Upper Swat Canal, Defying Mountains
02 June 2015
The Yusufzai Plain stretches from the Mahaban Mountains in the north to the line of the Grand Trunk Road, passing through Nowshera and from the Indus in the east just west of Mardan. Of all the districts of the North West Frontier, now called Khyber Pakhtunkhwa, this is agriculturally the richest and most prosperous.
In addition to these natural sources of irrigation, there were a number of artificial irrigation canals, especially in the more level part to the south of the area. Some of these dated back to the Middle Ages while others bore the names of governors from the time of the Saddozai rule in 18th century. Consequently, the country was generally prosperous in terms of agriculture. That said, there were, nonetheless, large rain-fed tracts of land away from the rivers where crop failure and famine were not unknown.
|Upper Swat Canal sweeping past the houses of Batkhela|
|The weir and the headworks on the Swat River|
|Ransomes and Rapier winches for the gates of the headwork|
Not far south of the proposed headworks, however, sat the mountain barrier of the Malakand Pass. Seemingly impassable, the pass could not rein in Benton’s soaring mind. With signature panache, he proposed a tunnel to carry the Swat waters down to the heart of the Yusufzai Plain.
Even as work on the headworks and canal regulator at Amandarra and canal excavation was taken in hand in 1909, G. L. Bill, a mining engineer, set about surveying for the shortest possible alignment for the tunnel. With the experience of building railway tunnels in the subcontinent behind them, British mining engineers were well acquainted with the kind of stratum they were to work in.
Still, digging a three kilometre-long tunnel for a canal was out of the ordinary. This was no railway tunnel where large steam-driven machinery could be trundled in on rails. Rather, it was a much narrower conduit with low clearance and a much sharper fall. Men had to dig in uncomfortably cramped quarters and the trolleys to remove debris could only be rolled in by a derrick placed outside the mouth of the opening. Just as they had come to dig the railway tunnels in distant Balochistan, Kashmiri and Pakhtun miners once again flocked to work under the Malakand Pass.
Almost in lockstep, the headworks, canal as well as the tunnel, named after Benton, were completed on schedule in early 1914. The gates of the regulator were winched up and nearly 2200 cusecs of water flowed into the Upper Swat Canal speeding down the tunnel and into the Yusufzai Plain in time for the final watering of the ripening wheat crop.
|The opening to Benton Tunnel|
Over time, a fine web of minor distributaries drew off from the main canal to increase the area under cultivation. As the 20th century drew to a close, rising population and changing cropping patterns warranted greater need for irrigation. To their credit, Pakistani irrigation engineers designed and executed an auxiliary tunnel running next to Benton Tunnel. At its lower end in district Mardan, this new outlet runs an 81 megawatt power station besides raising the current irrigated command of Upper Swat Canal to nearly 2.5 million acres.
|The headworks at night|
posted by Salman Rashid @ 12:00 AM,
- At January 17, 2016 at 8:54 PM, Muhammad Irshad said...
very good. I am one of the former of this project.and am thankful to Sir John Benton.
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