Water evaporating is a major component of the hydrologic cycle. That's generally what happens to water that ends up in the Mediterranean, so we'd essentially b

Water evaporating is a major component of the hydrologic cycle. That's generally what happens to water that ends up in the Mediterranean, so we'd essentially be taking the water that ended up in the ocean and putting it into an inland sea instead. Now that would probably have consequences for the Nile Delta, particularly in terms of saltwater intrusion... but the the Nile Delta is already somewhat screwed this way.[1] But I'm a meteorologist and not a hydrologist, so don't take my word on it. What I can say is that large bodies of water moderate temperature around them and create wildlife habitat, as North African lakes apparently did during the Pleistocene. The ecological impacts might be unpredictable, but they're definitely not unprecedented. Also when you say "reduction of water to current cities", you sound a lot like people here in the U.S. who think they will get less Colorado River water if it's stored in Lake Mead than if it was in Lake Powell. That's not how politics works; and storing the water in two dams only increases evaporation so everyone gets less water :( [1]: https://en.wikipedia.org/wiki/Nile_Delta#Sea_level https://en.wikipedia.org/wiki/Nile_Delta#Sea_level