Terrestrial aquifers contribute to sea level rise – out of sight/out of mind?
Recently, i remembered a piece of work i completed in my 3rd year of my undergraduate degree, examining the detrimental effects a sudden draining of Lake Superior, one of the Great Lakes in USA and Canada, could have on the Gulf Stream/North Atlantic Drift. Although possibly a little far-fetched, but definately plausible, this memory was jogged this morning by an article published recently by the United States Geological Survey (USGS) (2013) showing that, over the last 100 years, USA has depleted enough of its underground freshwater supply to fill up Lake Erie twice.
Lake Erie is the 4th largest of the 5 Great Lakes in North America, and the 10th largest globally, containing 116 cubic miles of water. To look at that another way, between 2001 and 2008, Americans brought enough groundwater above ground to contribute to 2.3% of worldwide ocean level rise (USGS, 2013).
The article continues, explaining that lowering aquifer levels can result in springs and wetlands (a huge carbon sink) turning dry, and are also removing a dependable source of water for local communities. Ultimately, in agriculture, this will result in an essential movement from water intensive crops such as corn, towards a different agricultural practice, so land owners can continue to turn revenue.
This map of major aquifers in the U.S. highlights the High Plains Aquifer (green) and the Dakota Aquifer (white, outlined in black), both depleted over the past century (L.F. Konikow, U.S. Geological Survey)
The uses for the groundwater are primarily for human consumption, although large quantities have been reported to be used in Alabama and Mississippi by rice farmers, flooding their paddy fields, and for other irrigation purposes.
Some states are aware that removing all of this water from aquifers can leave behind a barren and almost inhospitable environment for future generations, and they are actively pumping surface water back into the ground!
A famous landmark in USA, Mono Lake, has a super-high salinity, so much so that when I visited it and swam in it, I was permanently buoyant. However, this lake has been affected in the past due to water re-routing from it’s catchment to provide drinking water for Los Angeles. This lake was formed over 760,000 years ago, and has it’s high salinity because the water in the lake has no outlet to the ocean. Constant evaporation creates a high salinity level in the lake. It has various fascinating geological and ecological credentials, including tufa towers, once part of a wonderful underwater world. However, these features are visible above the surface today because of the re-routing of water, causing less water to be inflowing into the lake, making the effects of evaporation much more noticeable, thus lowering the lake’s surface level by ~31%.
Exposed tufa towers at Lake Mono, USA (Reference).
In my opinion, the USGS article showcases evidence that desalination plants and purification systems for water recycling could help to reduce the impact humans have upon the land they rely upon. I also expect that vast empty caverns underneath settlements can only spell disaster in a world where the population is constantly growing, and the weight bearing down upon the roof of these caverns will soon become too much. With increasingly common stories in the news publicising sinkholes and land slips, maybe it is time to seriously analyse our water extraction methods.
Posted on May 22, 2013, in Uncategorized and tagged aquifers, erie, fresh water, great lakes, lake, Lake Erie, Mono Lake, rise, sea level, sea level rise, terrestrial, United States Geological Survey, USA, USGS. Bookmark the permalink. 3 Comments.