Alternate thoughts on rainwater harvesting

ALTERNATE THOUGHTS
ON RAINWATERON RAINWATER
HARVESTING
D K Singhal July 2016

Rainwater Harvesting
2
In today’s time of depleting ground water level,
availability of less and less water, RWH appears asavailability of less and less water, RWH appears as
a potential solution.
Many environmentally cautious people have
already installed RWH systems in their houses,
offices and other buildings.
For buildings having a bigger rooftop area, RWHFor buildings having a bigger rooftop area, RWH
installation is mandatory.
Alternate Thoughts on Raiwater Harvesting, July 2016

So, Why Alternate Thoughts
3
Today, we see a lot of installations, though many
more need to be installed.more need to be installed.
Still, one is unable to understand the true cost of
water recovered.
Let us imagine a hypothetical case.
There is a three story building built in 400 m2 area,
with a rooftop area of 250m2, occupying 12
families with an average family size of 4.

4
The annual rainfall in the area is 800mm.
The residents have installed a RWH system.The residents have installed a RWH system.
Now, if there is a rainfall of say 20 or 30mm in a
day, first 2-4mm rainfall is absorbed by the roof.
In case there is a rainfall of more than 80mm in a
day, all of the rainwater quantity (20KL) cannot be
stored easily if you are using this water directly.
(You need very high storage volume and capital cost.)

5
If you recharge this water to the ground, yes; you
may recover maximum volume of rainwater; butmay recover maximum volume of rainwater; but
that means a boring in the ground having a suitable
capacity thus costing a lot of money.

How Much Water do You Get?
6
Anyway, the basic point, here is something else.
If we consider we are able to collect and reuse orIf we consider we are able to collect and reuse or
recharge 50% of the total rainwater, the collected
quantity will be around 100,000 liters.

Water Demand by the Residents
7
If you consider water requirement by a person to
be around 150 liters, all the residents need aroundbe around 150 liters, all the residents need around
7000 liter water.
So water recharge (to ground) will compensate just
15 days or 4% of their water demand.
In case of high rise buildings with more number of
occupants, this figure would be much less.occupants, this figure would be much less.
In case, they do not recharge the groundwater and
use this directly, the figures would be much lesser.

Huge Investments, Little Gains
8
Over the past couple of decades, there have been
many RWH installations.many RWH installations.
But, if we consider any city, have we quantified
percentage of houses with RWH?
Guess what could be this figure? 1%, 2%, 5%?
We are working towards RWH aggressively for
past decade, but why there exists so little
installation base?

Alternate Thoughts
9
A typical RWH system is in working condition for
365 days, 24 yours but is able to do its work only365 days, 24 yours but is able to do its work only
50-80 hours a year (during rainfall).
For the remaining period of time, it remains idle.
Does that mean its uptime is less than 1%.
Can we do something else to get better uptime?

Alternate Thoughts
10
If we are, somehow, able to increase recharge to
groundwater (as being done by RWH) by 100groundwater (as being done by RWH) by 100
times, probably we’d be able to maintain
groundwater levels.
How can this be done?

Think River Water Harvesting
11
River water harvesting uses a part of water flowing
in the rivers to recharge the ground water.in the rivers to recharge the ground water.
Since decades, rivers have been used to supply
water for mankind.
But, river water harvesting is something unusual.

A River
12
A river originates from mountains and carries a lot
of water.of water.
A part of water from the river is taken off through
canals etc., and is supplied to agricultural fields for
irrigation.
Some water is also taken off from it for industrial
and domestic purposes.and domestic purposes.
Remaining water goes to sea.

River Water to Sea
13
Unutilized river water, which goes to the sea is
actually the unused river water.actually the unused river water.
Generally the river water is much cleaner and
usable compared to sea water.
By not utilizing the river water, are we not
wasting this clean, usable form of water?

Harvesting
14
The river water harvesting is simple. Just install a
pump to withdraw river water, followed by apump to withdraw river water, followed by a
clarifier to settle down settleable solids present,
and have few recharge wells where the clarified
water is recharged to ground.
Water from most of the rivers is continuously
available for this purpose, and we may run theseavailable for this purpose, and we may run these
RiWaH systems for 10 months a year (excluding
summers with reduced water in rivers).

Advantages
15
Every year, we hear news about draught.
Every year, we hear news about floods.Every year, we hear news about floods.
By this we attack the problem in two directions-
“Maintaining the groundwater level” and
“Underground linking of the rivers.”
If we are able to divert a significant fraction of
river’s unused water going to sea for groundwater
recharging, both problems may be reduced
drastically.

Byproducts
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The clarifier sediments (sand) can be used for
construction purposes.construction purposes.

17
Think.

Thank You.
If you agree with this thought, please do share it
with others.
18
with others.
Maybe, together, we are able to maintain our
groundwater levels at affordable cost.
D K Singhal
deveshksinghal@gmail.com

Alternate thoughts on rainwater harvesting

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