Considering the amounts of fresh water needed by refineries, I don't think Arizona would be a good place for one. They are usually located on sea coasts near rivers so they can take advantage of low shipping costs and fresh water nearby.
Yuma is where the Colorado River empties into the Gulf of California. Water isn't an issue for the project.
I'm not aware that large quantities of fresh water are required by refineries. There are a large number of refining centers located in relatively arid country -- e.g., Artesia, NM, Borger, TX, Big Spring, TX, Cushing, OK, Tulsa, OK, Salt Lake City, UT, El Dorado, KS etc.
By and large, refineries are located near where the oil is (or was). The concentration on the Gulf Coast is likely attributable to import (now) and export (then) needs.