Monday, September 26, 2011

Affordable SEVAI Rainwater Technology-Dr.K.Govindaraju


Rain water Technology centre of SEVAI
Rain water is the ultimate source of fresh water. The activity of collecting rainwater directly or recharging into the ground to improve ground water storage in the quiver is called as Rain Water Harvesting. Rainwater harvesting is one solution to the problems of water shortage in the drier areas of India, but its implementation presents a number of challenges, of which storage is the main one. Conventional stone, brick or fibrocement tanks ARE cheaper alternatives. Rain water is to be harvested to conserve and augment the storage of ground water, to reduce water table depletion, to improve the quality of ground water, and to arrest sea water intrusion in coastal areas. For recharging ground water, rainwater may be harvested by two ways, Rain water that falls on the terrace of the buildings and in the open spaces around the buildings. Till about thirty years back, the areas around our homes and offices used to be unpaved and the rain falling on these areas would percolate into the soil and remain there for being drawn through shallow open wells. With the proliferation of flat complexes, not only have these areas been paved and percolation of rainwater into the soil almost totally stopped, the quantity of water drawn from the soil below has increased manifold. Consequently open wells and not - so - deep bore wells started drying up. The reason is that no sincere attempt is made to replenish the ground water table with rainwater during the monsoon. A rainwater harvesting system consists of three basic elements: a collection area, a conveyance system, and storage facilities. The collection area in most cases is the roof of a house or a building. The effective roof area and the material used in constructing the roof influence the efficiency of collection and the water quality. A conveyance system usually consists of gutters or pipes that deliver rainwater falling on the rooftop to cisterns or other storage vessels. Both drainpipes and roof surfaces should be constructed of chemically inert materials such as wood, plastic, aluminum, or fiberglass, in order to avoid adverse effects on water quality. The water ultimately is stored in a storage tank or cistern, which should also be constructed of an inert material. Reinforced concrete, fiberglass, or stainless steel are suitable materials. Storage tanks may be constructed as part of the building, or may be built as a separate unit located some distance away from the building. This technology is suitable for use in all areas as a means of augmenting the amount of water available. It is most useful in arid and semi-arid areas where other sources of water are scarce. Rainwater harvesting provides a source of water at the point where it is needed. It is owner operated and managed. It provides an essential reserve in times of emergency and/or breakdown of public water supply systems, particularly during natural disasters. The construction of a rooftop rainwater catchment system is simple, and local people can easily be trained to build one, minimizing its cost. The technology is flexible. The systems can be built to meet almost any requirements. Poor households can start with a single small tank and add more when they can afford them. It can improve the engineering of building foundations when cisterns are built as part of the substructure of the buildings, as in the case of mandatory cisterns. The physical and chemical properties of rainwater may be superior to those of groundwater or surface waters that may have been subjected to pollution, sometimes from unknown sources. Running costs are low. Construction, operation, and maintenance are not labor-intensive.-Govin


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