|Irrigation and water management in Ancient Sri Lanka
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|Author:||Rohan2 [ Wed Sep 21, 2005 2:59 am ]|
|Post subject:||Irrigation and water management in Ancient Sri Lanka|
Irrigation and water management in Ancient Sri Lanka
by Kamalika Pieris
@ The Island / Wednesday, September 21, 2005
The ancient Sinhalese showed considerable skill in the utilisation of water. Water was used in a variety of ways. It was used for landscaping, as at Sigiriya where there are fountains and waterways. There were royal watercourses, such as Madulupitiya, ela and Kendala ela in Uva. (Brohier. Pt 3. p34) Anuradhapura had ponds and baths fed by a network of underground pipes of stone or terra cotta. The forest monasteries had water holes cut into the rock. The rock slab sloping towards the hole provided a catchment area for rainwater and its depth ensured a water supply through months of drought.
There were city tanks, such as the Baswakkulama, Tissa and Nuwara wewa in Anuradhapura. Matale district had the Haliela, Ellawela, and Denagama, tanks. There were city tanks in Kurunegala, in the 13th and 14th centuries. Wells in the ancient cities were lined with brick, rubble or dressed granite, to ensure a clean supply of water. There were wells elsewhere too. A well dated to 11th century AD was discovered near the coastline at Kudramalai, in Wilpattu Park. It was lined with cylinders made of baked clay placed one above the other.
The Sinhala kings took an interest in water management. King Vasabha (65-109 AD) constructed eleven reservoirs and twelve canals including the Alahara canal. Some tanks had a circumference of about two miles. King Mahasen (274-301) built 16 reservoirs and Dhatusena, (455-473) built the Kala weva and Yoda wewa. Parakrama bahu I (1153-1186) is said to have constructed or restored 165 dams, 3910 canals, 163 major tanks and 2376 minor tanks. He is best known for the Parakrama, samudra. Parakrama bahu also constructed three dams at different points across the Daduru oya, and these were the headworks, of three river diversion schemes. By the fifth century, there were several magnificent irrigation schemes, based on the waters of the Malvatu oya, Kala oya, and Mahaweli ganga. Minneriya-Giritale Kavudulla-Kantale complex was one such gigantic scheme. Padawiya and Wahalkada, tanks fed an irrigation scheme extending to the coastline.
Sri Lanka is rich in water resources. It has several major rivers originating in the central hills and flowing towards the sea in a radial direction, These cover vast tracts of country and carry huge bodies of water. Brohier, reporting in 1934 stated that the Walawe Ganga, even at the height of drought had water and when full became a rapid and deep river. Malvatu oya, in 1859 was a torrent with banks about 60 to 70 feet high.’ Even smaller rivers such as Yan oya and Ma oya carried a large body of water for four months of the year. There were tributaries and streams. Kiri oya, in the Sigiriya region, Rowed through a mountainous valley until it reached Vavala wewa . It was thereafter fed by its main tributaries, the Kosgaha ala, Dehigaha ala, and Pihimbi ela. There were natural lakes as well. In the 1930s, Wilpattu had a string of villus or ‘lakelets’. Kokkare villu was nearly 3 miles in circumference and had water even during the driest period of the year. Sarath Amunugama observed that there are only two or three other countries that can say that their agriculture is so abundantly supported by an assured system of water. ‘Many countries can only hope that such a large part of their country will be irrigated as it is in Sri Lanka.’ (Daily News 23.2.2001 p 17.).
There were extensive irrigation systems all over the island, each designed to suit a particular terrain. The best known of these is the north central province system. The north central province needed to conserve water since the rainfall was seasonal. It received a lot of rain during the monsoon and very little thereafter. The region had rock outcrops and many ranges of hills. Huge earthen bunds were thrown across shallow valleys to create tanks. Anicuts were used to obtain water from the river to fill the tanks. These tanks had huge irrigation capacities and became immense sheets of water in the rainy season. Parakrama samudra could irrigate 7791 hectares, Padaviya, Giants tank and Minneriya served over 2000 hectares each. Kala Balalu wewa could flood a total level of nearly seven square miles at full supply. Contour channels conducted the water to and from the tanks. Four canals distributed water from Kala-balalu wewa. One of them, the Jaya Ganga took the water to Anuradhapura and onwards. Large tanks were connected to one another by transbasin canals. These transbasin or ‘yoda elas’ fed tanks along the way. They were also used for transport. Boats went on the Elahera canal.
