Accepted Papers - 3.pdf - UNESCO

RAIN WATER HARVESTING (RWH) IN
CHENNAI
Chennai gets an average of 1300 mm of rainfall
every year. But, this rainfall occurs in short spells
of a high intensity and nearly 65 percent of the
rainfall is lost due to surface runoff to the sea and
evaporation. With the open space area around
houses and buildings being cemented, rain water,
which drains off from terraces and the roofs is not
percolating into the soil. Therefore, precious rainfall
is being squandered, as it drains into sea eventually.
If better methods like roof top rain water harvesting
techniques are adopted, will have proper recharge
and the water will be available throughout the year.
RWH means catch the rain water where it falls.
It is the activity of direct collection of rain water.
Rain water can be stored for direct use or can be
recharged in to the ground water for later use. In
cities, due to shrinking of open spaces, rain water
can be harvested and recharged to the ground water.
So, the Government of Tamil Nadu made RWH
mandatory in all the houses. With the participation
of the public in RWH, roof top rain water can be
collected and stored in the place of generation itself.
This will improve the self-sustainability in fulfilling
the day to day water requirement of the public.
RAIN WATER HARVESTING STUDIES IN
INDIA
Deepak Khare et al (2004) have reviewed the
impact assessment of RWH on ground water quality
at Indore and Dewas, India. The impact assessment
of roof top rainwater harvesting on ground water
was carried out with the help working tube wells to
improve the quality and quantity of ground water.
The roof top rainwater was used to put into the
ground using sand filter as pretreatment system. This
lead to a reduction in the concentration of pollutants
in ground water which indicated the effectiveness
of increased recharge of aquifer by roof top rain
water. He observes that in certain areas, the amount
of total and faecal coliform were observed high in
harvested tube well water than normal tube well
water. The reason of this increase was poor
cleanliness of roof top and poor efficiency of filter
for bacterial removal. The author concludes that
quality mounting of rainwater harvesting is an
essential prerequisite before using it for ground
water recharge.
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Venkateswara Rao (1996) in his article has
reviewed the importance of artificial recharge of
rainfall water for Hyderabad city water supply.
Rainfall water from the roof tops of the buildings
recharged through specially designed recharge pits
in order to augment the ground water resource in
the city. This water meets almost 80% of domestic
water requirements, storm run off from the public
places like roads, parks, play grounds etc., is
recharged through naturally existing tank within the
city by not allowing municipal sewage and industrial
effluents in these tanks. He finally suggests that,
wherever natural tanks are not existing, community
recharge pits are to be constructed at hydro
geologically suitable location.
Sharma and Jain (1997) describe the ground
water recharge through roof top rain water
harvesting in urban habitation. In Nagpur city an
experiment was conducted where 80,000 litres of
water collected from the roof top of 100 m2 area
was recharged at the expense of Rs.1500/-. The rise
in water level up to one meter was recorded in the
recharge well and adjusting dug wells. The quality
of ground water was also improved as nitrate
concentrations got diluted considerably to desirable
limit. They conclude that such a practice, if
replicated on a large scale can bring out sustainable
augmentation to ground water reservoir.
Sekar Raghavan (2004) in his paper deals with
survey on constructions of roof top RWH structures
at Gandhi Nagar. He analyzed the RWH system
based on completeness viz., roof top and open space
RWH, apportioning of roof water, design of
structures and maintenance of RWH system. Finally
he concludes that 15% of the systems were very
good, 35% were good, 30% were satisfactory and
20 % were bad.
PUBLIC PARTICIPATION IN RWH
Indira Khurana and Suresh Babu explained the
experiences in community based water harvesting.
Centre for Science and Environment (CSE) had
been promoting the concept of rain water harvesting
doing research on community based water
harvesting. Some of the case studies from Alwar
and Laoriya in Rajasthan, Ralegaon
Siddhi,Darewadi and Hivare Bazar in
Maharastra,Raj-Samadiyala in Gujarat and Jhabua
in Madhya Pradesh are discussed in their article. In