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Inflatable rubber dams

June 19, 2017

THE irrigation department of Punjab has come up with a proposal of introducing inflatable rubber dams for the eastern rivers in the province to serve not only as small water storages, but also, improve the biodiversity of the area which was degraded owing to drying up of the waterways as a result of the Indus Water Treaty 1960.

The irrigation department has so far identified eight points — four each at Sutlej and Ravi rivers — for the construction of these proposed rubber dams.

The feasibility study and a detailed design for the pilot project in Bahawalpur district has been prepared by The Project Implementation Consultants — a joint venture of Messrs ACE, Nespak and SMEC.

“In fact, the consultants have studied three sites — one on the Ravi (Okara-Faisalabad bridge) and two on the Sutlej (Bahawalpur-Lodhran Road bridge and Bahawalpur N-5 bridge).

But the Bahawalpur-Lodhran Road bridge on River Sutlej has been selected for the construction of the first such facility, keeping in view the socio-political acceptability considerations, according to an official of the irrigation department, involved with the project’s planning.

This idea is in vogue in developed nations like the USA, Canada, Italy and Spain and developing states like China, India and Bangladesh. China boasts over 2,000 rubber dams, while Bangladesh has built several dozens of them so far.

“The inflatable dams are a good option during low flow as well as high floods. For in case of flood, the rubber weir may be deflated within hours to allow the strong current to pass through the channel while a concrete weir will be washed away”

“Currently, the proposal is lying with the donors, both the provincial government as well as the world agencies interested in lending for water projects, to seek funds for its implementation.”

The inflatable rubber dams are rubber-coated cylindrical fabrics placed across water channels, fixed to concrete foundation by bars and anchorage bolts, to raise the upstream water for irrigation, flood control or other uses. Air, water or a combination of both are used to inflate the tubes.

In the proposed Bahawalpur Bridge project, a 2.5 metres high and 155.3 metres long inflatable weir will be installed on top of the spillway which is divided into four bays, the official says, adding, it will create an approximately 13km-long lake upstream at a cost of around Rs3bn.

The cost includes the compensation amount to be paid to the owners of the land within the main creek of River Sutlej. The construction period will span over 18 months.

Besides serving as a water storage dam for irrigation purposes, it will also help recharge ground water aquifer and improve availability of water for drinking purpose in the project impact area.

Coupled with enhanced availability of tubewell irrigation due to recharged aquifer, it will help in improved crop yields and generate agro-economic benefits, the official says.

The 13km lake can also be used for fish farming as well as for recreational activities like boating, while its impact on biodiversity of the area will also be significant, he said, pointing out the additional benefits of the plan, adding, “Consequent upon the success of the pilot project, a series of similar projects will be replicated in the remaining reaches of Sutlej and Ravi rivers.”

A technical member of the project team says mechanical equipment of the rubber dam, including auto deflation system, air compressor for activating pneumatic valves, air blowers and control panels, will be housed in a four-story building.

The official says that initially construction points on the rivers have been identified where concrete foundations or platforms are already available in the form of bridges to keep the costs low.

About the strength and reliability of the fabric used, he says, “It could sustain knife cuts and has a life span of over two decades.”

A consultant of the water and power authority (requesting anonymity) supported the rubber dam proposal saying, “The technology may be used to build small reservoirs to meet the needs of the impact area, while it entails no damages in any respect.

The inflatable dams are a good option during low flow as well as high floods. For in case of flood, the rubber weir may be deflated within hours to allow the strong current to pass through the channel while a concrete weir will be washed away.”

Former Chairman Wapda, Engineer Shamsul Mulk, said he can give his professional opinion on the proposal only after going through its feasibility study but stressed that ‘known technologies’ should be preferred for the development of water reservoirs.

Published in Dawn, The Business and Finance Weekly, June 19th, 2017