Water Resources

Related Terms
Aquifer. An underground water stream that is saturated with water and transmits
water readily.

Saturation zone. The area where the water fills the aquifer.
Water table. The depth from the surface in the soil where all the pore spaces of
the soil particles are saturated with groundwater.

Runoff. The flow of water from perspiration back into the oceans through streams;
It consists wholly or partly of water contributed by the flow of water on land (surface
runoff) or/and by groundwater flow (base flow).

Sources of Water
Surface Water. Water available on the surface of the earth as a result of
precipitation or seepage from underground, which forms streams and rivers flowing
on land and finally joining the sea or forming lakes, ponds, etc. is referred to as the
surface water.
- Most of the Himalayan rivers are large and originate in the snow-covered high-
altitude areas, and as such they carry sufficient water throughout the year. They
are called perennial rivers.
- In contrast, the rivers of the peninsular India are seasonal. They carry no or
very little water in the dry summer season.
- The lagoons and backwaters found along the vast coastline of India also serve
as surface water resources. The water, being brackish, is used for fishing and
irrigating certain crops like paddy, coconut, etc. Kerala, Odisha and West
Bengal have a large number of lagoons and lakes.

Groundwater. The part of the water from perspiration that seeps through the
cracks and crevices into the ground, passes through various layers of sand, stones clay
and finally accumulates in the natural reservoir over the impervious bedrock is called
groundwater.
- The mountainous terrain in Northern India, spanning from Kashmir to
Arunachal Pradesh, has steep slopes and high runoff, and is mostly composed
of rocks which limits groundwater storage.
- The Indo-Gangetic-Brahmaputra alluvial plain is underlaid by thick piles of
alluvial sediment. This sedimentary fill serves as India's largest and most
productive groundwater reservoir.
 - The underlying geology of the Peninsular India, consisting of sedimentary,
basaltic, and crystalline rocks, limits the formation of large continuous aquifers,
and as a result, this region has limited groundwater potential.
- Coastal areas have a thick cover of alluvial deposits and form multi-aquifer
systems in many states. However, the risk of seawater ingress severely
constrains the development of these aquifers.

Need for Water Conservation

- Overexploitation of underground water resources often results in the lowering
of the water table.
- The loss of vegetation, as a result of reduction in available water resources,
causes drought and reduction of rainfall and lowering of water table.
- Irrigation utilises more than 90% of the total freshwater, out of which a lot of
water is wasted in its transmission from the source to the required places.
- Increasing industrialisation and rapid urbanisation and population growth
exerts excessive pressure on the existing water resources and results in water
scarcity.
- The underground water resources and rivers, lakes, etc. are polluted and their
water can be hardly used without adequate treatment, which causes a lot of
wastage of water.

Conservation Practices
Meaning. Conservation of water refers to the prevention and control of the
depletion and degradation of existing resources and making the best possible use of
the resources for the present and future needs.

