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 Post subject: Ancient irrigation works of Sri Lanka
 Post Posted: Tue Sep 20, 2005 3:47 am 
Ancient irrigation works of Sri Lanka

No historical account on the reservoir systems in the island will be complete without reference to the works of King Parakrama Bahu (1153–1186 AD). This ruler is reputed to have been responsible for the construction or the restoration of 165 dams, 3910 canals, 163 major tanks (=reservoirs) and 2376 minor tanks, all in a reign of 33 years, perhaps reaching the zenith of development in irrigation and agriculture of the Sinhala race during its 2500 year history.

Major irrigation schemes of Lanka, as evident from the earliest written records in the Mahawansa, date back to the fourth century B.C. (Brohier, 1934; Parker, 1981). Details of the historical aspects of the ancient irrigation works of Sri Lanka are dealt with by Brohier (1934, 1937), Fernando, A.D.N. (1979), Parker (1981) and Perera (1984). Arumugam (1969) provides constructional details of each major irrigation scheme.

The purpose and determination in the construction of the irrigation systems are depicted by the words of Parakrama Bahu the Great, 1153–1186 AD: Let not even a drop of rain water go to the sea without benefiting man. The final achievements were highlighted by Sir Henry Ward, Governor of Sri Lanka In: Collected Minutes of Brohier (1934): It is possible, that in no other part of the world are there to be found within the same space, the remains of so many works of irrigation, which are, at the same time, of such great antiquity, and of such vast magnitude as Ceylon. Probably no other country can exhibit works so numerous, and at the same time so ancient and extensive, within the same limited area, as this Island.

* Reservoirs are also referred to as tanks in English and as Wewa in Sinhalese. The word wewa may be incorporated in to the name of the reservoir when it is not followed by either reservoir or tank. As such there are inconsistencies in the ways of referring to different reservoirs.

According to Parker (1981) two irrigation systems were adopted from ancient times: the first was impoundment in reservoirs and the second was the diversion of rivers through excavated canals which conveyed the water into distant lands or reservoirs, supposedly a method of irrigation practised in northwestern and central India and also probably in southern India. However, Parker concluded that the formation of all reservoirs of a class with embankments much higher than those of simple village tanks was originally due to the constructive genius of the Sinhalese themselves.

The works at Panduwewa, according to Parker (1981), is the first great reservoir ever constructed, if the great lakes of Egypt, which are merely immense natural hollows into which streams were turned, are not considered. This reservoir is thought to have been built by King Dappula II (807–812 AD). The earliest constructive work which can be identified with certainity in the Island is the Abhayawewa in Anuradhapura, built by King Pandukabhaya in about 300 BC; this reservoir is now known as the Basawakkulamawewa.

Perera (1984) also surmised that water conservation and utilization by means of a tank (=reservoir) was mainly a Sinhala development. Perera (1984) traced six stages in the development of the irrigation systems;

(i) First Stage: collection of rain water in a pond or valley, lift irrigation using primitive implements to irrigate the surrounding paddies.

(ii) Second Stage: development of low artificial embankments or weirs built across the valleys of small ephemeral rivulets, such a tank would have a depth of 2.5 m, tank followed downstream by yet another tank and paddy fields.

(iii) Third Stage: improvement of the former type, the bunds strengthened; extent of irrigable land improved, but still not part of a complex network of tanks.

(iv) Fourth Stage: damming of the bed of comparatively large non-perennial rivers, e.g. Kala Oya (Dhatusena,459 AD), water distribution capabilities increased, special channels constructed to transmit water, catchments linked.

(v) Fifth Stage: construction of reservoirs on large, ephemeral rivers and tributaries, and linking these to anicuts built on rivers having catchment areas of perennial water supply in the wet zone e.g. anicut at Elahera across the Amban Ganga (tributary of Mahaweli Ganga; see De Silva, 1985 for details), built by Vasaba (65–109 AD), later enlarged and diversified by Mahasena (276–303 AD), feeds the Minneriyawewa. This stage was also characterised by building of spills and sluices.

(vi) Sixth Stage: trans-basin transfer of water from a perennial catchment to an ephemeral catchment based reservoir, e.g. Amban Ganga catchment linked with Kala-Oya catchment, highest complexity by 8th century AD.

All historical evidence indicates that the systems reached their highest complexity well over 1000 years ago, and it will be seen later that modern engineering has had little effect on the planning and layout of the old systems. The ancient irrigation systems in three districts, viz. Polonnaruwa, Anuradahapura and Ruhuna, are thought to have acted as the focal points of the civilization in these areas. Fernando, A.D.N. (1979) recognized 44 ancient, major irrigation reservoirs approximating 39000 ha of surface area. Almost all the major ancient irrigation works have now been rehabilitated, except perhaps for a reservoir or two which may have gone into disrepair and are covered by thick jungle. It is likely that most of the ancient works have been unearthed and their origins understood.

