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. I mean, there's not a lot of stuff other than what they're growing in that area. So with this surplus food, they can create trade routes. They can go and get metal to create weapons and tools and new technology.