December 21, 2014

Traditional irrigation in Mesopotamia

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Published as Chapter 25 of The Social and Environmental Effects of Large Dams: Volume 1. Overview. Wadebridge Ecological Centre, Worthyvale Manor Camelford, Cornwall PL32 9TT, UK, 1984. By Edward Goldsmith and Nicholas Hildyard.

Minimising the effects of salinisation

Irrigation has been practised along the banks of the Euphrates for thousands of years in conditions that are far less favourable than in the valley of the Nile. As Professor Gunter Garbrecht, Professor of Hydraulics and Hydraulic Engineering at the Technical University of Braunschweiz in West Germany, notes:

“First, the floods of the Tigris and Euphrates were very erratic and occurred at the ‘wrong time’, the period April-June being too late for the summer crops and too early for the winter crops. Secondly, the two rivers carried a much greater amount of sediment than the Nile river. And, finally, the very small incline of the alluvial plain (1:26, 000) and the fine texture of the soil easily gave way to waterlogging and salinisation (lack of natural drainage).” [1]

In spite of this, the local inhabitants practised irrigated basin agriculture as successfully as conditions permitted throughout much of the turbulent history of the area – the principal weapon against salinisation being alternate-year fallowing. Such fallowing allows the water table to fall after harvest, a process encouraged by evapotranspiration from the wild plants that take over once the land is temporarily abandoned. The mechanism is succinctly described by Professor McGuire Gibson of the University of Chicago.

“As a result of irrigation the water table in a field approaching harvest lies about half a metre below the surface. After the harvest the field turns green with Shok (Proserpina stephanis) and Agul (camelthorn, Alhagi maurorum). These wild plants draw moisture from the water table and gradually dry out the subsoil until winter, when they go dormant. In the spring, since the field is not being irrigated, the plants continue to dry out the subsoil to a depth of two metres, thus preventing the water from rising and bringing salt to the surface. Since they are legumes, the plants also replenish the land with nitrogen, and retard wind erosion of the topsoil. In the autumn, when the field is once again to be cultivated, the dryness of the subsoil allows the irrigation water to leach salt from the surface and carry it below, where it is normally ‘trapped and harmless’.” [2]

It is unlikely that there is a better means of preventing soil salinisation in the area. Indeed, J. C. Russell has described the traditional fallowing system as “a beautiful procedure for living with salinity”. What is more, he points out, “the rural villagers understand it, in that they know it works, and they know how to do it and they insist on it”. [3] Sadly, the same cannot be said for the modern technological methods of irrigation which are being imposed on the peasants today.

Both Adams and McGuire Gibson – who have made special studies of the history of irrigation in Mesopotamia – seem to agree that fallowing is the best, if not the only way, of combating salinisation in the area. Even then, in the long run, it still does not prevent salty water from being slowly brought up to the surface; as this happens the Shok and Agul roots slowly lose their capacity to ‘deep-dry’ the land, and, as a result, the top soil becomes increasingly saline.

Such soil can, of course, be removed by the farmers who can then work the deeper layers until they too grow unproductive. Eventually, however, the land must be abandoned – often for periods of between 50 to 100 years or more – as indeed it has been during the long history of vernacular irrigation in Mesopotamia.

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The El Shabana

Short-term and long-term fallowing were not the only measures used by traditional agriculturalists, to minimise the effects of salinisation. They were only two elements in a complex cultural behaviour pattern, which was perfectly adapted to local ecological exigencies. Clearly, the details of that cultural pattern have been lost to history.

Nonetheless, we can reconstitute many of its elements from studies of those tribes, which – at least until recently – practised traditional irrigation in the region. In that respect, the work of Robert Fernea, an anthropologist who has studied the social organisation and irrigation system of the El Shabana of Daghara, is particularly relevant. Indeed, Fernea sees the El Shabana’s social system as one which must once have been “typical” of all the tribal groups in Southern Iraq. [4]

As in all traditional societies, the technology employed by the El Shabana was very simple. Moreover, their land-tenure system was perfectly adapted to their agricultural practices. Joint ownership of land, for instance, was fairly common, this, Fernea considers, helped prevent having “plots without access to irrigation water”. [5]

It also prevented plots becoming too small for half of them to be allowed to go fallow at any given moment. In addition, the El Shabana established a symbiotic relationship with local nomadic groups – through marriage ties, economic interests and agreements to allow animals to pasture on fallow fields. When farming became particularly difficult, the farmers could thus revert to pastoral nomadism. The livestock they kept on their farms was, therefore, not only a source of income “but an ultimate insurance against drought, loss of land, or other crisis”. [6]

