Technologies/ Water India/ SDNP-Newsletter/SDNP-ENVIS Partners
The main objectives of Rain Water Harvesting are:-
This could be a land surface or a rooftop.
a) Land surface catchments: This is the simplest way of collecting rainwater. It involves improving runoff capacity of the land surface through various techniques including collection of runoff with drainpipes and storage of collected water. It provides an opportunity to collect water from a larger surface area. By retaining the flows (including flood flows) of small creeks and streams in small storage reservoirs (on surface or underground) created by low cost (e.g. earthen) dams, this technology can meet considerable water demand. However, during dry periods there is a possibility of high rates of water loss due to evaporation and infiltration into the ground. The technique is mainly suitable for storing water for agriculture purposes.
b) Rooftop catchments: This is more suitable for meeting individual water needs. In the most basic form of this technology, rain water is collected in simple vessels or drains at the edge of the roof and conveyed by pipes to containers for settling particulates before being conveyed to the storage container for domestic use. The water needs to be disinfected if used for drinking purposes.
b)Rainfall water containers: These can be battery tanks (i.e. interconnected tank) made of pottery, ferrocement, or polyethylene. The polyethylene tanks are compact, have a large storage capacity, are easy to clean and have many openings, which can be fitted with connecting pipes.
Traditional Systems of Rain Water Harvesting
Modern Systems of Rain Water Harvesting
ii) In townships where built-up areas do not have individual courtyards. The rainfall can be stored by constructing water bodies at different locations depending upon land contours. Though these water storage bodies have high initial cost but they are helpful in sustaining the groundwater table.
Computation of artificial recharge from Rooftop rainwater collection Major factors to be taken in account for computation are:
1) Roof top area (of an individual house or multistoried building)
2) Average annual monsoon rainfall
Following formula is applied for calculating the recharge:
Area of (sq m) x Amount of (m) = Volume of water
Catchment Rainfall received (cu m)
For example, if the catchment area of rooftop is 100 sq m (of an individual house) and the recorded average annual monsoon rainfall of that particular place is 780 mm, then effective annual rainfall contributing to recharge is approximately 70% i.e. 550 mm. Hence total water available will be 55 cu m which is enough for 100 days for a five member family @ approx. 110 litres/day).
Advantages of Rain Water Harvesting
Rain Water Harvesting systems are advantageous to the community and the environment as they:
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