When community come together to harvest rain, the per-capita investment goes down. For instance, Panchsheel Park Colony about 1000 residents pooled in Rs 4.5 lakh to harvest more than 170 million litres of water annually.
Rainwater harvesting methods are site specific and hence it is difficult to give a generalised cost. But first of all, the major components of a rainwater harvesting system - rain and catchment area - are available free of cost. A good proportion of the expenses would be for the pipe connections. By judiciously fixing up the slopes of roofs and location of rainwater outlets, this could be brought down considerably. However the cost varies widely depending on the availability of existing structures like wells and tanks which can be modified and used for water harvesting.
Typically, installing a water harvesting system in a building would cost between Rs 2,000 to 30,000 for buildings of about 300 sq. m. The cost estimate mentioned above is for an existing building. For instance, water harvesting system in the CSE building in Tughlakabad Institutional Area, Delhi, was set up with an investment of Rs 30,000 whereas those in the model projects ranged between Rs 70, 000 and Rs 8 lakh. The costs would be comparatively less if the system were incorporated during the construction of the building itself.
It is easier to calculate the payback when the rain water harvested is used for storage as it saves money spent on buying water from tankers or private suppliers. Recharging groundwater has less tangible benefits but none the less is very crucial and highly recommended.
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