ISLAMABAD: Amid troubled construction work, the Indus River System Authority (Irsa) has stopped filling the Tarbela dam to make way for the expected heavy inflow of water during the monsoon season.

A senior Irsa official told Dawn that water level in the reservoir had crossed the 1,511 feet mark almost a week ahead of the July 10 target date, after construction work on the Tarbela 4th Extension Project saw an unfortunate accident last week in which some Pakistani and Chinese workers died.

He said that engineering and irrigation experts had advised the water regulator to remain extra careful in building up water storage as the Pakistan Meteorological Department had predicted rains to be 10-20 per cent higher than normal. It was important, the official said, to leave sufficient storage capacity in the dam to absorb inflows in case of heavy rainfall and greater-than-anticipated river flows.

He said the Water and Power Development Authority (Wapda) had also advised that some space should be available in the reservoir to cope with an emergency situation in case of heavy flooding. Therefore, the Irsa members unanimously decided to let flows from upstream of Tarbela to flow downstream without any conservation.

Similarly, Wadpa requested the regulator to allow for a maximum drawdown of water from the Chashma barrage to help flush out the silt that had built up over the past couple of years and reduced its storage capacity.

This, however, led to a flood-like situation downstream from Chashma for a couple of days. Those flows have now reached Guddu barrage, where there is a low-to-medium flood.

Meanwhile, the flows in the Indus and Kabul rivers returned to normal on Sunday and the filling of Chashma barrage was resumed.

The official said a follow-up Irsa meeting was expected to be convened later this week to review the dam-filling criteria for Tarbela, depending on provincial irrigation requirements because provinces still required water for crop-watering before the advent of the regular monsoon season.

He said the filling would be resumed in a manner that the storage was built up at a rate of not more than one foot per day, to ensure the dam’s safety.

He said that temperatures in Skardu were rising again, which would lead to higher flows due to the melting of snow and rainfall.

The Federal Flood Commission on Sunday said the Indus continued to be in ‘low flood’ in Kalabagh-Chashma, Chashma-Taunsa and Taunsa-Guddu reaches. Kabul river was also in ‘low flood’ in the Warsak-Nowshera reaches.
The other main rivers such as the Jhelum, Chenab, Ravi and Sutlej were flowing normally on Sunday.

The water in the Tarbela and Mangla reservoirs on Sunday stood at 1,511ft and 1,219.65ft, respectively — 39ft and 22.35ft below their respective maximum conservation levels of 1,550ft and 1,242ft.

The combined live storage capacity of Tarbela, Chashma and Mangla reservoirs was recorded at 10.005 million acre feet (MAF) as compared to last year’s 10.76 MAF.

According to the Flood Forecasting Division (FFD), Saturday’s trough of the westerly wave over northern parts of Afghanistan was over north-eastern Afghanistan and its adjoining areas on Sunday.

The FFD predicted isolated thunderstorms and rain with one or two heavy falls over the upper catchments of all major rivers, including Punjab (Rawalpindi, Sargodha, Gujranwala, Lahore and Bahawalpur divisions), as well as Khyber Pakhtunkhwa and north-eastern Balochistan, over the next 24 hours.

Published in Dawn, July 11th, 2016