The ingenuity of the Sinhala irrigation engineers is best exemplified by the invention of the “biso-kotuwa” (which literally means queen - enclosure), later termed by Parker (1909, in 1981) “bisi-kotuwa”, the enclosure where the water level lowers. The “bisikotuwa” is the equivalent of the valve-pit, which functions in the regulation of the outward flow of water and is therefore essentially an invention made by the Sinhala irrigation engineers more than 2200 years ago. It has remained essentially unchanged since then (Brohier, 1934; Needham, 1971; Parker, 1981). “It was this (=biso-kotuwa) invention alone which permitted the Sinhalese to proceed boldly with the construction of reservoirs that still rank among the finest and greatest work of its kind in the world” (Parker, 1909, in Parker, 1981).

It is also recorded that in the design of dams built across rivers the early Sinhala engineers showed ingenuity. The dams were built at an oblique angle, exposing the masonry to a lesser degree of violent shocks caused by impact of large floating tree trunks and other debris.

No historical account on the reservoir systems in the island will be complete without reference to the works of King Parakrama Bahu (1153–1186 AD). This ruler is reputed to have been responsible for the construction or the restoration of 165 dams, 3910 canals, 163 major tanks (=reservoirs) and 2376 minor tanks, all in a reign of 33 years, perhaps reaching the zenith of development in irrigation and agriculture of the Sinhala race during its 2500 year history.


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 Post subject: Ancient Lankan water management: Success or failure?
 Post Posted: Wed Dec 24, 2008 1:34 pm 
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Ancient Lankan water management: Success or failure?

The evidence that the hydraulic system endured for over two millennia itself is sufficient to show not only that it was based on sound engineering principles, but that the polity and the management structure which sustained the system endured for that long till colonial interventions disliked the system. The final collapse of the system was due to the builders not providing sufficient spillage to meet unexpected contingencies like very heavy rainfall and consequent overflow of an abundance of water down the drainage system.

By Bandu de Silva
[Extracts from presentation made at the Pugwash Regional Workshop held at the Gale Face Hotel, Colombo on 23rd November 2007. The Pugwash Regional Workshop was held in Colombo this year partly to felicitate the newly elected President, Dr.Jayantha Dhanapala. The Pugwash Group first met in the fishing village of Nova Scotia in Canada with Albert Einstein and Bertrand Russell as original participants.]


The chronicle, Mahavamsa, records the great king Parakramabahu (12th Century) saying: " It is not fitting that persons in our situation to live enjoying our own ease, and unmindful of the interests of the people. And ye all, be ye not discouraged, when a necessary but a difficult work is on hand. Regard it not indeed as a work of difficulty, but following my advice accomplish it, without opposing my instructions…."

King Vijayabahu IV mobilized the chieftains, the soldiery, artisans, and craftsmen as well as the population at large, and collected a vast amount of implements to retore the irrigation works at Polonnaruva which had fallen into disuse. When the chieftains and men were reluctant to go, the women and the king took to the street, the women and children followed him saying "our king is going alone; let us follow him". The chiefs and men had to follow naturally. This is an illustration of the type of motivation. British Government Agent of Trincomalee found the same spirit of motivation still surviving among the emaciated and fever- ridden Sinhalese villagers in Kaddukulam Pattu in the 19th century. He decided to assist these people in their noble effort to maintain their village tanks.

The comprehension of the geographical distribution of the land and the drainage system following the climatic patterns was what compelled the ancient Sinhalese to explore ways of overcoming nature’s obstacles. Despite the dryness of the land, its undulating nature and the reddish brown soils which cover more than fifty percent of land in the dry zone under command irrigation works provided better scope for agriculture than the wetter parts of the island. More than sixty percent of the rain-fed and Chena (slash and burn cultivation) are also in the reddish brown earths of this region. Both soils and watering patterns led to sustain rice crops in the irrigated land and coarse grains, grain legumes, oil seeds and fibre crops in rain –fed uplands. (Panabokke). The chronicles compiled in the 4th and sixth centuries symbolically recorded the memory of the soil in the name the earliest migrants gave to the land when they called the place they landed "Tambapanni" (Copper coloured land). Deloraine Brohier has rerecorded her father’s excitement over re-discovering "Tambapanni."


Ancient strategies of combating climatic effects

Dr. C.R. Panabokke identified 487 small cascading irrigation reservoirs in nine selected watershed basins in the dry zone. Recently, a reference was made in Parliament to the existence of around 600 such small works in the Wanni.


