In Egypt, there is a 190 mi depression called the Qattara Depression. For decades, there has been talk of filling the depression with water to create an inland sea. Because the depression is in the desert, the constant evaporation would mean water would continually flow in (meaning hydroelectric turbines would continually move). Also, the constant evaporation could result in greater rainfall to the area which in turn would support vegetation. There has been talk about creating a channel linking the depression to the Mediterranean to allow saltwater to flow in, but there are those who think the constant evaporation would make the lake saline. So, I wondered if they could use freshwater from the Nile instead? What if they diverted water from the Nile right before it flowed into the Mediterranean and redirected it towards the depression (I think you mentioned redirecting Dorne's rivers in you economic development post)? Would they just need a canal/channel to do this, or would they need to dam the end of the river?
I think this project is the definition of "cool but impractical."
Look on the map below at the proposed routes to the Mediterranean, which have all been rejected for being too expensive (hence why the U.S proposed it as a showcase for the truly insane "Project Plowshare" (see above) as a means of reducing construction costs) and how much longer a canal linking the Qattara Depression to the Nile would be in comparison.
Next, look at the legend of the map that shows that the most logical paths for a canal to take would go through active oilfields and minefields left over from the Battle of El Alamein. I don't want to think about the engineering difficulties inherent in safely digging a canal through that terrain.
This is why, at the end of the day, the Egyptians went with the Aswan Dam project instead - which was itself an incredibly difficult public works effort in terms of the complexities of engineering and the competing tensions between economic development, environmental impact, social dislocation, cultural preservation, etc.
