I believe I participated in a discussion of this a year or two ago, but I'd like to start another thread on macroengineering -- this time doing it on the cheap. I think, e.g., that the East African Rift Valley could be turned into an inland sea similar to the Mediterranean with a little work.
In fact, it would seem, if my readings are correct, that just a tiny amount of excavation at it's northern extremity would start the process whereby waters from the Red Sea would flood a portion of the Rift Valley.
Now, with regards to this, there are some problems. One is moral. The impact of such a change would be far reaching and would affect the lives of humans and nonhuman animals, probably adversely in the case of the latter. Add to this the affect on the region's weather patterns and the like.
Another is whether this would work. Could a few well placed explosive charges actually begin this process? Or would it require much more effort because, e.g., lots of water might evaporate before have a large scale impact?
I look forward to your comments.