Published as Chapter 23 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.
The traditional irrigation system of the Chagga of Kilimanjaro in Tanzania is described by Fidelis T. Masao. Like the Sonjo, the Chagga have also practised irrigation agriculture since time immemorial. Early European travellers who visited the area were vastly impressed by the complicated network of irrigation furrows (mfongo) which collect water from the mountain’s streams and transport it over long distances to the fields below.
Indeed, according to Masao, even modern engineers have marvelled at the sophistication of the Chagga’s irrigation works, admitting that they themselves would require highly complicated equipment to achieve the results which the Chagga have achieved with the simplest technology. 
As with the Sonjo, it is only possible to understand the success of the Chagga’s irrigation system – as Masao points out – through “an understanding of their socio-political organisation and their rituals”.
The Chagga are organised into clans, which are powerful and cohesive social units, well capable of co-operative action. There is considerable division of labour among the clans. Some, like the Wako Makundi in Mamba, are specialised in making iron tools. The Wamasi specialise in cattle herding or bee-keeping.
In view of the importance of irrigated agriculture to the Chagga way of life, it is not surprising that some clans are specialised in the arts of irrigation. In one area, Siha, we find a clan – the Kileo – who are specialised in surveying furrows. In Uru East, another area of Chaggaland, the Temba, Ngowi and Njau clans are also specialised in furrow surveying.
As among the Sonjo, the myths and religion of the Chagga reflect the requirements of a society utterly committed to irrigation agriculture. This is made clear if one considers the procedure for deciding on the building of a new furrow and for implementing the decision. Traditionally, either a man of the appropriate clan would have a dream in which he conceived a plan to dig an irrigation canal, or a number of farmers would take the decision to build a new canal and would then elect a member of the appropriate clan to direct the work.
In both cases, the approval of the Mangi, or chief, had to be obtained. After that – in the Uru district at least – the head of the clan or the director of the project had to pray for a specific period until a sign was made that the prayer had been answered. Prayers were addressed to the last elder to have died; offerings were then made to him and to other important ancestral spirits whose assistance was thought necessary for the success of the project.
During this period, the members of the clan had to observe all sorts of taboos, including abstinence from sexual activity. If the sign that the prayers had been answered did not appear, the scheme was postponed until the shaman could be approached. The latter would then arrange for the ancestral spirits to be placated with offerings of beer, goats or sheep.
If the ancestral spirits were then appeased, certain members of the clan would have a vision in which they would see a large number of red ants marching in single file from the hut of the elder of the furrow-owning clan (or the hut of the project initiator) to the river from which the water was to be drawn. The implication, as Masao points out,
“is that deceased members of the clan have the power to demarcate the course of the furrow by sending red ants, which made the surveying work unnecessary.” 
Chagga myths and legends also reflect the tribe’s preoccupation with irrigation. Thus, an important hero is Mlatie of Mbokomu, a famous surveyor, who is believed to have been responsible for the most elaborate irrigation works and from whom the people of Mbokomu (who are noted for their expertise in building such works) are supposed to have derived much of their knowledge.
The sophistication of Chagga irrigation is also praised by other writers, such as K. M. Stahl and H. M. Johnstone. Both authors stress the degree to which that sophistication contrasts with the simplicity of the tools employed by the Chagga. Thus, the only equipment at the disposal of the surveyor consists of small sticks with which the intended course of the furrow is plotted.
The Chagga had no instruments for grading: their knowledge and skill, however, made up for that lack of technical instrumentation. Masao describes how they built their furrows. “The alignment”, he writes, “was done purely by eye. Here and there, the furrow was excavated under a rock or banked up”.  He goes on to note,
“Sometimes the furrows were six feet deep. The [Chagga] of those days knew the precise point of the river from which to take the furrow, selecting a spot where the flow was least turbulent and the current was directed so that it would not eat away the inlet. A favourable point was the tail end of a pond caused by a waterfall on the headwaters. From the main furrow, many branches were led off, these were further subdivided and eventually the field to be irrigated was flooded by innumerable grooves. Very often, a banked-up pond of considerable size was constructed and filled with water to enable one person to irrigate from this source while another used the main furrow; the water was then let out of the pond through a sluice into another furrow. Lately these ponds have been left to fall into disrepair.” 
