What is rainwater harvesting?

  • Rainwater harvesting is the storing and collection of rain water that runs off from tops of roofs, open spaces like parks and roads or especially prepared ground. This water can be used variously for purposes like drinking (after treatment), household use, livestock or even irrigation. It is also used for recharging groundwater, that is replenishing the water that has been extracted from the aquifers.

Why should rainwater be harvested?

  • Much of the water that we receive as rain simply runs off and gets wasted. In a country like ours where there is so much of pressure on water resources due to growing population pressures, it makes immense sense for us to store up this water and put it to good use. This water can be a useful supplement to the water available from other sources, thereby augmenting the total water availability. In fact, in some regions, rain is the only source of water available, and that too, in highly erratic spurts. In such regions harvesting of rainwater is the best option available to people, and has been known to bring about marked betterment in their living conditions, for example in many parts of Gujarat and Rajasthan.

  • Rainwater harvesting is also very important for recharge of groundwater as there has been massive over extraction of ground water in many parts of the country. Rainwater harvesting not only replenishes the store of underground water, it also improves its quality by effecting dilution of pollutants and other harmful substances.

  • Besides these, rainwater harvesting also prevents local flooding in many areas, caused by the run off water.

How can rainwater be harvested?

  • A major point in favor of rainwater harvesting is that the structure for this can be made from inexpensive, locally available material. It works both in individual households and for small communities. Rainwater harvesting structures can be made anywhere - individual homes, apartments, offices, institutions, slums, cities, villages - and ~y anyone - individuals or small communities.

  • Rainwater harvesting structures can be simple or complex. The main components in a rainwater harvesting system consist of a catchment area from where water is collected - this could be either from the ground like parks, playgrounds, roads, pavements, agricultural field etc, or from the rooftops - the channel or conduit through which water passes from the catchment structure into the storage area - these could be drains, pipes, rectangular or semi circular gutters or channels made of PVC material, galvanized iron sheets or even bamboo trunks cut vertically into two and the storage tank or other structures where the water gets collected. The size of tanks would depend on the amount of water available and the amount needed for use. The tanks can be made from RCC, plastic, galvanized iron etc. Even dried bore wells, tube wells etc can be used for collecting water. If rainwater is being harvested for recharge purposes, there need to be appropriate structures for this, for example subsurface dykes built into an aquifer, recharge of abandoned wells, service tube wells, recharge pits etc. Besides these the rainwater harvesting structures also requires arrangements to maintain the quality of water. Thus there have to be arrangements to ensure that the first flush of rainwater which would contain contaminants, is allowed to flow out. Filters made of cloth, charcoal, sand etc are put in place to filter out pollutants.

Is rainwater harvesting a new concept in India?

  • No, Indians have been harvesting rainwater since ancient times. Some of the traditional systems include Tankas which were small underground tanks built in houses in Rajasthan, especially Bikaner; Khadim or Dhora, which are embankments built along low hills lopes lying under rocky uplands for collecting water that runs down the slopes and using it for agricultural purposes later on; Bao/is or stepwells of Gujarat and Rajasthan, TheAhar Pynes of South Bihar- Ahars are catchment basins embanked from three sides and pynes are channels leading off from the third side; canals of West Bengal; Tanks, Phads and Bhandaras of of Maharashtra, Keres or tanks of Kama taka or Zings of Ladakh which were tanks for collecting melted glacier .Most of these traditional structures are now defunct, but efforts have been initiated by many communities to revive these.

  • What rainwater harvesting technique is most popular in urban areas?

  • The technique for collecting rainwater from rooftops is ­most popular in urban areas. Many state governments have passed laws making rainwater harvesting mandatory for all new buildings/ apartment etc. Some are even giving incentives in the form of rebate on property taxes.

How is rainwater harvesting being done in rural areas?

  • The stress in rural areas is on community based water harvesting systems with the revival of traditional systems. Communities are creating or reviving structures like check dams and johads to collect water.

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