Good thing to think of using
permaculture practices and applying principles in this situation. There might be some youtube videos in Swahili, there might be
local organizations that are doing permaculure in the country. There are certainly some in other parts of the continent.
Maybe Joseph Lentuyoi, the name coming up in the "similar threads" link below?
The only thing that can really work well in that kind of climate is a tree.
You probably want to look at "Greening the Desert" (
Geoff Lawton, I think), as a starting point. You grow things to accumulate
water in the form of dew, soak it into the soil, and begin to start localized weather patterns. You can also capture large quantities in the soil, digging cisterns, but that's not going to last the whole dry season. Air wells is another option, not too pricey, google Ethiopian
air well on youtube I think you'll find it. Or
Willie Smits, he's done reforestation in Indonesia, he's on TED talks. Some of what he's doing may be applicable. I'm talking about doing maybe 1-2 hours of research here, not overwhelming.
I think you'll probably also want to make some
hugel mounds--cut large branches off
trees and leave the tree, or coppice it, cutting it off high
enough that it will grow back (extending the life of the tree). Pile these up and cover with soil and mulch, then drop a cover crop on there (maize is OK, if you can bring buckwheat and sorghum they
should do well). if you can't get any seeds in, then whatever they have locally that they were going to plant in the ground will do (probably a sorghum?) The hills will drain better than growing on flat earth, and it's simple and easy to start out. They'll also stay wet later into the dry season.
Good luck, maybe others will have better ideas for you.