I've always wondered why oil pipelines didn't re-harness the energy it took to pressurize them and send the oil through those long tubes, and recycle it to bring in water, as it is a similar density. Have you ever been to a modern port where they pick up cargo containers? The lifting system now picks up a cargo container and put it onto the ship, it then has enough energy and leverage to take another container back, and so on. Think about how wise that is in the conservation of energy, and to think that it is only simple physics which allows this, well, it gives us hope for the other strategy I mentioned above.
Now then, let's say you were in the Middle East, and you wished to bring in ocean water using a separate pipe, but recycle the energy as you pump the oil out and into the pipeline. Once you bring the ocean water inland, you could then desalinate it, you might use natural gas which is also abundant in the region as your energy source. Once you had freshwater you can create an abundant of oasis like city. Of course, you might choose a different method, something more technologically advanced, something that hasn't been tried by humans as of yet.
Why not use laser evaporation techniques on the surface of the water to create clouds in the sky? Why not guide these clouds and keep them together using a specific frequency bombardment to align the molecules, allowing them to hold more water? Why not use lasers to vacate the air in front of the clouds which would suck the clouds along, and allow you to steer them as you go? And then, once you reach your destination, and put those clouds over the reservoirs you created, then why wouldn't you just turn off the frequency holding those molecules together, allowing the cloud to fall apart releasing all the water in the form of rain?
That's another way to transport the water. The only difference between an arid region and an agricultural one is water. Did you know the City of Los Angeles California was nothing more than a desert area until the Chandlers brought in the water? Now look at it, is the largest city in the United States of America. There are many giant cities in the world where water was diverted from rivers, or lakes to allow us to build these megacities.
Desalination is one way to make the water fresh and there are several others. In the future we may use a scheme similar to what I described above, who knows? The water is the key factor here, how you bring it in via canals, suction strategies, pressurized pipes, or modifying weather patterns doesn't matter as much as the fact that you actually do bring in the water. With water all things are possible. Indeed I hope you will please consider all this and think on it.