How does the amount of rainfall in the middle east impact on economic activities there?

The amount of rain that falls in the Middle East has had an impact on the various cultures that have inhabited the area, both in antiquity and in present times.  

Rainfall is very unpredictable, which means that rain-dependent agriculture is risky. People have traditionally combined extensive cultivation with animal husbandry to minimize risk and ensure their subsistence. On the other hand, people in the Middle East have developed complex ways to control and manage water. The invention of irrigation systems in antiquity led to the development of some of the world’s first civilizations: Ancient Egypt and Mesopotamia.

Lack of water has meant less agriculture, which in turn gave rise to nomad or semi-nomad cultures. These cultures have generally been pastoral, caring for herds of goats, camels or cattle. These animals and their products have been a major source of economic activity. Finally, travelling merchants have also been traditionally significant in these areas, due to the strong semi-nomad tradition of most tribes and the limited resources that exist in most areas, so commerce among different communities also provide an economic stimulus derived from the lack of reliable resources.