ISLAMABAD: The federal government has stopped irrigation and water authorities from accelerating the inflow of water into the Tarbela dam, desp­ite healthy river flows, after learning that the dam’s piezometers — devices that assess dam safety — have been out of order for nearly four decades.

The decision was taken at a meeting chaired by Minister for Water and Power Khwaja Mohammad Asif. It was endorsed by agencies dealing with dam safety and irrigation, including the Federal Flood Commission (FFC), the chief engineering adviser, the Indus River System Authority (Irsa) and the Water and Power Development Authority (Wapda), as well as provincial irrigation departments.

The ministry’s intervention in matters of water regulation and irrigation management, a role usually assumed by provincial irrigation departments, Irsa and Wapda, is a rare occurrence.

Ministry stops accelerated water inflow into Tarbela dam till the instruments are repaired

A piezometer is a geotechnical instrument installed in dams to monitor flows, seepage and ground pressure in order to determine the strength of dam structures and their filling criteria. An official privy to the matter said the piezometers at the Tarbela dam had not been functional since 1980.

The matter reached the federal minister when the agencies concerned considered filling up the Tarbela dam at a rate of 3-4 feet per day in view of substantial flows in rivers after the conservation level of the reservoir crossed 1,510 feet. The level currently stands at around 1,521 feet.

Mr Asif was apparently surprised to find out that the important safety instruments had been out of order for such a long time and questioned how the relevant authorities could consider building the dam’s storage level at an accelerated pace. They decided that the dam would be filled at the safe rate of one foot per day till its piezometers were repaired.

This is the third consecutive year in which the dam has not been filled to its capacity. Last year, the dam could not be filled to capacity in Rabi season despite heavy monsoon downpour because of a difference of opinion between the water regulator, Irsa, and the dam operator, Wapda.

Over the last two years, Irsa has issued orders for the Tarbela dam to be filled at a rate of 1-5 feet per day, even after the conservation level of 1,510 feet is reached, but Wapda has resisted Irsa’s repeated orders. At that time, Wapda insisted that its standard operating procedures (SOPs) required water conservation to not exceed one foot a day to ensure dam safety.

Then the Ministry of Water and Power decided to review the SOPs based on consultation with a team of dams and engineering experts comprising former Wapda engineers like Dr Azharul Haque, Tarbela dam general manager Abdul Khaliq Khan, and representatives of the National Engineering Services of Pakistan (NESPAK).

They reviewed dam parameters, structures and the SOPs and concluded that it was safe to fill the dam at a rate of one-to-three feet per day after the conservation level of 1,510 feet was reached. The filling plan was agreed to by all agencies concerned, including Irsa and Wapda, and the ministry endorsed fresh SOPs.

This year, the authorities had started filling the dam at a rate of three feet per day as per the revised SOPs when the ministry raised objections and claimed that it could endanger the dam’s structure.

According to sources, Irsa had stressed that the ministry was on board the plan for accelerated filling in the light of the SOPs revised last year. The matter was then taken to the Ministry of Water and Power which decided that the monitoring system must be repaired before the dam could be filled at any level above one foot per day.

There was a strong likelihood that Tarbela dam would not be filled to its capacity despite the availability of sufficient water, an official said. He added that the participants of the meeting were told that normal monsoon patterns had led to rain systems across the country but there was no immediate threat of major flooding. Low floods have been reported in certain locations in the Chenab command area.

Irsa had earlier proposed accelerated filling of the Tarbela dam to take advantage of substantial river flows and to conserve more water. It is generally believed that weather conditions have become unpredictable and, therefore, water storage should be built at a higher scale instead of one foot a day.

Published in Dawn, July 22nd, 2017