Sri Lanka: Tank Irrigation Farming in Dry Zones



  • United Nations University Institute for the Advanced Study of Sustainability (UNU-IAS); Japan Wildlife Research Center (JWRC)


  • 06/03/2012

  • REGION :

  • Southern Asia


  • Sri Lanka


  • This study was commissioned to be included in the publication “Socio-ecological Production Landscapes in Asia”. This chapter provides an overview of tank irrigation and agriculture in the area.


  • Water management, irrigation, drylands


  • Japan Wildlife Research Center (JWRC); Kaoru Ichikawa (UNU-IAS), ed.

  • LINK:


Summary Sheet

The summary sheet for this case study is available here.


[Note: this case study originally appeared in the publication Socio-ecological Production Landscapes in Asia.]

Sri Lanka is an island country in the Indian Ocean with an area of about 6,561,000 ha. The southern center of the island is dominated by highlands with about twelve high mountain peaks over 2,000 m (Imbulana et al., 2006). Sri Lanka has a tropical climate marked by high temperatures and high humidity, and the average annual temperature in the coastal and low-lying areas ranges from 27°C to 28°C, but the highlands enjoy a cool climate with the average temperature remaining at around 22°C throughout the year. Affected by seasonal winds twice a year, the southwest monsoon and the northeast monsoon, the annual precipitation varies according to the seasons. Using the annual precipitation of 1,875 mm as a guideline, the land is divided into two major parts: the dry zones, which account for approximately 70% of the country, and the wet zones (Editorial Department of Ninomiya Shoten Publishers, 2011). During the period of the northeast monsoon, which extends from December to February (Maha Season), rain falls mainly in the north, north central and eastern parts of the island. During the period of the southwest monsoon, which extends from May to September (Yala Season), large amounts of rain fall on the wet zones located in the southwestern part of the island (Imbulana et al., 2006). In the dry zones located in the northern and eastern parts of the country, on the other hand, 80% of the annual precipitation (about 1,100 mm) is concentrated in the Maha Season with the amount of precipitation during the Yala Season being only a little or almost none, depending on the year. Furthermore, due to the effects of the dry winds that blow during this season, the amount of water that exceeds the annual precipitation occasionally evaporates (annual evaporation; 1,700 mm to 1,900 mm), (Panabokke et al., 2002).

Photo 1. A small (village) tank (Photo Credit: U.S. Imbulana)

In order for people to live on land in the dry zones, it is indispensable to secure water resources and use them efficiently. Thus tank (weva) irrigation systems have been developed throughout the dry zones since ancient times and are still used extensively (Photo1). These dry zones consist of flat peneplains, which were formed by the erosion of old mountain ranges, and are generally hilly with many small valleys scattered everywhere. The permeability of the underlying rock is low and is only covered with a thin layer of soil. It is believed that these geographical features, which are suitable for building tanks, are also one of the factors that contributed to the development of the irrigation systems (Panabokke et al., 2002).

The Sri Lankan economy has been supported mainly by agriculture, forestry, and fisheries, however, in line with economic growth, the manufacturing, wholesale and retailing industries have expanded and clothing has become one of the largest export items nowadays in Sri Lanka. Production from agriculture, forestry, and fisheries accounts for about 13% of the country’s gross domestic product (GDP) with the agricultural population representing 44% of the workforce engaged in economic activities in 2010 (World Bank Data). Agricultural land occupies about 40% of the national land (FAOSTAT’s figure in 2009), and agriculture is divided into two major forms of management: plantations of black tea, natural rubber, coconuts, and other products, and small-scale individual farms centered on the cultivation of rice (Ministry of Agriculture, Forestry, and Fisheries, 2010). The latter form of agriculture prevails in the dry zones, which occupy the major portion of the country. While double cropping is possible using the biannual rainy seasons (Yala and Maha Seasons) in the wet zones where 30-40% of the total population of about 20,670,000 live (FAOSTAT’s figure in 2009), agriculture using irrigation systems is practiced in the dry zones. Approximately 40% or more of Sri Lanka’s annual rice production comes from the dry zones (FAO, n.d.).

