WATER RESOURCES

Q1. What do you understand by the term ‘water resource’?

A1. Water resource refers to any of the entire range of natural waters that occur on the
earth and are of potential use to living beings.
Q2. Give two points of difference between ‘surface water’ and groundwater’.
A2.
Surface Water Groundwater
1. Water on land surface as a result of Water collected under the surface of
precipitation or seepage from land.
underground.
2. Lower mineral content so soft water. Higher mineral content (hard water)
due to the cover of subsurface layer of
soil or rock.

Q3. What is meant by rainwater harvesting? Mention any two rainwater harvesting
systems practised in India.
A3. Rainwater harvesting refers to the system of collecting and storing rainwater,
preventing the loss of water through evaporation and seepage with the aim of
conservation and efficient utilisation of water. Khatri or Kuhl in Western Himalayas,
Baolis or Dighis in the Gangetic Plains, Johads in Central India, Bhandaras or Kere in
the Deccan Plateau, Surangam in Western Ghats, Korambu in Eastern Ghats and Zing
in Ladakh.
Q4. What is meant by the term irrigation?
A4. Irrigation refers to the process of watering of agricultural plants through artificial
means from wells, tanks, tubewells, canals, etc. Different crops need different
quantities of water at various stages of growth. High yielding varieties of crops require
higher input of water. Thus, to increase agricultural output irrigation is needed.
Q5. What is meant by the term ‘water scarcity’? What has caused this scarcity in India?
A5. Water scarcity is lack of fresh water resources to meet standard water demand. It
occurs in India because of:
 Highly irregular and uneven distribution of rainfall.
 Rapidly increasing population and increasing demand of water.
Q6. What is meant by traditional or conventional methods of irrigation? Name any two
conventional methods of irrigation.
A6. Conventional methods of irrigation are those which have been in use for centuries in
India. These include Tanks, Canals and Wells.
Q7. State any two drawbacks of Conventional methods of irrigation.
A7. The drawbacks are:
 A large quantity of water is not properly utilised.
 Crops are subjected to waterlogging resulting in poor yields.
 A large amount of cultivable land is utilised for preparing channels and
distribution of water which otherwise could be used for cultivation.
Q8. Give two advantages and two disadvantages of well irrigation.
A8. Advantages:
 Cheap source of irrigation.
 Independent source of irrigation.
Disadvantages:
  Difficult to dig wells in hilly regions.
 Well may dry up due to over withdrawal of groundwater.
 Depends on underground water resources whose distribution varies from region
to region.
Q9. Name any two states where well irrigation is practised.
A9. Uttar Pradesh, Punjab and Haryana.
Q10. Give one advantage and one disadvantage of tubewell irrigation.
A10. Advantages:
 It brings up clean water.
 It can irrigate large area of agricultural land.
 It is easier to bring up large amount of water in a short time period.
Disadvantages:
 They are expensive.
 They require continuous supply of electricity.
 Excessive use of tubewell can deplete the groundwater.
 It is useless if the water is brackish.
Q11. Name the two types of canals. Name two states where perennial canals are widely
used.
A11. The two types of canals are:
 Inundation Canals
 Perennial canals
In Uttar Pradesh, Punjab and Haryana perennial canals are widely used.
Q12. How are the fields irrigated using the Persian Wheel method.
A12. It is a partly submerged vertical wheel with buckets attached to the rim. As the wheel
is turned by draught animals rotating a geared horizontal wheel, the buckets are filled
and emptied into a trough above, which carries the water to crop-sown fields.
Q13. Name two states in which tubewells are extensively used.
A13. Punjab and Haryana.
Q14. State why tubewell irrigation is important in Punjab.
A14. Large area of fertile alluvial soil, large amount of groundwater and soft soil, huge
amount of electricity.
Q15. What is meant by rainwater harvesting? State any two methods of rainwater
harvesting.
A15. Rainwater harvesting refers to the process of conserving water by collecting and
storing rainwater that can be stored for direct use or can be used to recharge
groundwater. This can be done by:
 By collecting water from roof troops and storing it in tanks.
 By building Johads and Baolis.
 By Watershed Management.
Q16. What is watershed management? How is it beneficial for the farmers in the long
run?
A16. Watershed management refers to the efficient management and conservation of
both the surface and groundwater resources. It includes prevention of water run-
off as well as storage and recharge of groundwater. Watershed management
recharges both surface and groundwater. Therefore, it is significant in
maintaining the water supply for agriculture in the long run.
Q17. What is drip irrigation? How is it useful?
A17. This system consists of perforated pipes that are placed between rows of crops or
