ironically even though it is expensive:
https://mywaterearth.com/the-cost-of-desalination/
The cost is about double that of water obtained from building a new reservoir or recycling wastewater, according to a 2013 study from the state Department of Water Resources.in 2015. This plant will provide about 7 % of the water needed for San Diego and its surrounding area. They have more than 16 more plants in the works to provide water for California. That should answer your question of whether Desalinization is the solution for coastal regions with growing populations.
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I think over the next few years as more and more fresh water is required the cost of desalt plants will drop.
If, for instance, CA would build more reservoirs and a couple dams, they’d have plenty of water. It’s been known for decades. They whine about fish in the delta that need more fresh water mixed in with the salt water so they let the winter rains go into the ocean.
It’s insane. And then the illegal mj grows are vast and utterly destructive and use huge quantities of water that should stay in the rivers and streams and acquifers.
Corrupt commiepukers will continue to destroy whatever it is, they will always destroy since that is their objective.
There was an article a while back about how Israel developed a cost effective solution to Desalinization.