Iranamadu Tank (Tamil: இரணைமடு குளம் Iraṇaimaṭu Kuḷam; Sinhala: ඉරණමඩු වැව) is an irrigation tank in northern Sri Lanka, approximately 3 mi (5 km) south east of Kilinochchi.
In 1902 the Director of Irrigation H. T. S. Ward came up with proposals for building a new irrigation tank on the Kanakarayan Aru in northern Ceylon. Work in the tank, which had a catchment area of 227 sq mi (588 km2) and was to hold 26 ft (8 m) of water, began in July 1902[b] but was delayed by the World War I. Construction was completed in 1921 and the tank was filled and spilling in November 1921. The tank was created by joining up two low lying swamps of the Kanakarayan Aru. Construction was carried out manually and the labourers were housed in a new colony - present day Kilinochchi. The tank cost Rs. 194,000 to construct. The tank's name was derived from the Tamil words for two (iranai) and pond (madu).
In the 1940s a severe drought in the Jaffna islands resulted in large numbers of people migrating to the Kilinochchi area where they were given free land to farm near the Iranamadu tank. In 1951[d] the tank bund was raised to hold 30 ft (9 m) of water, increasing storage capacity to 71,000 acre⋅ft (87,577,210 m3). An additional sluice was built on the right bank and the tank was extended onto lands on both banks. The bund was raised to 32 ft (10 m) in 1954 to give a storage capacity of 82,000 acre⋅ft (101,145,511 m3).
By the late 1960s the tank had a water spread area of 5,750 acres (2,327 ha). The bund was 9,850 ft (3,002 m) long. There was a controlled overflow spill on the left bank. The left bank sluice was 5 ft by 4 ft whilst the right bank sluice was 4 ft by 2 ft 8 in. The tank was capable of irrigating 18,844 acres (7,626 ha) of land. The bund was raised to 34 ft (10 m) in 1975 to give a storage capacity of 106,500 acre⋅ft (131,365,816 m3).
Concerns were raised about the integrity of the bund during the monsoon rains of 1983. An investigation by K. Vigneswaran, Deputy Director of Irrigation, in early 1984 found that the bund was too weak to hold water higher than 32 ft (10 m) and so Vigneswaran ordered that water levels not exceed that amount. The tank was 6 mi (10 km) long, 1 mi (2 km) wide and 34 ft (10 m) in 2012. It was capable of irrigating 20,882 acres (8,451 ha) via 20 mi (32 km) of channels. By 2014 the tank was capable of irrigating 21,985 acres (8,897 ha).