Large-scale desalination sized as drought insurance

Mechanism

Seawater reverse osmosis (SWRO) plants push seawater through membranes at high pressure to produce drinking water that is completely independent of rainfall. For a coastal city facing recurring Day Zero risk, desalination is the one supply that cannot be emptied by drought.

Where it fits

Coastal cities and regions where drying is permanent rather than episodic. Israel's national program shows the ceiling: five-plus mega plants supplying roughly 80-90% of municipal freshwater, with competitive tendering driving prices down to record lows (Sorek B at about $0.41/m3).

Evidence: the outcome depends on procurement, not membranes

The technology is mature; the divergent outcomes are financial and contractual.

• Israel (success): competitive build-operate-transfer tenders, record low prices, paired with roughly 87-90% wastewater reuse for agriculture. The country now exports water to Jordan and refills the Sea of Galilee.
• Victoria, Australia (partial): a drought-panic procurement whose capital blew out to about A$4bn; the plant went straight into standby on completion and delivered first water only in 2017, while availability payments of about A$608M/yr are owed regardless of orders (roughly A$18-19bn over 27 years). Sydney's plant was mothballed 2012-2019 at about A$500k/day.
• Carlsbad, USA (partial): a 30-year take-or-pay contract made it the county's costliest source (about $3,500 per acre-foot in 2025), with $54M paid for unneeded water in a wet year.

Implementation path

1. Size against the permanent aridification trend, not the current drought.
2. Communicate the plant as insurance from day one: ratepayers will pay in wet years, and that must be the explicit deal.
3. Use competitive tenders and avoid rigid take-or-pay or availability-payment structures; build in flexible operating triggers (Victoria's post-2017 reframing, with 100-125 GL orders in dry years, shows what flexible use looks like).
4. Where a wastewater stream exists, evaluate potable reuse first: comparable projects cost roughly half as much per acre-foot in the San Diego region.

Trade-offs

• High energy intensity and brine discharge; marine rules can force expensive retrofits (Carlsbad's ~$159M intake retrofit).
• Wet-year payments are politically corrosive when the insurance framing was never made honestly.
• Coastal mega-plants concentrate supply in assets vulnerable to conflict, a critique raised for Israel's wartime exposure.
• Procurement done in drought panic locks in decades of cost; the contract structure matters more than the technology.