Characteristics of Tank Irrigation System

Distribution and Structure of Tank Irrigation System

It is believed that the irrigation systems in Sri Lanka were built from after the time the Aryans colonized the island in the fifth century B.C. These irrigation systems are found in all the dry zones of Sri Lanka (Table 1). One characteristic of the systems is that many small tanks are located close to each other, although there are regional differences, and there is one tank per 12 km2 area if the density of tanks is low and one per 1 km2 area if it is high. The highest density of small tanks is found in the Kurunegala district in the southern part of the North Western Province and the Anuradhapura district in the central part of the North Central Province (Panabokke, 2002; FAO, n.d.). However, not all tanks are used even today, and many of them have already been abandoned and have ceased to fulfill their functions.

Table 1 Number of Small Tanks in Each Province in Sri Lanka Dry Zones

Under the Agrarian Services Act No.58 of 1979, the current systems are classified into two major categories: minor/village irrigation or small scale/village tank systems, which distribute water to an area of less than 80 ha, and major irrigation or large tank systems that provide water to an area of 80 ha or more (Panabokke et al., 2002; Imbulana et al., 2006). It is considered that originally, small tanks were built by villagers at the community level, and later, larger tanks came to be built through the intervention of the government (Somasiri, 2008).

Small tank systems in general are found in cascade along inland valleys or streams in the dry zone. With many of the small tanks interconnected, the system is designed so that water flows from the upstream tanks to the downstream ones. Some of the tanks in this series of small tanks are connected to larger tanks or feeder canals, forming a complicated, large scale irrigation system that covers a large area of land. Each small tank has a small area of reservation catchment around it, and paddy fields and villages are spread along the downstream reaches. The next small tank and its reservation catchment is located just downstream from the paddy fields (Kono and Somarathna, 2000; Somasiri, 2008). In addition to rice growing using irrigation farming, during the Maha Season (November to March) when the rain falls, some farmers are engaged in a form of swidden agriculture called chena, which utilizes the highland slopes that cannot be irrigated. Furthermore, many farmers cultivate a wide range of fruits and crops (homegardens) and raise cattle around their houses in order to meet their own needs (Panabokke et al., 2002). Moreover, fish are caught in the small tanks and in addition to providing water for the paddy fields, these tanks are used for various purposes such as water supply for local residents and livestock husbandry (Panabokke et al., 2002) (Photo 2).

Photo 2. A small irrigation system managed by the farmers (Photo: U.S. Imbulana)

Management of Irrigation Systems

The ancient small-tank irrigation systems in Sri Lanka were built by local residents and have been managed by them over the years (Photo 3). In accordance with the customary rajakariya system, which governed land ownership, they have been managed by the local residents in a sustainable way on the instructions of cultivation and water distribution managers called velvidane (Somasiri, 2008). The residents are thus assured of a fair allocation of the resources and equal land ownership. Prior to the farming season, the residents hold meetings called kanna to discuss and decide on the dates when cultivation should begin, when the irrigation water should start to be channeled to the paddy fields, and when the irrigation canals should be closed, as well as the repair of the small-tank irrigation systems, the division of roles in such repair work, and other matters. In the years when there is little rain, a form of cultivation to conserve water called bettma is practiced in which only the paddy fields closest to the tanks are cultivated. Attention is also given to the equal use of water resources and soil by employing a system called kattimaru, which requires two to three farmers to take turns cultivating the paddy fields that are allocated to them (Somasiri, 2008).

With the colonial control of Sri Lanka by European countries such as Great Britain and the reform of political systems, however, the existing irrigation management systems run by local residents collapsed. The rajakariya system was abolished, and, as a result, the small-tank irrigation systems were left unmanaged, the land in the dry zones became devastated and the farmers were reduced to extreme poverty. In 1848, the residents rose in revolt in the Kandy region. In 1900, following this revolt, the British government established an Irrigation Department as part of its measures to cope with poverty and started to repair the devastated irrigation systems. The government took the main responsibility for their management, and the farmers were allowed to participate in discussions with administrative officials about the farm work and irrigation system management at meetings held before the farming season. However, since such meetings were held only twice a year and led by administrative officials, the opinions of farmers were not fully reflected in the management of the irrigation systems, and these meetings did not produce satisfactory results (Somasiri, 2008).

Photo 3. Livestock grazing in areas around a small tank (Photo: U.S. Imbulana)

With the introduction of the Paddy Land Act of 1958, the responsibility for the small-tank system was transferred to the Ministry of Agriculture and the present Department of Agrarian Development (DAD) was established. Since then, the DAD has been providing technical and institutional support to minor irrigation schemes as well as supporting repair work for the small-tank systems. Even after management responsibility was transferred to the provincial council, the DAD still provides various forms for support to minor irrigation systems (Imbulana, US, personal communication). Although many issues still remain, minor irrigation is currently managed mainly by the farmers.

