Tarbela dam trade-off: To store more water, govt must cut power production

The national grid has almost no room to handle routine production reduction.

Zafar Bhutta August 22, 2011

ISLAMABAD: A decision by the Indus River System Authority to reduce outflows from the Tarbela dam has caused power production in the country to fall by 1,500 megawatts, increasing the overall power shortage by about 35%, reflecting just how little room the national grid has to make adjustments for even routine shortfalls.

In the case of Tarbela, the flows were reduced because the water flow from the eastern tributaries of the Indus River – the Ravi and the Sutlej – had increased, allowing Irsa to fill up the Tarbela dam for the winter growing season that is due in the coming months.

The change in river flows is not unusual, nor is the need to store water something that is unprecedented. Yet the power generation system in the country has been so utterly crippled by the government’s failure to manage it that even routine shortfalls in one area cannot be overcome by increasing production in other parts of the country.

In the case of Tarbela, the dam had been producing an average of 3,500 megawatts of electricity (about 24% of the nation’s total) before Irsa decided to reduce the water flow from the dam from 120,000 cubic feet per second to 80,000 cubic feet per second.

That 25% drop in water flows from Tarbela caused a 43% drop in electricity production at the dam, in turn raising the electricity shortfall in the national grid by close to 35%. Tarbela is currently producing 2,000 megawatts of hydroelectricity, the cheapest form of power by far in the national grid.

Officials at the Pakistan Electric Power Company (Pepco), the state-owned firm that coordinates activity in the power system, said that the total electricity production on Sunday was an average of 13,000 megawatts. Demand, however, was estimated at closer to 17,275 megawatts, rising to 19,000 megawatts during peak hours, according to Ijaz Rafique, the spokesman for Pepco.

Rafique claimed that several power plants that had been closed for routine maintenance are now coming back online and should help alleviate some of the problems. Among the power plants expected to resume production is the Chashma Nuclear Power Plant (Chashnupp) II.

However, Chashnupp-II can only produce a maximum of 300 megawatts. It is unclear how much power the other plants can produce, but it seems unlikely that they will be able to make up for the shortfall from Tarbela.

Irsa’s decisions on water flows are determined primarily by the agricultural cycle and the provinces’ needs. Water flows in the western tributaries of the Indus – Kabul, Jhelum, Chenab – as well as the Indus itself, have declined by about 25% in recent days.

A spokesperson for Irsa told The Express Tribune that since Sindh is now getting water from the eastern tributaries, there was a need to reduce water flows from Tarbela to the province. “We need to get Tarbela’s water level back up to 1,550 feet from its current level of 1,540 feet,” said Khalid Idris Rana, the Irsa spokesman.

Rana added that Irsa would begin increasing water flows in the next couple of days – enough to generate an additional 300 megawatts. He said that the full outflow of 120,000 cubic feet per second would be restored by August 29.

Published in The Express Tribune, August 22nd,  2011.

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