buried along their root lines and give water directly to the crops. Its advantages are:
 Evaporation of water is drastically used.
 Water is conserved.
 Most advanced and efficient means of irrigation allows grower to customise an
irrigation programme most beneficial to each crop.
Q18. Explain briefly the need to conserve water.
A18. There is a need to conserve water because:
 Overexploitation of groundwater often results in lowering of water table.
 Irrigation utilises more than 90% of the total freshwater.
 The increase in population results in water scarcity.
 Our water resources like the groundwater, rivers, lakes etc are polluted.
Q19. What is meant by furrow irrigation? What is its advantage?
A19. It is a type of flood irrigation in which the water poured on the field is directed to flow
through narrow channels dug between the rows of crops, instead of evenly distributing
the water throughout the whole field. Its advantage is a large land area can be irrigated
with the help of this method.
Q20. Give a geographical reason for each of the following:
i. Need to adopt different means of irrigation.
i. It is because:
 About 75 per cent of the total cultivated area depends on rainfall for crop
production.
 The rainfall is highly irregular and uneven.
 The availability of surface and ground water, varied relief features, soil and
climatic conditions from place to place require different means of irrigation.
 The dry period is very long in India as there is rainfall for 3 to 4 months only.
ii. Need for conserving water.
ii. It is because:
 Declining availability of fresh water;
 irregular and uneven distribution of rainfall;
 increasing demand for water.
iii. Man is responsible for water crisis in India.
iii. Overexploitation of groundwater resources by tubewell and well irrigation,
polluting the surface as well as groundwater and wastage of water.
iv. Inundation canals are being converted ton perennial canals.
iv. It is because:
 Inundation Canals remain functional only during the rainy season as they use
excess water when the rivers are in flood while perennial canals can supply water
throughout the year.
 Inundation Canals can irrigate small areas whereas perennial Canals can irrigate
large areas.
v. Tank irrigation is preferred over other means of irrigation in Peninsular India.
v. Tanks are most widely used in Peninsular India, in the states of Maharashtra and
Gujarat because:
 The rivers of the Deccan are not snow-fed 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.
 The natural hollows formed by the undulating surface make tank building easy
and cheap.
vi. Groundwater reserves are depleting at a fast rate.
vi. It is because:
 due to increase in population, irrigation and industrialisation, the demand for
water has risen manifold, resulting in overexploitation of underground water and
lowering of water table.
 the loss of vegetation causes drought and reduction of rainfall, lowering of water
table and depletion of ground water resources.
vii. Well irrigation is mainly confined to the alluvial plains.
vii. It is because:
 The Alluvial plains are made up of soft soil in which it is easy to dig wells;
 The depth of the water table does not exceed 15m;
 The ground water is available in plenty due to proximity of perennial rivers.
viii. In Tamil Nadu, nearly one-third of the net irrigated area is under canal
irrigation.
viii. Most parts of Tamil Nadu get winter rains while summers are dry. Canals
provide water during the dry season.
ix. Drip irrigation reduces loss of water through evaporation.
ix. It is because it contains perforated pipes that are placed between rows of crops
which give water directly to the crops.
x. canals make the soil infertile.
x. It is because water table is few feet below the ground causing alkaline salts to
come to the surface, mix with the soil making it infertile.
xi. Tubewell irrigation is quite expensive.
xi. Because it requires continuous supply of electricity.
xii. Excessive accumulation of salts makes the soils unsuitable for cultivation.
xii. It is because roots are unable to absorb water the plants require to grow; changes
in the pH leads to change in the composition of nutrients and hence their
absorption by the plant.
xiii. Many farmers in India still use wells.
xiii. It is because wells are cheap, simple and dependable source of water for farmers.
xiv. There is very little recharge of groundwater.
xiv. Rainfall in India occurs in short spells of high intensity. Due to such intensity and
short duration, most of the rain flows away rapidly and does not recharge the
groundwater.
xv. The traditional wells dry up.
xv. Due to over-withdrawal of the groundwater and lowering of the water table.
xvi. Modern means of irrigation are gaining popularity.
xvi. They are scientific so ensure best utilisation of water minimising wastage.
xvii. Sprinkler irrigation helps in conserving water.
xvii. No loss of water due to seepage and evaporation.
xviii. Spray irrigation is quite expensive.
xviii. Require installation of network of pipes with nozzles all over the field so spray
irrigation is expensive.