Water is an essential natural
resource for sustaining life and environment. India has 300 mm more average
rainfall than the world average of 800 mm though a large amount of it is allowed
to run into the river and not properly harvested either to recharge the
catchment area of hill sources or collected for proper utilization. The storage
of rainwater in different ways has been an integral part of India ’s
tradition, though of late, piped water supply schemes have adversely affected
this traditional wisdom. Harvesting of rainwater is one of the effective ways
to tackle water shortage in hills and also will help in controlling floods and
soil erosion.
The technology used for Roof Top Rain Water Harvesting
system consists of collecting the rainwater falling on the roof of individual
houses by means of gutters provided at the lower ends of the roof. The
collected rainwater is conveyed by pipes to filtration unit and then to storage
containers. The water from these containers is abstracted by tap. The initial
rainfall of about half hour is diverted through the bypass system, which may be
contaminated by dust, bird dropping, leaves, twigs, insects etc. Disinfection of the collected water is provided by means of
bleaching powder/chlorine tablets.
Based on the area of the catchment available from the
roofs, the average annual rainfall of the region, the run off coefficient of
the roof material- Slate, RCC, CGI etc. the water storage capacity is
calculated for the dry period. The storage reservoir could be of Ferro-cement,
RCC, GI steel, synthetic polymer etc. Owing to cost effectiveness, lesser area
requirement and ease of construction and maintenance, ferrocement tanks have
been preferred in Swajal.
The average cost of an individual rainwater-harvesting unit
using GI gutters, ferrocement tank of 7 kl. capacity comes around Rupees
Twenty Thousand. The
operation and maintenance
mainly comprises the cleaning of roof for leaves, twigs etc. before rain and
diversion of initial rain through bypass system. In Swajal, a total of 1158
individual Roof Top Rain Water Harvesting units have been constructed in 69
villages.
All attempts should be made to harvest rainwater as rain is
the only source of water, which does not carries a price tag at the point of
delivery.
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