Detailed case study of the water conservation measures undertaken by Sai Poorna Paradise Apartments.

1. Water Management at Sai Poorna Paradise Apartments
1.0 Introduction
Sai Poorna Paradise, situated in HSR Layout, southeastern Bengaluru, is an apartment
complex surrounded by the Begur, Somasandra, and Agara lakes. It was established in 2008
and consists of two blocks (A and B) with a total of 88 flats, out of which 80 are currently
occupied. The apartment is home to 192 residents. The community does not have a Cauvery
water connection, so they primarily relied on water tankers for their water needs.
In an effort to enhance water resource management, the Residents Welfare Association
(RWA) undertook measures on both the supply and demand fronts. These measures
included the implementation of rainwater harvesting and individual household metering.
These initiatives have substantially reduced the apartment's reliance on water tankers. This
report details the water management practices in Sai Poorna Paradise Apartments.
Map location of Sai Poorna Paradise Apartments
2.0 Water Demand
The apartment complex requires about 50,000 - 55,000 litres of fresh water a day, and the
per-person water consumption is around 250-300 litres a day.
3.0 Sources of Water Supply
3.1 Cauvery Water Supply
Sai Poorna Apartments opted against obtaining a BWSSB (Bengaluru Water Supply and
Sewerage Board) Cauvery water connection due to the steep sum required as a deposit.
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2. Instead, The association has chosen to enhance water supply through alternative initiatives.
These include
3.2 Borewells
Each block has two operational borewells drilled in 2005, with depths of 980ft and 990ft,
respectively. Over time, the borewell yield began declining, leading to a rise in the
apartment's reliance on tanker water from 2017 onward.
3.3 Water Tankers
Starting in 2017, the apartment complex heavily relied on water tankers as its main water
source. On a daily basis, approximately 11-13 water tankers were procured for a span of eight
months, from November to June. Each tanker had a capacity of 5000 litres and came at a
cost ranging from Rs.550 to Rs.600. As a result, Sai Poorna Paradise incurred an annual
expenditure of approximately Rs.16-18 lakhs for water tanker services.
4.0 Rainwater Harvesting
Between 2017 and 2018, Sai Poorna Paradise successfully implemented rainwater harvesting.
This involved utilising the apartment's expansive rooftop area measuring 2,248 square
metres. The harvested rainwater serves a dual purpose: recharging groundwater and being
stored for subsequent use within the premises.
4.1 Rainwater Harvesting Potential
The estimation involves calculating the annual volume of rainwater that can be collected
from rooftop surfaces and surface runoff. This calculation assumes a runoff coefficient of 0.7
for paved areas and 0.9 for rooftops.
The following table represents the rainwater harvesting potential of Sai Poorna Paradise:
Rainwater Harvesting Potential
Type of
catchment Area (sqm)
Runoff
coefficient
Runoff generated
at 30mm rainfall
(in KL)
Annual runoff at
974.5mm rainfall
(in KL)
Rooftop area 4064.5 0.9 109.74 3564.77
Paved area 10099.4 0.7 212.09 6889.35
Rooftop
area+paved area
runoffs 14163.9 1.6 321.82 10454.08
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3. The rainwater harvesting potential calculations indicate that Sai Poorna Apartments have
the potential to harvest 10.45 KL of rainwater annually, of which rooftop harvesting could
notably yield 3.56 KL.
4.2 Rooftop Rainwater Harvesting
Regular rooftop cleaning is conducted to ensure the water’s cleanliness for harvesting. The
initial few mms of rainfall is isolated for each rain event as it may contain leaf litter and other
contaminants. The water, post the separation, undergoes filtration in a rainwater filter and
subsequently passes through an in-pipe sand filter, referred to as the Indore filter. This
innovative filter incorporates jelly stones or crusher chips with sizes ranging from 20mm to
40mm. After filtration, the water is let into the borewells. A portion of the
rooftop-generated rainwater is guided to a sump tank via a controlling valve.
Rainwater filter (left) and the Indore Sand filter (right)
Rooftop rainwater entering the borehole directly (left) and a part of rooftop rainwater
entering the sump tank (right)
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4. 4.3 Recharge of Surface Runoff
Sai Poorna Paradise features a total of four recharge wells designed to manage surface
runoff effectively, excavated in 2018 and 2019 by the builders. These wells, each measuring 5
ft in width, comprise two that are 15 ft deep, and the other two which were initially 5 ft
deep. These pits have since been deepened to 10 ft to allow for increased recharge volume
and strategically situated along the apartment's low-lying gradient to ensure water runs in
their direction.
Recharge wells
4.4 The Impact
The implementation of direct borewell recharge has significantly enhanced borewell yield.
Consequently, the community's reliance on water tankers has diminished, dropping from 11
to 2 tankers over a three-month period (April-June) in a year. This reduction in tanker usage
has resulted in cost savings, bringing down expenses from Rs. 18-20 lakhs to below one lakh
rupees.
Note: As mentioned earlier, the apartment's proximity to lakes, which were typically dry for
most of the year, experienced a transformation due to rejuvenation efforts. The refilled
lakes likely contributed to the improvement in borewell yield, in conjunction with the direct
borewell recharge strategy.
5.0 Water Demand Management
The apartment charges a fee of Rs. 100 per kilolitre (equivalent to 10 paise per litre) for
water usage. The objective of the RWA was to attain complete independence from water
tankers. To achieve this, they introduced individual household metering in the year
2019-2020. Following the installation of these dedicated household meters, the water
demand experienced a 50% decline. That is, the aggregate water demand decreased from a
range of 50,000 to 55,000, down to 27,000 litres per day.
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5. In the words of M Somanna, ex-president of the RWA, “After implementing individual
household metering, residents became conscious about water consumption, and the water
demand reduced drastically.”
6.0 Wastewater Management
Sai Poorna Paradise has a Sewage Treatment Plant (STP) with a capacity of 60,000 litres. The
treatment process involves phases such as solids separation, aeration, decanting, and
storage. During 2019-2020, the STP underwent an upgrade that incorporated silicon diffusers
to enhance aeration efficiency. Prior to the implementation of these diffusers, sludge
removal occurred monthly via trucks. However, the utilisation of silicon diffusers resulted in
nearly negligible sludge generation, lowering both the management and costs required for
sludge removal. The treated wastewater from the STP is used for flushing and gardening.
With the implementation of individual household metering, there was a notable reduction of
50% in the inflow to the STP. This reduction in inflow has also led to a significant decrease in
the operational costs associated with running the STP, including maintenance and electricity
expenses. Previously, the apartment incurred an annual expenditure of Rs 90,000 for STP
operations, which has now been notably reduced to Rs 30,000.
“Save water! Water conservation is a must for future generations; otherwise, we will have to
drink recycled water in the future. Make the best use of rainwater as it's the purest form of
water”
- Mr Somanna, Ex-President of the Resident Welfare Association
7.0 Suggestions
To better the operational ability of the measures put in place, the installation of meters on
the borewells would provide valuable insights into their yield and their behaviour in terms of
recharge and seasonality patterns, allowing for better water management.
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