water resources

2.  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.
The majority of human uses require fresh water.
 Fresh water is a renewable resource, yet the
world’s supply of groundwater is steadily
decreasing.
 While 67% of Earth’s surface is covered by water,
only less than 2.7% of global water is freshwater.
Most of the freshwater (2.05%) are locked in ice
caps and glaciers. Only 0.65% is available for
human use.

3. Over two thirds of the
earth's surface is
covered with water,
97.2% of which is
contained in the five
oceans. The Antarctic
ice sheet, containing
90% of all fresh water on
the planet, is visible at
the bottom.
Atmospheric water
vapour can be seen as
clouds, contributing to
the earth's albedo.

5. Iceberg and Polar cap store most of the fresh water
on Earth

6. Reservoir Volume of water
(106 km³)
Percent
of total
Ocean 1370 97.25
Ice caps & glaciers 29 2.05
Groundwater 9.5 0.68
Lakes 0.125 0.01
Soil Moisture 0.065 0.005
Atmosphere 0.013 0.001
Streams & rivers 0.0017 0.0001
Biosphere 0.0006 0.00004

9.  Water in agriculture: water plays the most important role in
agriculture. Agriculture is impossible without irrigation
throughout the crop season. Irrigation ensures proper plant
growth.
 Water for Municipal use: Municipal; demand includes
water for domestic purposes. Commercial uses, street
washing, lawn and garden irrigation, fire protection.
 Balancing the ecosystem: Water is not only important for
human beings but also plays an important role to balance the
entire ecosystem by various ways; by its presence in the
atmosphere it absorbs the sun’s heat. The rain water scours
the hills and carries the sediments into rivers, valley etc.
percolating water into rock crusts takes part in the formation
of mineral deposits. In polar regions, water in the form of the
caps influences climatic and geographical changes.

10.  Water for industries: water is used in huge quantities in
the industries like steel industry, chemicals, fertilizers,
textiles, cement, electricity, petrochemicals & paper.
Mining, food etc.
 Water for power: Thermal power plants also requires large
volume of water for the purpose of cooling and disposal of
fly ash. Water is used in thermal power generation.
 Water for fish, wildlife and recreation: Fish, wildlife and
recreation facilities play an important role in nation’s life
and adequate water supplies for their continued
development & important. Swimming, boating, fishing is
the important outdoor recreational activities which are
impossible without water.

11. Uses of water- Different types
 Consumptive use: water is completely utilized and it
is not reused. Ex. In domestic application.
 Non-Consumptive use: Water is not completely
utilized and it is reused. Ex. Hydro power plant.
Other important uses of water:
 Used for domestic purposes. Ex. Drinking, Cooking.
 Used for commercial purposes. Ex. Hotels
 Used for irrigation (60-70%)
 Used for industrial operations (20-30%). Ex.
Refineries
 Used for moderating climate and diluting pollutants.

12.  As our country is essentially an agricultural
based country, the crops are to be developed
for the production of different types of food
grains.
 The requirement of water varies from crop
to crop.
 Different research stations are busy in
identifying the water needs of all the crops.
 Most of these crops are shallow rooted, thus
water being extracted from top layers of the
soil.
 Soil moisture available in the top layers is
essential for such crops.

13.  Hence, it is advocated to keep the top-soil always
moist so that crops do not wilt under no water
condition.
 Several scientific methods of ploughing are
developed to maintain the moisture in the topsoil
for longer periods.
 Requirement of maintaining the water storage for
breeding the fish and prawn culture is attaining
importance whenever we go for storage project.
 Since fish cannot travel against flow when the
velocity is high, special structures are provided
adjacent to the weirs to maintain low velocities.
 Such structures are known as fish ladders.

14.  The different purposes of the
multipurpose projects have their
conflicting affect on the environment.
 However, depending on the priority of
the water needs of the area to be served,
the planning has to proceed in such a way
that the impact on environment is kept to
be minimum while serving the urgent and
primary needs of the people of the area.

15.  Water that is available in the deeper layers
of the earth is known as Groundwater.
 This water has been trapped inside the
earth’s crust for several centuries.
 The water that is lying under the ground has
the capacity to move in general direction of
its slope with a very small velocity.
 The bodies that contain such water are
known as Aquifers.

16.  Water from these aquifers can be drawn by
digging wells and pumping water from these
wells.
 Some of these wells can supply very large
quantities of water.
 In some cases, the drinking water needs of
cities are completely met by the
groundwater bodies.
 In the agriculture sector also, groundwater is
supporting the growth of crops enormously in
certain agricultural dominated areas.

17.  Wells are used to bring groundwater to the
land surface by means of pumps.
 Wells can be deep wells and shallow wells
depending upon the depth at which ground
water is available.
 Sometimes open dug wells are used where
the water table is high.
 In the case of deeper and hard rock
aquifers, Tube wells are constructed.
 In such cases deep well pumps such as
turbine pumps or jet pumps are used to lift
water to the surface of the ground.

