You can't possibly get a civilization out of a desert. People need water source to feed their animals. Rivers make sense. If you got animals, your first priority is water. If you see a river, u will camp next to it and allow your animals to drink from it. From that, u will eventually grow naturally as more come and live with you. From this you got the seeds for a city and eventually a civilization. Even how large the rivers can determine how large the settlements will become. Smaller rivers will have smaller settlements and therefore won't become anything 'big' as an empire. Possibly a kingdom though.
You forget the other possibility. Sea-faring kingdoms, you can establish this also if you have access to the sea. A trade based society. Having the interior dependent and having the external world dependent on the interior products. You just place yourself in the middle and get in on the action. But this would've come much later in human history, as they would need knowlege of navigation, star knowledge, weather knowledge, boat knowledge. Water/Food are important also so they would've needed to be farmers by this time or had access to farmers.