Comment by dubyah
2 days ago
Because the economics of desalination require locking in long term purchase/production rates at prices that dwarf current and other sources of water. SD's Poseidon desal is projected at ~$3.7k per acre ft for 2026 whereas SDCWA SWP water is ~$1.5-1.9k acre ft. Leak fixes, groundwater recharge, local aquifers, water banking, potable reuse, etc. are all more economical means of bolstering water supply.
A big factor in determining desalination placement in the region are the groundwater basins. Limited size and availability makes the case for desalination as means for resiliency. Another is that situating adjacent to power plants so as to use their already coastally degraded intakes/outfalls. Doheny is to use subsurface slant wells for intakes, but it's also lower output too.
As for LA. they're working on getting their potable reuse plants/projects up and running. The largest indirect potable reuse plant in the world has been operating in OC for ~18 years. Lower operating costs than desalination, reduced wastewater discharge, and reduced coastal impact.
that's very insightful. But if I can dive a bit deeper, why can't desalination be made at a grander scale? why aren't desalination plants trying to fill up artificial lakes for example, where those lakes are also being topped-up with reused potables. Would it help if there were much larger nuclear powerplants in the desert that take in salt water via an aqueduct from the sea and send back fresh water to artificial lakes, depositing the waste into the desert? Salton sea might be a good enough spot in socal for example, where it is already toxic and salty.
The few times I've been to the Salton area, I was amazed at the agriculture in the middle of the desert, including things like citrus plants, despite smelling the stench of salton from there. There are various lakes that dry up all the time like big bear, what would it take to keep such basins capable of sustaining fresh watter topped up with desalinated fresh water, instead of directly consuming it? In other words, making desalination an upstream element, with the goal of resisting drought overall, not just immediate fresh water supply.
I've ever wondered about places like death valley, if the elevation there is so low, is it easier to build geothermal plants that could desalinate at a greater rate there?
And since I'm asking dumb questions already, if an aqueduct to LA is possible at a 4 hour driving distance, then I know it would be costly, but is it that impractical to build an aqueduct from the great lakes, which have no shortage of fresh water, and evaporation loss could easily be recouped by the sheer volume of available fresh water supply.
The Owens River source for LA is so good because it’s basically a continuous gradual decline from the source to the city, requiring no pumps.
Pumping is very energy intensive. At around 2000-3000 ft the energy needed to pump fresh water starts to equal the energy needed to desalinate the same amount of salt water.
Even if it’s just going up then back down again like the Tehachapi Mountains only like 1/3rd of the energy can be reclaimed.