Is
the world running out of water? Not really.The world
water crisis has more to do with managing water resources
badly than with a lack of resources.We need to understand
the nature of water scarcity to take the appropriate
action.Water poverty, or water insecurity, is the
lack of access to safe and affordable water to satisfy
a person's needs for drinking,washing and their livelihoods.
When a large number of people in an area are water
insecure for a significant period of time there is
water scarcity.Water scarcity can be physical, economic
or institutional.We also need to understand how much
water we have.Discussions of water availability tend
to include only the “renewable water resources”
- that is only some 40% of the total rainfall worldwide.The
other 60% is crucial for both food production and
the environment.
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1. |
Nature
of water scarcity: inequitable access contributes
as much, or more, to water poverty as does scarcity
in resources. |
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i.
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Physical
water scarcity, where the resources
cannot satisfy the demands, dominates water
poverty in the arid areas of the Middle East,North
Africa and the dry parts of Asia.
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ii.
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Economic
water scarcity, where lack of
water infrastructure is more important than
the lack of resources, affects the overwhelming
majority of water-poor farmers in Sub-SaharanAfrica |
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and many others
in parts of Asia.
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iii.
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Institutional
water scarcity, where water
resources and infrastructure may be available,
but people are water-poor because they are tail-enders,
or landless farmers, or do not have rights to
land or water, affects poor rural people anywhere,
even in the heart of well-endowed irrigation
systems.
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Projected
Water Scarcity in 2005
Source: IWMI
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| 2. |
The
myopic focus of water resources management on
blue water alone needs to be replaced by an
approach to manage the complete water-cycle,
including green and blue water. |
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i.
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Traditionally,what
is defined as renewable water resources is only
the rainfall that runs off into
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rivers and recharges the groundwater;
this is only 40% of total rainfall - we call this
the blue water.
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ii.
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Sixty percent
of all rainfall never reaches a river or aquifer;
it replenishes the soil moisture and evaporates
from the soil or is transpired by plants - we
call this the green water.
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.
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This
finger diagram gives a visual representation
of the amount of water from rainfall that goes
to different types of water resources and uses,
as discussed in points i and ii above
Source: Comprehensive Assessment
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iii.
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Green water
cannot be piped or drunk, and is therefore safely
ignored by urban water managers. But green water
is crucial to plants, both in ecosystems and
in agriculture, and needs to be managed carefully.
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iv.
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Management
of water for food and environment should take
into account the complete hydrological cycle,
including all rainfall and evapotranspiration,
that is, both green and blue water.
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 |
.
Left
hand photo of a river in Brazil
represents blue water while green
water is represented by the plants
growing in a garden in South Africa
in the right hand photo
Photographs by Sanjini de Silva,
IWMI |
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World
map of Green and Blue water dependence
in food production
Source: Johan Rockstrom |
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v.
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The traditional split between rainfed and irrigated
agriculture has become obsolete. It should be
replaced by water management for agriculture,
accounting for the complete spectrum from pure
rainfed, via rainwater harvesting, to supplemental
or deficit, to full irrigation.
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