WORLD WATER DAY
Save for a rainy day
While we gear up to celebrate yet another World Water Day on March 22, a reader throws light on the importance of rainwater harvesting
Water is essential for human survival. The total quantity of available water in the world is constant. According to a report of the United Nations Environmental Program (UNEP), more than 97 per cent of the available water is in the form of sea water while the quantity of fresh water is less than three per cent. Out of this fresh water, 77 per cent is ice locked away in the glaciers and the polar ice caps and 22 per cent is ground water. This leaves less than one per cent of fresh water supply to take part in the hydrological cycle, about half of which is found in rivers, lakes and swamps. Yet, on the global scale, availability of fresh water is more than enough to meet the demand in the present and the foreseeable future. But this water is not available everywhere, all the time or in proper quality and form. As a result, scarcity and pollution of water have led to a situation where at least 20 per cent of the population living in Third World’s cities and 75 per cent of its rural population do not have access to reasonably safe supplies of water even for drinking. Most parts of the country receive enough rainfall. A large portion of rain water flows to rivers, lakes, ponds and seas; some of it gets evaporated or seeps into the ground. During this course, rainwater gets contaminated with impurities. In most hilly regions, there is abundant rainfall, but the people face acute shortage of drinking water as most of the rainwater flows down to the plains. If we can tap rainwater before it reaches the ground, the problem of providing drinking water in hills can be easily solved with least expenditure. The water so collected can be stored in safe water storage structures. Rainwater is the purest form of raw water available on earth. Rainwater harvesting is the process of collection of rainwater from rain receiving surfaces like building roof tops, courtyards, playgrounds, hill slopes, places of worship, or specially made mini-catchment surfaces. The water is collected in storage tanks installed above ground, partly above and partly under ground, or fully underground depending on the local situation. Since the water is collected before it comes in contact with any contaminated surface, it remains free from physical, chemical and faecal contamination. For removing suspended impurities, if any, the water is collected in reservoirs. (The writer is an executive engineer in Uttarakhand Jal Sansthan, Dehradun)--- published in doonplus 19 march2008