Water Resources

Question 1

what are the consumable sources of water?

Answer 1

1. Surface water (0.03%)

2. Ground water(0.66%)

Question 2

why should we conserve water?

Answer 2

1. overuse of water leads to lowering of water table
2. no vegetative cover due to deforestation leads to less rainfall.
3. shortage of water due to overpopulation
4. water used up in irrigation

Question 3

what is rain water harvesting?

Answer 3

increase of ground water by collecting rain water in sub surface tanks.

Question 4

what are the benefits of rain water harvesting?

Answer 4

1. helps meet increasing demand for water
2. raises the water table
3. reduces water loss by run off- thereby reducing soil erosion.
4. enhance quality of ground water
5. helps in supplying water in summers.

Question 5

how does roof top rain water harvesting work?

Answer 5

water collected in catchments- sent to storage tanks via conduits- gets filtered by first flush filters before entering storage tank- stored in storage tanks: water may get used for house hold purposes - gets into recharge facility which allows absorption in ground water - then goes to overflow outlet in case water exceeds capacity of tank.

Question 6

what are the different types of recharge facilities?

Answer 6

1. borewells/dug wells
2. recharge pit- pit with brick lined walls which have holes at regular intervals for absorption of water
3. percollation pit- bored unlined hole of width of 30cm and depth of 3m - 10m
4. trenches- dug in the ground and filled with rocks and pebbles, so surface run off water gets collected in them and then absorbed by the soil.

Question 7

what is watershed management?

Answer 7

efficient management and conservation of both ground and surface water.

Question 8

why is irrigation needed in India?

Answer 8

1. India has irregular rainfall: gets rains in the first 4 months rest of the year remains dry.
2. distribution of rains: some parts of the country receives excess rainfall and other parts receive very low rainfall.
3. different crops have different requirements for water.
4. Nature of Soil.

Question 9

what are the different types of crops?

Answer 9

1. Kharif - require most amount of water, are grown during the monsoon, grown in areas where irrigation system is non existent.
2. Rabi crops- require lesser rain, grows in remaining water absorbed by ground after kharif crops, requires irrigation system to some extent.
3. Zaid crops- Summer crops, fully depend on irrigation, grown in regions of well developed irrigation system.

Question 10

which soil fails to retain moisture?

Answer 10

sandy or loamy soil.

Question 11

Where can wells be dug?

Answer 11

In regions having consumable ground water with soft soil and soft rocks.

Question 12

what are the three types of well irrigation?

Answer 12

Persian wheel method
lever method
inclined plane method

Question 13

explain how Persian wheel method works

Answer 13

the wheel is attached to a belt with multiple buckets attached to it. the wheel is moved by animals thus making the belt with buckets move. the buckets pick up water from the well and pour them into troughs which carry the water to the feilds.

Question 14

explain how lever method works method works

Answer 14

water is lifted from shallow wells, a weight is put on one end of the lever which makes the end having the bucket rise thus getting water out of the well.

Question 15

explain how inclined method works method works

Answer 15

cattle is made to move up and down a slope multiple times so as to pull out water from a well.

Question 16

what are the advantages of well irrigation?

Answer 16

the wells are cheap to make.
independent source for small farmers
no extra cost to be payed as cattle can be used to bring water out.

Question 17

what are the disadvantages of well irrigations?

Answer 17

wells dry up if not used
tedious to take out water from well
can not be built in hilly or stony regions.

Question 18

what are tube wells?

Answer 18

wells dug to great depths very deep into the water table from which water is pulled via electricity operated pumps.

Question 19

how deep are tube wells?

Answer 19

20m to 30m

Question 20

what are the requirements for tube wells?

Answer 20

cheap power supply
plenty of ground water at great depths
soft lands and soft rocks.

Question 21

State advantages of tube wells

Answer 21

permanent source of water
not time consuming
availability of clean water
can bee switched off when not in use.

Question 22

state disadvantages of tube wells.

Answer 22

very expensive as continuous electricity is required.
water table drastically lowers in case of excessive use.
useless if water is brackish.

Question 23

what are inundation canals?

Answer 23

canals that rise from high bank of rivers which carry flood water from the rivers for irrigation.
do not have dams or barrages.

Question 24

what are perennial canals?

Answer 24

canals that get water from large perennial rivers. water gets divided from the river into the canals by using dams and barrages.

Question 25

what are the advantages of canals?

Answer 25

useful to irrigate region away from water source useful in regions of scanty rainfall useful in areas with erratic seasonal rainfall.

Question 26

what are the disadvantages of canals?

Answer 26

they are not a reliable source of water. only used during monsoon months. unlined canals cause waterlogging due to excess water absorption. due to rise in water table, alkaline salts are deposited in soil, which makes soil unusable. expensive to construct.

Question 27

what is tank irrigation?

Answer 27

small bund of earth and stone built to collect water and pass it through canals to give water supply

Question 28

why is tank irrigation practiced in deccan plateau region?

Answer 28

because the rocks are hard and constructing wells is difficult. uneven surface provides natural depressions that can be turned into tanks.

Question 29

what are the advantages of tank irrigation?

Answer 29

storing rain water useful in areas of seasonal rainfall raises water table

Question 30

what are the disadvantages of tank irrigation?

Answer 30

silt gathers in the tank which spoils the water loss of water by evaporation takes up large area which could have otherwise been used for cultivation it is dry during summers- not useful for cultivation of Zaid crops.

Question 31

why is the conventional method of irrigation not effective?

Answer 31

excessive water during the monsoon months and rest of the year is dry which leads to spoilage of crops. low lying areas get waterlogged due to which crops cant grow. fields are irrigated via trenches dug on the ground which takes up extra space.

Question 32

what is waterlogging?

Answer 32

layer of water formed on land due to excessive rise in water table, reduces breathability of the soil.

Question 33

what is spray irrigation?( method, usage)

Answer 33

water is supplied through hose which has one end as a sprinkler that sprinkles water across the fields used in golf fields lawns etc.

Question 34

advantages/ disadvantages of spray irrigation

Answer 34

advantage- efficient usage of water | disadvantage- complex setup, expensive

Question 35

what is drip irrigation?( method, usage)

Answer 35

water supplied directly to plant roots through perforated pipes used in orchards and vegetable gardens.

Question 36

advantages/ disadvantages of drip irrigation

Answer 36

advantage- saves water, direct supply of water to plant roots, prevent water loss due to evaporation disadvantage- plastic pipes contaminate soil, pipes may get clogged, difficult to set up, expensive