Changes

By the 4th and 3rd millennium BC, more complex societies developed with larger settlements. In particular in southern Mesopotamia (southern Iraq), where we see the first cities form. <ref> For information about 4th millennium BC canals and irrigation in southern Mesopotamia, see: Wilkinson, T. J. 2003. Archaeological Landscapes of the Near East. Tucson: University of Arizona Press, pg. 89.</ref> However, the region is very dry and depended heavily on two major rivers, the Tigris and Euphrates. Irrigation began to become more complex, with longer channels and managed by groups of people at different points, including controlling sluices that would release water to different areas. This development is similar to the Indus region along the Indian and Pakistani border, where the Indus river became important in dry regions as major cities developed. Similar types of canals to those of southern Mesopotamia seem to have developed, leading to also large cities by the 3rd millennium BC.<ref> For more information on irrigation in the Indus region, see: McIntosh, Jane. 2008. The Ancient Indus Valley: New Perspectives. ABC-CLIO’s Understanding Ancient Civilizations Series. Santa Barbara, Calif: ABC-CLIO, pg. 115 </ref>

In Arabia, already new forms of water capturing technologies may have developed. This includes surface channels and dams to capture water from the highlands and bring the water down to lowland region. Some have suggested that already underground channels, called falaj/qanats, were already developed, but this is not universally accepted. <ref> For information on early Arabian irrigation and types of features, see: al-Jahwari, Nasser Said. 2009. “The Agricultural Basis of Umm an-Nar Society in the Northern Oman Peninsula (2500-2000 BC).” Arabian Archaeology and Epigraphy 20 (2): 122–33.</ref>