Also - there are lots of un-earthed treasures to be found under the saharan which was once a lush environ and have been covered with sand - so prior to flooding it, we need to lidar and excavate it.
What if we vaccuumed up all the sand and built a new island/continent with the material and just revealed everything underneath - then flooded it. (I believe UAE is in the market for more sand-built-land-masses)
I'm sure someone has done the math to figure out what the proper length is for such a canal, to avoid problems with scaling. And if you've ever been near an ocean for much time, you know the salt tends to get around. So I'm not sure how in a multi-year project you keep that to a minimum.
So even if you evaporate a lot of water, it won't fall where you need it or where you can collect it.
It doesn't increase rainfall.
Israel is actually desalinating water and rejuvenating a river, which eventually will reach the dead sea (although that's not why they are doing it, but it makes the point that evaporating water isn't doing much).
Maybe you mean on a far larger scale?
Well - the ocean itself is much larger, and water evaporates from its surface all the time. Humans aren't going to make an evaporation zone larger than the ocean.
Also: Water does not (mainly) evaporate because of heat, but rather because of wind. There's lots of heat in the desert, but not much wind. The ocean has a ton of wind.
That said, none of this contradicts the overall point you were making.
Some call that par for the course, others unsustainable. Still others don't make a distinction and see them as the same.
That's not unusual in desalination however, many facilities are combo plants, they're producing power and then using waste heat for desalination.
Salt was used as money.
EDIT: Only a fn idiot without knowledge of history would downvote a comment... Jimminy Carter, what type of stupid are you trying to promote?
Never heard this saying before. I've heard "worth his weight in gold".