Rainwater Harvesting:
Best Practices in Rural and Urban Areas
An Environmental Management Project
Group 9
Section E, PGP20
GARIMA RAMOLE PGP/20/264
KUNAL BRAHMA PGP/20/276
RAJKUMAR E PGP/20/287
SANJANA S. KUMAR PGP/20/291
UDAYKUMAR M N PGP/20/302
Introduction:
Rainwater harvesting (RWH) is a method of storage and collection of rainwater into natural
reservoirs or tanks, or the infiltration of surface water into subsurface aquifers which is not lost
as surface run off.
RWH can be done at two levels
• Micro level (Used in small scale like households)
• Macro level (a large-scale application like in public places)
Rainwater harvesting is important to conserve the current water resources.
The reason for RWH can be classified in 2 ways- economic and environmental.
Economic
• RWH leads to reduced water bills from the municipalities
• Reduction in demand of water - water supply utility saves money on treatment and
pumping
• Reduces cost of infrastructure necessary for water supply in both rural and urban areas
Environment
• Conservation of energy – pumping of water to our homes can be checked
• If water is hard, adding soft rainwater improves water quality
• Improves groundwater situation by recharging groundwater by rainwater
• Reduces demand for water at city/village level, which reduces dependency
Other aspects
• RWH is simple, cost-effective, easy to construct and maintain at both levels
• Viable in urban and rural areas, slums, low income housing and high rise apartments
• Can offset the need for multipurpose river projects which incur huge setting up and
maintenance costs
Rainwater harvesting (RWH) is an age-old concept in our society.
•
Fig.1. Rainwater storage reservoir at Dholavira (Rann of Kutch) – Harappan civilization (2500-1900 BC)
The Harappan civilisation (2500-1900 BC) was comprised of a number of urban centres.
Dholavira, in the great Rann of Kutch (in present-day Gujarat, western India), is one of many
such centers.
The city of Dholavira was built in a semi-arid region with an average rainfall of 260 mm
annually. There were no perennial water sources which the city could make use of.
Subterranean water was saline and not fit for consumption, potable water was scarce. How did
the city of Dholavira manage to survive such crisis?
The city had two storm water channels, Manhar (north) and Mansar (south) which flanked the
city. As the city was laid out on a 13 m gradient (higher in the east to lower in the west), this
was ideal for reservoirs. It seemed the planners knew this. They made a series of 16 water
reservoirs between the inner and outer walls of the city to collect the monsoon runoff from the
channels, which amounted to 250,000 cu.m. of water.
Inside the bastion (inner city), there were giant storm drains with apertures. These weren't for
effluent, as archaeologists 1st thought, since they weren't connected to housing or bathing
platforms. These were for rain. The air-apertures ensured simple passage of rain.
To the casual visitant, the foremost placing feature of Dholavira is its water management
system. One gets the sense that each drop of water had to be saved. Concerning 25 of the city's
250 acres square measure occupied by sixteen rock cut reservoirs of assorted sizes. Connected
by channels and dams, the reservoirs square measure quite opened up and should have
intercalary to the aesthetic charm of this planned town.
In one among the older water harvest home systems, concerning one hundred thirty metric
linear unit from Pune on Naneghat within the Western Ghats, an oversized variety of tanks
were cut within the rocks to supply drink to tradesmen UN agency wont to follow this ancient
trade route.
In our report, we might herald to lightweight the simplest practices of rain harvest home in
rural additionally as urban areas in Asian nation.
Ecosystem Services of Water
• Production/Provisioning Services
• Regulation Services
• Cultural Services
• Supporting Services
Traditional Rain-Water Harvesting Systems
Rain Water Harvesting In Ralegan Siddhi:
Ralegan Siddhi is a village in Parner taluka situated in Ahmadnagar district, Maharashtra. The
exact location is displayed in the above Figure. It is at 87 km distance from Pune city. It is a
dry area experience frequent drought with scanty rainfall ranging between 400-500 mm and
temperature varies from 28°C to a maximum of 44°C. The village is surrounded by hills in
northeast and south sides. The land is wavy and sloping vary from 3-15%.
In the year 1970, Ralegan Siddhi was considered one of the poorest village in India. Every
family has hardly one acre of farming land. Internal Food production constituted for only 30
per cent of the requirements in the village and most men moved to nearby cities every year to
look for job.
This project was to develop a sustainable water management model to save the rain water by
involving the people from the village themselves and volunteers in it. On seeing other
successful ventures in water conservation and the economic development, Anna Hazare
encouraged the people to come forward and work collectively for soil conservation and water
harvesting. The astonishing transformation that took place in Ralegan Siddhi started showing
results in a short span of 15 years in 1980s.
The 1991 Census showed a population of 1982 living in 310 households. The sex-ratio was
902 females per 1,000 males. It was 1029 in 1971 and 1013 in 1981. This decrease in the ratio
is explained by the return of migrated male ones back to the village with substantial
improvement in both the social and economic conditions of the village.
