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Senanayaka Samudraya, the largest irrigation reservoir of Gal Oya River |
Gal Oya (Sinhala: ගල් ඔය; Tamil: கல் ஆறு) is a river in southeast Sri Lanka. Flowing about 108 km distance, it is the 16th longest river in the country (Withanage et al., 2014). It rises in Madolsima Hills at an elevation of 5000 ft. above mean sea level and flows towards the east coast of the country and joins the Indian Ocean 16 km south of Kalmune (Withanage et al., 2014). It is situated between Mahaveli Basin to the west, Maduru Oya, Mundani Aru and Andalai Oya Basin to the north, Ambalam Oya, Pannal Oya, Karanda Oya, Heda Oya and Kumbukkan Oya Basin to the South and Indian Ocean to the east (Zahir & Kaleel, 2014).
History
The Gal Oya River is the main source feeding the Gal Oya scheme, the first major irrigation project undertaken by independent Sri Lanka that dammed the Gal Oya at Bintenne and other smaller rivers to create Senanayaka Samudraya, the largest reservoir in the country (Gunawardena, 2003; Withanage et al., 2014).
In October 1937, the Inginiyagala Hydrometric station was established as the first hydrometric station of the Gal Oya River. However, it was closed in November 1949 with the start of the construction work of Senanayaka Samudraya.
The River Basin
The Gal Oya River basin extending in an area of about 1,873 km2 is the 44th basin among the named 103 major river basins in Sri Lanka (Withanage et al., 2014). The average annual rainfall of the catchment is around 1,594 mm and the average discharge to the sea has been estimated as 86.20 MCM per annum. Reservoirs situated in this river basin are given below (Withanage et al., 2014).
Reservoirs & Anicuts in the Gal Oya River Basin
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#) Alahena Wewa
#) Ampara Wewa
#) Ekgal Oya Wewa
#) Gal Oya Anicut
#) Konduwatuwana Wewa
#) Namal Oya Wewa
#) Senanayaka Samudraya
#) Weeragoda Wewa
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#) Aligalge Wewa
#) Chadayanthalawa Wewa
#) Eragama Wewa
#) Himidurawa Wewa
#) Malayadi Wewa
#) Pallan Oya Wewa
#) Walathapitiya Wewa
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The three main tributaries of the Gal Oya River are Hamannawe Oya, Pammedilla Oya, and Dahamala Oya. The Senanayake Samudraya which is the largest irrigation reservoir of Gal Oya was constructed at the confluence of Pansal Oya, Sellakka Oya and Gal Oya at Inginiyagala.
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References
Books, Journal Articles
1) Arumugam, S., 1969. Water resources of Ceylon: its utilisation and development. Water Resources Board. pp.162-178.
2) Gunawardena, C.A., 2003. Encyclopedia of Sri Lanka. Sterling Publishers Pvt Ltd. ISBN: 81-207-2536-0. p.122.
3) Withanage, N.S., Dayawansa, N.D.K. and De Silva, R.P., 2014. Morphometric analysis of the Gal Oya River Basin using spatial data derived from GIS. Trop Agric Res, 26(1), pp.175-188.
4) Zahir, I.L.M. and Kaleel, M.I.M., 2014. Using geo-spatial technology to flooding potential model in Galoya river basin. KALAM International Journal of Faculty of Arts and Culture, South Eastern University of Sri Lanka. pp.1-9.