A world water crisis

Fear mongering about the depletion of natural resources is an age-old tradition (see Limits to Growth). The focus is usually on fossil fuels and minerals, so when I came across a new book on water as “the defining crisis of the 21st century,” I gave it a close and skeptical read.

It turns out to be pretty good, and the author, Fred Pearce, a correspondent for the New Scientist, seems quite reasonable. (I reviewed the book for today’s SF Chronicle.)

The indisputable reality is that we’ve been diverting and damming up our rivers for irrigation, and it has led to many of them drying out — the Rio Grande and the Indus, for starters. That has led people worldwide to pump out water from underground aquifers beyond their ability to refill. This recent Emerging Trends Report excerpt captures this problem:

[…] Depletion has compacted aquifers’ sediments, irreparably damaging their ability to hold water in the future. Many deep aquifers, such as the massive Ogallala in the US or the Nubian in Saharan Africa, have a recharge rate that runs to centuries, if not millennia, making such water sources for all intents and purposes nonrenewable; this can generally be said to be true for aquifers in most low rainfall regions of the world. Like river deltas, coastal aquifers, if drawn down too severely, can be inundated with salt water and ruined (see diagram above), as is the case in parts of the Gaza Strip, Florida and the Indian state of Gujarat.

To bring it home, consider that each year California pumps out 15 percent more water from the ground than the rains replenish, and Arizona 100 percent more.

Thanks to BP television spots, a lot of folks are familiar with the term “carbon footprint.” In the coming years, I think “virtual water” — the amount of water it takes to produce a given product — is a useful concept that will be a bigger part of the public debate as the water problem gets more attention. To self-servingly and lazily quote my own review:

It takes 207 gallons of water to produce a two-egg omelet, two pieces of toast and a cup of coffee. That’s nothing compared to the 3,000 gallons of water needed to grow the feed for the portion of a cow that goes into a Quarter-Pounder, or the 500 to 1,000 gallons of water behind every quart of milk the cow produces. A pound of sugar takes 400 gallons, and a pound of rice can require up to 650 gallons. 

Pearce’s point is not that we all need to stop taking shorter showers, it’s that sanity has to be restored to irrigation. The world grows twice as much food as it did a generation ago, but it takes three times more water from rivers and underground aquifers to do it. Many parts of the world have to do a better job of matching the crops they grow to the fresh water availability, not the other way around: picking crops you like and then going out and getting water for them.

And on the conflict side, things would probably get worse. “If you stand back and look at the past 50 years, all these parties have been competing with each other for resources,” David Phillips, a water adviser to the Palestinian Authority recently told the Financial Times. “There have been some agreements but essentially they’ve been competing in a zero-sum game.”