Deduru Oya Dam

Deduru Oya Dam

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Did you know that the Deduru Oya is the sixth-longest river in Sri Lanka? With the building of a dam throughout this massive water body, it offers water for irrigation and agriculture to over 27,000 acres of land within the Kurunegala and Puttalam districts. The towers of the sluice gates stand tall much like guarding soldiers.
Site studies and design of the dam were accomplished by engineers from the Ministry of Irrigation.

Area of the location:-

  • Deduru Oya Dam is built in the Kurunegala District of Sri Lanka.
  • The dam, which measures about 2,400 m (7,900 ft) wide, creates the Deduru Oya Reservoir, which is about 75,000,000 m3 (2.6×109 cu ft).
  • Water from the reservoir is used to irrigate approximately 11,000 hectares (27,000 acres) of farmland, even as also powering a 1.5-megawatt hydroelectric electricity station, operated through the Ministry of Power and Energy.


According to history, it’s believed that during the reign of King Parakramabahu I (1153-1186 AD), an irrigation system evolved focusing the Deduru Oya.
Remnants of an excellent historical past remain with the archaeological findings of the Katuwannawa Asanagharaya, which is a quick distance from the reservoir and is thought to been built in the distant past.

Annual rainfall:-

  • The annual precipitation in the basin varies from 1100 mm in the coastal place to 2600 mm in mountainous place.
  • Deduru Oya basin receives approximately 50% of the yearly rainfall at some stage in inter-monsoon months (March, April, October, and November), about 35% in the course of South-West monsoon months (May to September), at the same time as up to 15% at some stage in North-West monsoon months (December to February).

Related rivers:-

  • The main tributaries of the Deduru Oya namely Ratwila Ela, Dik Oya, and Kospothu Oya is at the starting point of the basin.
  • Kimbulwana Oya, Hakwatuna Oya, and Maguru Oya are in the middle reaches of the basin.
  • At the same time as the opposite tributaries particularly Kolamunu Oya, Thalagalla Ella meet the river downstream of the proposed dam site.

Other purposes:-

In addition to the 8 sluice gates, water from the reservoir is channeled from the reservoir (for irrigation) via three canals. They are named as the left canal, central canal, and the south canal. The south canal measures up to 33 km (21 mi). It is pumping water from the Deduru Oya Reservoir to the Inginimitiya Reservoir at a flow rate of three hundred cu ft/s.

Deduru Oya Dam is a beautiful site that shouldn’t be missed to visit.

Photo courtesy : Onal Karunaratne




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