Rainwater harvesting.
- It is the method of conservation of water by collecting water during rainfall and
storing it for use directly or recharging it into the ground to improve
groundwater storage in the aquifer.
- Traditionally, the following mechanisms have been followed in India:
• Collecting rainwater from rooftops and storing it in tanks built in their
courtyards, as well as collecting it from open community lands and storing
it in artificial wells.
• Harvesting rainwater runoff by capturing water from swollen streams
during the monsoons and storing it in water bodies.
• Harvesting water from flooded rivers.
- The traditional water storage mechanisms are known by different names in
different areas.
Name Region Name Region
Bhandaras/Kere Deccan Plateau Khatri/Kuhls Western
Himalayas
Kunds Thar Desert Pukur/Khal/Bol West Bengal
 Surangam Western Ghats Zing/Zong H.P., Ladakh, J&K
Cheruva A.P./Telangana Dongs Assam
Korambu Eastern Ghats Khadin/Tanka Gujarat
Johads Central India Baolis/Dighis Gangetic plains
and Rajasthan
- Components of a water harvesting system:
o Catchment of a water harvesting system is the surface which receives
rainfall directly, such as the terrace or courtyard of a building, unpaved
lawn, open ground, temporary structures like sloping sheds, etc.
o Conduits are pipelines or drains that carry rainwater from the catchment to
the harvesting system. They may be of any material like PVC, asbestos,
galvanised iron, etc.
o First flushing device to ensure that the runoff from the first spell of rain,
carrying a larger number of pollutants, is flushed out and does not enter the
system.
o Filters to remove dirt and debris from the water before entering the storage
facility.
o Storage facility in the form of containers like RCC (reinforced cement
concrete), masonry or plastic water tanks, which may be cylindrical or
rectangular.
o Recharge facility to recharge groundwater aquifers with the collected
rainwater as an alternative to storing it.
Borewells and Used to raise the water table by collecting rainwater
dug-wells through an ideal rainwater harvesting system and
then diverting the water to the borewell or dug-well.
Recharge Pit A hole excavated into the ground, lined with a
brick/stone wall with openings at regular intervals.
Percolation Pits A bored hole of up to 30cm diameter drilled in the
(Soakaway) ground to a depth of 3m to 10m.
Recharge Excavated on the ground and refilled with porous
Trenches media like pebbles, boulder or brickbats to harvest
the surface runoff.
Permeable Used to retain a large proportion of the rainwater
Surfaces falling on it, yielding only 10-15% as runoff, e.g.: a
patch of grass.
Porous tiles Installed on pavements and footpaths.
- Need: While India receives rainfall of above the average amount, most areas
have acute shortage of water. This is because the rainfall in India occurs in short
spells of high intensity, due to which, most of the rain falling on the surface runs
off rapidly, leaving very little for the recharge of groundwater. This deprives
most parts of India from water resources, even for domestic uses.
- Importance:
o Rainwater harvesting increases availability of surface water during dry
seasons.
o It reduces dependence on underground water and maintains the water
table.
o It improves the quality of groundwater by diluting salinity.
 o It prevents soil erosion and flooding, especially in urban areas, and
improves soil moisture.
o It reduces the wastage of water due to runoff and makes rainwater available
for other productive uses.
- States/UTs like Karnataka, Tamil Nadu, Gujarat, Kerala and New Delhi have
made it a part of the State policy to mandate the installation of rainwater
harvesting systems atop different buildings.

Watershed Management. It refers to the efficient management and

conservation of both the surface and groundwater resources. It includes prevention of
runoff as well as storage and recharge of groundwater by various methods like
percolation pits, recharge wells, borewells, dug-wells, etc.

Haryali. It is a watershed development project started by the central government

aiming to enable the rural people to conserve water for irrigation, drinking, fisheries
and afforestation.

Irrigation
Meaning. It is the process of watering of the agricultural plants by artificial
measures such as from canals, wells, tube-wells, lakes, etc. derived from the existing
natural sources of water like rivers, tanks, ponds or underground water.

Need.
- The monsoon rainfall in India is highly erratic and uncertain in place and time
– sometimes it arrives early and the other times it gets delayed. It is also
uncertain in terms of continuity, rhythm and intensity during the rainy season,
leading to water scarcity and withering of crops.
- The rainfall in India is also unevenly distributed. Most parts of the country
receive most of the rainfall from the SW monsoon, which, being orographic in
nature, leaves Saurashtra, Kutch, parts of Punjab and Haryana and western half
of Rajasthan in the arid zones.
Sometimes, floods are seen in the wet areas while at the same time the arid
zones would be in the grip of a drought; irrigation can solve this problem by
diverting the excess water from the rivers to the drier areas.
- The monsoon rainfall is torrential, giving very little time to the soil to absorb
water. Thus, most of the surface water is wasted, which has to be compensated
by irrigation.
- Different kinds of crops require different quantities of water for their growth.
o The kharif crops occupy the largest area in the country and are dependent
on monsoons. If irrigation facilities are not developed at a place, they are
grown entirely rainfed.
Rabi crops are grown on soil moisture left after the harvest of kharif crops
or over the area where assured irrigation is available.
Zaid crops are exclusively irrigated crops.
 o HYV-seeds requiring higher quantity of chemical fertilizers need more
moisture, which can be supplied only through irrigation.
o Crops like sugarcane need higher quantity of water, which could be
managed only through an efficient irrigation system.
- Many rivers in India, especially those in the central and southern parts, are not
perennial and carry insignificant flows during the rabi season. Therefore, to
effectively utilise the water of these rivers, irrigation must be employed.
- Irrigation is a must to maximise the production of crops in India.

