The following article was published by The Wilson Center’s New Security Beat blog. It reports on a study published in the August issue of Nature Magazine. Titled “Water balance of global aquifers revealed by groundwater footprint” the Nature study’s abstract mentions that “...humans are over-exploiting groundwater in many large aquifers that are critical to agriculture, especially in Asia and North America. We estimate that the size of the global groundwater footprint is currently about 3.5 times the actual area of aquifers and that about 1.7 billion people live in areas where groundwater resources and/or groundwater-dependent ecosystems are under threat. That said, 80 per cent of aquifers have a groundwater footprint that is less than their area, meaning that the net global value is driven by a few heavily over-exploited aquifers.”
If you are especially interested in the graphics, I suggest clicking through to the New Security blog, where you can view higher resolution pictures.
Stress Levels of Major Global Aquifers Revealed by Groundwater Footprint Study
In the “first spatially explicit comparison of groundwater use, availability, and environmental flow for aquifers globally,” a new article in Nature finds that the “size of the global groundwater footprint is currently about 3.5 times the actual area of aquifers.” An aquifer’s footprint is the theoretical size it would need to be to sustainably support use at its current rate, so groundwater footprints being much larger than their corresponding aquifers is a sign of overuse.
Authors Tom Gleeson, Yoshihide Wada, Marc F. P. Bierkens, and Ludovicus P. H. van Beek used the Global Groundwater Information System and a recharge model to calculate the global rate of water use compared to water available in aquifers. They particularly highlight overuse in six major aquifers: the Western Mexico, High Plains, North Arabian, Persian, Upper Ganges, and North China Plain.
Some aquifers are replenishable, like many in India, for example, but are being refilled more slowly than they are being drained. Others – called “fossil aquifers” – are not, like the Ogallala aquifer in the midwestern United States and the Sana’a Basin in Yemen. Geological changes mean that streams streams which once deposited water no longer reach them. Once water is depleted from the fossil aquifers, farmers must turn to other forms of irrigation or cease agricultural production altogether. Even before aquifers run dry, falling water tables increase the cost of irrigation by forcing farmers to drill deeper and deeper for access to water.
To read the full article, please click here: http://www.newsecuritybeat.org/2012/08/stress-levels-major-global-aquifers-revealed-groundwater-footprint-study/