HYDERABAD: : Dams made of rubber! This may sound strange but rubber tubes, resembling cycle tubes and several thousand times bigger, are being used in many countries to impound water in rivers and streams.

Now India will join their league when the first rubber dam is built across the Janjhavathi in Vizianagaram district, Andhra Pradesh. Part of the dam was recently installed on the Janjhavathi before floods brought the work to a halt. ,The Janjhavathi dam will impound one thousand million cubic feet (tmcft) of water and irrigate 24,000 acres.

Also, the country's first irrigation canal with geo-membrane lining has been taken up at Wazeerabad in Nalgonda district.

Rolls of skin-thin membrane made of high-density polyethylene, brought from Austria, will be spread on the canal bed before covering it with conventional slabs. This will reduce seepage to zero and ensure more water supply to tail-end areas. Austria has developed and perfected the technology of rubber dams and geo-membrane lining for optimum use of water from the numerous rivers, which perennially flow down the snow-capped Alps. Putting on hold a Rs. 4,000-crore loan sought by Andhra Pradesh to execute irrigation projects, Austria has offered it rubber dams and membrane technology. The tube-like dam is inflated with water or air to impound the river during floods and is deflated to release excess water. The synthetic rubber is 10-mm thick and reinforced with nylon and webbing. It is ceramic-coated for protection against cuts.

The dam, operated manually or remotely, is usually 200 metres long and can rise up to a height of 10 metres when inflated. Water in the tube serves as a barrier against water outside.

Rubber dams are pre-fabricated and used in about 20 countries for their high elasticity; resistance to abrasions, corrosion, ageing, earthquakes and radiation, and zero maintenance. They can be easily replaced and transported and will not cause silting.

Laid across nearly 200 rivers, the dams are ensuring supply for irrigation, power generation and drinking water. Naruse (Japan), Mirani (Australia), San Gabriel (U.S.), Non Wai (Thailand), Charlo (Canada) and Vaca (the Philippines) are among the places where they exist.

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