Although Pakistan has the largest contiguous irrigation system in the world, it was facing numerous water-related challenges which include increasing water stress and looming threat of climate change. - File photo

ISLAMABAD: The World Bank’s executive board would approve $840 million for the fourth project for Tarbela Dam’s extension on March 8, sources said on Thursday.

The financing will include $400 million from the International Development Association, an affiliate of the World Bank, and the total cost of the project has been estimated at $914 million.

In its appraisal report, the bank termed the project a “low-risk, high-reward operation” aimed at providing about 4,000GWh annually of low-cost and low-carbon power.

The project will facilitate a sustainable expansion in the country’s electricity generation capacity with the installation of a 1,410MW hydropower plant on an existing dam with an already constructed tunnel, thus keeping the cost to a minimum and doing away with the social and environmental challenges often associated with large dams.

The project envisages installation of hydropower units on the dam’s existing tunnel number four and will have no impact on the water releases from the dam. The water which currently flows through the spillway will be diverted to the tunnel where it will pass through three 470MW turbines and generate electricity which will be transmitted to the common grid.

Under the project, a powerhouse will be constructed to house the power plant, a penstock connecting tunnel 4 to the power units and construction of raised intakes; and installation of three 470MW turbines, generators, transformers, ancillary electro-mechanical equipment and a short transmission line to connect the grid.

The appraisal report says that tunnel 1 to 3 and 5 have sufficient release capacities to meet any water demand downstream.

The connection to tunnel 4 and intakes will be planned and constructed in such a manner that any interruption in operations of power units will be avoided.

Pakistan currently has storage capacity sufficient for about 30 days of water and about one-tenth of the hydropower generation potential installed at the Indus system. This indicates the potential for adding storage capacity in the Indus Basin system and Diamer-Bhasha and Dasu dams are amongst the top-priority projects on the river.

Analysis of cumulative impact clearly shows enhanced benefit in terms of reduced sediment load thereby prolonging the useful life of Tarbela and other dams below, increased storage capacity resulting in more sustained water supply for agriculture, better flood management, increased low-carbon, environment-friendly hydropower generation and increased climate change resilience.

Increased storage upstream on Indus would result in more regulated flows in the system downstream thereby cultivation in the river bed based on residual moisture during the dry season may get affected, according to the appraisal report.

Although Pakistan has the largest contiguous irrigation system in the world, it was facing numerous water-related challenges which include increasing water stress and looming threat of climate change.

To meet increasing food production demands, Pakistan has been expanding the surface water supplies to the Indus Basin Irrigation System over time by capturing more water from the rivers. Post Tarbela canal diversions has reached as high as 10 MAF, however it has now been declined due to reduced storage because of sedimentation and several other factors such as state of the infrastructure and a sequence of dry years.