As regards the operation and maintenance of the irrigation works, those Chagga who wished to use water had to join a furrow board, run by furrow elders. Everyone had to take their turn in repairing and cleaning the furrows. Those who failed to do so had to pay a heavy fine of several barrels of beer. The furrow was owned by the clan and most of the members of a furrow board would be members of that clan: others, who were admitted as auxiliaries, had to pay prescribed contributions. Non-members of the furrow board could use the water by paying so many barrels of beer a year.
If a furrow was damaged as a result of an accident, one of the elders would sound a horn in the evening. This was known as ‘Ole lo mfongo’ the call to the furrows. The next morning, everyone would leave their normal work and set about repairing the damage. Anyone who did not take part without good reason was fined.
Sir Charles Dundas, who visited the Chagga, was impressed by the way in which the maintenance and operation of the irrigation system was organised. “No small degree of regulation is necessitated and, moreover, within the course of the furrow, order must prevail”, he wrote in his book, Kilimanjaro and its Peoples. He went on to surmise,
“It is to these circumstances that we may attribute, in a great measure, the early institution of chiefship with the consequent development of a stable organisation.” 
Whatever the truth of that statement, there is little question that without the stability of its social organisation, Chagga society would not have been able to operate its highly complex irrigation system.
Masao is also impressed by the operation of the furrows and, in particular, by the absence of conflicts over the use of water.
“So well are matters run by the furrow elders that the number of cases arising out of disputes over water rights are exceedingly few.”
The normal procedure for regulating water supplies was for the person whose turn it was to use the water, to do so from dawn until noon. He then had to turn back the water so that other people could use it for their daily needs – be it cooking, washing, brewing beer or peeling coffee. If the person in question was unable to complete irrigating his plot, he could finish doing so the next day. Anybody could use the water at night – so long as the water was back in the furrow by four o’clock the next morning.
As Masao notes, the irrigation “more than anything shaped the life patterns of the [Chagga]“.  Huxley also stresses how the co-operative nature of Chagga society was associated with the need to keep the irrigation furrows in good order; to maintain maximum water flow; to repair the banks; and to regulate the use of the furrow. 
Unfortunately, as with so many tribal societies today, the traditional Chagga way of life – and with it, the survival of their irrigation system – is threatened by development. Piped water has been introduced and the people are becoming lax in the maintenance of the furrows. Indeed, the furrows have already been allowed to fall into disrepair. The result, as Masao points out, can only be a lower agricultural output.
In some parts of Kilimanjaro, however, efforts are being made to strengthen the furrow banks with concrete – a sign, perhaps, that all is not yet lost. Nevertheless, the shortage of land in the area has forced people to cultivate the ravines down to the rivers. Trees required for preserving the catchment area have been cut down and, as a result, some feeder springs have dried up and rivers have ceased to flow.
That trend will undoubtedly get worse unless action is taken soon. If it is not, there will be less water available for the furrows and their maintenance will quickly become uneconomic. When that happens, the Chagga’s highly efficient irrigation system will sadly, but inevitably, fall into disuse.
|1.||Fidelis T. Masao, “The irrigation System in Uchagga: An Ethno-Historical Approach”. Tanzania Notes and Records No.75, 1974.|
|5.||Charles Dundas, Kilimanjaro and its Peoples, London 1924, p.262, Quoted by F.T. Masao, op.cit. 1974, p.6.|
|6.||F.T. Masao, op.cit. 1974; p.7.|
|7.||E. Huxley, The Sorcerer’s Apprentice. London, 1956, p.67. Quoted by F.T. Masao, op.cit. 1974; p.8.|