Dragonfly Gazette

GA Project WET Newsletter

The Georgia Project WET newsletter features articles of interest to WET Teachers and Facilitators - available by email only. It includes state-specific background information for WET activities, thematic lesson plans, interviews with water professionals, and a forum for Teachers and Facilitators to share their ideas and accomplishments.

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The "Lake" Effect

Georgia be dammed!
Wink! You probably know that Georgia has virtually no natural lakes (not counting a few isolated oxbows and Carolina bays) and that our largest bodies of fresh water were formed when dams were constructed across rivers.  

In fact, there are more than 4,600 dams in the state, most of which are privately owned. Only four states (Texas, Kansas, Missouri and Oklahoma) have more dams than Georgia. The reservoirs which are formed behind the dams provide drinking water, recreation, power and wildlife habitat.


Something's rotten

While we generally believe reservoirs are good and necessary to have, they present an ecological problem.  The very construction and existence of a reservoir is actually an alteration of a river ecosystem, impacting life forms and habitats that were once supported by the river.
But there is more -- a recent research study from Washington State University found a disturbing connection between increased greenhouse gases and reservoirs! They say the world's reservoirs produce over 1% of all greenhouse gases entering the atmosphere.

Decomposing organic matter
As it turns out, reservoirs are a particularly large source of methane, a greenhouse gas that is 34 times more potent than carbon dioxide over the course of a century. Reservoir methane production is comparable to that of rice paddies or biomass burning, both of which are included in emission estimates of the Intergovernmental Panel on Climate Change.  

In a natural system, carbon enters a lake as organic matter (such as falling leaves or soil suspended in runoff) and is cycled through the food chain, feeding plants and then animals. Some carbon settles to the lake bottom and is buried in sediment, and some is released back into the atmosphere as carbon dioxide and methane. As with all biological processes, lake emissions are temperature dependent, rising and falling along a temperature gradient.  

Unlike natural water bodies, reservoirs usually require the flooding of large areas of land containing huge amounts of organic matter, like forests and fields.  As the organic matter decomposes under the water, it produces large amounts of carbon dioxide, methane and nitrous oxide. Reservoirs also receive a lot of organic matter and nutrients like nitrogen and phosphorous from upstream rivers, 
which can further stimulate greenhouse gas production.  


Role of natural lakes in climate change
Research is also underway on the role of natural lakes in the production of greenhouse gases.  A group of researchers from Rensselaer Polytechnic Institute have taken on the challenge of predicting lake emissions for thousands of lakes across the country.  The team will use lake temperature data estimated over the next 90 years to forecast changes in lake metabolism -- the absorption versus emission of carbon -- and seek to draw conclusions based on those estimates.

And BTW, are our dams safe? Check yours out!
EPD Safe Dams Program FAQ: 

List of Dams in Georgia:   https://en.wikipedia.org/wiki/Category:Dams_in_Georgia_(U.S._state)

High Hazard Dams in Georgia:

Augusta area:  http://chronicle.augusta.com/news/2017-02-13/corps-engineers-says-thurmond-dam-failure-won-t-happen

Read more in the Full PDF version below...