Two thoughts collided in my head in the last 10 min before I conceived this post on Thursday.
One, was the thought that if you irrigated the Sahara eventually the climate of the are would change sufficient to self-sustain without pumping in more wanter. This would also help a lot in the whole “food-growing area” thing.
Second is that such a scheme would require a lot of water from the sea. Now you could use a nuclear reactor or three to get the power (I also hear it’s quite sunny around those parts), but this would take a lot of water out of the sea.
Then it struck me – isn’t sea level supposed to be rising anyway? Bingo, two birds with one stone!