Conventional methods of irrigation.

- (Surface/ordinary) Wells:
Meaning A well is a small hole dug in the surface of the earth to obtain
water from the subsoil for domestic as well as irrigation
purposes.
Requirements o The soil must be soft and porous to easily dig the wells.
o The underground water table must be high.
Areas o Northern plains – U.P., Punjab, Haryana, Bihar;
Reasons –
▪ High water table, especially in the Ganga plain;
▪ Soft alluvial soil, allowing easier digging;
▪ Adequate rainfall which constantly replenishes
groundwater;
o M.P., A.P., Rajasthan, Gujarat, Maharashtra, etc.
Types Unlined Such a well is dug by a farmer near the field at
places where the water table is high. These are not
lined with bricks, stones or cement and as such are
cheaper and easier to dig.
Lined Such a well is lined with bricks, stones or cement
and are mostly covered for safe drinking water
supply, other domestic purposes and irrigation. It
is perennial and more expensive to dig.
Supplying Persian ▪ A partially submerged vertical wheel with
water wheel / buckets attached to the rim is turned by
rehat draught animals rotating a geared horizontal
wheel.
▪ The buckets are filled and emptied into a
trough above, which carries water to the fields.
▪ It is popular in Punjab, Haryana and western
Rajasthan.
Lever ▪ The lift consists of a strong log laid across a
fulcrum, a bucket attached to the long arm by
a bamboo/rope and a heavy weight attached to
the other side.
▪ When the bucket is full, the rope is gently
released and the bucket comes up as the stone
goes down.
Inclined ▪ A pair of bullocks move down from the slope,
plane / specially constructed from the wall of the well,
mhote and a bucket or leather bag which is
 discharged into the connecting channel
pulling from behind.
▪ After discharging, the bullocks move up until
they reach the top during which the bucket
reaches the surface of water and gets filled.
▪ This process is repeated again and again as
desired.
Other methods include piccottah, dhenkli, rehat and pumps
run by electricity.
Advantages o They can be dug at a very low cost which is well within the
means of poor farmers.
o They are an independent source of irrigation unlike canals
which are controlled by higher agencies.
o Oxen kept for ploughing can be used for drawing water
from the wells at no extra cost to the farmers.
o They occupy a less area and can be dug at any convenient
place.
Disadvantages o They depend on groundwater resources whose
distribution varies with region.
o They are not deep enough and may get dried in the
summer. They also dry up due to over-withdrawal.
o They are difficult to dig in the hilly regions of the north or
the stony areas of the Peninsula.
o Availability of electricity and diesel to operate pumps to
draw water is costly and erratic in many places.

- Tube-wells:
Meaning A tube-well is a very deep bore at a depth of 20-30m dug into
the ground with a drilling machine from where water is lifted
up with the help of electric power-driven pumps.
Requirements o High water table with perennial water supply at great
depths.
o Level land and soft ground, preferably with alluvial soil, so
as to facilitate deep digging.
o Large fertile agricultural land in the surrounding areas, so
that the cost of boring a tube-well can be compensated
with the output.
o Availability of cheap electricity to run the tube-wells.
Areas Northern plains – Punjab, Haryana, U.P., Bihar, West Bengal,
Rajasthan, M.P., Gujarat. Reasons –
o High water table, especially in the Ganga plain;
o Soft alluvial soil, allowing easier digging;
o Adequate rainfall which constantly replenishes
groundwater;
o Availability of cheap hydroelectric power to operate the
pumps of tube-wells.
Advantages o It can irrigate a larger area of agricultural land as
compared to wells.
 o It is a perennial source of irrigation as it is drilled up to the
permanent water table, and is useful in conditions where
surface wells dry-up easily.
o It occupies a lesser area as compared to surface wells.
o It does not cause pollution and brings up clean water.
o It does not strain the men or animals as it is driven by
electric power.
o It is an independent source of irrigation.
Disadvantages o It is very expensive to set-up and to use as it requires
continuous electric power supply.
o Excessive use of tube-wells can lead to large-scale
depletion of the groundwater table.
o It is not fit for areas with brackish groundwater.
o It can irrigate still less area as compared to canals.

