According to history, the diversion of the river Euphrates for irrigation had been done     as   far back as 4500 B.C., in Babylonia. Similarly, there had been river diversions in China, Egypt, Pakistan and India in subsequent times.  It is most likely that the art of reservoir construction owes its origin to the early people of the Euphrates valley. Earth dams for the storage of water for irrigation, as attested both by history and the remnants of ancient structures, have been used since the early days of civilization.  However, techniques or reservoir construction to regulate water for irrigation had been invented by the ancient people of Ceylon in 400 B.C., by constructing the “Bisokotuwa” or the sluice.
Irrigation in Sri Lanka had been practiced for a period of more than 2500 years. The massive irrigation systems built by our ancient kings made our people not to depend on external sources for the purpose of feeding her people. Unfortunately after this illustrious period from 500 BC to 1200 AD due to reasons not well known, the irrigation systems in the country went into disuse and that glorious hydraulic civilization collapsed.
 
During the colonial period, British Governors realizing the great potential in the ancient irrigation works, a separate department distinct from the former Public Works Department to handle irrigation works, was established in 1900. Most of the British Governors who served in Sri Lanka during the colonial administration deserve the gratitude of the people of this country specially Sir Henry Ward (1855-1869) and Sir William Gregory (1872-1877) regarding their contribution to rehabilitate the ancient irrigation systems. Sir Henry Ward allocated a fair portion of the country's revenue towards the restoration of ancient irrigation works and Sir William Gregory successfully completed his programme of work with equal vigour.

  In the early 1930-1940 period the need for the resettlement of the people in the Dry Zone of Sri Lanka and greater emphasis on the local effort for food production resulted in throwing the Irrigation Department to the front line of development activity.
The Irrigation Department while exclusively engaged in the restoration of our
ancient irrigation systems during the past 100 years celebrated her Golden Jubilee in1950, virtually coinciding with the construction of the Gal Oya reservoir. It was the first major multipurpose project ever undertaken in this country. A careful analysis of the activities of the past in relation to the organizational aspects shows that J.S. Kennedy (1935-1939) had a vision to reorganize the Irrigation Department. His vision was implemented by S.G. Taylor (1939-1950).  The momentum gathered during Taylor's time was further accelerated by both W.T.I.Alagaratnam (1952-1955)
and A.E.C.de.S. Gunasekera (1955-1965).  Between  1950 and 1975departmental activities were focused towards the construction and augmentation of major reservoirs such as Kantale,Hurulu Wewa,Padviya,Kaudulla,Rajangana and Wahlkada.    The contribution made by the Irrigation Department in the planning and design of  the Uda Walawe reservoir, SamanalaWewa and the Mahaweli Development
Progoramme in the recent past, exhibited the specialized technical knowledge gained by the departmental experts in the planning and designing of water resources. The Irrigation Department was the local agency that coordinated the Mahaweli feasibility studies under U.N.D.P. Assistance.