From Henry Parker’s Deduru Oya Report, 1890

‘’ The ultimate objective of all these works was to supply the village fields with water. Where springs exist, where a running stream is available, or where the rainfall of the district is not only abundant but regular, or, better still, pretty evenly distributed throughout the year, it might be sufficient for this purpose simply to build a bund by which to impound the springs, to intercept the stream, or to store up the supply of rain or spring water; and this was no doubt the origin of tanks.

But it must have been soon perceived that in many cases this was not enough to ensure more than a precarious supply of water, and that to render the irrigation and cultivation of fields perfectly secure, other measures were necessary. The replenishment of tanks, therefore, was provided for, either by conducting any surplus water that might accumulate in one tank into another below it, or by supplementing the supply by means of a channel from some running stream, or some large reservoir.

Henry Parker’s observations sum up how in stages the ancient Sinhalese tackled the problem of climatic effect in the dry zone where the earliest settler concentration is found. Minor irrigation works which had been the mainstay of early endeavour of the population and continued to be so to the present, could meet temporary climatic effects like yearly dry spells but not prolonged or unusual drought conditions.


Larger irrigation works which required greater investments were introduced gradually had to be constructed to meet prolonged water shortages for agriculture, animal husbandry and community use. This resulted in storage reservoirs of great dimension and feeder networks of canals and channels connecting with the network of smaller reservoirs and to the fields. It is said that Minneriya, one of the first storage and distribution tanks also sustained the cultivation of 80,000 fields.

Building small reservoirs to tap catchment surface flow was sufficient for small rural communities but found insufficient to meet growing population demands. Giant enlargement of Kurundi-wewa (Kurungama of inscriptions) to cater for the large monastic establishment at Kurundi village by building the Tannimuruppu tank (Brohier) points to this growing demand.

Shift to trans-basin canals through Yodha-Elas

Four Examples:

- Yodha-ela South-North direction) connecting Kala-Oya (perennial) [with Kala- Wewa as storage tank] to Anuradhapura. Success celebrated by renaming it `Jaya-ganga’ (River of Success).

- A second parallel Yodha-ela connected Mirisgoni Oya flowing from Matale hiils to carry water to Nachchaduva-Wewa and Nuwara-Wewa in Anuradhapura.

[Water requirements had increased due to population growth and inadequacy of small reservoirs and higher evaporation rate].

- Elahera Yodha Wewa (south-north-east direction) transferred water from Ambanganga (perennial) to reservoirs in the Tamankaduwa area.(Minneriya, Kaudulla and Gantalava).

- Low ridges running in north-south direction or north-eastern directions provided sites for impounding large volumes of water by constructing anicuts (dams) across the valleys. Reservoirs fed by these canals have higher `heads.

-Minipe anicut on Mahaweliganga (south-north-east direction).

Tapped a point lower down in the mighty river, and carried water through a canal to Minneriya and Gantalava traversing over 50 miles.

Measures to control evaporation rate

*Protection of catchment areas, embankments and canal bunds. –afforestation, strict punishments for violations like damage to embankments and water-tapping.

*Protection against winds- e.g. tree –lined wind barriers; lining of vulnerable embankment and canal bund surfaces with dressed stones – (Relapanawa =wave-breakers).

-Accumulation of knowledge gained through evolutionary experimentation on problems relating to construction of embankments; canals and weirs.

-observation in the case of climatic change patterns (observation of skies, sun and moon; humidity rate of winds; birds’ signs).The cooing of Niyam-Kobeyya (wild pigeon) heralding drought and mating call of ’Eti-kukula’ heralding rain.

-Creating an alert community conscious (self-help) farming community ever ready to meet the challenge of small mishaps like bursting of dams.


Natural calamities are listed among the reasons for destruction of some of the major reservoirs. This has been specially mentioned by early British engineers in respect of the Giant Tank. The dry zone then, as it is today, would have been visited by cyclones bringing heavy downpours which the system could not sustain. A single breach could have damaged the whole net work.

Shift from Nuvarakalaviya to Tamankaduwa

* Moving closer to perennial sources of water;

*Population increase demands greater agricultural output

*Decrease in productivity of old lands after one and half millennia of exploitation.

The centre of polity shifted to Polonnaruva in the 10th century after the Cola occupation, but the interest in that region was manifest a few centuries earlier. Foreign invasion could not have been the single cause for the shift as many historians believe.

A greater cause could have been the effects on the environment itself like its degradation of the traditional agricultural area after a millennium and a half of utilisation through the loss of fertility of the land including the rise in levels of salination resulting from continued use of surface irrigation.

There are references to drought and pestilence from time to time. This would require new lands to be opened up and seems to have encouraged chena (slash and burn) cultivation.

Silting itself, which presents a serious problem with modern reservoirs like Gal Oya and Uda Walawe, not to speak of others, could have presented a problem considering the system was in use over one and half millennia.

Tamankaduwa already had a few large reservoirs like Minneriya, Gantalava, and Padaviya. These derived water from the perennial river Mahaweli. The system was extended by Parakramabahu, the greatest of Tank builders.