The level of literacy has gone up from 30.4% in 1971 to 39.65% in 1981, and further increased
to 50.95% in 1991. As of now, according to the villagers, everyone in 15 to 35 age group is
educated or at least not an illiterate. At present, the literacy rate is estimated to be 65 %, which
is well above the national average rate of 52%.
METHODOLOGY AND RESULTS OF WATER HARVESTING STUDIES:
Structures were created to save every drop of water by using simple and effective technology.
A voluntary labour system called 'shramdan' was used for this project. They constructed the
nala bunds to increase the water levels, successfully as the first step. The villagers also cleared
the silt and renovated the tanks. Due to the constant percolation of water, the groundwater table
started rising. For soil conservation and to save water by checking the run off, gully plugs and
contour trenches were built on the hill slopes. This process was further augmented through
afforestation, underground check dams and cemented bandhras built at strategic locations. As
a result, Irrigation potential in the village increased from 0.5 % in 1975 to 70 % in 1985.
Government schemes were utilised to plant 300,000 trees in and surrounding the village. So
now, this sustainable model developed is capable of dealing with recurrent drought. Now, water
is also available in summer. Because of the increased supply of irrigation water, land that was
lying bare was now used for farming and the total area under cultivation has increased from
630 hectares to 1500 hectares. The average yields of the crops has also increased substantially.
As per the recent estimate, 48 nala bunds, 5 cement check dams and 16 Gabion structures are
constructed. This water management model resulted has increased the availability of
groundwater and has facilitated for the construction of community wells. More than 25% of
the households earn nearly 5 lakhs per year. As per the Indian standards, Ralegan Siddhi is
considered a rich village now with an increase in per capita income of households.
Rainwater Harvesting In Urban Areas
CHARACTERISTICS OF URBAN WATER DEMAND
The high population density and sheer number of residents lead to a huge demand for water in
urban areas, exceeding the water available within geographical limits. Moreover, the demand
pattern is highly skewed, with the well-off accessing more water than the poor who have to
make do with very little, mainly from public tanks and hand pumps. Thus the demand is highly
concentrated and much of it goes unmet.
SOURCES OF WATER IN URBAN AREAS
There is a great demand for perennial sources that can provide uninterrupted supply of water
to cities. For this reason, rivers, lakes, tanks and underground aquifers are the primary sources.
For example, Bengaluru relies on lakes and tanks in and around the city, while Chennai now
relies mainly on the Veeranam Lake 235 km away. Delhi is dependent on the Yamuna River,
while Thiruvanathapuram depends on the Aruvikkara reservoir on the Karamana River.
USES OF WATER IN URBAN AREAS
The various purposes for which water is used in urban areas include:
• Domestic or household
• Non-domestic or commercial/tertiary sector
• Industrial (small and large scale factories)
• Recreational, such as boating, fishing and water sports
• Environmental, such as maintenance of micro climate
• Agricultural such as parks, household cultivation etc.
COST OF WATER
Water is heavily subsidized in urban areas of India. Higher income group has more access to
water connections. So the rich are subsidized while poor make do with public stand posts and
hand pumps. True cost of water must include not only the capital cost and the operation and
maintenance cost of supplying water, but also the opportunity cost (the cost of forgoing a better/
higher paying use of the water), economic externalities (the positive or negative side-effects
associated with the consumption of water), the environmental externalities (cost associated
with public health and ecosystem maintenance) and the social cost.
In order to estimate the true cost of water, a water audit must be conducted which consists of
the following steps:
• Water use inventory
• Metering
• Review maintenance practices
• Water efficiency plan
• Implementation and follow up
NEED FOR RAINWATER HARVESTING IN URBAN AREAS
• Supplements traditional sources
• Urban flood mitigation
• Artificial recharge of depleting ground water sources
• Restoring lakes and other water bodies
CASE STUDY: RWH IN BANGALORE CITY
Features of the city
The city is located 920m above sea level. So all rain-water flows out of the city, with no surface
flow into the city. There were over 270 lakes and tanks in 1972, but less than 80 now. Two
major river sources are being resorted to- Kaveri and Arkavathy. Kaveri is 95km away and
500m below city, which implies huge pumping costs. Large section of population dependent
on bore wells (around 1 lakh).
Average rainfall is 970 mm across 59 days from April to November. Rainfall is well distributed
and bi-modal with peaks in April-May and September-October. Rainfall intensity is less than
50 mm per hour. Generally, roofs are flat and accessible. Up to 20% of requirement can be met
through rooftop harvesting.
DOMESTIC ROOFTOP RWH IN BANGALORE
Features necessary to install rooftop system:
Install
First Rain
Slope Roof Gutters and Filter Storage Recharge
Separator
Down-pipes
The study covers a house under construction in a suburb called Vidyaranyapura. Water supply
lines have not yet reached the locality.
