The Sumerian World (Routledge Worlds)

Overall, the natural hydraulic landscape of anastomosing rivers and marshes was
taken advantage by early communities who probably used levee crests for palm gardens,
levee slopes for supplementary cultivation, with wetlands and perhaps tidal areas
providing marshland resources alongside flood recession agriculture (Kouchoukos 1998 ;
Pournelle 2007 ). Gradually, however, this landscape mosaic became more managed
so that what had been a ‘natural’ landscape became transformed into a ‘cultural’ lands-
cape with canals and fields becoming more formalized and extensive (Algaze 2008 ).
Nevertheless, ‘natural’ elements presumably persisted but were also managed in order to
conserve their valuable resources. This was a landscape mosaic in which rivers, marshes
and artificial channels all played a role, and presumably where artificial canals became
increasingly significant and elongated by the later third millennium BC.

THE LAYOUT OF CANALS AND WATER SUPPLY

River levees and the framework for Sumerian irrigation

One question raised by the textual evidence is the paucity of records of large canals.
Whereas the embankments of smaller canals of 6 – 9 m^2 cross section (Civil 1994 : 135 ) were
quite common, administrative records relating to Ur III Umma and Girsu appear silent
on the existence of larger canals. Mathematical texts also point to rather short canals by
implying that most canals and irrigation ditches (pa 5 sigin Sumerian) were mainly

1. 8 – 2. 16 km long (Powell 1988 : 163 ). On the other hand, in his royal inscriptions Ur
   Nammu claims to have authorised the excavation of major works, and records of large
   canals, such as the 50 km Nina canal, were occasionally recorded (Rost 2010 : 16 – 17 ).
   If canals were constructed to flow down the longitudinal gradient of the plain, due
   to its very low gradient, it would have been necessary for the head gates of canals to
   have been up to 40 km upstream from the point where water was distributed for
   irrigation (Hunt 1988 : 201 ). However, a key advantage of the Mesopotamian landscape
   is the presence of riverine levees raised 1 – 3 metres above plain level and which con-
   tributed a gradient normal to the main river that was significantly steeper than that
   of the plain itself. Such levee back-slopes that led away from the stream towards
   adjoining basins provided natural drainage and were highly suitable for cultivation
   (Adams 1981 : 8 ).
   The significance of gradient is demonstrated by statistics provided in irrigation
   reports of the Shatt al-Gharraf area (Cotha Consulting) (Table 2. 1 ).

–– Tony J. Wilkinson ––

Table 2. 1 Range of gradients of floodplain and levee slopes in the Gharraf East Area, near Tello-Girsu

Orientation of gradient Mean regional gradient Range of gradients

Longitudinal(over 130 km) 0. 05 / 1000 ( 1 : 20 , 000 ) 0. 04 / 1000 ( 1 : 25 , 000 ) to

0. 45 / 1000 ( 1 : 2222 )

Transverse(gradients for main channel levees):

Gharraf ( 1500 m) 2 / 1000 = 1 : 500

El Amah ( 1700 m) 1. 4 / 1000 = 1 : 714

Shattrah ( 3200 m wide) 0. 8 / 1000 = 1 : 1250

Note: From Cotha 1959 b: 14 Table A. VIII- 1.