(i) Rain water passed into drain does not enter the ground but is taken out of the urban area and poured into a water body at quite a distance with or without treatment. However, ground water is being withdrawn everywhere for drinking, industrial and irrigation purposes. As a result, the level of ground water is going down and arid conditions are being faced in many areas. In rain water harvesting, rain water from a building is passed directly into ground dug-wells or water pumps. This recharges ground water.
(ii) Installation of solar water heaters is a method of saving electricity which is always in short supply due to rapid urbanisation, industrialization and intensive agriculture. Coal/gas based power plants are polluting units they add carbon dioxide to the atmosphere causing global warming. Saving electricity is now valued social resonsibility.