18.  These tube wells in many cases yield
significantly high discharges.
 In a way, groundwater is the water that is
available at the place of its use.
 Thus this water can be lifted from the wells in
the agricultural fields and supplied to the crops
raised in that field.
 Hence, there is no need to send water to long
distances.
 This incidentally reduces the water losses
considerably.
 Use of ground water for nearby areas also does
not pose the problems of environmental
degradation.

19. Over utilization of ground water:
Over utilization of water leads to,
 Rapid depletion of water resources,
 Ground subsidence,
 Lowering of water table
 Water logging

20. Effects of over utilization of ground water:
Reasons: Economic development, rapid industrial growth
and population explosion.
The use of ground water and surface water rates
which are higher than that of recharge ultimately leads to
 Water scarcity
 Water logging
 Salinity
 Alkalization
 Water pollution

21. Water scarcity is the lack
of fresh water resources to
meet water demand. It
affects every continent and
was listed in 2015 by
the World Economic
Forum as the largest global
risk in terms of potential
impact over the next decade.

22. Water scarcity can result from two mechanisms:
 Physical (absolute) water scarcity
 Economic water scarcity
Physical water scarcity results from inadequate
natural water resources to supply a region's
demand. Around one fifth of the world's
population currently live in regions affected
by Physical water scarcity, where there is inadequate
water resources to meet a country's or regional
demand, including the water needed to fulfill the
demand of ecosystems to function effectively.

23.  Economic water scarcity is caused by a lack of
investment in infrastructure or technology to draw
water from rivers, aquifers or other water sources,
or insufficient human capacity to satisfy the
demand for water. One quarter of the world's
population is affected by economic water scarcity.
Economic water scarcity includes a lack of
infrastructure, causing the people without reliable
access to water to have to travel long distances to
fetch water, that is often contaminated from rivers
for domestic and agricultural uses.

24.  On a global basis, fresh water is a
increasingly scarce resource. It is partially
caused by increasing population coupled by
change of consumption pattern and climate
changes.

25.  Industrialized / developed countries tend to
use more water in their industrial production.
 Other countries tend to use more water for
agricultural uses.

26.  Floods:
 The flood hazard itself cannot be prevented,
but thorough understanding of the land
conditions which are prone to a given hazard
and the processes which could culminate in
the damage to life and property it is possible
to minimize the damage through
preparedness for a particular eventuality.
 Flooding takes place when the river channels
are unable to contain the discharge.

27.  In the tropical countries, floods are caused
by various factors:
 (i) Climatologically (rain),
 (ii) Part climatologically (coastal storm
surges, estuarine interactions between
stream flow and tidal conditions) and

28.  (iii) Others (failure of dams and other control
works, excessive release from dams). Floods
could get intensified because of basin
characteristics, network characteristics, and
channel characteristics, each of which has
both stable (unvarying) and variable
components (Table 2.1) unvarying and
variable characteristics.

29.  The improper land-use practices accentuated
the flood devastation.
 There are hardly any forests left in the
catchment area of the rivers.
 It is well known that the forest areas are
characterized by high infiltration capacity
and transmissibility.
 The infiltration capacity of the forest areas is
2-3 times greater than in the open fields.
 The surface runoff in the forested areas may
be as little as one-tenth of that of the open
fields.

30.  There is hardly any protective vegetation on
the banks of the Save and Limpopo rivers.
 Crops are grown right to the edges of the
rivers, even on river slopes.
 Thus, the combination of absence of forest
cover on one hand, and inappropriate
farming practices on the other, intensified
the floods.
 Floods can be mitigated by structural, water
control and non-structural measures.

31.  The structural methods include dams,
reservoirs, and retarding basins, channel
management and embankments.
 The water control methods include flood
proofing and catchment modifications.
 Schemes of drainage and flood protection,
flood forecasting, flood warning and
emergency preparedness systems, flood
insurance, public information and education,
and flood relief constitute the non-structural
methods.

32.  Drought is lack or insufficiency of rain for an
extended period that causes considerable
hydrologic imbalances and consequently
water shortages, stream flow reductions and
depletion of groundwater levels and soil
moisture.
 Drought is the most serious physical hazard
to agriculture in nearly every part of the
world.

33.  Drought not only leads to serious economic
consequences but also leaves behind untold
human misery.
 Among all the natural disasters, drought
affects largest number of people in the
world.
 Shortage of water for even the basic needs is
the main problem in the drought areas.

34.  Even the shallow rooted crops do not grow in
such areas.
 Getting sufficient drinking water is another
problem needing immediate attention in
these areas.
 Some measures like infiltration wells,
underground dams, small watersheds, are
being taken up to alleviate the sufferings of
the people residing in the drought prone
areas.

35.  Certain advance techniques such as Cloud
Seeding and Artificial Rains are also being
tried with varying successes.
 However, these methods are quite expensive
and unpredictable in their success.
 Scant rains for extensive periods also lead to
ecological changes.
 Ultimately, Government has found
reasonable remedies in the form of
development of small watersheds in such
areas.

