The Technology of Ancient Irrigation in Sri Lanka
Together with the rise in population irrigation engineering developed bringing advanced and ambitious irrigation works. According to historical descriptions building giant-sized reservoirs had been started in the 1st century B.C. during the reign of King Wasabha (67 – 111 BC). According to the historical records the king built 11 large reservoirs and two irrigation canals.
Construction of large reservoirs had been started in the 1st century B.C. during the reign of King Wasabha (67 – 111 BC). Historical records narrate that the king built 11 large reservoirs and two irrigation canals.The first great reservoir of the world ever constructed, according to Henry Parker, a British colonial irrigation engineer (1873-1904) in British Ceylon (1815-1948), was Panduwewa or Panda Wewa (1,360 acres) of Sri Lanka built by King Dappula II (807–812 AD). That is when the great lakes of Egypt, which are merely immense natural hollows into which streams were turned, are not considered.
The ingenuity of the Sinhala irrigation engineers is best exemplified by the invention of a sluice called “biso kotuwa”. The “biso kotuwa” 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. “It was this invention alone which permitted the Sinhalese to proceed boldly with the construction of reservoirs that still rank among the finest in the world. Without some efficient means of regulating the discharge of the water through the sluices, the provision of reservoirs for storing water could never have extended beyondthe minor tanks”.(Ref: H. Parker, Ancient Ceylon, 1909)
As a result, in the dry Zone emerged three main complex irrigation systems, i.e. Malwathu Oya-Kala Oya, Mahaweli-Amban Ganga and Walawe-Kirindi Oya irrigation systems.
Today, Sri Lanka has 59 giant tanks spread out in 13 districts of the dry zone irrigating the paddy cultivation. Among the largest ancient tanks are Parakrama Samudra, Minneriya Tank, Kaudulla Tank & Kantali Tank with gross capacities of 109,000 Ac. ft, 110,000 Ac. ft, 104,000 Ac. ft. and 114,000 Ac. ft. The largest modern tank is Senanayake Samudra with a gross capacity of 770,000 Ac. ft. (Ref. irrigation Department of Sri Lanka, 2 Nov. 2010 www.irrigation.gov.lk)
A publication by the United States Bureau of Reclamation referring to the history of earth dams in the world, mentions “one earth dam eleven (11) miles long, seventy (70) feet in height and containing about 17 million cubic yards of embankment in Ceylon (Sri Lanka) in the year 504 BC”.
