Next to air, water is the other most important requirements for human life to exist.it is the Nature's free gift to the human race.it is available in various form such as rivers, lakes,streams,etc. The importance of water in human life is so much that the development of any city of he world has practically taken taken place near the some source of water supply.It may further be noted that the water is available in solid,liquid,and gas forms.
Sources of water
Water resources are natural
resources of water that are potentially useful. Uses of water
include agricultural, industrial, household, recreational and environmental activities.
All living things require water to grow and reproduce.
Fresh water is a renewable resource, yet the world's supply
of groundwater is steadily decreasing, with depletion occurring most
prominently in Asia, South America and North America, although it is still
unclear how much natural renewal balances this usage, and whether ecosystems are
threatened.The framework for allocating water resources to water users (where
such a framework exists) is known as water rights.
Surface water
Surface water is water in a river, lake or fresh
water wetland. Surface water is naturally replenished by precipitation and
naturally lost through discharge to the oceans, evaporation, evapotranspiration and groundwater
recharge.
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| surface water |
Although the only natural input to any surface water system is
precipitation within its watershed, the total quantity of water in that
system at any given time is also dependent on many other factors. These factors
include storage capacity in lakes, wetlands and artificial reservoirs, the
permeability of the soil beneath these storage bodies, the runoff characteristics
of the land in the watershed, the timing of the precipitation and local
evaporation rates. All of these factors also affect the proportions of water
loss.
Human activities can have a large and sometimes devastating
impact on these factors. Humans often increase storage capacity by constructing
reservoirs and decrease it by draining wetlands. Humans often increase runoff
quantities and velocities by paving areas and channelizing the stream flow.
The total quantity of water available at any given time is an
important consideration. Some human water users have an intermittent need for
water. For example, many farms require large quantities of water in
the spring, and no water at all in the winter. To supply such a farm with
water, a surface water system may require a large storage capacity to collect
water throughout the year and release it in a short period of time. Other users
have a continuous need for water, such as a power plant that requires
water for cooling. To supply such a power plant with water, a surface water
system only needs enough storage capacity to fill in when average stream flow
is below the power plant's need.
Nevertheless, over the long term the average rate of
precipitation within a watershed is the upper bound for average consumption of
natural surface water from that watershed.
Natural surface water can be augmented by importing surface
water from another watershed through a canal or pipeline. It can
also be artificially augmented from any of the other sources listed here,
however in practice the quantities are negligible. Humans can also cause
surface water to be "lost" (i.e. become unusable) through pollution.
Brazil is estimated to have the largest supply of fresh water in the world, followed by Russia and Canada.
Under
river flow
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| Ground water |
Groundwater
Groundwater is fresh water located in the
subsurface pore space of soil and rocks. It is also water that is flowing within aquifers below the water table. Sometimes it is useful to make a distinction between
groundwater that is closely associated with surface water and deep groundwater
in an aquifer (sometimes called "fossil water").Groundwater can be thought of
in the same terms as surface water: inputs, outputs and storage. The critical
difference is that due to its slow rate of turnover, groundwater storage is
generally much larger (in volume) compared to inputs than it is for surface
water. This difference makes it easy for humans to use groundwater
unsustainably for a long time without severe consequences. Nevertheless, over
the long term the average rate of seepage above a groundwater source is the
upper bound for average consumption of water from that source.
The natural input to groundwater is seepage from surface water.
The natural outputs from groundwater are springs and seepage to the
oceans.
If the surface water source is also subject to substantial evaporation, a groundwater source may become saline. This situation can occur naturally under endorheic bodies of water, or artificially under irrigated farmland. In coastal areas, human use of a groundwater source may cause the direction of seepage to ocean to reverse which can also cause soil salinization. Humans can also cause groundwater to be "lost" (i.e. become unusable) through pollution. Humans can increase the input to a groundwater source by building reservoirs or detention ponds.
Frozen
water
Several schemes have been proposed to make use of icebergs as
a water source, however to date this has only been done for research
purposes. Glacier runoff is considered to be surface water.
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| frozen water |
The Himalayas, which are often called "The Roof of the World", contain some of the most extensive and rough high altitude areas on Earth as well as the greatest area of glaciers and permafrost outside of the poles. Ten of Asia's largest rivers flow from there, and more than a billion people's livelihoods depend on them. To complicate matters, temperatures there are rising more rapidly than the global average. In Nepal, the temperature has risen by 0.6 degrees Celsius over the last decade, whereas globally, the Earth has warmed approximately 0.7 degrees Celsius over the last hundred years.