36.  Dams are the major structures in any
reservoir from the point of view of structural
importance; design details and cost.
 The dams are of different types depending
on different criteria.
 Depending on the material used for
construction, dams can be: masonry dams,
concrete dams, earthen dams, rock fill dams,
steel dams and timber dams.

37.  Based on the design, the dams can be:
gravity dams, arch dams, buttress dams, and
multiple arch dams.
 Similarly, based on the purpose, the dams
are known as overflow dams and non-
overflow dams.

38.  The masonry and concrete dams are more or
less leak proof and hence seepage is not
possible.
 However in the case of earthen and rock fill
dams, seepage of water can be expected, in
good quantities and therefore, possibilities of
water logging on downstream side will be the
adverse effect on the environment.

39.  The water resources projects are constructed
to several purposes depending on the needs
of people of the area to be served. Whenever
the projects are developed to supply water
for different purpose, the projects are
termed as multi-purpose projects.

40.  The different purposes can be: irrigation and
agriculture, hydropower generation, drinking
water supply, water for Industries, flood
control, navigation, recreation and
amusement parks and afforestation.
 Of all the above purposes, irrigation and
agriculture occupies higher priority, as the
production of necessary food grains for one
billion population of the country is the
primary concern to us.

41.  In order to develop the industries and other
power needs, the next priority is the
Hydropower development.
 The emphasis is increasing on the
hydropower, as the natural resources for
other forms of energy such as thermal, are
becoming scarce.
 Due to rapid development of urban areas,
scarcity of drinking water has surfaced in
most of the cities.
 Hence, the present emphasis is on bringing
water to the cities from storage reservoirs.

42.  Slowly, water needs for drinking purposes is
occupying priority when compared to other
needs.
 In the flood plains, the problem of
inundation of adjacent habituated areas is a
priority, as during every flood the losses in
respect of human and cattle life, crops,
property and fertile soils, are bringing misery
to the people.

43.  With every increasing movement of men and
material, the transportation by navigation is
also recognized as a viable mode.
 In the recent times, water has been used for
recreational purposes also.
 In some countries, water sports are gaining
popularity.
 In order to develop greenery in many dry
areas, Government is encouraging people to
go in for tree plantations on a large scale
resulting in afforestation.

44.  Inadequate access to safe drinking water by
over 1.1 billion people
 Groundwater overdrafting leading to
diminished agricultural yields
 Overuse and pollution of water resources
harming biodiversity
 Regional conflicts over scarce water
resources sometimes resulting in warfare.

45.  Population Growth: In 2000 the world population was
6.2 billion. The UN estimates that by 2050 there will be
an additional 3.5 billion people with most of the growth
in developing countries that suffer water stress. Thus,
water demand will increase unless there are
corresponding increase in water conservation and
recycling of this vital resource.
 Expansion of business activity: Business activity
ranging from industrialization to services such as
tourism and entertainment continues to expand rapidly.
This expansion requires increased water services
including both supply and sanitation, which can lead to
more pressure in water resources and natural ecosystem.

46.  Rapid Urbanization: Urbanization requires significant investment
in water infrastructure in order to deliver water to individuals and to
process the concentrations of wastewater- both from individuals
and from business. These polluted and contaminated waters must be
treated or they pose unacceptable public health risks.
 Climate change: Climate change could have significant impacts on
water resources around the world because of the close connections
between the climate and hydrological cycle. Rising temperatures
will increase evaporation and lead to increases in precipitation,
though there will be regional variations in rainfall. Both droughts
and floods may become more frequent in different regions at
different times, and dramatic changes in snowfall and snow melt
are expected in mountainous areas.
 Pollution: Many pollutants threaten water supplies, but the most
wide spread, especially in developing countries, is the discharge of
raw sewage into natural waters; this method of sewage disposal is
the most common method in underdeveloped countries, but also is
prevalent in quasi developed countries such as China. India. Nepal
and Iran.

47.  Water conservation refers to reducing the usage of
water and recycling of waste water for different
purposes such as cleaning, manufacturing and
agricultural irrigation.
 It is a practice in which people, companies and
governments attempt to reduce their water usage.

48.  When washing dishes by hand, don’t let the water run while
rinsing. Fill one sink with wash water and the other with rinse
water.
 Run your clothes washer and dishwasher only when they are
full. You can save up to 1,000 gallons a month.
 Water your lawn and garden in the morning or evening when
temperatures are cooler to minimize evaporation.
 Wash your fruits and vegetables in a pan of water instead of
running water from the tap.

49.  Adjust sprinklers so only your lawn is watered and
not the house, sidewalk, or street.
 Some refrigerators, air conditioners and ice-makers
are cooled with wasted flows of water. Consider
upgrading with air-cooled appliances for significant
water savings.
 Plant in the fall when conditions are cooler ad
rainfall is more plentiful.
 Use the garbage disposal sparingly. Compost
vegetable food waste instead and save gallons every
time.

51.  Desalination of sea water can be done either via
distillation or membrane process.
 Both process requires large amount of energy and
thus costly, which means desalination remains an
expensive option for providing reliable fresh water
supply, restricted to only economically well-off
countries.