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.

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too many straws in the milkshake

People talk about the Ogallala aquifer, which provides irrigation water to a large swath of the Midwest, drying up.  And that is a concern, yes.  But take a look at Yemen: their aquifer has been essentially unregulated for decades, and the water table is now 500 m below the ground surface, declining about 3-6 m per year (compare with up to 1 m per year in the worst parts of the Ogallala).  Every farmer that can afford it in his fields and every person who can afford it in his home has a private well.  How much water do they use?  As much as they feel like.  The water is increasingly used for qat, a mild stimulant plant chewed by all classes, but whose production is concentrated among tribal leaders, military officers, and politicians.  The “qat lobby” has convinced the government not to enforce a 2002 law stipulating that no well may be dug without government approval.

The water is essentially drying up beneath the city of Sanaa, and has already perhaps dried up in Taiz.  Sanaa may become the first capital city to fail due to complete exhaustion of its water resources.  Realizing the political instability inherent in this prospect, places like Saudi Arabia and Germany are offering support to develop alternate water supplies, which amount to desalination in this part of the world.  That or moving qat production elsewhere.  Perhaps the city could survive on its own water resources if 90% of the water were not being used for agriculture (40% for qat).  The desperate fight between urban water demand (mainly ordinary people) and agricultural demand (here the qat lobby), largely for an inessential crop, should strike fear in the heart of all Californians.  Better our convoluted regulations and water diversions than that mess…