What exactly is the "cost" to the environment?
Exactly. Especially compared to the environmental cost of bringing it in from hundreds of miles away, and taking it from the farmers?
Partly this, it seems:
“In Huntington Beach, about 107 million gallons of seawater a day would be used to produce about 50 million gallons of drinking water.
“However, this would leave behind about 57 million gallons of brine — highly concentrated saltwater — that would be diffused while being sent back into the ocean.
...
“The facility, in total, would kill marine life in about 100 billion gallons of seawater per year,” a report by the staff of the California Coastal Commission states.”
Huntington Beach is already completely built out, so I can’t see any damage to be done at all. It isn’t like they are putting it in Big Sur.
Only in California does it make sense to divert rainwater to the ocean, then build a plant to desalinize it.
Desalination is good for the environment and rate payers by far.
What do you do with the salt you remove?