- Canals:
Meaning A canal is a big water channel taken out from the rivers to
divert the water far away from the river to the agricultural land
being irrigated.
Requirements o Low level relief with deep fertile soil.
o Perennial source of water.
Areas o Northern India – U.P., M.P., A.P., Rajasthan, Haryana,
J&K, Assam, Tripura, Bihar and West Bengal.
Canals are more prevalent in northern India as compared
to the south, because –
▪ The northern rivers are perennial – they are snow-fed
from the Himalayas.
The southern rivers, however, are seasonal.
▪ The terrain is almost flat, level, extensive and made of
soft, thick layers of alluvium, which facilitates the
construction of canals.
The southern terrain is rocky and difficult to dig.
▪ The demand for irrigation and its economic benefits is
greater in the north, as this is predominantly an
agricultural region where proportion of arable land is
the highest due to high fertility of soil.
o Southern India – Canals of the Nizamsagar,
Nagarjunasagar and Tungabhadra projects and of the
Krishna and Godavari deltas are the most important.
Types Inundation canals Perennial canals
Taken out directly from the Taken out from the perennial
rivers without constructing rivers by constructing
any barrage or dam. barrages or dams to regulate
the flow of water.
They use the excess water of They can draw water
rivers at the time of floods, throughout the year and
and so remain operational irrigate larger areas.
during the monsoons only.
Advantages – Advantages –
▪ Easily and cheaply built.
 ▪ Useful in controlling ▪ These canals provide
floods. water throughout the year.
▪ The rainfall deficiency in
many areas is made up by
these canals.
 Sandy patches in
Rajasthan now yield
good harvests;
 Punjab and Haryana
have become the
granaries of the
country;
 Tamil Nadu makes up
the lack of rainfall in
the summer; etc.
▪ Larger areas can be
irrigated.
Disadvantages – Disadvantages –
▪ Not very useful during dry ▪ At places where the
season. unlined canals flow at the
▪ Only lower-level regions ground level and between
can be irrigated, as once raised high banks, the
the rainy season is over water table reaches the
and the floods subside, the surface and soaks into the
level of water falls below adjoining areas, making
the canal head. the soil waterlogged.
▪ Waterlogging decreases
the absorption capacity of
the soil, so, a little excess
rainfall, in the absence of
proper drainage, damages
the standing crops,
houses, stored food grains
and fodder.
▪ If the water table is a few
feet below the ground, salt
effervescence occurs,
which makes the soil
unproductive.
▪ It is expensive to construct
these canals with ample
lining and suitable
barrages, dams or weirs
properly.

