LAHORE: With River Jhelum hitting a massive flow of over 500,000 cusecs on Friday morning, Mangla dam has almost been filled to its original capacity of 1,242 feet, or 7.3 million acre feet (MAF), turning its lake into the biggest water reservoir in the country.

Water level in the lake has gone up by 17 feet over the past three days, raising hopes that it will be filled even to its enhanced capacity. The dam was raised by 30 feet in 2012, increasing its capacity to 2.88 MAF.

Last year, the water level in the dam got stuck at 1,240 feet before declining. This year it got stuck at 1,232 feet before receding and had gone down to 1,225 feet by Wednesday.

Know more: Tarbela, Mangla reservoirs likely to reach maximum level by Tuesday

But with the last part of the monsoon season producing a spell of massive rains in the catchment areas, the dam for the first time may be filled to its optimum level.

According to officials of the Indus River System Authority (Irsa), the inflow at Jhelum touched the mark of 516,000 cusecs on Friday morning. As a result, the lake attained a level of 1,236 feet, with only six feet needed to fill it to its capacity.

The authority was storing only 300,000 cusecs per hour and releasing over 200,000 cusecs to regulate the flow and control the flood situation downstream. At that rate, the lake would be filled to capacity in about 10 hours.

“The authority decided to open spillways because water inflow was not receding,” said Rana Khalid of Irsa. By the afternoon, Irsa received intimation that the rain-producing system had started weakening across the border and the inflow might start receding within 24 hours.

It decided to release additional water from the Mangla lake because it was confident that it could fill the dam by the time water flows went down.

The filling up of Mangla dam has enabled Irsa to start cutting releases from Tarbela dam. By Friday afternoon, the authority had reduced releases from Tarbela from 135,000 to 100,000 cusecs and warned the National Power Control Centre that it would be further cutting the releases to 40,000 cusecs because of the water relief from Mangla.

The additional water being released from Mangla will go to the Trimmu Barrage and fall into River Indus in seven days.

Most of the water requirements of Sindh, which is getting 160,000 cusecs from the Indus arm, will be met by the releases from Mangla. Thus, some additional water may be saved in Tarbela, the water level where has dropped by almost 17 feet over the past two weeks.

The official said the unexpected relief from Mangla lake was improving the overall water situation in the country.

But the water releases from Mangla dam have shocked irrigation and agriculture planners because tributaries of Chenab and Jhelum rivers downstream the dam are recording just under 200,000 cusecs.

“Between Mangla dam and Rasool Barrage, over 180,000 cusecs are being added to the system,” said an official of the Punjab irrigation department.

With releases from Mangla increasing to about 300,000 cusecs by Friday afternoon, the cumulative impact of water would be closer to 500,000 cusecs, which can threaten cities like Jhelum and other towns along the river and inundate large swaths of agriculture land. The official said that it was the flip side of the filling up of Mangla which otherwise was a cause for joy.

Published in Dawn, September 6th, 2014