FAQ's Rain Water

What is rain water harvesting?
It is simply a way of catching and collecting the rainwater and using it for consumption or recharging the ground water table. Usually in urban areas, the rain water can be harvested from the roof or any other elevated part in the building through which it can be collected in a tank or such structures on the ground from which the collected water percolates to the ground water level. Before it goes into the groundwater, it has to be treated appropriately.

What is the need of RWH?
Water shortage is a serious problem throughout the world. With an increasing population, more and more water is required for domestic, industrial and agricultural purposes. In most communities, the rate of withdrawal is very high compared to the rate of recharging the water table. Therefore, fresh water which was once considered an inexhaustible resource, is now fast becoming a scarce commodity. The problem of groundwater depletion and water scarcity in cities and elsewhere can be best tackled by harnessing every drop of rainwater, which usually goes waste as run-off water, for the purpose of artificial recharge of the water table

What are the benefits of rainwater harvesting?
Rain water harvesting is one of the most promising solutions to the problem of water scarcity. It helps to recharge the ground water by collecting rainwater during monsoons and thus prevents surface run-off of the rain water. In India ground water is a common source for irrigational and domestic purposes. The collected water can also be used for other purposes such as in gardening, washing clothes and car, etc. RWH also helps in overcoming the problems of floods and water stagnation during the months of monsoon. Apart from these, this is simple to install and operate and also it is not a very costly technology.

Does the collected rain water requires treatment?
Yes, the collected rain water requires treatment even though rain water is not in itself contaminated but as there are many pollutants and impurities present in the atmosphere, such as suspended particulate matter, harmful gases like oxides of nitrogen and sulphur, etc which either react with the rain water or get dissolved in it; therefore treatment of the rain water becomes important. Treatment is all the more necessary as ground water once polluted cannot be treated back.

How does it works?
There are 3 basic requirements in RWH: a catchment area, collection devices and a conveyance system. The catchment area, in simplest words is the area which catches the rain water. Rooftop or land surface can be treated as catchment areas. Rooftop is the main catchment area in urban areas. The collection device stores the harvested water. Conveyance system usually comprising of pipes transports the harvested water from the catchment area like rooftop to the storage device. There are also provisions for the treatment of the collected water.

Is RWH a traditional way of conserving water?
Yes, RWH is a traditional way of conserving water. Infact, our ancestors harvested and conserved rain water just as they grew crops on lands. It is just that we lost touch with our traditional practices. But today as we face acute water shortages, this tradition has been revived. However in many parts of India, the traditional structures of water harvesting still exists. For e.g. - johads and baoris in Rajasthan, zings in Ladakh, eris in Tamil nadu, temple tanks, etc.

What is a check dam?
Check dams is another way of conserving and storing water. These are structures constructed to control the velocity of running water along the gullies. Johad is an example of a small earthen check-dam used to collect and store the rain water. After the revival of the johads in Alwar, Rajasthan the ground water level has risen by almost 6metres and the forest cover has increased by 33%.

What are beris or kuis?
Beris or kuis are another traditional way of water harvesting found in Rajasthan which are 10-12 m deep pits dug near tanks to collect the seepage. Kuis can also be used to harvest rainwater in areas with meager rainfall. The pit has a narrow mouth which prevents the collected water from evaporating. However the pit gets wider as one moves under the ground so that the water can percolate into a large surface area. The water is used sparingly as a last resort in crisis situations such as droughts, etc.

Is RWH a feasible technology in India?
The feasibility of rainwater harvesting in India or any area is highly dependent upon the amount and intensity of rainfall. Other variables, such as catchment area and type of catchment surface, usually can be modified according to household needs. As rainfall is usually unevenly distributed throughout the year, RWH serves as only a supplement to other sources of household water. Therefore RWH may help to a great extent in solving the water crisis but it can never be relied for year round supply of water.

What is first-flushing?
The first spell of rainfall carries comparatively larger amounts of contaminants from the atmosphere and surrounding surface. Therefore, the run-off from the first spell of rainfall should be prevented from entering the system. For this a valve has to be installed which flushes out the run-off water from the first spell of rain. This process is called first flushing.