Giant’s Tank

Artificial means of irrigation were brought to perfection by king Parakramabahu the Great in the 12th century. In addition to several great works attributed to this king, Henry Parker assigns the marvelous work, the Giant’s Tank in Mannar district to him.

This reservoir and its head works are of special significance because the vast acerage it intended to irrigate though consisting of excellent land extending along the coast for over 35 miles and covering over 40,000 acres was in the driest parts of the island. Even under Dutch colonial rule some of these lands were cultivated under the direction of Vanniyars of Pahangama (Pannamkamam) who obtained lease from the Dutch. The importance is that this reservoir served the important economic zone of the pearl fishery for which a seasonal large population congregated along this coastal belt.

The principle used for the Giant’s Tank was different from others. An alteration from the general design was used to suit the lay out of the land. Because of the nature of the terrain, Instead of throwing an embankment across the river encompassing the valley around for several miles over a large area of the river basin, which was the accepted principle followed to impound the water in other places, a causeway (Tekkama) was constructed with cut granite using a rocky foundation in the river at a point up the river.

A channel was cut a hundred feet above the causeway through which water was conducted to a distance of four miles almost parallel to the river diverging thereafter to a distance of six and half miles to emerge in the plain to join the great reservoir which covered an area of 7,000 acres, making it the second largest reservoir in the island. A total distance of 17 miles was traversed though the direct distance was only nine miles, the serpentine course being part of the design intended to reduce the gradient.

The levels taken along this canal in the course of modern schemes for restoration of the ancient works disclosed a striking illustration of the exactitude with which the ancient Sinhalese worked.

Hydraulic experiment

R.L. Brohier, the doyen of Sri Lankan surveyors, in his masterly work on ancient irrigation works, observes that in the very early days, the irrigation works were less pretentious undertakings. So limited were the needs of the early iron age men who inhabited the island. This authority, nevertheless, goes to assert that these early works, serve to illustrate the " gradual assimilation of that ingenuity …sufficiently associated with a remarkable people who have left their mark on the face of the country but have themselves passed away."

Henry Parker, identified Panda-wewa, near Wariyapola which has been built by throwing an embankment across the valley of the Kolmunna-Oya as one of the earliest built reservoirs. The reservoir which has been repaired and enlarged over the ages since its original construction, stood 24 feet in height and a mile to mile and a half and said to have flooded an area of 1,000 to 1,200 acres before the bund burst in 1805 owing to a flood.

Parker remarked although the size of the reservoir was surpassed by other early samples ,

" we cannot fail to be astonished at the boldness and originality of the early engineers who ventured to construct such an earthen bank across a valley down which floods of considerable volume pass in the rainy season…..The old designer of the works must have been a highly intelligent man to overcome it successfully …….He made every effort to reduce the quantity of the earth work to a minimum; to effect this, the line of the bank was turned about in order to avoid low ground, in a manner never found in later works of large size".

The conclusion is that the early works could not have merely served the communal needs of the people but it would be natural to presume on such evidence that an adequate population who understood rice- growing existed in the northern parts of the island at even this early period. (pre-Christian era).

Was the Sri Lankan experiment a success or failure? The accolades paid by 18th century Dutch and 19th century British engineers on the skills displayed by early Sinhalese builders of hydraulic works, leaves no room for questioning their wisdom on the water management system to meet the climatic variables. Even where the wisdom of some of the works like the Alavakka canal which carried water to the Giant’s Tank was questioned by some, later examination of these works show that the criticism had been based on paltry evidence and the builders made no mistake.

The evidence that the hydraulic system endured for over two millennia itself is sufficient to show not only that it was based on sound engineering principles, but that the polity and the management structure which sustained the system endured for that long till colonial interventions disliked the system.

As I pointed out, the final collapse of the system was due to the builders not providing sufficient spillage to meet unexpected contingencies like very heavy rainfall and consequent overflow of an abundance of water down the drainage system. Evidently, the population was sufficiently geared to meet the situation but the collapse of the social organization which maintained the system resulting from disturbance of settlement patterns after wars with invading forces, could be the reason why the system could not be maintained in its pristine condition after the 13th century. The organization of the Vanniyar system of administration in the Tank country it self point to some feeble attempt to restore the social organization which was needed to maintain the reservoirs and canals. Western colonial intrusions from the beginning of the 16th century delivered the final blow to the social system. The major irrigation schemes which had been working even after the arrival of the colonial powers, collapsed consequently.

This is no reflection on the wisdom behind the ancient works.


Related:
1)Ecosystem based indigenous water management
2)Pugwash, Lunuganvehera, and the destruction of the commons
3)Vewa - The man-made reservoirs
4)Irrigation and water management in Ancient Sri Lanka


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