On the other hand, major irrigation had less farmer participation in its management until the 1980s. Subsequently, the Irrigation Department in charge of major irrigation systems started introducing and implementing various projects to promote participatory management of the large tank systems. One of these initiatives was a project to repair the Gal Oya Left Bank system in eastern Sri Lanka, and this project began in 1981. In this project, a committee consisting of farmers and administrative officials was organized to jointly repair the irrigation systems. In addition, representatives of the farmers participated in planning meetings held in each season. The farmers were thus given the opportunity to have their opinions reflected in the decisions on the areas to which irrigation water should be distributed according to the amount of water in the small tanks, how the operating and maintenance budgets should be allocated, and other matters (Amarasinghe et al., 1998).

Since the 1980s, meanwhile, new legal systems and organizations have been put in place to support participatory management. In 1984, a new Irrigation Management Division was established under the Ministry of Irrigation to officially introduce a process that involved local residents in major irrigation projects. In the second half of the 1980s, the practical management of part of the equipment (such as the water distribution canals) for major irrigation systems was transferred to farmer organizations. With the revision of the Agrarian Services Act in 1991, these farmer organizations were legally approved, and with the revision of the Irrigation Ordinance in 1994, they were granted the related rights and began to take responsibility for irrigation system management (Somasiri, 2008).

Functions and Benefits

The irrigation systems are designed to store rainwater brought during the short rainy seasons to secure the water resources that make it possible to cultivate rice (double cropping) and other crops (such as red pepper and onions) throughout the year even in the dry zones with unstable rainfall, and this ensures food security for the local residents (Kono and Somarathna, 2000).Water resources are used not only for the residents, but also for livestock for drinking and other purposes.

In addition to their direct use, tanks provide the functions of maintaining a cool and comfortable microclimate, groundwater recharging, soil conservation and such. In addition, besides contributing to sustaining agricultural biodiversity, the tanks, which are spread throughout areas covering 70% of Sri Lanka’s land and have existed since days long past constitute part of the most varied wetland ecosystem in the country (FAO, n.d.). Furthermore, since early on, they have been used as a place for the social activities of local residents such as meetings, bathing and performing social and cultural functions (FAO, n.d.; Panabokke et al., 2002).

Challenges and Responses

In the past, a self-sufficient life was sustained in the dry zones of Sri Lanka by combining irrigation farming, rainfed chena farming, home gardens, as well as livestock raising, fishing and food gathering in nearby forests, with most of the irrigation water provided from the small tanks. However, starting with the abolition of Rajakariya system in the colonial period, subsequent changes in various socio-economic factors have made it difficult to maintain such agroecosystems even at present, where efforts including the rehabilitation of irrigation systems and promotion of participatory management are in place. One of the contributing and confounding factors in this situation is the reduction in available land owing to the increase in population and other factors. Since the productivity of irrigation and chena farming in fragmented and limited areas of land is relatively low and thus the income of the farmers has declined, fewer farmers intend to invest in the management of minor irrigation systems (Panabokke et al., 2002).

With the aim of repairing the devastated irrigation systems and to manage them efficiently, the Sri Lankan government has implemented various projects. Minor irrigation projects such as the Village Irrigation Rehabilitation Project and the National Irrigation Rehabilitation Project were conducted in the 1990s with the support of the World Bank. As for major irrigation, the Integrated Management of Major Irrigation Schemes Programme has been in place since the late 1900s.

In order to cope with these problems and operate and maintain sustainable irrigation systems efficiently, it is indispensable to manage the systems by involving the local residents. In the 10-year Comprehensive National Development Programme called “Mahinda Chintana (2006-2016)” announced in November 2006, the Sri Lankan government formulated a strategy to achieve economic growth and eliminate poverty through agricultural development and cited as the priority issues in the agricultural sector: (1) improvements in the productivity of irrigation farming, water management, and facilities operation and maintenance, (2) the promotion of marketing and crop diversification, and (3) participation by resident organizations (FAO, 2011).

As described above, the Sri Lankan government has long established laws and systems for participatory management and has been implementing these initiatives on a project basis, but in the future, it will need to continue taking such measures as government financial support for farmers organizations, on-site implementation of the related policies, the granting of economic incentives to encourage participation by the local residents, and the establishment of cooperation between the government and the farmers (Somasiri, 2008).


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