 Nevertheless, as in Egypt, the small city-states of Sumer depended on the rivers and so, the cycles of agricultural production were organized around them.The rivers also provided communications materials.In Egypt, the Nile's papyrus became a medium for writing while in Mesopotamia, the rivers yielded the alluvial sediments the Sumerians used to fashion the clay tablets on which they inscribed their wedge-shaped, cuneiform script.