making matters worse.
Conditions in the region are so dry that rainfall is mostly soaked up by the ground, Allis said.
"We're going to have to see sustained wet periods before we start getting normal flow into the lakes," he said.
Lake levels are affected by other natural factors, including evaporation driven by certain weather conditions, Allis said.
"Precipitation is certainly one of the main drivers for water levels, but evaporation is also another big component," he said. "We had a pretty warm summer, and if we start seeing really, really cold conditions as temperatures change over the fall, we start seeing really high evaporation."
Commercial shippers are forced to lighten their loads to keep freighters and other vessels from bottoming out in unusually shallow ports and harbors, Allis said.
"When water levels are this low, that's less cargo that commercial vessels can be loading up as they're getting in and out of harbors," he said.
For a Rogers City limestone quarry and a cement manufacturer in Alpena, this means more trips and higher shipping costs, according to managers at the plants.
Water levels have dropped around a foot or more since mid-June at the Port of Calcite, where Carmeuse Lime and Stone fills massive lake freighters, Plant Manager Ray LeClair said.
"Because of the draft of boats, we are seeing a drop of what we can put on the boats because of water levels," he said.
Freighters leaving the port are drafting at 24 feet, meaning this is the minimum depth of water they need to move, LeClair said. Earlier in the shipping season, boats were drafting at almost 25 feet.
"For that one foot, it equates to about 2,000 tons that cannot be loaded on a vessel," he said, adding this figure varies from freighter to freighter, depending on size and hull design.
As a result, Carmeuse's customers must either accept less tons or get an extra shipment at some point in the season, LeClair said. While shipping by boat is one of the cheapest modes of transportation there is, adding extra trips drives up the cost.
Lafarge's cement plant in Alpena is facing a similar situation, Production Manager Robert Keen said. In addition to shipping less cement, the plant also receives fuel on in-bound freighters.
Keen estimated water levels to be about eight inches below normal. Each inch subtracts about 100 tons from what freighters can safely carry.
"There's not much we can do, but it does affect the bottom-line cost, and it does for everybody," he said. "Everybody who ships on the lake has two choices: raise the prices or absorb the cost. In our case, we typically just absorb the cost."
Changes in lake levels can happen in cycles, Keen said, and Lake Huron's waters likely will rise eventually.
Along with commercial shippers, recreational boaters are affected as well, Allis said.
"We hear from a few marinas that it's just the structure of their facilities are not designed to handle water levels so low," he said.
While most motor boats can handle shallow waters, sail boats have keels that stretch down several feet. In Rogers City's marina, there's still enough room for all but the largest sail boats, Harbormaster Roger Wenzel said.
"We're still at eight feet coming in the channel," he said. "Hopefully by spring we'll have water back up."
If the situation gets worse, harbor employees might have to turn larger sail boats away, hurting marina business, Wenzel said.
"If it gets around that we don't have enough water for big sail boats, they'll just bypass us," he said.
Regularly updated preliminary water measurements can be found online at glakesonline.nos.noaa.gov.
Jordan Travis can be reached via email at email@example.com or by phone at 358-5688.