LAHORE, Aug 29: The Water and Power Development Authority (Wapda) has, for the first time since commissioning of Tarbela Dam, changed its criteria and is filling the reservoir five feet a day even after a level of 1,510 feet, which according to independent experts, is against traditional dam safety parameters.

The Wapda act has unnerved hydrological experts, except for its own who insist that alternative filling criteria does allow “such storage.” It has not been exercised in the past because the situation was never so desperate, they say.

The critics, however, insist, “Wapda is confusing security parameters with margins of maneuvering and exerting pressure on dam safety. It would have long-term consequences for the structure.”

In the last six days, the authority has taken the dam level from 1,507 feet to 1,533.88 feet – a massive filling of 27 feet; storing around one million acre feet in a week. Though, hitherto, exercised filling criteria restrict it only to a daily filling of one to one-and-a-half feet storage after the level of 1,510 feet. According to that criterion, it could have taken the authority at least three weeks to fill the lake to that level. But, it has done the feast in six days only, triggering fears about the impact on the dam safety.“This is risky, to say the least,” says Chaudhry Mazhar Ali – a well-known hydrological expert. The authority is clearly “encroaching upon dam safety parameters.” Such hasty filling does not mean that everything would blow up immediately but it would certainly have long-term consequences for the dam and allied structures. That is why it is very necessary for the technical people to not only operate within the prescribed limits, but also make those limits public so that pressure could be built on them when they violate those limits.

So far, publicly known limits, even to the experts, put restrictions on filling beyond 1,510 feet, he said and claimed: “All such bodies must have technical oversight over them, so that they do not budge under political pressure and play with such vitalstructures.”

“After the level of 1,510 feet, filling the dam becomes sole prerogative of Wapda,” says Rana Khalid of the Indus River System Authority (Irsa). “So, only it (Wapda) can give answers about the filling procedure and its consequences, if any. The authority’sindent does not matter after that level and it becomes irrelevant because of prescribed safety parameters. It is a fact that such fast filling has never happened before. Everyone had questioned it in different meetings but Wapda has been defending it allalong, citing alternative filling routes proposed by the builders of the dam,” he concluded.

A Wapda spokesman, however, maintained that the present dam filling rate was within the prescribed rule curve – the criterion that provides guidelines for filling the Tarbela Dam. This curve is for low discharges.

“As such water flow situation had never been experienced in the previous years this rule curve was not used before. While following the rule curve, Wapda is considering the water inflows and outflows for safety of the dam. It, as usual, is also closelymonitoring various factors relating to dam safety, including pore pressure and seepage from the dam, which are within the safe limits.”