It is estimated that 70% of worldwide water is used for
irrigation, with 15–35% of irrigation withdrawals being unsustainable. It
takes around 2,000 – 3,000 liters of water to produce enough food to satisfy
one person's daily dietary need. This is a considerable amount, when
compared to that required for drinking, which is between two and five liters.
To produce food for the now over 7 billion people who inhabit the planet today
requires the water that would fill a canal ten meters deep, 100 meters wide and
2100 kilometres long.
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| agriculture use |
An assessment of water management in agriculture sector was conducted in 2007 by the International Water Management Institute in Sri Lanka to see if the world had sufficient water to provide food for its growing population. It assessed the current availability of water for agriculture on a global scale and mapped out locations suffering from water scarcity. It found that a fifth of the world's people, more than 1.2 billion, live in areas of physical water scarcity, where there is not enough water to meet all demands. A further 1.6 billion people live in areas experiencing economic water scarcity, where the lack of investment in water or insufficient human capacity makes it impossible for authorities to satisfy the demand for water. The report found that it would be possible to produce the food required in future, but that continuation of today's food production and environmental trends would lead to crises in many parts of the world. To avoid a global water crisis, farmers will have to strive to increase productivity to meet growing demands for food, while industry and cities find ways to use water more efficiently. 1
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 furrow and overhead sprinkler irrigation
are usually less expensive but are also typically less efficient, because much
of the water evaporates, runs off or drains below the root zone. Other
irrigation methods considered to be more efficient 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, usually offer greater potential to minimize runoff, drainage
and evaporation. Any system that is improperly managed can be wasteful, all
methods have the potential for high efficiencies under suitable conditions,
appropriate irrigation timing and management. Some issues that are often
insufficiently considered are Stalinization of groundwater and contaminant
accumulation leading to water quality declines.
As global populations grow, and as demand for food increases in
a world with a fixed water supply, there are efforts under way 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. 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).
It is estimated that 22% of worldwide water is used in industry. Major
industrial users include hydroelectric dams, thermometric power plants, which use water for cooling, ore and oil
refineries, which use water in chemical processes, and manufacturing
plants, which use water as a solvent. Water withdrawal can be very high
for certain industries, but consumption is generally much lower than that of
agriculture.
Water is used in renewable power generation.
Hydroelectric power derives energy from the force of water flowing downhill,
driving a turbine connected to a generator. This hydroelectricity is a
low-cost, non-polluting, renewable energy source. Significantly, hydroelectric
power can also be used for load following unlike most renewable
energy sources which are intermittent. Ultimately, the energy in a
hydroelectric power plant is supplied by the sun. Heat from the sun evaporates
water, which condenses as rain in higher altitudes and flows downhill. Pumped-storage
hydroelectric plants also exist, which use grid electricity to pump water
uphill when demand is low, and use the stored water to produce electricity when
demand is high.
Hydroelectric power plants generally require the creation of a
large artificial lake. Evaporation from this lake is higher than evaporation
from a river due to the larger surface area exposed to the elements, resulting
in much higher water consumption. The process of driving water through the
turbine and tunnels or pipes also briefly removes this water from the natural
environment, creating water withdrawal. The impact of this withdrawal on
wildlife varies greatly depending on the design of the power plant.
Pressurized water is used in water blasting and water jet
cutters. Also, very high pressure water guns are used for precise cutting. It
works very well, is relatively safe, and is not harmful to the environment. It
is also used in the cooling of machinery to prevent overheating, or prevent saw
blades from overheating. This is generally a very small source of water
consumption relative to other uses.
Domestic
use (household)
It is estimated that 8% of worldwide water use is for domestic
purposes. These include drinking water, bathing, cooking, toilet
flushing, cleaning, laundry and gardening. Basic domestic water
requirements have been estimated by Peter Gleick at around 50 liters
per person per day, excluding water for gardens.
Drinking water is water that is of sufficiently high quality so
that it can be consumed or used without risk of immediate or long term harm.
Such water is commonly called potable water. In most developed countries, the
water supplied to domestic, commerce and industry is all of drinking water
standard even though only a very small proportion is actually consumed or used
in food preparation.
844 million people still lacked even a basic drinking water
service in 2017. Of those, 159 million people worldwide drink water
directly from surface water sources, such as lakes and streams.
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