The first great civilizations all developed in river valleys, as the rivers provided a source of water and irrigation for crops. Over time, these civilizations developed a surplus of food that allowed them to create specialization of trades.

The Tigris-Euphrates Rivers gave rise to the first civilization, Mesopotamia, around 3500 BCE. The city-states in Mesopotamia began to irrigate their land using the two rivers. Egypt developed along the Nile, which had a different type of flood cycle than the Tigris and Euphrates. While the Tigris and Euphrates had unpredictable floods that varied in scope, the Nile had predictable flooding patterns. The Tigris and Euphrates had floods that could be much greater in volume one year than in other years, so the people in Mesopotamia had to control the flooding with dikes. The people along the Nile used the river's predictable flooding patterns to irrigate their crops, and they also developed dikes, canals, and basins.

The Indus River is longer than the other rivers, and its annual length of flow is two times that of Nile and three times as long as the Tigris and Euphrates. In its upper plain, the Indus has several tributaries, but in its lower plain, it is like the Nile in having few tributaries. The Indus, like the Nile, also floods in a way that creates rich alluvial soil. 

There are more similarities between the rivers of the ancient world than there are differences. The three river valleys supported large populations of people because the advantages they offered for agriculture. The rivers flooded their banks annually, leaving behind a very fertile layer of soil that was extremely arable. The rivers also connected urban areas for the benefit of trade and the exchange of ideas. The Indus River and Nile River, in particular, were given a certain spiritual significance by their civilizations. Large and important urban centers developed along all three of the river valleys, supported by agricultural growth.

A major difference existed between the rivers in terms of the level of flooding. The Nile River flooded very regularly and with the least amount of property damage. The Tigris and Euphrates Rivers could flood with devastating effect for its inhabitants. The Indus River also could be calamitous in terms of inundation. Of the three rivers, the Nile is the only one to support two culturally different civilizations and is the only one that flowed from the south.