(A comment I made on an article on the orange website.)
There are some crucial details here I'm not understanding.
The article says Israel needs (or needed?) 1.9Gm³/year (60 kiloliters per second, 60kℓ/s) of water, of which it got 1.5Gm³/year (48kℓ/s) from natural sources; but now (or when the plants opened?) it gets 127Mm³/year from the 2005 Ashkelon desal plant, 140Mm³/year from the 2009 Hadera desal plant, and 150Mm³/year from the new Sorek plant. These total 417Mm³/year (13kℓ/s), but the article says Israel's current total is 600Mm³/year (19kℓ/s) from desalination plants, which is more than 417. Also, it says, Israel now gets 55% of its domestic water from desalination. But 55% of 60kℓ/s is 33kℓ/s, which is 14kℓ/s more than the 19kℓ/s it says Israel gets from desalination. I suspect there's some confusing mixing of categories here leading to these numbers not adding up properly.
The other really crucial questions are about capex and opex. How much do these plants cost to build, and how much do they cost to run? How much of that is the energy cost?
They give the figure that the Sorek plant's reverse osmosis runs at 70 atmospheres (7.1 MPa; fucking Christ on a stick, why do people keep inventing new non-SI units?) which means that each liter of output water requires 7.1kJ of mechanical energy to force it through the membrane. There are presumably some other energy costs, but that may be the bulk of it. At US$100/MWh (US$28/GJ; fucking non-SI units again), which is a reasonable ballpark for the levelized cost of electrical energy, that's about 200 μUS$/ℓ or 200 US$/Mℓ. Irrigation water is commonly quoted in US$ per acre foot in the US; this is US$240 per acre foot, which would be a very competitive cost.
But it says the cost is US$0.58/kℓ, which is 580 US$/Mℓ or US$715/acre foot, about three times the cost of the mechanical energy and high enough that many crops are uneconomical. It is crucial to understand where that extra cost is coming from.
One of the comments on the Ensia version of the story claims that the new Carlsbad desal plant is selling its water for US$2000/acre foot. I don't know if that's true, but it's about 150% higher than the projected costs.
Links, in case the Scientific American web site is lost:
Bar-Zeev et al.'s article about their bioflocculation anti-biofouling prefiltering apparatus DOI: 10.1016/j.watres.2013.03.013
"Climate change in the Fertile Crescent and implications of the recent Syrian drought" doi: 10.1073/pnas.1421533112