Top 1. Introduction: pressures on water resources
 See also our Digest on Ecosystem Change
Around the world, human activity and natural forces are reducing
available water resources. Although public awareness of the need to
better manage and protect water has grown over the last decade, economic
criteria and political considerations still tend to drive water policy
at all levels. Science and best practice are rarely given adequate
consideration.
Pressures on water resources are increasing mainly as a result of
human activity – namely urbanisation, population growth, increased
living standards, growing competition for water, and pollution. These
are aggravated by
climate
change and variations in natural conditions.
Still, some progress is being made. More and more, officials are
evaluating water quantity and quality together, and coordinating
management efforts across borders.
More...
Top 2. Where and in what forms is water available on Earth?
The world’s water exists naturally in different forms and locations:
in the air, on the surface, below the ground, and in the oceans.
Freshwater
accounts for only 2.5% of the Earth’s water, and most of it is frozen in
glaciers
and icecaps. The remaining unfrozen freshwater is mainly found as
groundwater,
with only a small fraction present above ground or in the air.
Looking at how water moves through the Earth’s
water
cycle helps us understand how it interacts with the
environment and how much is available for human use.
More...
Precipitation – rain, snow, dew etc. – plays the key
role in renewing water resources and in defining local climatic
conditions and
biodiversity.
Depending on the local conditions, precipitation may feed rivers and
lakes, replenish
groundwater,
or return to the air by evaporation.
More...
Glaciers
store water as snow and ice, releasing varying amounts of
water into local streams depending on the season. But many are shrinking
as a result of
climate
change. River basins are a useful “natural
unit” for the management of water resources and many of them are shared
by more than one country. The largest river basins include the Amazon
and Congo Zaire basins. River flows can vary greatly from one season to
the next and from one climatic region to another. Because lakes store
large amounts of water, they can reduce seasonal differences in how much
water flows in rivers and streams.
Wetlands – including swamps, bogs, marshes, and
lagoons – cover 6% of the worlds land surface and play a key role in
local
ecosystems
and water resources. Many of them have been destroyed, but the remaining
wetlands can still play an important role in preventing floods and
promoting river flows.
More...
Of the
freshwater
which is not frozen, almost all is found below the surface as
groundwater
. Generally of high quality, groundwater is being withdrawn
mostly to supply drinking water and support farming in dry climates. The
resource is considered renewable as long as groundwater is not withdrawn
faster than nature can replenish it, but in many dry regions the
groundwater does not renew itself or only very slowly. Few countries
measure the quality of groundwater or the rate at which it is being
exploited. This makes it difficult to manage.
More...
Top 3. How much freshwater is available in different countries?
The quantity of
freshwater
that is available to a given country, without exceeding the rate at
which it is renewed, can be estimated taking into account the amount of
precipitation, water flows entering and leaving the country, and water
shared with other countries.
The average amount available per person varies from less than 50
m3 per year in parts of the Middle East to over 100 000
m3 per year in humid and sparsely populated areas.
The United Nations has kept a country by country database of such
estimates for several decades.
Though the database has become a common reference tool, it has some
drawbacks. Figures only indicate the maximum theoretical amount
available for a country and may be an overestimation. Moreover, annual
and national averages tend to mask local and seasonal differences.
More...
Top 4. How can human actions seriously affect water resources?
Water resources face a host of serious threats, all caused primarily
by human activity. They include pollution,
climate
change, urban growth, and
landscape
changes such as
deforestation.
Each of them has its own specific impact, usually directly on
ecosystems
and in turn water resources.
More...
If inadequately managed, activities like farming, forest-clearing,
road-building, and mining can lead to too much soil and suspended
particles ending up in rivers (sedimentation). This damages aquatic
ecosystems,
impairs water quality and hinders inland shipping.
More...
Pollution can harm water resources and aquatic
ecosystems.
Major pollutants include for instance organic matter and disease causing
organisms from waste water discharges, fertilisers and
pesticides
running off from agricultural lands,
acid
rain resulting from air pollution, and
heavy
metals released by mining and industrial activities.
More...
The effects of extracting too much water, both from surface waters and
groundwater,
have been dramatic. A striking example is the drastic reduction in size
of the Aral Sea and Lake Chad. Little is being done to address the
causes, which include poor water management practices and
deforestation.
In recent decades, much more water has been extracted from underground
sources. The benefits of withdrawing
groundwater
are often short-lived, while the negative consequences – lower water
levels and depleted resources, for example – can last a long time.
