Lake Michigan is no longer just a Great Lake; it is a great unknown.
More ominous than the all-time low the lake touched this winter is the fact that it came after languishing for 14 years below its long-term average — another record. And when it did initially drop below that long-term average, it plunged three feet between 1998 and 1999 — yet another record for water lost from one year to the next.
The lake level, of course, has been in constant flux since record-keeping began a century and a half ago. Tracking it on a graph is like looking at an EKG monitor. Little blips and dips reflect seasonal oscillations that cause the lake, in a typical year, to vary about a foot between summertime high and wintertime low.
In addition to those annual ebbs and flows are larger swings that span decades tied to long-term weather patterns, with Lake Michigan’s record high topping out more than 6 feet above the record low set this January.
Draw a red line through the middle of all those highs and lows and you get what was, up until 1999, Lake Michigan’s long-term average surface level — 579 feet above sea level.
That year the lake mysteriously took its 3-foot dive, and it has stayed down for nearly a decade and a half — and counting.
Low water levels in the Great Lakes pose potential operating and efficiency problems for Midwest power plants.
It’s one of several ways power plants are increasingly vulnerable to climate change and extreme weather, an issue recently highlighted in a Department of Energy report.
Several plants in the Midwest have already had to take action in response to water-related conditions. Others must monitor conditions carefully to avoid being left high and dry.
Michigan’s Cloverland Electric Cooperative knew it had a problem last year. Output at its hydroelectric plant at Sault Sainte Marie kept dropping dramatically before bouncing back up.
“We experienced about a 60-80 percent drop in the plant’s output,” says Phil Schmitigal, Cloverland’s Director of Generation.
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Midwest generating plants that use nuclear energy, coal, or gas boil water to make steam that runs generators. Then they use more water to condense the steam for reuse.
Facilities along the Great Lakes typically use pumps to draw cooling water from the lakes into the plant.
“Those pumps will require a certain amount of suction head that’s above the water level of the pipe,” notes Kent Zammit, Senior Program Manager for water and environmental matters at the Electric Power Research Institute. In extreme cases, a drop in water levels could let vapor form and cause the water pump’s impeller to shake violently.
“You usually have quite a bit of leeway before you start running into this problem,” says Zammit. Power plant designs generally anticipate a variety of high and low-water level conditions over several decades.
Temperature is a bigger problem.
“As you lower water levels, you tend to see increased temperatures,” says Zammit. As a result, power plants draw in warmer water.
“Lake temperature does have a significant impact on our efficiency,” notes spokesperson Bill Schalk at Indiana Michigan Power’s Cook Nuclear Plant. There would have to be “a drastic change” before the plant couldn’t operate or faced safety problems.
Nonetheless, he adds, lower efficiency reduces the facility’s output. That, in turn, raises the cost per megawatt, though Schalk said the company doesn’t release specifics.
Drawing in warmer water for cooling can also raise the discharge temperature for both nuclear and fossil fuel plants, notes Zammit. Consequently, plants can have problems complying with permits from state environmental agencies. Permits generally have seasonal temperature limits to protect fish and other organisms living near water discharge points.
Wow! A clean, simple statement of the problem, straightforward listing of the major inputs into the balance equation, and well-presented observational data and intuitive illustrations.
Rarely have I seen it done better for the general reader/consumer.
amazing what media can be when done right.
Casing point the Great lakes of Central Asia
The Aral Sea has been virtually wiped out by the lack of environmental policy from the states bordering the sea….or that should probably be “the Aral Pond” now! The economic impact of its disappearance has been pretty huge, many are calling it one of the worse environmental disasters of the last century.
By contrast, the Caspian Sea was falling in height for many decades, but then dramatically reversed course and start rising back in 1978 going up 3m until it stopped around the late 90’s.
http://en.wikipedia.org/wiki/Caspian_Sea#Hydrology
Now while “natural” climate variations (rather than AGW) are blamed for the Caspian’s recent behaviour & the Aral sea’s drainage was mostly a case of over consumption of the rivers feeding into it, the tale of both of these does demonstrate that tiny variations in conditions can have a dramatic impacts downstream. The US great lakes will be no different. Roll the dice with climate change and we could easily see dramatic changes in water levels.