Uma Oya Hydropower Complex. The Uma Oya Hydropower Complex (also internally called Uma Oya Multipurpose Development Project or UOMDP) is an irrigation and hydroelectric complex  in the Badulla District of Sri Lanka. Early assessments of the project date back to 1989, when the first studies was conducted by the country's Central Engineering and Consultancy Bureau. The complex involves building a dam across Dalgolla Oya, and channelling water over a  tunnel to Mathatilla Oya, both of which are tributaries of the Uma Oya. At Mathatilla Oya, another dam is constructed to channel  of water per annum, via a  headrace tunnel to the Uma Oya Power Station, where water then discharged to the Alikota Aru via a  tailrace tunnel.

The construction of the complex was inaugurated in April 2008 by former President Mahinda Rajapaksa and President Mahmoud Ahmadinejad. The total project cost is estimated to be approximately  (approximately ), 85% of which is provided by the Government of Iran.

The project was  officially inaugurated by the President of Iran Dr. Ebrahim Raisi and President of Sri Lanka Ranil Wickremasinghe on the 24th of April 2024.

History 
In 2008 Sri Lankan government began the project with Iranian funding and the foundation stone for the project without obtaining Environmental Clearance for the project. Environmental Impact Assessment (EIA) Report of the Uma Oya Project was prepared by the University of Sri Jayawardhanapura and was submitted in November 2010. During the 30 working days the EIA was open to the public for review and comments Central Environmental Authority received many letters from environmental organizations who called the EIA inadequate. However despite the objections CEA gave clearance for the project.

Puhulpola Dam 

Dalgolla Oya is impounded by the roller-compacted concrete Puhulpola Dam (PD), which is a gravity dam measuring  and  in length and height, respectively. The damming of this river creates the Puhulpola Reservoir (PR), which has a gross storage of . The dam has a volume of approximately , and consists of three chute spillways, allowing a combined discharge of up to .

Water from the Puhulpola Reservoir is channelled to the Dyraaba Dam's reservoir via a  horse-shoe shaped free-flow conveyance tunnel, measuring  and  in width and height respectively, and with a discharge capacity of . Construction of the tunnel was completed on . To build the tunnel, a drill-and-blast excavation method was used to displace approximately  of earth.

Dyraaba Dam 

With a concrete volume of more than , the Dyraaba Dam (DD) measures , , and , in length, height, and crest width, respectively. It is constructed  above mean sea level (MSL), and can withstand an estimated flood level of  MSL. Just like the Puhulpola Dam, the Dyraaba Dam consists of three chute spillways, allowing a combined discharge of up to .

The dam creates the Dyraaba Reservoir (DR) which has a gross storage of  and active storage of . Water from the reservoir is channelled through a  long circular pressurised-flow headrace tunnel measuring  in diameter, which has a discharge capacity of . To build the tunnel, a  long TBM was used to displace approximately  of earth.

Uma Oya Power Station 
The two pelton turbine generators of  are fed via a  vertical pressure shaft, after passing through the long tailrace tunnel.  of earth was cleared to create the underground Uma Oya Power Station cavern. The  power station will generate up to  per year.

The  switchyard premises is built at  above MSL. Power from the switchyard is delivered over  of double-circuit 132KV transmission line, consisting of more than 70 transmission towers, to the Badulla Substation.

The annual discharge of approximately  of water from the power station is distributed out via a  cross-basin tailrace tunnel for agriculture use on  or existing land and  of new lands, including irrigation of 14 separate tanks.

See also 
 Electricity in Sri Lanka

References

External links 
 
 
 
 
 
 
 
 

Water supply and sanitation in Sri Lanka
Dams in Sri Lanka
Hydroelectric power stations in Sri Lanka