The driving force of this urban development is likely the significant population growth, as seen in a proliferation of villages and small towns in the IVth millennium BC. Subsequently, it may be that as the climate became drier, some of the villages were abandoned causing market towns to grow and evolve into cities. As some branches of the river became dry, it was necessary to dig canals and establish a complex system of water distribution, and also to bring more land under cultivation by draining swampy areas and irrigating dry land. The accompanying need to organize a work force and coordinate the construction gave birth to the Sumerian civilization, the first to have a hierarchical organization.[7] Studies of human settlements in certain regions of lower Mesopotamia, performed by the American archaeologist Robert Adams, show a decrease in the number of villages, and a concomitant increase in the number of cities and population increases in existing cities, during the period between 3000 and 2500 BC. These really were cities in the true sense of the word: Uruk, one of the largest and oldest, occupies 550 hectares with a wall of circumference 9.5 km. The reconstitution of Uruk’s urbanization in 2500 BC is shown in Figure 2.3 of the following chapter.
The notion of writing first appeared in this urban civilization, in particular in Uruk about 3300 BC (and perhaps also in Suse to the east). One of the oldest texts describes the creation of man, vegetation and animals, and the first five cities (Eridu, Bad Tibira, Larak, Sippar, and Shuruppak). It goes on to argue for the vital need to maintain the hydraulic system, mentioning the necessity of “the cleaning of the small ditches.”[8] Another account contains the following:
“At this time, water was short in Lagas, there was famine in Girsu. Canals were not dug, vast lands were not irrigated by a shadoof (shaduf),[9] abundant water was not used to dampen meadows and fields, because humanity counted on rainwater. Asnan did not bring forth dappled barley, no furrow was plowed nor bore fruit! No land was worked nor bore fruit! No country or people made libations of beer or wine, […] sweet wine […], to the gods. No one used the plow to work the vast lands. (…) In order to dig the canals, in order to dredge the irrigation ditches, in order to irrigate the vast lands by a shadoof, in order to utilize abundant water so that the meadows and fields were moistened, An and Enlil put a spade, a hoe, a basket, a plow, the life of the land, at the disposal of the people. After this time, human beings gave all their attention to making the barley grow.” (there follows a list of numerous canals dug by the leaders of Lagash) [10] [11]
A third text describes periods of famine, caused by a conflict between the “waters of the primordial sea” having invaded the earth and the beneficial water of the Tigris.11 Does this perhaps refer to the conflict, common to all deltaic and estuarine zones of large rivers, between fresh and salt water, the latter useless for both cultivation and human consumption?
“Famine was severe, nothing was produced, The small rivers were not cleaned, the dirt was not carried off, On the steadfast fields no water was sprinkled, there was no digging of ditches, In all the lands there were no crops, only weeds grew.”
