MUKESHPATELSCHOOLOFTECHNOLOGYMANAGEMENT&ENGINEERINGSHIRPUR, DIST.DHULIA(M.S)-425405. ROOF TOP RAINWATER HARVESTING SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE2NDYEARB.TECH.TRIMESTERVBYSNEHAL JAIN Roll No: 912 (SAP ID) 2011 –2012
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concept of water harvesting is not new for India. Water harvesting techniques had been evolved
and developed centuries ago.
Living creatures of the universe The paper outlines rainwater harvesting is being frequently used
these days, however, the are made of five basic elements, viz., Earth, Water, Fire, Air and Sky,
Obviously, water is one of the most important elements and no creature can survive without it.
Despite having a great regard for water, we seem to have failed to address this sector seriously.
Human being could not save and conserve water and it sources, probably because of its
availability in abundance. But this irresponsible attitude resulted in deterioration of water bodies
with respect to quantity and quality both. Now, situation has arrived when even a single drop of
water matters. However. “Better late than never", we have not realized the seriousness of this
issue and initiated efforts to overcome those problems.
Ground water resource gets naturally recharged through percolation. But due to indiscriminatedevelopment and rapid urbanization, exposed surface for soil has been reduced drastically with
resultant reduction in percolation of rainwater, thereby depleting ground water resource.
Rainwater harvesting is the process of augmenting the natural filtration of rainwater in to the
underground formation by some artificial methods. "Conscious collection and storage of
rainwater to cater to demands of water, for drinking, domestic purpose & irrigation is termed as
Rooftop Rain Water Harvesting is the technique through which rain water is captured from the
roof catchments and stored in reservoirs. Harvested rain water can be stored in sub-surface
ground water reservoir by adopting artificial recharge techniques to meet the household needsthrough storage in tanks.
The Main Objective of rooftop rain water harvesting is to make water available for future use.Capturing and storing rain water for use is particularly important in dryland, hilly, urban and
coastal areas. In alluvial areas energy saving for 1m. rise in ground water level is around 0.40
Most residents in Dewas, Madhya Pradesh, have wells in their houses. Formerly, all that those
wells would do was extract groundwater. But then, the district administration of Dewas initiateda groundwater recharge scheme. The rooftop water was collected and allowed to pass through a
filter system called the Dewas fillter, designed by Mohan Rao , district collecter of Dewas, and
engineers of the rural engineering services. The water thus filtered is put into the service
tubewell.
The filter consists of a polyvinyl chloride (PVC) pipe 140 mm in diameter and 1.2m long. Thereare three chambers. The first purification chamber has pebbles varying between 2-6 mm, the
second chamber has slightly larger pebbles, between 6 and 12 mm and the third chamber has the
largest - 12-20 mm pebbles. There is a mesh at the outflow side through which clean water flows
out after passing through the three chambers. The cost of this filter unit is Rs 600.
When rainwater is harvested in a large rooftop area, the filtering system should accommodate theexcess flow. A system is designed with three concentric circular chambers in which the outer
chamber is filled with sand, the middle one with coarse aggregate and the inner-most layer with
Recharge pits are small pits of any shape rectangular, square or circular, contracted with brick or
stone masonry wall with weep hole at regular intervals. to of pit can be covered with perforated
covers. Bottom of pit should be filled with filter media.
The capacity of the pit can be designed on the basis of catchment area, rainfall intensity and
recharge rate of soil. Usually the dimensions of the pit may be of 1 to 2 m width and 2 to 3 m
deep depending on the depth of pervious strata. These pits are suitable for recharging of shallow
aquifers, and small houses.
Soak away or Recharge Shafts:-
Soak away or recharge shafts are provided where upper layer of soil is alluvial or less pervious.These are bored hole of 30 cm dia. up to 10 to 15 m deep, depending on depth of pervious layer.
Bore should be lined with slotted/perforated PVC/MS pipe to prevent collapse of the vertical
sides. At the top of soak away required size sump is constructed to retain runoff before the filters
through soak away. Sump should be filled with filter media.
Rainwater harvesting is an important new technique to confront the increase in shortage of water
and to manage the water judiciously. However a systematic and structural procedural approachis required to ensure that the maximum benefit is drawn from this technique. Great care is also
required to ensure that negative externalities are not generated by the adoption of this technique
such as pollution of ground water or flooding damage to structures, or weakening of foundations