Shame on me for repeating news from reporters without looking into the numbers in greater detail. I’m not terribly surprised to find out that a swath of recent research on the dynamics of climate, ice cover, evaporation, and flow rates in the Great Lakes system has been published. There’s a great article chock full of details and solid explanations of the research here on the National Geographic Water Currents blog. Here’s the take-home message, which should settle the debate on why water levels are so low in the Great Lakes:
Lake water levels are heavily influenced by the amount of ice cover in the winter. Ice cover in the winter affects when and how much the lake evaporates in the summer. Ice cover has been at record lows, with a singularity in the winter of 1997-1998. Since then, significant evaporation has started earlier in the summer, and the lake water has been getting steadily warmer. This means that the annual onset of water level declines is starting earlier in the year, too, which all leads to lower average water levels.
The scientists apparently don’t want to speculate on the influence of climate change, since water levels aren’t yet statistically different from historical ranges. Fine, but increasing surface temperature and decreasing ice cover/snowpack are two clear factors in favor of this explanation. I suspect that the drought is the short-term driver of losses in the Great Lakes system, but climate change is the long-term driver, perhaps of both the Great Lakes system and the drought itself.
Happy Thanksgiving to all — let us be thankful for what we have to drink!
I’ve mentioned that water levels in the Great Lakes have declined recently, and that this is probably related to climatic factors like recent droughts. Low flows on the Mississippi River suggest that droughts are, indeed, a big factor in the upper Midwest right now. In fact, the Army Corps of Engineers is trying to manage the reservoirs on the Mississippi and Missouri Rivers to balance conservation and water flow. Their latest decision to keep more water stored in an upper Missouri reservoir may mean that barge traffic on the Mississippi near St. Louis and Illinois may shut down early next year, absent heavy rain/snow. The Missouri River flows into the Mississippi River just north of St. Louis, and in a normal year, up to 60% of the combined flow comes from the upper Missouri watershed. This year, however, approximately 78% of the combined flow has come from the upper Missouri — which means that the flow from the upper Mississippi (Minnesota, Iowa, Illinois, and even Lake Michigan) is a mere 22% of the flow. In other words, the upper Mississippi makes up a smaller piece of the pie than in a normal year, plus the whole pie is smaller than a normal year. Rough times.
There’s not much to be done in the midst of a drought except draw down our reservoirs (this is why we save up our water every wet year) and increase dredging to deepen existing shipping channels. But I can say that this saga tells us that the problems of the Great Lakes are not due to a couple of extra diversions here and there — the middle of the country is in a tough drought, and there’s less water to go around. Another year like this, and we’ll be praying for rain.
I suppose my inherent optimism makes me bring this story to light: right now, Texas beaches are cleaner than in years. Runoff is so historically low this year, so far fewer stormwater pollutants have been flushed off the streets and surfaces, shepherded into conveyance, and discharged into the Gulf of Mexico. Fewer pollutants in the Gulf shore means cleaner beaches. Hopefully people escaping the heat at the beach are enjoying the better quality of the experience. And it’s probably best to avoid the beach after the next big storm rinses everything off.