WATER RESOURCES

1. Rain water Harvesting : Is a technique of collection and

storage of rain water into natural reservoirs or tanks, or
the infiltration of surface water into subsurface aquifers
(before it is lost as surface runoff). One method
of rainwater harvesting is rooftop harvesting.
2. Conservation of water: Water conservation refers to the preservation,
control and development of water resources, both surface and
groundwater, and prevention of pollution.
3. Importance / Advantages of rainwater harvesting :---
i. Reduces the cost for pumping of ground water.
ii. Provides high quality water, soft and low in minerals.
iii. Reduces soil erosion in urban areas.
iv. The rooftop rainwater harvesting is less expensive.
4. Objectives of Rainwater harvesting:
i. To meet the increasing demand of water.
ii. To prevent surface runoff.
iii. To avoid flooding of roads.
iv. To raise the ground water level.
v. To improve the quality of ground water/ reduce the
pollution of ground water.
vi. To reduce soil erosion.
vii. To supplement the household requirement of water
during summer.
5. Reasons to conserve water are
i. Rainfall is seasonal, unreliable and erratic. The farmers
cannot fully depend on it for successful harvest.
ii. The ever growing industries not only take up a lot of
water but also pollute it as well.
iii. India has seasonal rainfall which is not evenly
distributed throughout the country. Certain areas
experience scarcity of water, so conservation is
necessary.
iv. The water table is lowered due to overexploitation of
underground water.
6. Reasons for the need of rainwater harvesting.
i. The annual precipitation received in form of rain is
4000 cu. Km which goes wasted as surface runoff
adding upto the volume of river water and thus causing
floods.
ii. This rain water can be tapped for direct use or
recharging ground water aquifers.
iii. Such a large volume of water can be put to many uses
and thus make up the acute shortage.
7. 2 advantages of primitive methods of irrigation is they
are cheap and simple.
8. Difference between Surface and ground water.
Surface water- It is water found in a river, lake or other
surface cavities.
Surface water is usually not very high in mineral content.
Surface water is called as soft water due to its less
 mineral content.
Groundwater is water contained in or by a subsurface
layer of soil or rock.
Groundwater commonly contains less contamination than
surface water because the rock tends to act as a filter to
remove some contaminants.
Due to the minerals picked up while filtering through the
rocks, groundwater is typically considered to be hard
water.
9.
Perennial Canals Inundation Canals
i. These flow throughout These provide irrigation
the year mostly during the rainy
season.
ii. These are constructed by These are drawn directly
putting some form of from the rivers without
barrage across the river making any kind of
barrage or dam.
iii. These irrigate large areas These irrigate small
areas.

Give Reasons why:--

10. In many places Inundation canals are being
converted into Perennial canals in order to supply water
even in dry season as well as regulate the flow of water
at the time when the river gets flooded during rain.
11. The sprinkler is less in India because it is
expensive, new and farmers are not aware of its
benefits.
12. Ground water reserves are depleting at a fast rate
due to over exploitation and increase in population.
13. Tube well irrigation is important in Punjab because
Punjab has large tracts of fertile alluvial plains as well
as plenty of waters from its perennial rivers.
14. Tube well irrigation is quite expensive because it
requires continuous supply of electricity, pump and
pipes.
15. Many farmers in India still use wells because they
are cheaper, easy and simple to construct.
16. There is very little recharge of ground water due to
lack of vegetation most of the rain water goes waste in
form of surface runoff.
17. Modern means of irrigation are gaining popularity
as the use of water is conserved and can flow can be
customised.
18. Spray irrigation is quite expensive as it requires
complex machinery.
19. Tube wells are very useful during periods
of drought when a surface well dries up because not
dependent on failures of rain. Plentiful water is available as it
lifts water from great depth.
 BOOK ANSWERS.

a. Canal irrigation is more wide spread in northern India.

(i) The rivers are perennial as they are fed by the melting snows.
(ii) The surface of the land is almost flat and soft. Hence it is
easy to dig canals. (iii) The demand for irrigation is very great in
North India as a variety of crops are grown. (iv) Type of
cultivation is intensive.
b. Wells Tube wells Tanks Canal Spray Sprinkler Drip Furrow.
c. i. Tank irrigation is more important in Deccan Plateau: i Rivers
are not snow-fed mainly dependent on the rainwaters. ii Streams
become torrential during the rainy season but dry up when rain
ceases. iii Hard rocks do not absorb water. Terrain is very uneven
with many natural depressions.
ii. Rainwater harvesting has a number of benefits. a. Reduces the
cost for pumping of ground water. b. Provides high quality water,
soft and low in minerals. c. Reduces soil erosion in urban areas. d.
The rooftop rainwater harvesting is less expensive. e. Supplements the
household requirement of water during summer. f. Such a large
volume of water can be put to many uses and thus make up the acute
shortage.
iii Tube-well irrigation is more important than ordinary well
irrigation. a. Plentiful water at great depths. b. Level land and soft
soil. c. Large fertile area can be irrigated. d. availability of cheap
electricity.
d. Conservation of water: Water conservation refers to the
preservation, control and development of water resources, both
surface and groundwater, and prevention of pollution.
2 Modern Methods to conserve water: Modern method: Drip Spray
Sprinkler and Furrow. 2 Traditional methods are Wells tanks and
canals.