The north central irrigation system employed small tanks as well. Inscriptions dated between first to third century AD mention more than a hundred and fifty village tanks. These tanks were constructed in shallow valleys, in cascade formation. A cascade consisted of four to ten small tanks", in a six to ten square mile area. The placement of the tanks and channels were carefully calculated to ensure that the water went from one tank to the next through gravity. These tanks helped to maintain the water table. They were a part of the social system as well. There was one temple for each cascade. Recent surveys showed that there was a tank for every 1.5 sq. km in the Rajarata and in the Kurunegala district. Rajarata alone has 457 cascades with nearly 4200 small tanks. According to a current survey, there are about 15,500 small tanks in the dry zone. Most are now abandoned.
In the 1930s, Brohier observed that there were remains of innumerable tanks, some ‘very ancient’, from Hambantota, to Tangalla. Instead of large reservoirs, this area had a multitude of small tanks, without sluices, clustered in cascade formation around the Walave, Kirindi, and Menik Gangas. In the 1930s about 440 were found within 142 sq. miles, in the basin of the Mau ara, a tributary of the Walawe Ganga. These tanks had earth bunds called vetiya, curved in downstream direction. These were diversion structures built to raise the excess monsoon water above the fields and divert it into the well-drained soils in the valley sides. This allowed cultivation of paddy crop at the bottom of the valley and other field crops along the sides of the valley. In the south-eastern dry zone, particularly in the Hambantota district, the rainy season was shorter but the intensity of rainfall was higher.
Mannar had an abundance of freshwater along the coastline in the 1930s. Brohier speculated that there had been a system of irrigation using a network of subterranean rivers in the Mannar area He found several wells and thought that there would have been many more which would have tapped the deep-seated spring waters that lay down below... (Brohier Pt 2 p 20.)
The hill country had a different set of irrigation systems. The terraced paddy fields received water from perennial streams sent down from one terrace to the other in an intricate network of long canals. Ma eta starting near Hewaheta, was over 20 miles long and ended at Hanguranketa. Hewaheta and Kotmale had about 900 irrigation channels. Walapane area had over 418 irrigation channels in the 1930s. Most were ancient constructions. There were small hill tanks as well. Baddeulpote wewa, Rattriya, Ulpote, and Wewatenne wewa are ancient tanks.
There were transbasin diversion canals. Uma oya basin had more than ten overland transbasin diversion canals. One channel from Pattipola encircled the mountain and dropped from an elevation of 6000 to 3500 feet in a length of ten miles to Erabedda. Another channel started from Uma oya went across Talpitigalle Estate, crossed the gap in the mountain side and linked with a natural watercourse which thereafter sent the water by gravitation into an entirely different valley at Wiyaluwa Korale. This is a remarkable achievement. Bodi eta started from the Behhul oya, went in and out of ravines and carried water for eleven miles down the valley.
There were underground tunnels as well. West bound water from Dambagastalawa oya was diverted east to Uma oya basin through a horse shoe shaped tunnel 221 metres long, 10 feet high and 1.2 metres below the surface level of the dividing ridge. The tunnel was 2133 km above sea level and the distance from the source to tunnel intake site was about 304 km. It had been constructed over extremely difficult terrain. Five shafts had been dug into the tunnel. They had functioned satisfactorily, though not lined with masonry. The tunnel had been destroyed when the railway was put up at Pattipola, so valuable information was lost. This Bhoo ela has been tentatively dated to the 14th century. In Udakanda, in Upper Uva, ten tunnels were designed to take water from the wood above to the fields in the deep valley beneath.
These irrigation systems did more than simply supply water for growing rice. They functioned as water and soil conservation systems as well. Small streams were utilised . Not a drop of water was wasted. The Jaya ganga from Kalawewa, to Anuradhapura ran on a contour and therefore collected the runoff from the upper slopes during rain. It absorbed the water of the streams it passed and fed chains of tanks down the valleys it travelled.. It was a combined irrigation and water supply channel.
Sri Lanka’s ancient irrigation system is considered unique and unsurpassed in the ancient world. It displayed certain unique engineering skills of which the best known is the ‘biso kotuwa.’ The biso kotuwa, regulated the outward flow of water from the reservoir. It allowed the controlled and timely release of water from large reservoirs while guarding against sudden surges that may pose a danger to the sluice barrel. In 1909 Parker declared that the Sinhalese were the first inventors of the valve pit. Europe had started to employ valvepits in their reservoirs only in the 19th century.
