Twelve thousand million tonnes of water a day

I've been interested in the mention of “12,000m tonnes of water” to be shipped out every day. The figure is clearly ridiculous, but it is interesting to think of the logistics if it was to be true. When assessing a figure spat out by someone, I like to try to put it into some kind of perspective and see if it passes the “sniff test". Below are some figures that might instantly put this one to bed.

Most things are possible, but with only 1,534m tonnes of rain falling per day over the entirety of New Zealand (on average), it's a non-runner from the start. Using 100% of the rain that falls on New Zealand (which is the only source of freshwater and leaves Kiwis with no water), an average of 16m would have to fall over the entirety of New Zealand and all of it collected before any evaporates to make 12,000m tonnes possible. According to NIWA, an average of 2.1m falls per year, somewhat short of 16m!

The alternative is that they (whoever “they” is) would have to desalinate on a scale not seen before and install just over 100 times the total desalination capacity in the world today. I can't even think of the electricity bill to run it, but I guess it is theoretically possible.

Anyway, assuming it could be done, you then have the job of getting the water to market. It's quite a large volume so you would need some supertankers. The Seawise Giant, the world's largest supertanker, carries 564,763 deadweight tonnes. To export 12,000mt/day is 21,248 loads/day which is one every four seconds. This, with many hundreds of terminals nationwide, is of course possible, but if a return journey averages 30 days, you will need a fleet of more than 600,000 Seawise Giants. That might strain the best of the shipbuilders' supply chains for some years.

Assuming that in the long term it could be done, a willing seller needs a willing buyer. Global freshwater use is around 10,000mt/day for all uses, so if their plan comes to fruition, we will be able to more than sate the thirst of the world!

We might be thirsty and hungry in New Zealand but at least we'd be rich - global water tariffs (including wastewater disposal) is USD2.03/m3. Assuming only 10% of that cost is for freshwater and 90% for wastewater, our 12,000m tonnes per day works into USD889b or NZD1.482 trillion/day, or NZD541/annum trillion in export earnings, which is actually four times world GDP and works out to NZD108,200,000 for every New Zealander. This might be welcome, but just think of the resulting Auckland house prices!