Science, Science and Society

A very different form of mining…

I came across this last week, and thought it was certainly an interesting way of addressing New Zealand’s mining issues.


The conversation around whether, and if so to what extent, New Zealand should mine its national parks for mineral resources is a heated (haha) one.  And, I might add, not one into which I’m going to assert myself.

Now, someone* has gone and suggested another way that New Zealand could benefit from mining but, wait for it, without having to open ground at all.  How, you say?  By water mining.

Yes, dear readers, you read that correctly.  Water mining.  Now, I know the term evoked for me images of men with shovels**, down shafts, trying vainly to lift water.  Or something.  But it’s not that at all.  Instead, it basically means harvesting the inevitable product of cloud seeding - water.  And, certainly, atmospheric moisture which could be turned into rain/snow is something of which we’re not short.  Not at all.  I live in Wellington, and sometimes would be quite happy if it were less…precipitous…here.

So how does cloud seeding work?  Well, it’s something humanity’s been playing with for a while now.  I won’t get into some of the mad conspiracy theories about Soviets/Americans and secret programmes, but the science itself has been around for a few decades.  There are different ways of doing it, but one of the ways we kiwis would consider is through the addition of small amounts of silver iodide crystals into the high bits of clouds, where water droplets are hanging about at less than zero degrees C.  Apparently, said addition triggers a reaction which makes the droplets freeze - they then begin to fall, turn back into water on the way down, et voila!  Rain.  Or, possibly, snow if they hit a mountaintop on the way down.  Either way, it’s accessible precipitation.

You can also use dry ice, which works slightly differently: it cools the surrounding air so quickly that water vapour reverse-sublimes straight into ice.  Hoo-har.  It should be mentioned that existing water droplets are still needed, though, to ensure the ice crystals can grow large enough for them to descend from the heavens.

And cloud seeding can be done either by aircraft, or from the ground.

Of course, this sort of technology can also be used to suppress fog and rain.  This is important for airports.***  )r the opening ceremony of 2008’s Olympic Games in Beijing.

Anyhoo, back to thoughts of using it here.  It might well work, for example, in the Southern Alps to increase Canterbury’s water supply (good for irrigation and energy production).  And we needn’t, according to  Assoc. Prof. Bardsely, worry that it would decrease Canterbury’s winter rainfall.

Issues to consider?  Well, primarily the safety aspect of it, to be honest.  Silver iodide is a pretty toxic substance, but it’s only harmful if encountered in an intense or continued fashion.  Chronic exposure doesn’t count, apparently. And studies looking into its accumulation in the environment haven’t been able to pick up anything above normal background levels.  Our neighbours over the Tasman are experts on this, it would seem, as they’ve been using cloud seeding for some time, and so have been studying its effects.  The verdict of peer-reviewed science as to its danger?  It’s fine.****

So, an interesting idea!  And it does sort of make sense - given that we have a natural resource in abundance, and one which is unlikely to run out soon (in fact, climate change scenarios suggest parts of NZ might get wetter and wetter) and requires no breaking of ground, perhaps it’s something to be seriously considered.


And no, I’m not pleased that Wellington’s going to get colder and soggier.  Luckily this is a brilliant city despite that.


*Associate Professor Earl Bardsley, of the Department of Earth and Ocean Sciences, University of Waikato

** Or spades.  Shovels might work marginally better, though

*** Although clearly it was not in use the morning I got fogged in at Hamilton airport. For a while.  Very sleep deprived.  Hurrah for Foyle’s War and my netbook…

**** Well, according to the Weather Modification Association