Sunday, 13 February 2022

Mahaweli Ganga

Mahaweli Ganga
Mahaweli Ganga (Sinhala: මහවැලි ගඟ; Tamil: மகாவலி ஆறு) is the longest and largest river system in Sri Lanka. It is 315 km long and is longer than the combined length of any other two rivers in the country (Bandara, 1985). The headstreams of the river originate at altitudes of over 1,340 m above sea level and they form the main river before it flows through lowland plains and enters the Indian Ocean at Trincomalee (Bandara, 1985). It conveys the largest volume of water in Sri Lanka amounting to one-seventh of the total runoff (Hewavisenthi, 1997).
King Aggabodhi I (575-608 A.D.) developed the Manimekhala Dam, an anicut across the Mahaweli Ganga river at Minipe (Arumugam, 1969). The Kingdom of Gampola was known as "Ganga Siri Pura" as its environmental association with the Mahaweli Ganga river (De Silva, 1990)

River basin
The Mahaweli Ganga river basin extending in an area of about 10,320 km2 is equivalent to 15% of the country’s land area and is the largest river basin (Dissanayake & Weerasooriya, 1986; Diyabalanage et al., 2016; Hewavisenthi, 1997). The annual discharge of the river is about 8.4 billion cubic meters which is used to irrigate over 140,000 ha of land in downstream areas (Diyabalanage et al., 2016).
In the 1960s, a Master Plan for the development of water resources of the Mahaweli Ganga river basin was formulated by the United Nations Development Programme (UNDP) and Food and Agriculture Organization [(FAO) Hewavisenthi, 1997]. It included the construction of multipurpose reservoirs, the development of irrigation infrastructure in new areas, and improving existing irrigation infrastructure (Hewavisenthi, 1997). The programme was carried out stepwise over more than 30 years making it the largest multipurpose national development program in Sri Lankan history. Under this project, the surplus water of the Mahaweli Ganga river was diverted into the adjacent river basins of Kala Oya, Malwatu Oya, Yan Oya, and Maduru Oya.


1) Bandara, M., 1985. The Mahaweli strategy of Sri Lanka, great expectation of a small nation. In Strategies for river basin management. Springer, Dordrecht. pp. 265-277.
2) De S. Hewavisenthi, A.C., 1997. Management of the Mahaweli, a river in Sri Lanka. Water international, 22(2), pp.98-107.
3) De Silva, N., 1990. Sri Lankan architecture during the period 1200-1500 A.D. Wijesekara, N. (Editor in chief). Archaeological Department centenary (1890-1990): Commemorative series: Volume III: Architecture. Department of Archaeology (Sri Lanka). p.77.
4) Dissanayake, C.B. and Weerasooriya, S.V.R., 1986. The environmental chemistry of Mahaweli river, Sri Lanka. International journal of environmental studies, 28(2-3). pp.207-223. 
5) Diyabalanage, S., Abekoon, S., Watanabe, I., Watai, C., Ono, Y., Wijesekara, S., Guruge, K.S. and Chandrajith, R., 2016. Has irrigated water from Mahaweli River contributed to the kidney disease of uncertain etiology in the dry zone of Sri Lanka?. Environmental Geochemistry and Health, 38(3), pp.679-690.

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This page was last updated on 11 May 2022
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