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Comment by tda | Hacker News Reader

That is what I intuitively thought, until I learnt that salinity in the Persian Gulf (a huge body of water connected to the ocean) is up significantly due to desalination. Salinity has risen 50% over the last two decades. See e.g. https://financialtribune.com/articles/people-environment/434...

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Simple math will tell you that this increase cannot be due to desalination. Look:

Volume of the Persian Gulf = Area (251,000 sq km) * average depth (50 m) = 12,000 cubic km approx.

Total amount of desalinated water produced in the world, per annum = 86 million cu. m = 0.086 cu. km,

So if all of the world's desalinated water was taken from the Persian Gulf, for 150 years, the salinity would only increase by 0.08*150/12000 = 0.1%, roughly.

Edit: the entire article is bad, and the headline is sensationalist bullsh#t.

Always good to do some math. I double checked your input figure, and that should be per day, not per year. So 365 times as high. Other assumptions being the same that would give 0.2% rise per year, or 4% in twenty years. Not 50%, but not insignificant.

You are right, thanks for pointing this out. I hate making mistakes like that.

It doesn't need to be responsible for all of the change, it might only be one among many contributing factors like climate change.

In that context, it would be shortsighted and naive to pretend it couldn't have any impact at all even on bigger and longer scales.

Except that the article you link to explicitly states two opposing theories as to why the salinity is so high, and has risen so much.

The two competing theories seem to be 1. desalination and 2. climate change causing excessive evaporation.

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