As for the rainwater issue, well they engineered themselves into that but that cistern idea was great.
[1] https://en.wikipedia.org/wiki/National_Audubon_Society_v._Su...
I imagine it would be incredibly difficult/expensive to treat that water even to graywater level, let alone potability.
The big one that just went up in San Diego only cost $1 billion, and will provide 7% of the total water needs of San Diego county.
As TFA mentions, desalination is incredibly power-hungry. Additionally, it creates ultra-salty brine as a byproduct, which is difficult to dispose of -- if you just dump it into the ocean, you'll kill fish.
Finally, desalination plants are a great option for supplying water when nothing else is available, but as soon as you can get water from pretty much anywhere else, they become extremely cost-inefficient. Take the case of Santa Barbara as a great example: drought from 1986-1992, built a desal plant for $34 million. Turned it on in March 1992, it ran until June 1992, and then it started raining ... hasn't been used since.
(http://www.santabarbaraca.gov/gov/depts/pw/resources/system/...)
"Overall, it would appear that benthic infaunal communities and sea grasses are the most sensitive to the acute effects of concentrate discharge; some communities seem to be tolerant of effects of up to 10 psu increases, while others are affected by increases of only 2-3 psu. However, few studies have evaluated discharges to embayments, where less dispersion of the discharge may occur, and the chronic impacts on demersal vertebrates, particularly those which have significant life history behaviors (i.e., reproduction, migration) driven by salinity variations."
There are also many concerns with the effluent than just salinity.
http://www.swrcb.ca.gov/water_issues/programs/ocean/desalina...
The brine can be evaporated into salt as well, right?
It seems to mean that problems like this have to be solved via an entire system and not via individual components.
You can save a lot of energy by getting some water out of sea water, leaving extra-salty brine, rather than trying to get all the water out, leaving dry salt.
Desalination brine could be a big increase in efficiency for them in place of ordinary sea water.
[1] http://www.cargill.com/corporate-responsibility/environmenta...
In the next 20 years, solar will take care of that problem regardless.
If the infrastructure is available, it would be interesting to force things like watering lawns with only water from something like a desalination plant.
To supply 10 million households with drinking water from sea water, then, produces 200 million tons of salt. The current global salt market is 250 million tons, at a price of about $50 / ton. I find it unlikely that the market would bear dumping that much salt on it at a price that would make producing the salt worth it.
Disposal is probably a cheaper course.
Dumping 200 million tons of new "solar salt" on the market would collapse prices and signal the end for the existing player in the salt industry. I don't think this would be an issue in the long term as salt derived from a hypothetical mass-desalinization industry is essentially free. Replacing heavy industry with the byproduct of an essential and beneficial process is the very definition of economic and environmental efficiency.
California gets a secure water supply, consumers and industry get cheaper salt, and the imprint of the salt mining industry is no longer a concern in the environment.
*Source: http://www.saltinstitute.org/salt-101/production-industry/
http://www.wbez.org/series/curious-city/how-much-road-salt-e...
Obviously a little drive, but salt prices are high up here ;)
They relied on a moisture condenser built into the side of the rock initially (there is often very moist air caused by the cold air from the atlantic hitting the warm air from the med), but with expansion it wasn't enough and is now used primarily to provide irrigation to the nature reserve.
It would be cheaper to use eminent domain on water rights and pay the fifth amendment just compensation costs.
I hope you're being sarcastic? As the article clearly reminds, desalination uses tons of energy and so will require releasing even more CO2 into the atmosphere. The whole point is that better conservation of rain water will be more sustainable AND less expensive.
The main problem with this approach is that while desalination (and, for that matter, rainwater capture and treatment and reuse of sewage) would provide ample water for cities and towns, it wouldn't really make a dent in the shortfall for agriculture. The author suggests leaving the rivers and snowpack for the farmers, but the problem is there is no snowpack and the rivers are dry. So none of this is a complete solution.
BTW you're right that agriculture water usage is much bigger than "city" usage, but the latter is still not negligible.
This is a pretty reasonable assumption, since the solar in use would presumably be built out specifically for the desalination. The solar capacity in the scenario wouldn't exist unless it were used for desalination, because it wouldn't be built.
I have no real opinion on the economic feasibility of large-scale desalination, but it seems reasonable to assume that someone building a desalination facility in California can get the sunshine they need onsite, without taking energy from existing solar sources.
Rainwater collection is not a substitute for desalination because in many years there is little or no rain. The author's principal position is that there is no drought because once every 10 or 20 years there is (or was) a wet one; of course, to conclude this he includes the extremely wet 2004 and excludes the extremely dry 2013-2015. Even if we ignore his cherry-picking, that position is not a sensible one; it is equivalent to asserting that with an infinitely large reservoir, California would always have enough water regardless of the consumption rate. The reality is that consumption exceeds the long-term average supply by a considerable margin and has increased due to population growth even as the likely future supply is shrinking. Furthermore, large quantities of water cannot be stored forever; it evaporates, seeps into the ground, or both. The wet years, rare even in the past and likely to be moreso in the future, don't come often enough to keep reservoirs full. There's also the problem of the inland cities, where even historical average rainfall is far below 14 inches a year, which the author conveniently ignores.
Rainwater collection and recycling of treated sewage are therefore necessary but insufficient measures (at least in southern and inland California; they're probably sufficient for places like Eureka). In addition to those measures, additional sources will have to be found and/or large-scale reductions in consumption will be required. Desalination is perhaps the only plausible means of increasing supply (all Western river systems are already critically oversubscribed), and while it is costly, it does come without the political problems of forcibly reducing consumption. As such, I predict that solar-powered desalination will eventually become the central piece of the state's response to its water shortage. It does a good job of matching plentiful resources (solar energy, ocean water) to visible needs (more water for coastal cities). It does not address the needs of agriculture, but nothing can. The only policy options with respect to agriculture are in assigning the required curtailments. For political reasons, they'll probably also build more storage, but the practical benefits of that storage to agricultural users will be minimal as it will be empty or dead pool most of the time.
These aren't things anyone wants to hear, but they're reality. The author, like many others, is whistling past the graveyard. Anyone who believes that simple, inexpensive measures can address the problem is in denial of its true scope and scale.
1. Storing rainwater (underground, with very little evaporation) is much more energy efficient than desalination. Could this alone fix all the problems of water supply even just for cities? Maybe not, but what it can do, it can do very efficiently. Even if it's not at all cheap and easy: I didn't run the numbers, but I'm pretty sure that building that kind of distributed storage capacity is much more expensive upfront than building an "equivalent" desalination plant. The difference is that the desalination plant will burn energy forever, while the water storage will use much, much, much less. Even if the historical average were say half the 14 inches quoted in the article, you would "just" need to cover a bigger catchment area.
2. We don't have infinite resources, and we can only build so much electrical power capacity from solar every year. As long as most of the electrical power generation emits CO2 (and worse), the more electrical power you use for desalination, the more CO2 you're going to emit.