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How Does a Hydro Power Plant Operate?

Let’s Get to Know about ‘Laxapana Complex’


Laxapana Complex can be described as Kehelgamu – Maskeli Oya complex, as the five power stations in the Laxapana Complex are situated along Kehelgamu oya and Maskeli Oya. The main large reservoir at the top of Kehelgamu oya is Castlereagh reservoir, where the rain water from the catchment area above the reservoir gets collected. Main reservoir associated with Maskeli oya is Maussakelle reservoir.

The Process in Brief

Water collected in the Castlereagh reservoir is brought down along a power tunnel to Wimalasurendra power station to operate the two hydro turbine-generators, each 25 MW in capacity. Water released from Wimalasurendra power plants after operation, gets collected in Norton pond, which is not a large reservoir. This water is brought down along another tunnel to Old Laxapana power station to operate five turbine-generator units, where 03 units are of 8.33 MW and other two units of 12.5 MW. Water released after operations of Old Laxapana machines gets collected in Laxapana pond.

Similarly, water collected in Maussakelle reservoir is taken along a tunnel to operate the two Canyon machines of 30 MW each. Water discharged after operations gets collected in Canyon pond. This water is brought down along another tunnel to operate the two New Laxapana machines which are 50 MW each. These two machines release the water to Laxapana pond as Old Laxapana machines.

Water collected in Laxapana pond is taken along a tunnel to operate the two machines, which are 37.5 MW each, at Samanala power station at Polpitiya. Water released from Samanala machines flow into the Kelani river, which is formed by Kehelgamu oya and Maskeli oya.

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Let’s Get to Know about ‘Mahaweli Complex’

The Objectives

The primary objective of the Mahaweli system is to provide water to irrigation and other usages. Power generation is the secondary purpose. Ceylon Electricity Board and Water Management Secretariat of Mahaweli Authority of Sri Lanka jointly decide the water utilization of these reservoirs, in a manner in which both parties benefit, ultimately giving the maximum benefit to the country.

The Process in Brief

The first reservoir in Mahaweli complex is the Kotmale reservoir. Water is taken to operate the three turbine –generator units (each of 67 MW) at Kotmale power station. Water released after operations flows along the river into the Polgolla barrage, which is a small pond. From Polgolla barrage, water is diverted to North Central province for irrigation and other purposes. This is done by carrying the water through a long tunnel to Ukuwela power station to operate two 20 MW machines. Water released after operating these 02 units flow to Bowatenna reservoir. Water is sent to Anuradhapura district direct from Bowatenna reservoir, and water used to operate the 40 MW machine at Bowatenna power station is sent to Elahera anicut, again to distribute for irrigation.


When water spills over the Polgolla barrage, during rainy seasons, it flows along the Mahaweli river to the large Victoria reservoir. The three 70 MW hydro units at Victoria power station operates using water from Victoria reservoir. Water released after operations at Victoria power station flows to Randenigala reservoir, which is the largest reservoir in Mahaweli complex. Water at Randenigala reservoir is used to operate the two 60 MW machines at Randenigala power station and then released to Rantambe reservoir. Though said a reservoir, it is also a small pond which can be regulated. Water at Rantambe pond is taken to operate the two machines at Rantambe power station, which are of 25 MW capacity each. The discharged water from Rantambe power station is sent to Minipe anicut. This water is then distributed to right and left banks of Minipe canals to use for downstream irrigation and other purposes.

The Objectives

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