More...
 See also GreenFacts' digest on Climate Change
Climate
change appears to increase existing pressures, for example in
areas already suffering from water shortages. Land and mountain
glaciers
are shrinking more rapidly in recent years. Extreme weather events
stemming from global warming, such as storms and floods, are likely to
become more frequent and severe. However, based on current knowledge,
scientists can only make general predictions about the impact of climate
change on water resources.
More...
Top 5. How can the growing demand for water be met?
 Demand for water is increasing
Meeting a continuous and ever increasing demand for water requires
efforts to compensate for natural variability, and to improve the
quality and quantity available.
More...
Rainwater has been collected for thousands of years
in many parts of the world. Today, this technique is used in Asia to
replenish underground supplies. It is relatively inexpensive and has the
advantage of allowing local communities to develop and maintain the
required structures themselves.
Diverting surface water into the ground can help
reduce losses from evaporation, compensate for variations in flow, and
improve quality. Middle East and Mediterranean regions are applying this
strategy.
Dams and reservoirs have been built to store water
for irrigation and drinking. Moreover dams can provide power and help
control floods, but they can also bring about undesirable social and
environmental impacts.
Transferring water between river basins can also help
alleviate shortages. China, for instance, already has major interbasin
links, and is planning more. The impact of these projects on people and
the environment must be monitored closely.
More...
Wastewater is now reused for different purposes in
many countries, especially in the Middle East, and this practice is
expected to grow. Worldwide, non-potable water is used for irrigation
and industrial cooling. Cities are also turning to water re-use to
supplement drinking water supplies, taking advantage of progress in
water treatment.
More...
Desalinated water – seawater and other salty water
that has been turned into
freshwater
– is used by cities and by industries, especially in the Middle East.
The cost of this technique has dropped sharply, but it relies heavily on
energy from
fossil
fuels and hence raises waste management and
climate
change issues.
More...
Top 6. How could water resources be developed sustainably?
Using water resources
sustainably
is challenging because of the many factors involved, including changes
in climate, the natural variability of the resource, as well as
pressures due to human activity.
At present, most water policy is still driven by short-term economic
and political concerns that do not take into account science and good
stewardship. State-of-the-art solutions and more funding, along with
more data on water resources, are needed especially in developing
nations.
To assess the state of our water resources, we must fully appreciate
the roles of different parts of the
water
cycle – such as rain, meltwater from
glaciers,
and so on. Otherwise, it remains difficult to develop adequate
protection and mitigation strategies.
Poor water quality and unsustainable use of water resources can limit
the economic development of a country, harm health and affect
livelihoods. Hopefully, more
sustainable
practices are starting to be adopted.
More...
When managing water resources, more attention should be paid to
increasing existing natural resources and reducing demand and
losses.
The traditional response to rising demand for water was to store
surface water in reservoirs, divert flow to dry regions and withdraw
groundwater.
Now these methods are increasingly supplemented by water reuse,
desalination and rainfall harvesting. Certain regions are even going to
the extreme of exploiting non-renewable groundwater resources.
Some countries have programs to reduce demand and losses from urban
water distribution systems but more efforts are necessary. However, this
will involve changes in behaviour requiring education and political
commitment. Such efforts to conserve water and reduce demand are not
only useful in regions where water is in short supply, they can also
bring economic benefits in wetter regions.
Decentralised approaches to water resource management that focus on
river basins are increasingly pursued even across borders. Exchanging
information between countries that share river basins will yield both
economic and environmental benefits.
More...
Top 7. Conclusions on water resources
Decentralised approaches to water resource management that focus on
river basins are increasingly pursued even across borders. Exchanging
information between countries that share river basins will yield both
economic and environmental benefits.
It has become evident that:
- Changes in climate are affecting water availability
- Pollution, water diversions and uncertainties about the
abundance of water are threatening economic growth, environment, and
health.
- Underground
water is often being overexploited and polluted.
- To augment water supply, traditional techniques – such as
rainwater collection – are now being supplemented by newer
technologies like desalination and water reuse.
- Political support is needed to improve information collection
that can in turn enable better decision making about the management
and use of water.
More...
© GreenFacts 2008. All rigths reserved. This text is a faithful summary of the
leading scientific consensus report produced in 2006 by the United Nations Educational, Scientific and Cultural Organization (UNESCO):
"The United Nations World Water Development Report" Learn more... | 
