God filters the salt out of ocean water for free. We refer to it as rain. Sll that needs to be done is capture the rain.
I’ve designed a system that seperates salt from ocean water using the sun via solar evaporation.
There are places whee it just doesn’t rain much. On the other hand, the enirowhackos tearing down dams means that an awful lot of desperately needed fresh water is being allowed to flow out into the oceans. If all the rivers were equipped with locks, the fish could still swim upstream along with barge and boat traffic. While the locks were closed, the upstream water could be diverted into canals. If the Mississippi River was diverted 90% of the time, that would be over a billion cubic feet of water per hour. The Sacramento River fifty million cubic feet per hour. Columbia River half a billion. It seems incredibly wasteful to see all that rainfall going out to sea.