In the 1960s, the engineers working on Magamwewa-Urusita wewa near Embilipitya found an old sluice exactly where they intended to construct the new one. (Punchihewa p3). Another old sluice was discovered at a site around Kalawewa. This was destroyed and a new sluice added. (Mendis p37.)
The sluice at Maha Alagamuwa wewa, Kekirawa was destroyed by the contractors, on the orders of the Mahaweli Authority, despite the pleas of the villagers it was a well-preserved specimen. (Daily News 6.9.2003 p 17.)
However, when, in the 1970s, engineers found a 6th century sluice at Maduru oya, exactly at the spot at which the modem engineers were going to build the new one, the matter received publicity.
The anicut is now considered a significant achievement of ancient technology. The anicut or amuna are dams built at an angle across a part of a river to pile up the water behind it. A canal cut at this point took the water to the tanks. Even when the natural water level was low, the canal could be fed since the water level had been artificially raised. By the Polonnaruwa period, anicuts were built even across the largest rivers. Galkadawela amuna across the Malvatu Oya in Anuradhapura and Ridi Bendi Ela amuna across the Deduru Oya near Wariyapola are examples of these anicuts.
Anicuts built of both wedged and round stone were found in perfect preservation during the British period. They had been fitted together most carefully, the different layers being placed alternate, parallel to and at right angles to the course of the stream. Some of dim slabs measured 11 feet. Some of the better preserved examples of anicuts have been regrettably destroyed by the Irrigation dept. during the last hundred years without proper study or recording. Today their sites are occupied by modem concrete anicuts that use the same ancient canals.
Brohier, himself a surveyor, stated that the ancient engineers were highly skilled at surveying. They knew levelling. They were able to accurately work out heights and distances and were able to determine even small differences in elevation. Most of the irrigation schemes are on land that appears flat, but is actually undulating. Channels were traced on gradients that would call into use the most precise instruments of the modem age to establish. Mnipe ela had a gradient of 6 inches to a mile. The canals were serpentine to reduce the gradient. ‘The levels taken along this canal in the course of modern schemes for restoration of the ancient works have disclosed a stirring illustration of the exactitude with which the ancient Sinhalese worked.’
The ancient engineers employed different engineering techniques in different terrain. The Giants tank and Akattimurippu tank were designed to suit a flat terrain without rocky hills or elevated ground. There were two parallel line of embankment towards the sea which were then joined by a flat curved bund, the bund thus enclosed the tank on three sides, making it possible to irrigate the land on both flanks as well as the land in front. The British condemned this as unsuccessful engineering, but Brohier saw the thinking behind it. Work on the Giants tank appears to have been done in sections. The earthworks at the two ends of the embankment and the feeder channels were constructed simultaneously. Usually, the transbasin canals were built first and the tank was built thereafter.
The state, monasteries, villages, families, and individuals all owned irrigation works and canals. Samantapasadika written by Buddhagosa, in fifth century talks of villagers constructing tanks and mentions tanks which were individually and communally owned. Kahambiliyawa inscription of Vickrarnabahu I (1111 - 1132) also refers to communal ownership of tanks. There was an organised system for the proper maintenance of irrigation works. Stone inscriptions refer to the positions of irrigation engineer, officer in charge of canals, supervisor of irrigation works, supervisor of the water supply and inspector of reservoirs.
There were regulations governing the maintenance of small irrigation works in villages. Samantapasadika said that it was an offence to take cattle into the lake, raise waves in the reservoirs, or divert water that led to another person’s field. Breaching the dam of a reservoir was considered equal to theft, and the persons responsible had to pay compensation. There was a well-organised system of distribution of water to ensure an equal share for all cultivators. For his share of the water, (diyamura) a person had to pay a stipulated amount to the owner of the tank. (diyabedum).
