[LINK] Not just oil: US hit peak water in 1970 and nobody noticed
kim at holburn.net
Wed May 26 08:47:40 AEST 2010
> The concept of peak oil, where the inaccessibility of remaining
> deposits ensures that extraction rates start an irreversible
> decline, has been the subject of regular debate for decades.
> Although that argument still hasn't been settled—estimates range
> from the peak already having passed us to its arrival being 30 years
> in the future—having a better sense of when we're likely to hit it
> could prove invaluable when it comes to planning our energy economy.
> The general concept of peaking has also been valuable, as it applies
> to just about any finite resource. A new analysis suggests that it
> may be valuable to consider applying it to a renewable resource as
> well: the planet's water supply.
> The analysis, performed by staff at the Pacific Institute,
> recognizes that there are some significant differences between
> petroleum and water. For oil, using it involves a chemical
> transformation that won't be reversed except on geological time
> scales. Using water often leaves it in its native state, with a
> cycle that returns it to the environment in a geologic blink of an
> eye. Still, the authors make a compelling argument that, not only
> can there be a peak water, but the US passed this point around
> 1970, apparently without anyone noticing.
> They make their case based on three ways in which water can run up
> against limits on its use. The first is peak renewable water, for
> sources that rapidly replenish, like river basins or snow melt. The
> classic example here is the Colorado River where, for most years
> since 1960, essentially no water has reached the ocean. Although
> actual water use is governed by a series of interstate and
> international agreements, these simply serve to allocate every drop
> of water. Similar situations are taking place in other river basins,
> such as the Jordan.
> The second is what they term peak nonrenewable water, as exemplified
> by the use of aquifers that replenish on time scales that make them
> closer to a finite resource. (This issue is so well recognized that
> it has a Wikipedia entry.) At the moment, the Ogallala and Central
> Valley Aquifers in the US, along with a number in China and India,
> are being drained at a rate that far exceeds their recharge.
> Ultimately, usage will necessarily peak and start dropping, as it
> gets harder to get access to the remainder. Eventually, these water
> supplies will tail off to something in the neighborhood of their
> recharge rate.
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