Two of the tribe’s important features were its tradition of hospitality and the existence of mutual obligations between its different members. Together, they not only made it possible to spread the risks of farming but also strengthened the co-operation required to clean and maintain the irrigation canals and to dig new ones. The tribe also had the ability to fragment into its component parts when necessary which, as McGuire Gibson notes, “removes the necessity for sustaining a large number of labourers and for them being forced or tempted to make work for them”. [7]

In more general terms it clearly enabled the tribesmen to reduce their impact on their environment to a sustainable level. McGuire Gibson considers the land-tenure system of the El Shabana to have been so well suited to their traditional methods of extensive cultivation that “the two aspects of agriculture must have evolved together in this region”. [8]

For his part, Fernea argues that the most adaptive features of the tribe’s social organisation was its ability to prevent the concentration of wealth and power. Thus, the society was egalitarian. It was run by the shaykh – or chief – who was regarded as being no more than the first among equals. His main function was to lead his people into battle and to act “as a reservoir of tribal law and an astute judge . . . enforcing culturally defined and traditional norms”. [9]

Moreover, the shaykh had no real political power: indeed, as Fernea points out, the segmentary lineage structure of the tribe had an almost “decentralising tendency”. That tendency was accentuated by the frequent revolutions, which would replace “a shaykh from one lineage with a man from another section of the tribe”.

Lastly, the shaykh was not motivated to build up large land-holdings – his prime interest being in acquiring prestige. For that reason, if for no other, shaykhs did not invest in new irrigation schemes for personal gains and aggrandisement. Instead, what wealth they acquired was ploughed back into the social group “in the form of hospitality, help in crisis and the like.” [10]

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The earliest historical experience in Mesopotamia

Irrigated agriculture in Mesopotamia was carried out as far back as the 4th or 5th millennium BC, by local communities, which were probably very similar to the El Shabana both in their social structure and in their irrigation methods. However, some time during the 3rd millennium, there seems to have been a massive increase in irrigation works in the Euphrates Valley. These do not seem to have been designed to improve the irrigation system of the local tribesmen but rather to satisfy the requirements of a burgeoning urban society. Adamns writes,

“It is noteworthy that the objective of urban supply, rather than irrigation, is stressed in the few early royal inscriptions dealing with watercourse maintenance and that the principal terminological distinction, is between navigable and non-navigable channels rather than between rivers and artificially constructed canals.” [11]

Particularly significant, was the building, in Southern Iraq (in the basin of the Lower Diyala River, which occupies about 8,000 square kilometres along the North-Eastern margin of the lower Mesopotamian Plains) of a vast canal by King Entemenak of Girsu around 2400 BC. [12]

The canal was intended to supply water from the Tigris in order to irrigate an area east of Girsu, which formerly had been watered by the Euphrates. The canal, which was so large that it was simply referred to as ‘the Tigris’ – led to seepage, flooding and over-irrigation and a rise in the groundwater level. [13] Indeed, shortly after the reign of Entemenak, saline land “is attested in records of ancient temple surveyors”. [14] It is attested in literary texts. Thus, in The Atrahasis Epic, we read:

“The black fields become white

That broad plain was choked with salt,” [14a]

During the same period, we also learn that there was a gradual but marked reduction in the cultivation of salt-sensitive wheat, which was replaced by salt-tolerant barley. Thus, around 3500 BC, it appears that as much wheat as barley was grown in Southern Iraq: by the reign of Entemenak of Girsu (2500 BC), wheat accounted for only one sixth of production: by about 2100 BC it accounted for no more than two percent of crops; and by 1700 BC, no wheat was grown at all.

Soil fertility also declined dramatically – largely as a result of salinity. In 2400 BC the average yield of barley per hectare in Girsu appears to have been 2,537 litres. By 2100 BC, that yield had declined to 1,460 litres; and by 1700 BC, the yield at Larsa nearby, had fallen to an average of 897 litres per hectare. Indeed, the southern part of the alluvial plain “appears never to have recovered fully from the disastrous general decline which accompanied the salinisation process”.

As a result, many of the great Sumerian cities “dwindled to villages or were left in ruins”. [15] By the 20th century the “former Garden of Eden had become a region of poverty and misery”. [16]

Adams and Jacobsen argue that there is probably “no historical event of this magnitude for which a single explanation is adequate”. Nevertheless, it seems beyond question, “that growing soil salinity played an important part in the break-up of Sumerian civilization”. [17]

Walters – who has made a meticulous study of a large number of cuneiform inscriptions, many of which refer to the administration of irrigation works in South Mesopotamia – does not consider that the spread of salinisation as far as the Larsa area can be explained by the building of Entemenak’s canal alone. Instead, he postulates that similar large-scale water projects were undertaken around Larsa itself.

