Globally Important Agricultural Heritage Systems (GIAHS)

The Cascaded Tank-Village System in the Dry Zone of Sri Lanka, Sri Lanka

GIAHS since 2017


Detailed Information



Global Importance

The first large reservoir built in recorded history was Abayawewa in 3rd Century BC. From that day onwards Sri Lankan tank builders have developed a remarkable expertise on controlling large bodies of water which allowed them to build massive reservoirs which no other civilization ever could have dreamt of.

The global significance of this system is really high thanks to the practical solution it provides to absorb shocks of natural disasters such as flood occurrence which can be controlled by storing water and drought occurrence by reducing the water loss from tanks due to existence of the surrounding ecosystem. Indeed, the system provides solutions to water shortage in paddy farming with traditional crop management knowledge but also local drought resistant varieties.

Food and livelihood security

The production system of the CTVS is circular and much diversified. It involves production from the paddy field, home garden, upland crop field/chena (shifting cultivation), tank, forest and the kattakaduwa. The paddy fields produce paddy; uplands produce other cereals, vegetable, spices and oil crops; tanks produce fish and some edible plants; forests produce timber and medicinal plants; home garden produces nuts and fruits; kattakaduwa produces medicinal plants, material for making mats and some handicrafts (rattan, reed). The tank bed during dry season, the scrublands, and the paddy fields during off-season, serve as grazing lands for the cattle and buffalo.

This water management systems allows the farmers to produce several types of crops but it also relies on forests. These natural parts provide fuel wood, medicine, timber, fencing materials, household and farm implements, food, fruits, vegetables. Specifically they harvest raw materials from this vegetation for cottage industries.


The Cascade systems, as a diversified system including water areas, crop production and cattle, gathers a high biodiversity. Indeed, Sri Lanka has 82 species of indigenous freshwater fish belonging to 11 families. A recent study in the Palugaswewa cascade has shown that in the kattakaduwa, the tank bund, and the tree belt alone there are 226 plant species.

Farmers in the CTVS still cultivate few traditional rice varieties such as Suwandel, Rathdel, Kaluheenati, Kuruluthuda, Kuru wee, Suduru samba, Kahata wee, Pachchaperumal, Elankalian, Madathawalu, Hetadha Wee, Hondarawalu, Girisa, and Heenati.

Concerning the forest areas included in the area, several indigenous and protected timbers can be found and are still conserved thanks to the sustainability of the system even if land pressure leading to deforestation is an actual threat.

Local and traditional knowledge systems

The system consists of a series of tanks (minor water reservoirs) set one after the other on a natural drainage line in a watershed. These tanks are built by constructing an earthen dam across the water stream in the valley. Rainwater is collected in the tanks. Excess water, from tank at the higher elevation, spills over to the one below. Paddy fields are located in the valley of the drainage line below the tank. A sluice releases water for irrigating the paddy.

The drainage also passes to the tank below. The watershed of the tank comprises of several land uses such as forest, village hamlets, paddy fields and uplands of crop fields (former chena lands) and the tanks. The sustainability of this irrigation system has been secured through associated land use segments. These land uses are: natural tree strip (gas gommana), upstream medow (perahana), soil ridge (potawetiya), seepage interceptor (kattakaduwa), natural drainage (kiul ela) and hamlet buffer (thisbambe).

The cropping calendar is based on the rainfall pattern. There are two seasons of cultivation based on rainfall pattern, these are: maha (major) and yala (minor) seasons. There are two farming components important in the system namely: upland crop cultivation and lowland paddy cultivation. Paddy Crop is protected from birds and pest damage leaving a small portion of land (kurulu paluwa) to attract birds for pest management and if necessary supplement these actions with use of plants or plant extracts (bio-pesticides). In addition, the farmers keep adapting their management of the reservoirs and the water resource by changing the sowing technics on dry lands, practicing temporal redistribution of plots of land of common areas during drought periods, etc.

Cultures, value systems and social organizations

The culture in the CTVS has been developed centered on inter linkages among the village, the temple, tank and the stupa as stated before. The cultural aspects such as livelihood, knowledge, belief, art, law, morals, custom, and other capabilities and habits are developed to lead a simple and happy life while sustaining the natural resource base in the village and in surrounding area.

Traditional dancing, folklore, folksong, folk poems, folk music, rituals, traditional festivals, and folk drama, have been evolved in the village tank farming culture during its long existence. For instance, Pal kavi are poems recited in the night at watch hut to protect fields from wild animals as well as NelunKavi which are poems recited by women when weeding and filling in vacancies in paddy fields. Folk dances in the area depict activities related to agrarian life, such as kalagedi natuma, Kulunatuma (depicting winnowing of rice in the threshing floor), and dance depicting harvesting of paddy.

Landscapes and seascapes features


The dry zone landscape has been completely changed to give rise to a panoramic view with the development of the village tanks in the cascading system. The tanks make water bodies here and there in the undulating landscape, giving an attractive view. These water bodies located one after the other are associated with various vegetation, including lotus, water lilies, many other flowering plants and trees. Due to long existence, these tanks have become almost like natural wetlands creating a unique ecosystem that attract various types of birds. The paddy fields, forest patches and home gardens combined with the tanks make a mosaic of beautiful scenery. This mosaic changes its color and appearance all year round as the cultivation progress and seasons change.