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A
Lesson
There was a thirsty crow. It peered into an earthen pitcher. There
was water at the bottom. "Dregs," it cawed alarmed. But
it was thirsty. It began to drop pebbles into the pitcher. Drop by
drop, the water rose to the top. The crow drank and flew away sated.
It could have used a pneumatic drill to smash through to the water.
It didn't.
This water harvester of a crow could teach us a thing or two.
The water arithmetic.
We stare at the dregs of our ingenuity, at a resource scientifically
misutilised. We are cawing alarmed. But we only keep cawing, raucously
at that. Lets get on, like the crow. Fashion a pebble-by-pebble approach
to meet our needs.
First recognise that the source
of all water on earth is not the river, is not the underground aquifer,
is not the lake, well or stream. Rain is the source of all water.
Second, recognise that in India the monsoon is a deluge.
Rain spatters the earth. Fills ponds. Lakes brim. Rivers heave. But
the monsoon is also brief. We receive most of its rainfall in just
100 hours out of 8,760 hours in a year. But this is enough to meet
our water needs, provide food security and eradicate rural poverty.
Water Balance
in India
According to a study, India receives 400 million hectare meters
(mham) of rain and snowfall. Another 20 mham flow in as surface
water from outside the country. This total 420 mham provide
the country with river flows of 180 mham. Another 67 mham is
available as groundwater. About 173 mham is lost as evaporation
or becomes soil moisture - which can be captured directly as
rainwater or as runoff from small catchments in and near villages
or towns. If even 20 - 3- mham can be captured through rainwater
harvesting, tremendous pressure can greatly extend the availability
of clean water. Why is Cherrapunji today short of drinking water
when it gets more than 11 meters of rainfall annually? Simply
because it does not capture the rain that falls over it. |
Third, recognise the rainwater
needs to be harvested through capturing, storing and recharging it
and later using it during prolonged parched periods. The key component
of water management is 'storage' especially in India. Small means
even more water. Michael Evenari, an Israeli scientist's study clearly
demonstrates that ten dams with one hectare catchment will store more
water than one dam of ten hectare. Several other studies conducted
by the Central Soil and Water Conservation Research Institute in different
parts of the country revealed similar results.
Any land can be used to harvest rainwater. (See
potential) In tune with the terrain, with nothing imposed. It
is just a matter of using material locally abundant - stones, mud,
bamboo etc.
The hidden link: The
most beautiful thing about water harvesting is that there is a human-rain-land
synergy. What the table shows clearly is that rainwater harvesting
is possible in all human-land-rain scenarios.
Synergies exist between rainfall, human population density and
land availability
|
Region
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Annual level of rainfall
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Rain yield potential from
one hectare of land (*)
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Human population density
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Land availability for water
harvesting
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Surface quality for water
collection efficiency
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Number of people whose water
needs can be met at 100 litres per person per day from one
hectare of land
|
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Rural-arid
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100 mm
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1 million litres
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Low
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High
|
-
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27
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Rural-humid
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2,000 mm
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20 million litres
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High
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Low
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-
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553
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Urban
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-
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-
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Very high
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Very low
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More rooftops and built-up surfaces available
with high runoff
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(*)Assuming rainwater collection efficiency of 100 per cent
Water is what we make of it. COLLECTIVELY,
promoting environmental self-reliance.
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