It seems that there has been increasingly more news about polar ice and the contribution that this melting ice will have on rising sea levels. There are many vivid, photographs and videos that show the acceleration of massive chucks of polar ice crashing into the sea or of lone 1 000 pound polar bears riding a shrinking piece of polar ice in a growing sea of open water (Polar Bears in Trouble). Numerous time-lapse photos taken over past decades show how this ancient glacial ice has rapidly begun to retreat from contact with the oceans revealing long hidden ice-carved valleys in full view.
A recent study sponsored by the American Geophysical Union adds even more fuel to sea level rise from two very unlikely sources: groundwater depletion and reservoir storage levels. The amount of projected level rise may not seem like a lot – “…research suggests that by 2050, groundwater pumping will cause a global sea level rise of about 0.8 millimeters per year” – but its volume is large! Just as important will be the impact of future freshwater needs for agriculture to feed the world’s expanding population as more and more of this precious resource is lost from the land and moved to the oceans.
It is difficult to imagine just how much freshwater is extracted from wells for irrigation and drinking, the the study’s author (from Utrecht University in the Netherlands) notes that “groundwater contributions to sea level rise are expected to become as significant as those of melting glaciers and ice caps outside of Greenland and the Antarctic.”
Reservoirs have been important to managing river flow and storing large quantities of water for use not only for consumption but also for hydroelectric power generation. With the exception of just a few countries, dam construction has been on a decline. The study also concluded that the “net effect of additional factors influencing the amount of terrestrial water entering the oceans includes marsh drainage, forest clearing, and new reservoirs.”
The AGU study in this issue of Water World: Groundwater Pumping Leads to Sea Level Rise Cancels Out Effect of Dams concludes that “one way to decrease groundwater’s contribution to sea level rise is to improve water efficiency in agriculture — to grow more with less groundwater.” This “option” is becoming less of an option – and more of a necessity – in many parts of the world.