This great information is from what I consider to be a valuable email_interview with
Kevin Byrne
3.4. Increasing pressure on water resources
3.4.1. Population growth
The world population increases at a rate of some 211,000 people each
day, with estimates showing a 50% increase to 9.3 billion by 2050,
with the greatest increases occurring in urban areas.[1] This is an
obvious challenge to achieving universal drinking water and
sanitation coverage. Not only must services cope with all those
currently lacking access, but in addition, development must keep up
with a huge demographic growth.
3.4.2. Agricultural practice
Whilst most agriculture is rain fed, in developing countries,
irrigated land accounts for about one fifth of the total arable land.
Irrigation accounts for approximately 70% of all water withdrawals.
This is predicted to increase by 14% over the next 30 years, with the
expansion of irrigated land by a further 20%.
We are globally reliant on food crops produced via irrigation. In
1998, in developing countries, two fifths of all crops were produced
on irrigated land. There is a strong positive relationship between
investment in irrigation and poverty alleviation. In India, for
example, 69% of people in non-irrigated areas are categorised as
poor, whereas this falls to 26% in irrigated areas.[2]
However, of the 93 developing countries surveyed by the FAO, 10 are
already using 40% of their renewable freshwater for irrigation.[3]
Between 15-35% of irrigation withdrawals are estimated to be
unsustainable, with water “overdrafts” occurring in both
developing and developed nations.[4]
3.4.3. Economic growth
Humans can survive on just two litres of drinking water per day,
which is less than one cubic metre per year. Increasing sanitation
requirements and lifestyle demands result in a much greater water
“footprint” – in general, the wealthier the country, the larger
the per capita water “footprint”. The average person in Mali, for
example, uses 4 cubic metres per year, compared to 215 in the USA.
Global annual water use by industry is expected to rise from an
estimated 725 cubic kilometres per annum in 1995, to 1,170 cubic
kilometres per annum in 2025 – increasing the proportion of water
used by industry from 22% to 24%.[5]
As countries develop, so their domestic and industrial water demands
increase.
3.4.4. Pollution
A growing population, intensification of agriculture and
industrialisation all potentially increase the pollution burden of
fresh water systems. Some of the main types of pollution include:
organic matter, acidification and heavy metals from industry and
domestic sewerage; and nutrients, salinisation and sedimentation from
agricultural runoff. Pollution further reduces the water available
for human and agricultural use and carries a high environmental cost.
3.4.5. Water stress
Water stress results from an imbalance between the demands of water
use and available water resources.
Water stress indices can be calculated based on the ratio of total
water use to renewable water supply (from streams, rivers and shallow
groundwater). Areas where water use is equal to or in excess of 40%
of the renewable water resources, are considered to be in relative
water stress.[6] This is likely to result in severe restrictions to
both economic development and human health.
There are four ways in which people contribute to water stress:
Excessive withdrawal from surface waters e.g. as a result of river
diversion for irrigation, the Aral sea has shrunk to less than half
its original size in just 30 years with the additional effect of
doubling its salt concentration;[7]
Excessive withdrawal of water from underground aquifers e.g.
excessive fresh water extraction along the west coast of India has
caused sea water to enter aquifers rendering it unfit for human use;
Pollution of fresh water resources – this may render them unusable
without incurring high clean up costs;
Inefficient use of fresh water – leaking systems, wasteful
irrigation or industrial practice and excessive consumption can all
contribute.
3.4.1. Population growth
The world population increases at a rate of some 211,000 people each
day, with estimates showing a 50% increase to 9.3 billion by 2050,
with the greatest increases occurring in urban areas.[1] This is an
obvious challenge to achieving universal drinking water and
sanitation coverage. Not only must services cope with all those
currently lacking access, but in addition, development must keep up
with a huge demographic growth.
3.4.2. Agricultural practice
Whilst most agriculture is rain fed, in developing countries,
irrigated land accounts for about one fifth of the total arable land.
Irrigation accounts for approximately 70% of all water withdrawals.
This is predicted to increase by 14% over the next 30 years, with the
expansion of irrigated land by a further 20%.
We are globally reliant on food crops produced via irrigation. In
1998, in developing countries, two fifths of all crops were produced
on irrigated land. There is a strong positive relationship between
investment in irrigation and poverty alleviation. In India, for
example, 69% of people in non-irrigated areas are categorised as
poor, whereas this falls to 26% in irrigated areas.[2]
However, of the 93 developing countries surveyed by the FAO, 10 are
already using 40% of their renewable freshwater for irrigation.[3]
Between 15-35% of irrigation withdrawals are estimated to be
unsustainable, with water “overdrafts” occurring in both
developing and developed nations.[4]
3.4.3. Economic growth
Humans can survive on just two litres of drinking water per day,
which is less than one cubic metre per year. Increasing sanitation
requirements and lifestyle demands result in a much greater water
“footprint” – in general, the wealthier the country, the larger
the per capita water “footprint”. The average person in Mali, for
example, uses 4 cubic metres per year, compared to 215 in the USA.
Global annual water use by industry is expected to rise from an
estimated 725 cubic kilometres per annum in 1995, to 1,170 cubic
kilometres per annum in 2025 – increasing the proportion of water
used by industry from 22% to 24%.[5]
As countries develop, so their domestic and industrial water demands
increase.
3.4.4. Pollution
A growing population, intensification of agriculture and
industrialisation all potentially increase the pollution burden of
fresh water systems. Some of the main types of pollution include:
organic matter, acidification and heavy metals from industry and
domestic sewerage; and nutrients, salinisation and sedimentation from
agricultural runoff. Pollution further reduces the water available
for human and agricultural use and carries a high environmental cost.
3.4.5. Water stress
Water stress results from an imbalance between the demands of water
use and available water resources.
Water stress indices can be calculated based on the ratio of total
water use to renewable water supply (from streams, rivers and shallow
groundwater). Areas where water use is equal to or in excess of 40%
of the renewable water resources, are considered to be in relative
water stress.[6] This is likely to result in severe restrictions to
both economic development and human health.
There are four ways in which people contribute to water stress:
Excessive withdrawal from surface waters e.g. as a result of river
diversion for irrigation, the Aral sea has shrunk to less than half
its original size in just 30 years with the additional effect of
doubling its salt concentration;[7]
Excessive withdrawal of water from underground aquifers e.g.
excessive fresh water extraction along the west coast of India has
caused sea water to enter aquifers rendering it unfit for human use;
Pollution of fresh water resources – this may render them unusable
without incurring high clean up costs;
Inefficient use of fresh water – leaking systems, wasteful
irrigation or industrial practice and excessive consumption can all
contribute.
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