The house has installed a sump with capacity of 8000L. Overflow from sump leads to a storm-
water drain. For ground area, slopes lead water to percolation pit. Estimated to harvest 115,700
L of rain water of which 32,400L to be recharged. Cost incurred was Rs 4000.
COST SAVING FROM DOMESTIC ROOFTOP RWH
• Cost of installing roof-top RWH system (adjunct to existing structure) – Rs 4000-6000
• Generation capacity – 80 kilo-litres per year
• Assuming 20 year life period
• cost works out to Rs 4/kL
• City supplies at Rs 15/kL
Cost of installing an exclusive RWH system
Storage at Rs 2.5/L 6000*2.5= 15000/-
Pipes to lead to storage tank 1500/-
Pump to place water in overhead tank 2500/-
Pipeline for pump 2000/-
Labour 2000/-
Total Rs 23000/-
Generation capacity – 70 kilo-litres per year
Assuming 20 year life period cost works out to Rs 16.5/kL
City supplies at Rs 15/kL, but marginal cost of production is Rs 45/kL
CHEMICAL ENGG DEPT OF IISc
Similar rooftop system with a sump capacity of 30000 L is estimated to harvest 377,000 L of
rain water. This results in a savings of Rs 22,650/year. The cost incurred is Rs 11000
NARASIPURA RWH SCHEME
Colony of 4 sq km area. RWH incorporated more by serendipity than design. wo tanks in
Narasipura 1 and Narasipura 2 collect rain water and act as percolation pits. This recharges 15
bore-wells in the area which supply water to 3000 houses. Sewage collected from each house
is treated physically and biologically and led to the tank in Narasipura 2. Thus, the area has a
decentralized system where the loop of water supply and sewage treatment in completed in a
small geographical area, economically and in an ecologically sustainable manner.
INDUSTRIAL UNIT OF ESCORTS-MAHLE-GOETZE
New Approaches to Rain Water Harvesting
With the technological advancement, new approaches to rainwater harvesting are getting
discovered.
Two of them are:-
1) Rainsaucer
2) Groasis Waterboxxx
1) Rainsaucer
Rainsaucer is a product of Rainsaucers
Inc., a US based company that believes in
producing simple RWH solutions with
extreme affordability. It comprises of a
fabric (that acts as a catchment for
rainwater) and drums. The fabric is made
of polyethylene, which reduces the
chances of contamination of rain water
compared to rooftop rain water catchment.
Its implementation in the town of
Quetzaltenango, Guatemala helped in
reducing the residents’ dependency on
bottled water. Rainsaucers is now trying to
implement this product in India.
2) Groasis Waterboxxx
Waterboxxx is a product of Groasis, a
Netherlands based organisation.
Rainwater is collected through dish which
acts as a catchment, and then the water
passes into the chamber. It saves more
water than drip irrigation as the chamber
prevents the water from evaporating. It
contains a wick through which the water
stored in the chamber gets dripped into the
soil. The capillary system through which
water flows into the soil also remains
intact with this system.
Challenges to Rain Water Harvesting
There are many challenges to rain water harvesting. Some of them are-
1) Water Quality: The quality of water collected through rain water harvesting is not pure
enough to be considered as potable drinking water. With increasing levels of pollution in
the air, the rain water is also getting affected drastically.
2) Technical Issues: Installing a rain water harvesting system can be a challenge, especially
in urban areas where technical knowhow is required. There might be cost overheads and the
system installed may become inefficient.
3) Policy Issues: A state-wide policy and guidelines are required in order to make rain water
harvesting a success. Without proper guidelines, like design specifications of water tank,
pipes etc people will end up building improper systems for harvesting rain water.
4) Managerial Issues: Without sense of ownership rain water harvesting systems will not be
sustainable. Commitment of people must be paramount. Proper maintenance of the system
is required in order to reduce contamination of water collected and also to keep the system
efficient.
5) Climate Change: Climate changes pose a real threat to the rain water harvesting systems.
Without rain these systems (on which large money are invested) are doomed to be a failure.
Conclusion:
Efficient RWH will be achieved once all the stakeholders within the society work towards it.
References
1) http://www.facilitiesnet.com/green/article/Steps-in-a-Water-Audit--9364?source=next
2) http://www.rainwaterclub.org/docs/R.W.H.industries.urban.pdf
3) http://www.rainwaterharvesting.org/Solution/History_tour0.htm
4) http://blog.shunya.net/shunyas_blog/2008/08/dholavira-a-har.html
5) http://www.rainsaucer.com/
6) https://www.groasis.com/en
7) http://www.rainwaterharvesting.org/rural/Ralegan.htm
8) http://eng.warwick.ac.uk/ircsa/pdf/10th/5_13.pdf
