If you are a journalist that wants to start covering the environmental issues that are relevant to the Great Lakes region there are three issues that you must become aware of: changing water levels, water and waterway use, and fishing. These topics are currently very important to the people living in the region and they are the most talked about in the media. Below you will find a quick description of each of the issues and many links to resources that allow you to go in depth in each subject area.
Changing Water Levels-
Change in the water levels of the Great Lakes is natural. Water levels change seasonally each year and can vary dramatically over longer periods. Over time the levels have been both higher and lower than they are today.
Lake levels are most generally affected by the difference between the amount of water coming into a lake and the amount going out. When a period of above-average rainfall occurs alongside cooler cloudy conditions there will be less evaporation and the lake levels will rise. Likewise, long periods of lower-than-average rainfall and warmer temperatures results in the lowering of water levels.
The recent decline of Great Lakes’ water levels, now at lows not seen since the mid-1960s, is due mostly to evaporation during the warmer-than-usual temperatures of the past three years, a series of mild winters, and smaller-than-average snowfall in the Lake Superior region.
Because the major factors affecting the water supply to the lakes–precipitation, evaporation and runoff–cannot be controlled or predicted for more than a few weeks into the future, the influence of man-made regulation of lake levels is very limited. Nature has most of the control, adding water through snow and rain, and taking it away through evaporation.
There are three types of lake level changes: short-term, seasonal, and long-term.
Short-term changes
Some water level fluctuations are not a function of changes in the amount of water in the lakes, but are due to wind or changes in air pressure. These short-term movements are often due to storms or ice jams and can last from a couple hours to several days.
This can occur when sustained high winds from one direction push the water level up at one end of a lake, and causes the level drop the same amount at the opposite end. (See the picture below) These events are most common on Lake Erie because of its east-west orientation.
Seasonal changes
In the fall and early winter, when the air above the lakes is cold and dry and the lakes are relatively warm, a lot of water is evaporated from the lakes. This causes water levels fall to their seasonal lows.
As the snow melts in the spring, the amount of water flowing off the land and into the lakes increases. Evaporation from the lakes is also less in the spring and summer when the air above the lakes is warm and moist and the lakes are cold. With more water entering the lakes than leaving, water levels rise to their highest in the summer.
The range of seasonal water level changes in the Great Lakes averages about 12 to 18 inches from winter lows to summer highs. Seasonal rises begin earlier on the more southern lakes because of the slightly warmer climate.
Long-term changes
Long-term lake level changes occur over a periods of several years. Many wet and cold years in a row will cause water levels to rise. Likewise, many warm and dry years in a row will cause water levels to decline. Over the last century, the range from extreme high to extreme low water levels has been nearly 4 feet for Lake Superior and between 6 and 7 feet for the other Great Lakes. The last few years have been very hot and dry in the Great Lakes region and this has caused the lake levels to decrease. Many attribute this decline to global warming.
For more information about climate change and the Great Lakes visit this site
There is lots of information available on this subject. Check out the links below for in-depth data and background.
A publication by the Great Lakes Commission that explains the natural function of the Great Lakes ecosystem, how human behavior influences the system, how water levels are currently controlled, the effects of lake level fluctuations, and the best ways to live along the shoreline. It is a very informative resource for background information on lake level change.
This lake level data has been collected and archived by NOAA’s National Ocean Service Great Lakes. These water levels make up one of the longest high quality water and climate data sets in North America with water gage records beginning around 1860 and sporadic records back to the early 1800’s.
October 2007 Great Lakes water level summary- Army Corps of Engineers
Gives the water level changes for all the lakes for the month of October and compares them to the long-term average.
Data from the Department of Fisheries and Oceans (DFO) and the Canadian Hydrographic Service (CHS) that gives the gaging stations’ hourly water level data and graphs for the past and current month.
Recent and Predicted Water Levels of the Great Lakes
Data from the Department of Fisheries and Oceans (DFO) and the Canadian Hydrographic Service (CHS) that includes average monthly water levels for any year and compares it to the previous year. Records are available from 1918-1996.
Great Lakes Water Level Photo Gallery
Organized by region, this gallery contains both current and historical images of the coastline and links to related water level updates.
More information on these topics coming soon
