Alternate thoughts on rainwater harvesting

ALTERNATE THOUGHTS ON RAINWATER ON RAINWATER

HARVESTING

D K Singhal July 2016

Rainwater Harvesting2

� In today’s time of depleting ground water level,

availability of less and less water, RWH appears as availability 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, RWH � For buildings having a bigger rooftop area, RWH

installation is mandatory.

Alternate Thoughts on Raiwater Harvesting, July 2016

So, Why Alternate Thoughts3

� 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.



� 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.)



� If you recharge this water to the ground, yes; you

may recover maximum volume of rainwater; but may 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 or � If 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 Residents7

� If you consider water requirement by a person to

be around 150 liters, all the residents need around be 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 Gains8

� 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 Thoughts9

� A typical RWH system is in working condition for

365 days, 24 yours but is able to do its work only 365 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 Thoughts10

� If we are, somehow, able to increase recharge to

groundwater (as being done by RWH) by 100 groundwater (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 Harvesting11

� 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 River12

� 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 Sea13

� 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?


Harvesting14

� The river water harvesting is simple. Just install a

pump to withdraw river water, followed by a pump 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 these available for this purpose, and we may run these

RiWaH systems for 10 months a year (excluding

summers with reduced water in rivers).


Advantages15

� 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.


Byproducts16

� The clarifier sediments (sand) can be used for

construction purposes.construction purposes.


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Think.


Thank You.

� If you agree with this thought, please do share it with others.

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with others.

� Maybe, together, we are able to maintain our groundwater levels at affordable cost.

D K [email protected]


Alternate thoughts on rainwater harvesting

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