LAHORE: As the floods have reduced the country’s water requirement and caused indirect conservation at the Indus arm, Tarbela Dam got filled on Thursday – second time this season – providing additional one million acre feet.

The dam was filled first time on the night between Aug 20-21 but its depletion started very next day as base flow of all rivers dipped exceptionally: river Indus came down 145,000 cusec from 218,600 cusec; river Kabul from 51,200 cusec to 30,700 cusec; river Jhelum from 33,500 cusec to 23,700 cusec and river Chenab from 58,200 cusec to 46,300 cusec.

The situation forced the provinces to compel the Indus River System Authority to draw water from the dams to save standing crop. By Sept 5, the dam level had come down by 16.30 feet – from maximum 1,550 feet to 1,533.70 feet, when flooding started on three western rivers – Jehlum, Chenab and Ravi – providing water planners a chance to squeeze supplies from Tarbela and start saving some water.

“It was basically indirect saving of water,” says an official of the Punjab Irrigation Department. The water requirements came down as floods spread across Punjab. All this water had to ultimately travel to Sindh, giving Irsa a chance to reduce releases meant for Sindh and conserve additional water. That is how Tarbela Dam was allowed to improve by almost 17 feet in the last two weeks, or around one million acre feet.

Similarly, Mangla Dam had dipped by around 17 feet by Sept 2 before it started improving. In the next 15 days, levels of both dams improved by 17 feet each and provided two million acre feet of additional water to the country.

“These two million acre feet would be instrumental in substantially reducing Rabi shortages,” he said and added: “The planners earlier feared around 20pc shortage during the coming Rabi season. However, now these shortages would come down to much more manageable seven to eight per cent which means a huge relief in irrigational and agricultural terms.”

“Currently, Sindh has water requirements of 120,000 cusec whereas water at Guddu Barrage is well over 300,000 cusec,” says an official of Irsa. That is why huge quantity of water has started going downstream Kotri Barrage. So far, 3.3maf has gone down to Kotri Barrage. Even on Thursday, 36,000 cusec water was flowing down. The authority has calculated that around 2.5maf more water will flow downstream Kotri, taking the total flows closer to six million acre feet, which should go a long way to replenish sub-soil water and check sea intrusion.

“The floods have helped both reservoirs on three counts: additional water, reducing irrigation requirement and damaging many canals,” said another official of the Irrigation Department. Many canals – Upper Chenab, MR Link Canal, Lower Chenab and Rangpur – have been damaged and closed, saving still more water for the reservoirs. Overall, this 2maf water is crucial for the country regardless of other damages that the flooding wreaked, he concluded.

Published in Dawn, September 19th, 2014