Indeed, in the archives, he found a reference – dated 1881 BC – to a major project involving “the building of a wall above a reservoir at the mouth of the Isin Canal”. [18] That wall was big enough “to require an inventory of at least 1.3 million bricks” as well as the despatch of many workers and much material.

The project appears to have been the work of Sumuel, King of Larsa; its object was to divert water for Larsa’s own agricultural needs, from a canal serving the territory of the rival city of Isin. A vast bureaucracy was created to administer and maintain the Larsa canal and many of the tablets studied by Walters clearly illustrate the inefficiency and corruption of the bureaucrats involved.

From 1200 to 100 BC to the end of the Assyrian Empire in the late 7th century, the Diyala area was a “disputed borderland”, marched over and sacked by armies of rival Empires. [19] A measure of order seems to have been established by Alexander the Great and his heirs, who encouraged urbanisation on the Greek model. As a result, the population increased and agriculture was intensified.

Those trends continued during the Sassanian period (AD 226-637). Thus, in the 6th century – probably during the reign of King Chosroes the First – the giant Nahrawan Canal system was built, its aim being to supplement “the limited and fluctuating supplies of the Diyala River with almost unlimited water from the Tigris”. [20]

The construction of the Nahrawan Canal made it necessary “to criss cross formerly unused desert and depression areas, with a complex – and entirely artificial – brachiating system of branch canals”. [21] That expansion depended also

“on the construction of a large supplementary feeder canal from the Tigris, which, with technical proficiency that still excites admiration and without apparent regard for cost, brought the indispensable additional water through a hard, conglomerate headland, across two rivers and thence down the wide level left by the Dabban River of antiquity.”

Three hundred kilometres of the canal still remain. They illustrate “not only . . . the size of the system but also the attention lavished on such ancillary works as thousands of brick sluice gates along its branches”. As Jacobsen and Adams point out

“. . . we are dealing here with a whole new conception of irrigation which undertook bodily, to reshape the physical environment at a cost which could be met only with the full resources of a powerful and highly centralised state.” [22]

From a study of land-tax receipts (which reached a level they have never equalled at any other time) and from our knowledge of the distribution of settlements, it now seems clear that the Nahrawan Canal and its associated works brought the entire surface of the Euphrates plain under cultivation. This led to still more urban growth, indeed

“Ctesiphon, the Sassanian capital, contained a larger urbanised area within its walls alone than the total area of all occupied sites within the 8,000 sq. km composing the lower Diyala basin at the period of the greatest ascendancy of Eshnunna around 2000 BC.” [23]

The result was an increased dependence on outside markets, and also the take-over of the irrigation system by the state bureaucracy.

Like other irrigation works of the period, the Nahrawan Canal served, principally, to supply water to the newly founded royal cities, together with the agricultural areas on which they depended for their food. Since the Sassanian Empire, like the British Raj in India, depended for much of its income on an agricultural tax, the canal also served to finance the state bureaucracy and the dynasty’s costly imperial policy.

The Canal may also have served to reduce the power of the landed nobility and otherwise to enhance the power of the central government. The Sassanian Empire was, thus, effectively funded by pillaging the alluvial soils of Mesopotamia and by destroying the social and cultural pattern of the communities they sustained.

Indeed, the building of such massive water development schemes caused numerous social and ecological problems. To begin with, there was a steep increase in population – probably as a result of the increased economic activity brought about by the new water works. Adams writes,

“Quite possibly, this led for the first time to a condition of general water shortage rather than local shortages based on uneven distribution.” [24]

Social disintegration quickly followed, and with it, the inability to ensure that the irrigation works were properly maintained (which Jacobsen rather superficially attributes to the breakdown of the central administration). The final stage in the drama – to quote Jacobsen and Adams – “assumes in retrospect, a kind of historical inevitability”. The area was virtually abandoned.

By the 12th century, “Only a trickle passed through the upper section of the main canal to supply a few dying towns in the now hostile desert”. [25] Still more serious was the predictable and dramatic increase in soil salinisation, which led to whole areas being abandoned. Forty percent of the Sassanian settlements were never afterwards re-occupied and major canal branches and their adjoining cultivated districts were permanently abandoned. As a consequence, Islamic tax collections never approached their Sassanian highs, and

“the prosperity of Baghdad as the seat of the Abbasid Caliphate had to rest more on foreign conquests and tribute than on a secure economy in the city’s immediate ruralities.” [26]

Inevitably, the large-scale, centralised irrigation systems broke down under the strain of social upheaval.

“What replaced it, at catastrophically lower levels of population and economic interchange, was the first, simplest and most resilient of configurations . . . which had been antecedent to cities and hence would survive their destruction.” [27]

In other words, those small-scale communally-managed, traditional systems which alone were adapted to the social and ecological requirements of the area.

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