It would leave the silt behind, but then the sun would come and everything would dry up. So the Sumerians are presented with this challenge of how to deal with all of this dry land but having the flooding. So they're able to figure out that they're able to irrigate. They're able to take the water from the river and move it to where the crops are growing. So they can grow lots and lots of wheat and barley. They love their cereal. But this gave them a surplus of food, which is going to help them deal with the second problem, which is they have a lack of natural resources.