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Water resources

2007 Schools Wikipedia Selection. Related subjects: Geology and geophysics

   Water resources are sources of water that are useful or potentially
   useful to humans. It is important because it is needed for life to
   exist. Many uses of water include agricultural, industrial, household,
   recreational and environmental activities. Virtually all of these human
   uses require fresh water. Only 2.5% of water on the Earth is fresh
   water, and over two thirds of this is frozen in glaciers and polar ice
   caps. Water demand already exceeds supply in many parts of the world,
   and many more areas are expected to experience this imbalance in the
   near future. The framework for allocating water resources to water
   users (where such a framework exists) is known as water rights.

Water and conflict

   Throughout history, water resources have occasionally been the source
   of conflict. Examples include:
     * Well poisoning
     * Privatization and Water Pricing in India ,
     * Privatization and Water Pricing protests in Cochabamba, Bolivia in
       2000

   Nevertheless, some claim that the issue does not get the attention it
   deserves, in particular with regard to security.

Threats to fresh water

   There are many things that are a threat to the Earths fresh water
   supply. Here are a few of them.

Climate change

   Climate change will have significant impacts on water resources around
   the world because of the close connections between the climate and
   hydrologic cycle. Rising temperatures will increase evaporation and
   lead to increases in precipitation, though there will be regional
   variations in rainfall. Overall, the global supply of freshwater will
   increase. Both droughts and floods may become more frequent in
   different regions at different times, and dramatic changes in snowfall
   and snowmelt are expected in mountainous areas. Higher temperatures
   will also affect water quality in ways that are not well understood.
   Possible impacts include increased eutrophication. Climate change could
   also mean an increase in demand for farm irrigation, garden sprinklers,
   and perhaps even swimming pools.

Depletion of aquifers

   Since competition for water is growing, underground aquifers are
   becoming depleted. This is mainly due to irrigation by groundwater.
   Millions of small pumps are currently taking water out of aquifers to
   irrigate crops. Irrigation in dry areas such as India is supplied by
   groundwater.

Pollution and water protection

   Polluted Water
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   Polluted Water

   Water pollution is one of the many concerns of the world today. World
   governments have strived to find solutions to eliminate this problem.
   Many programs strive to protect our water resources. They are usually
   funded by donations from generous people.

Uses of fresh water

   Uses of fresh water can be categorized as consumptive and
   non-consumptive (sometimes called "renewable"). A use of water is
   consumptive if that water is not immediately available for another use.
   Losses to sub-surface seepage and evaporation are considered
   consumptive, as is water incorporated into a product (such as farm
   produce). Water that can be treated and returned as surface water, such
   as sewage, is generally considered non-consumptive if that water can be
   put to additional use.

Agricultural

   A farm in Ontario
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   A farm in Ontario

   It is estimated that 70% of world-wide water use is for irrigation. In
   some areas of the world irrigation is necessary to grow any crop at
   all, in other areas it permits more profitable crops to be grown or
   enhances crop yield. Various irrigation methods involve different
   trade-offs between crop yield, water consumption and capital cost of
   equipment and structures. Irrigation methods such as most furrow and
   overhead sprinkler irrigation are usually less expensive but also less
   efficient, because much of the water evaporates or runs off. More
   efficient irrigation methods include drip or trickle irrigation, surge
   irrigation, and some types of sprinkler systems where the sprinklers
   are operated near ground level. These types of systems, while more
   expensive, can minimize runoff and evaporation. Any system that is
   improperly managed can be wasteful. Another trade-off that is often
   insufficiently considered is salinization of sub-surface water.

   Aquaculture is a small but growing agricultural use of water.
   Freshwater commercial fisheries may also be considered as agricultural
   uses of water, but have generally been assigned a lower priority than
   irrigation (see Aral Sea and Pyramid Lake).

   As global populations grow, and as demand for food increases in a world
   with a fixed water supply, there are efforts underway to learn how to
   produce more food with less water, through improvements in irrigation
   methods and technologies, agricultural water management, crop types,
   and water monitoring.

Industrial

   A power plant in Poland
   Enlarge
   A power plant in Poland

   It is estimated that 15% of world-wide water use is industrial. Major
   industrial users include power plants, which use water for cooling or
   as a power source (i.e. hydroelectric plants), ore and oil refineries,
   which use water in chemical processes, and manufacturing plants, which
   use water as a solvent.

   The portion of industrial water usage that is consumptive varies
   widely, but as a whole is lower than agricultural use.

Household

   Drinking water
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   Drinking water

   It is estimated that 15% of world-wide water use is for household
   purposes. These include drinking water, bathing, cooking, sanitation,
   and gardening. Basic household water requirements have been estimated
   by Peter Gleick at around 50 liters per person per day, excluding water
   for gardens.

   Most household water is treated and returned to surface water systems,
   with the exception of water used for landscapes. Household water use is
   therefore less consumptive than agricultural or industrial uses.

Recreation

   Whitewater rapids
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   Whitewater rapids

   Water has a lot of recreational value.

   Recreational water use is a very small but growing percentage of total
   water use. Recreational water use is mostly tied to reservoirs. If a
   reservoir is kept fuller than it would otherwise be for recreation,
   then the water retained could be categorized as recreational usage.
   Release of water from a few reservoirs is also timed to enhance
   whitewater boating, which also could be considered a recreational
   usage. Other examples are anglers, water skiers, nature enthusiasts and
   swimmers.

   Recreational usage is non-consumptive. However it may reduce the
   availability of water for other users at specific times and places. For
   example, water retained in a reservoir to allow boating in the late
   summer is not available to farmers during the spring planting season.
   Water released for whitewater rafting may not be available for
   hydroelectric generation during the time of peak electrical demand.

Environmental

   A natural wetland
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   A natural wetland

   Explicit environmental water use is also a very small but growing
   percentage of total water use. Environmental water usage includes
   artificial wetlands, artificial lakes intended to create wildlife
   habitat, fish ladders around dams, and water releases from reservoirs
   timed to help fish spawn.

   Like recreational usage, environmental usage is non-consumptive but may
   reduce the availability of water for other users at specific times and
   places. For example, water release from a reservoir to help fish spawn
   may not be available to farms upstream.

World water supply and distribution

   Projected water distribution in 2025
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   Projected water distribution in 2025

   Food and water are two basic human needs. As the picture shows, in
   2025, water shortages will be more prevalent among poorer countries
   where resources are limited and population growth is rapid, such as the
   Middle East, Africa, and parts of Asia. By 2025, large urban and
   peri-urban areas will require new infrastructure to provide safe water
   and adequate sanitation. This suggests growing conflicts with
   agricultural water users, who currently consume the majority of the
   water used by humans.

   Generally speaking the more developed countries of North America,
   Europe and Russia will not see a serious threat to water supply by the
   year 2025, not only because of their relative wealth, but more
   importantly their populations will be better aligned with available
   water resources. North Africa, the Middle East, South Africa and
   northern China will face very severe water shortages due to physical
   scarcity and a condition of overpopulation relative to their carrying
   capacity with respect to water supply. Most of South America,
   Sub-Saharan Africa, Southern China and India will face water supply
   shortages by 2025; for these latter regions the causes of scarcity will
   be economic constraints to developing safe drinking water, as well as
   excessive population growth.
   Retrieved from " http://en.wikipedia.org/wiki/Water_resources"
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   with only minor checks and changes (see www.wikipedia.org for details
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