Damage to Munda Headworks: 160,000 acres in KP may remain unirrigated

ISLAMABAD: Two canals of Munda Headworks on the Swat River in Khyber Pakhtunkhwa may remain closed for three years due to the serious damage caused by the recent devastating floods.

“The canal closure will deprive its command area of 160,000 acres of irrigation for three years affecting the people who are directly dependent upon agriculture,’’ relevant top officials of the water resources ministry and the KP irrigation department told The News.

“This time, three bays of the headworks got washed away, as the self-destructing weir at the left bank of headworks did not breach to reduce the pressure of flood water on the structure of headworks.”

According to an official document of the KP irrigation department, the flood bypass channel with its self-destructing weir did not function as intended and the entire flood was directed towards the barrage itself. Three of 8 bays at the barrage have been destroyed completely, including the bridge deck, piers, and hoists, with damage also incurred on the hoisting mechanisms of two bays (Bay 3 and Bay 7).

A more comprehensive damage assessment is ongoing. Doaba Canal Headworks and the head reach of Doaba Canal have received significant damage and at the time of filing this report, the Doaba Canal is out of service.

Lower Swat Canal headworks and the head reach of the Main Canal have also incurred a significant damage but can provide a reduced level of service.

The self-destructing weir was constructed to breach when a flood of a big scale was to hit the headworks and divert the flood flows into the Swat River through the by-pass route, ensuring the safety of headworks structure. Nonetheless, the self-destructing weir didn’t collapse as the KP irrigation department failed to maintain it.

So the failure in the functioning of self-destructing weir has led to the washing away of three gates out of 8, apart from massive damage to the structure of the headworks.

From headworks, two canals come out. From the left bank of headworks, Lower Swat Canal originates irrigating 125,000 acres of land and from the right bank, Doaba Canal comes out irrigating 35,000 acres of land.

Now under the new scenario, both the canals will not be able to irrigate their command areas of 160,000 acres of land at least for three years and the headworks will take an equal time to become functional.

The barrage was swept away in 2010 floods and was rebuilt with eight vertical gates. Each gate is 60ft wide and 5ft in height and can be raised to leave a clear waterway opening of 23.5ft from the sill to the soffit of the gate. A steel gantry structure equipped with electric winches, counterweights allows for the gates to be raised and lowered. With all eight gates fully raised, this new barrage was estimated to have a capacity of 225,000cfs without water impacting the raised gates.