just keep pumping

A lot of the world’s major agricultural regions are irrigated by groundwater rather than surface water.  Even locations with enough rainfall to avoid irrigation under normal conditions are adding capacity to irrigate with groundwater under drought conditions (my home state of Georgia is a prime example).  Well, worrywart scientists have done some large-scale analysis to put numbers on which of 800 aquifers worldwide are being overexplioited for irrigation.  Lots of anecdotal evidence does not make a scientific fact, after all.

It must be an important study, because it was published recently in Nature:

…in most of the world’s major agricultural regions, including the Central Valley in California, the Nile delta region of Egypt, and the Upper Ganges in India and Pakistan, demand exceeds these reservoirs’ capacity for renewal.

…In calculating how much stress each source of groundwater is under, Gleeson and colleagues also looked in detail at the water flows needed to sustain the health of ecosystems such as grasses, trees and streams.

That’s a troubling development, which doesn’t surprise me of course, because of the implications for agriculture when these groundwater sources run out.  And before agricultural collapse, we’ll probably see major impacts to the environment as far as ecosystems drying out and creeks/streams drying up.  We won’t even have anything nice to look at while we die of starvation.

Ok, it’s not quite that dire, of course.  The first step is to identify the problem after all.  But at some point, nations will need to examine the unregulated groundwater extraction for irrigation and ask if the water use is worth the risk.  The ongoing US drought, for example, has many wondering why you would ever grow rice, cotton, or pecans in a place like California or Texas.  In news that should shame us, Saudi Arabia made a push in 2009 to shift its domestic agriculture away from water-intensive wheat and soy beans in order to conserve its limited water supplies.  Of course, non-representative government doesn’t really have to worry about public outcry to get things done (see: China).  But let’s hope that our governments take heed before the tragedy of the groundwater commons plays out on a large scale.

Kansas and Texas: the next Yemen

I wrote earlier about the groundwater overdraft in Yemen, which was largely due to irrigated farming (specifically for qat, a mild stimulant).  I sort of brushed off the idea that the Ogallala aquifer was drying up.  But, researchers recently used satellite data to show that yes, it is drying up, and at an alarming rate.  In the southern portions, the aquifer may be unable to support irrigation as soon as 30 years from now.  The northern portions seem to be holding steady in water level, due to rainfall and infiltration from lakes, so only Kansas and Texas would be affected.  The same study showed that groundwater tables fluctuate widely in California’s Central Valley, although a clear decline is not evident.  These are major farm belts in the US, and the loss of irrigation water would be, quite simply, devastating for those areas.  We would do well to take heed and adopt proper policy measures to sustain these critical but not unlimited water resources.