References are from: S. Bandaranayake (ed). The settlement archaeology of the Sigiriya-Dambulla region; R. L. Brohier Ancient irrigation works in Ceylon vols. 1-3. R. A. L. H. Gunawardana. Domination and resistance, 1989; Sudath Gunasekera. Journal of Royal Asiatic Society, Sri Lanka vol. 50. 2004 Rukshan A. Jayawardene. Economic Review vol. 23 (7) 1997; H. Parker, Ancient Ceylon; Gamini Punchihewa. Daily news -Artscope. 30.7.03; W. I. Siriweera History of Sri Lanka; M. U. A. Tennakoon, Economic Review. Jan. 2002 D. L. O. Mendis C. G. Uragoda and V. E. A. Wickramanayake Scientific principles seen in ancient artefacts Naresa 1995.
|Author:||LankaLibrary [ Tue Dec 26, 2006 11:45 pm ]|
|Post subject:||The Ancient Water Heritage of Sri Lanka|
The Ancient Water Heritage of Sri Lanka
By D.L.O. Mendis, Sri Lanka
Abstract from 3rd IWHA conference, Egypt 2003
Sri Lanka is an island in the humid tropics near the southern tip of India, with a bi-modal rainfall pattern called monsoon rains. The ancient water and soil conservation ecosystems of Sri Lanka are better known as ancient irrigation systems (Brohier, 1934; Arumugam, 1969). Irrigation is only one of their functions, although arguably the most important one. Other functions include flood control, drainage, soil conservation, and conservation of fauna and flora after the introduction of Buddhism in the 3rd century BC. (Weeramantry, 1997). The term water and soil conservation ecosystems is therefore a more appropriate description. Thomas Tredgold's definition of Civil engineering as "the art of harnessing the great sources of power in nature for the use and convenience of man", has been incorporated in the charter of the Institution of Civil Engineers,
London. This conforms to the concept of dominating nature as against the concept of adapting to nature. The latter may be further subdivided into two categories, namely active adaptation, and passive adaptation. The ancient water and soil conservation ecosystems of Sri Lanka are a classic example of man's active adaptation to nature. These systems had been constructed over a long period of time, beginning in about the mid first millenium BC. There are three important aspects of these systems that merit study, namely
- their evolution and development over a long period of time
- their stability and sustainability over an even longer period
- their final apparently irreversible decline after about the 12th century.
These ancient systems consist of interconnected large reservoirs and channels, mainly in the ancient Rajarata or king's country, and cascades of small reservoirs called village tanks after the Portuguese tanque. Both sub-systems are necessary for irrigated agriculture in the way that both hands are necessary for all human activities. One can never hear the sound of one hand clapping. A map called the Water Resources Development Plan prepared in 1959 on a hydraulic engineering basis has been used to identify sites for new large reservoirs, ignoring the ancient ecosystems. (see Table attached).Two major reservoir projects, Uda Walawe and Lunuganvehera selected from this map, in the southern area, ancient Ruhunarata, have been responsible for destruction of some of the ancient ecosystems, and proved to be unstable, contributing to civil strife and insurrection in the early 1970's and late 1980's. Despite this, another large reservoir, Moragahakande, was selected from this map for costly Feasibility studies in the face of reasoned criticism, and was short-listed for foreign funding for construction recently. In the course of looking for alternatives based on the ancient water and soil conservation ecosystems, an unique large reservoir called Parakrama Sagara in ancient chronicles, was re-discovered. It is in fact a series of large reservoirs joined together by canals that had been surveyed and documented in 1855 by three British surveyors, Adams, Churchill and Bailey. (Brohier, 1934).Their report had been included in the inspection minutes of the Governor Sir Henry Ward, but ignored by irrigation engineers ever since. Instead, ancient ecosystems in the vicinity had been restored on a hydraulic engineering basis, thus obscuring the ancient Parakrama Sagara. This in itself is a fascinating story, specially because Moragahakande has now been shelved despite hectic lobbying.
A related development is the proposed Water Museum at Minneriya, another large ancient reservoir of about 2500 hectares built by king Mahasena (276- 303) and known to have been functioning continuously from the time it was built. This led to the Water Heritage of Sri Lanka under which a number of water heritage sites and monuments will be developed as water museums and centres, starting with Minneriya. In this connection this author who has done research on the subject for many years including at the Needham Research Institute, Cambridge, England, under the late Dr Joseph Needham, visited Museums and Science Centers in Canada and USA, and published a book titled Sri Lanka Water Heritage, recently. His visit was returned by the Director General of the Canadian National Museum of Science and Technology, Ottawa, and his wife, a Heritage Specialist in her own right, and a joint Water Heritage project is in the offing.
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