the two main rivers they had and lived off of were the euphrates and the tigris rivers
the mesopotamians moved to the zagros foothills then problem arose and the problems were over population, food shortage, and not enough space. since they needed more room they moved to sumer to back then modern day sumer
there were problems though because depending on how much rain they got they would get to much and then it would flood onto land and it would drown the plants. the solution they had was to build irrigation systems and to build levees to control the water flow
People who lived in different villages may have worked together to clear the silt from the canals to keep them open. around 3500 and 3000 B.C.E., villages grew into towns. Some towns in Sumer became cities with populations as large as several thousand people.
they mainly fought over the water because the villages higher up the irrigation systems were blocking the water and the villages lower down the line were not getting any water
the advancements of the Sumerians led to the creation of the dam and the irrigation system but i also led to the Sumerian villages becoming the first city and becoming famous city-states in history