- Tanks:
Meaning A tank is a small bund of earth or stones built in the areas of
natural depression across a stream to impound water by
building earthen embankments or masonry walls, which is
then led through the narrow channels to the cultivated fields.
Requirements o Hard impervious rocks below the tanks to prevent seepage
of water.
o Uneven terrain with natural depressions is preferable.
o Adequate rainfall to fill up the tanks.
Areas o Prevalent in the southern states, especially A.P. (Nellore),
Telangana (Warangal) and Tamil Nadu (Chingleput,
North and South Arcot).
Tanks are more important in the Deccan because –
▪ Canal irrigation cannot be afforded as the rivers of the
Deccan are not perennial and are mainly dependent on
the rainwater. There are many streams which become
torrential during the rainy season but dry up when the
rain ceases. Moreover, the surface is hard and sloppy.
▪ The Deccan Plateau consists of underlying hard rocks
which are impervious, i.e., do not absorb water, so
wells cannot be made.
▪ The terrain of the Deccan plateau is uneven with many
natural depressions, where tanks can be easily built.
▪ The Deccan receives monsoon type of climate, so, the
tanks collect rainwater and help in raising the water
table.
o Other states include southern West Bengal, south-eastern
Rajasthan, Bundelkhand area in U.P. and southern Bihar.
Advantages o They occupy less area in comparison to canals and can be
easily built in the regions where canals cannot be built,
e.g.: in the hard rocky terrain of the Deccan plateau.
o They are highly significant in storing excess rainwater
which would otherwise flow out to waste. The stored water
is not only used for irrigation but also for domestic
purposes.
o They help to raise the underground water table.
o They are cheaper than any other type of irrigation as the
rainwater is collected in natural pits and depressions
which are easily available in peninsular India.
Disadvantages o Due to stagnation of water, siltation takes place and water
becomes unsuitable for cultivation. Regular desilting is
necessary.
o Most tanks are non-perennial and dry up in summer or
when monsoon fails. Considering this and the large area
they occupy, they become costly as compared to wells.
o They occupy a large fertile area which otherwise could
have been utilised for growing crops.
o Due to the large area coverage and their shallow depth,
much of the water is wasted through evaporation or
underground sinkage.
o The lifting of water from the tanks and bringing it to the
fields is a strenuous and costly task.
 - Drawbacks of a conventional system of irrigation:
• A large quantity of water is not properly utilised.
• Crops are subjected to cyclic changes of flooding and water stress situations
by providing heavy irrigation at one time and leaving the fields to dry up for
about 10-15 days. This results in poor yield.
• Fields situated in low-lying areas get excess water causing prolonged
waterlogging and resulting in poor yields.
• About 10-15% of the land is used up for preparing channels and distribution
lines, etc., which decreases the effective area for cultivation.
• Extensive areas of arid and semi-arid regions are no longer cultivable due to
salt effervescence.

Modern Methods of Irrigation.

- Sprinkler (‘overhead’) irrigation:
• In it, water is piped through hoses from the source of water to one or more
central locations and is sprayed directly to the required plants through a
fixed or movable (mounted on a moving platform) high-pressure pipe fitted
with a nozzle on top.
• Advantages –
o No loss of water by seepage or evaporation.
o No interference with cultivation and increases yield.
o Easy mechanization.
• Disadvantages –
o High initial and operating cost.
o Suitable for crops which require less water; some sensitive crops may
suffer leaf scorch because of the salt deposited on the leaves after water
evaporates.
o Only beneficial for a small area.
o Direction of wind affects the water application efficiency.
- Drip/localised/low-volume/trickle irrigation:
• This system consists of perforated pipes (drippers) that are placed between
rows of crops or buried along their root lines, which apply the water directly
near the roots.
• It is usually used to irrigate fruits and vegetables.
• Advantages –
o High water application efficiency.
o Minimised fertiliser and nutrient loss due to localised leaching.
o Less soil erosion and weed growth.
o Less wastage of applied water through evaporation.
• Disadvantages –
o Initial cost could be more than sprinkler systems.
o Clogging may occur if the water is not properly filtered.
o The sun can shorten the usable life of the drippers.
- Spray irrigation:
• In it, a long hose is set to a water source on one side and on the other, the
water is released through spray guns to the field.
 • Advantages – Efficient utilisation of water; reduction in the amount of water
needed to irrigate a unit area.
• Disadvantages –
o Expensive to install as it requires complex machinery.
o Water is lost through evaporation.
o Plant diseases caused due to excess moisture can occur in case of over-
watering.
- Furrow irrigation:
• In it, the water poured on the field is directed to flow through narrow
channels or furrows of equal dimensions dug between the rows of crops,
instead of evenly distributing the water throughout the whole field.
• It is useful where water is easily available.