Ghazi Barotha Hydropower Project is located on the Indus River downstream of Tarbela Dam. The project utilizes the hydraulic head available between the tailrace at Tarbela Dam and the confluence of Indus and Haro rivers for power generation. In this reach Indus River drops by 76 m in a distance of 63 km.
Ghazi Barotha Hydropower Project consists of three main components, the Barrage, the Power Channel and the power complex.
The Barrage located 7 km downsteam of Tarbela Dam, provides a 71 M cu m storage pond allowing for the re-regulation of the daily discharge from Tarbela by diverting the flow into the Power Channel. The principal features include 20 No. Standard bays, 8 No undersluices and 8 No head regulator bays in addition to rim embankment fuse plug and dividing island.
The Barrage is able to pass the design flood of 18,700 cumecs, equivalent to the flood of record, through the standard bays and undersluices at the normal pond level of El. 340. The fuse plug has been provided to pass the extreme floods up to the capacity of Tarbela’s spillway and tunnels equaling 46,200 cumecs.
The Power Channel:
Ghazi Barotha Hydropower Project holds the record for the biggest lined channel in the world. The channel is some 51.90 km long with a concrete lining and design flow of up to 1,600 cumecs at a water depth of 9 m. It has a bottom width of 58.4 m.
The power Channel has a near contour alignment with hills on the left side and the land naturally draining towards the Indus River on the right side.
The power channel intercepts fifty-three nullahs (natural streams) of which twenty-seven major nullahs have required separate water bridges called super passages to take them across the channel. The remaining fifteen minor nullahs are being discharge into the power channel through individual inlets whilst one nullah is passing underneath the channel through a culvert.
In addition to the thirty-four road bridges, including bridges for both the Islamabad –Peshawar motorway and the GT road, the power Channel is crossed by 12 pedestrian bridges.
The main railway line joining Rawalpindi to Peshawar required the construction of the second longest single span railway bridge in Pakistan.
The Power Complex:
The power complex begins with two head ponds with a combined live storage capacity of approximately 25.5 M cu m, sufficient flow capacity for the daily requirement of 24 hours peak generation. This means that in May and June when there is reduced generation from Tarbela and Mangla as a result of low reservoir level, Ghazi Barotha Hydropower Project provides peak production of 1,450 MW.
The five generation units in the powerhouse are each fed by a 10.6 m diameter steel lined penstock. Each of the five 290 MW turbo- generators can take a peak flow of 460 cumecs.
Due to the very special nature of this project it has been necessary to provide .a self-priming siphon spillway of 1,600 cumecs capacity, with energy dissipation in a stilling basin and a baffle chute.
The power transmission is through 500 kV circuits to WAPDA’s national grid system.
Mechanical and Electrical Equipment:
The installed capacity is 1,450 MW, consisting of five units each of 290 MW. The units have a design flow of 400 cumecs at optimum gate opening and 460 cumecs at full gate opening for a design head of 69 m.
The principal items of power equipment are as follows:
- Five 257/295 MW Francis turbines each with a 290 MW generator which together have a combined power generating efficiency of 94%
- Five three –phase banks of transformers, each single –phase unit being 107.5 MVA
- 500kV conventional outdoor switch gear configured in –one- a half breaker arrangement
- 12 cranes with lifting capacities from 6 to 450 tons.
With a project which is spread over such large area it was considered necessary both for safety and efficiency that it should be monitored and controlled centrally . This has been achieved by providing two independent distributed control system (DCS) one each at the Barrage and power complex which share information through a fiber optic cable Link.
Construction of the Barrage and power Channel was started in December 1995 and the power complex in February 1997.
Impounding of the Barrage started on 17th February 2003, with filling of the Power Channel beginning on the 9th April, 2003, while the 500 kV switchyard was energized on 30th April 2003. Unit No 1 testing and commissioning started with the first mechanical run on 13th May 2003 and, trial generation started on 16th June 2003. With generation of 50 MW .290 MW, the rated capacity of Unit No 1, was fed into national grid starting 24 July 2003. The construction of North Headpond was completed in December 2004, thus completing the implementation of the Project works.
The PC-1 of the Project was approved by Government of Pakistan in July 2004 at a total cost of Rs. 89,840 million. The total cost which has been incurred on this project is Rs. 96,957 million.
Water and Power Development Authority, WAPDA House, Lahore, Pakistan.
Pakistan Hydro Consultants a joint venture of National Engineering Services Pakistan (Pvt) Ltd, .Pakistan Binnie & Partners (Overseas) Ltd, UK Harza Engineering Company intem’l, USA Embanks Preece Ltd, UK.