Inflatable dams for shp projects

Inflatable weirs, also known as rubber dams are flexible elliptical structures made of rubberized material attached to a rigid concrete base and inflated by air, water, or combination of air and water. The experience of inflatable dams in India is very limited as there are only three installations so far. Use of inflatable weir for diverting water in hydropower projects has not been experienced in India till date even though worldwide over 4,000 installations exist and more than 10 manufacturers offer this type of weir. Different types of diversion weirs including rubber dam used for diverting water for small hydropower (SHP) projects were studied and presented in this paper. The design of diversion weir depends on the desired level of pondage, quantity of water to be withdrawn and length of weir. Three different sites were selected for the present study. Rubber dam was compared with commonly used structures for diverting water in to hydropower plants in the state of J&K of India viz raised gravity weir, trench weir, bush and boulder weir and “mathu bund”. The annual cost of these different types of weirs for same hydraulic conditions and different discharge values computed and were compared with that of rubber dam. Operation and maintenance cost and cost of losses on account of head, water loss and repair were taken into account for different types of weirs for calculating annual cost. Possible damage that may be caused by major floods to different types of weir were also worked out as damage due to flood is minimal in rubber weirs due to inherent feature of deflation. The cost of different types of weirs was worked out from engineering designs and drawings. As there was not a single rubber dam for hydropower projects in India, the cost of rubber dam was estimated based on personal communications with the international manufacturers and practitioners of the subject area, as well as case studies of already constructed rubber dams in India installed for purposes other than hydropower. The ease of inflation and deflation reduces the flood damage cost, O&M cost, sediment removal cost and repair work cost. With the comparative analysis, it is found that average annual cost of imported rubber dam, raised gravity weir, bush and boulder, mathu bund and trench weir is 31%, 60%, 114%, 129% and 135% respectively higher than Indian rubber dam. The results show that use of rubber dam for SHP projects is not only cost effective but also energy efficient hence is recommended in SHP projects.