Chashma Barrage’s de-silting improves water flows for irrigation

LAHORE: Chashma Barrage that assumes an immense importance for its water diversion from Indus River to fertile lands in two provinces has seen a fast decline in sediments on the riverbed, improving water flows for the betterment of irrigation and power generation, it was learnt on Friday.

Sher Zaman Khan, chairman of Indus River System Authority (Irsa) termed the development as a breath of fresh air especially when the large dams: Mangla and Tarbela are gradually losing their storage capacities.

“The achievement is made by the better regulation of the reservoir by the project authorities and the staff,” Khan said in a letter to Water and Power Development Authority (Wapda) early this month.

The process of sediment accumulation in Chashma Barrage on Indus River has partly been reversed with the improved operation of reservoir and without spending any money, he added.

Water watchdog Irsa, under the 1991 Water Appropriation Accord, distributes water to vast land in Khyber Pakhtunkhwa and Punjab, while diverting surplus water to River Jhelum at Chashma Barrage situated in Mianwali district.

It is also one of the first barrages that regulate flows of River Kabul that empties into Indus River upstream near Attock.

Sediment management is also important for efficient power generation at Chashma hydropower station having installed capacity of 184 megawatts.

Contrary to main function of other barrages, a small storage reservoir has been provided at the barrage to primarily re-regulate the downstream supplies of Tarbela dam and unregulated flows of River Kabul.

However, the dwindling storage capacity of the barrage has for long been a source of concern for water regulator.

Since its inception in 1971, more than half of its storage capacity was lost due to buildup of sediments.

A hydrographic survey of Chashma Barrage found that the rate of sediment deposits remained very small in 2017 as compared to 2012.

A reclaim of 2,000 acre-feet in live storage of the barrage has also been witnessed during the last five years, according to the survey conducted by International Sediment Research Institute of Wapda.

By managing the flushing of the reservoir through better operation, Irsa chairman said “the deepest point of the lake also shows positive sign of reduction (in sediments)”.

The Punjab Irrigation Department handled a similar kind of problem through civil works involving construction of subsidiary weirs at different barrages, which require funds.

Khan, however, said Wapda authorities managed the same by making an exceptional regulation of Chashma Barrage and thus saved huge amount of national exchequer.

“The professional and dedicated approach of the chief engineer and others is commendable,” he added, hoping that such kind of professionalism would be a beacon of dedication amongst all the departments.