The two rivers that helped the civilization become successful are Tigris and Eurphrates RIver.
Problems arose with lack of space and they moved to the plains by the Tigris and Euphrates river.
They used to farm in Zagros foothills, but then population grew and needed more space for crops.
With the rivers near by they had trouble controling the water supply. They dug canals and built dams to control the water.
After they built irrigation systems they started filling with silt. Everyone worked together to keep the canals from being clogged. As they started working together they started building bigger communities
As cities grew many people fought over their right to use more water.
Overall, with the community that worked together turned what was a small community to the rise of city-states.