Water Resources

ICSE Class 10 · Geography · Chapter 8

What this chapter covers

Water as a resource
Sources of water: surface water
Sources of water: ground water
Need for conservation
Rainwater harvesting and its importance
Irrigation and its importance
Wells and tube wells
Tanks
Canals
Drip and sprinkler irrigation
Comparing the methods of irrigation
Common mistakes to avoid

Key definitions

Surface water is the water found on the surface of the land in rivers, streams, lakes, ponds, tanks and reservoirs.

Ground water is the water that has seeped down through the soil and rocks and is stored in the pores and cracks of the rocks below the surface.

Rainwater harvesting is the collection and storage of rain water where it falls, from roofs or the ground, either for direct use or to recharge the ground water.

Irrigation is the artificial supply of water to agricultural land from wells, tanks, canals and other sources, to make up for rain that is too little, too uncertain or badly timed for the crops.

Drip irrigation is a method of irrigation in which water is supplied drop by drop directly to the roots of plants through a network of plastic pipes fitted with small outlets called emitters or drippers.

Sprinkler irrigation is a method of irrigation in which water is pumped under pressure through pipes and sprayed over the crop through rotating nozzles, so that it falls on the plants and soil like rain.

Key points

Water resources are the sources of usable fresh water: surface water in rivers, lakes, tanks and reservoirs, and ground water stored in rocks below the surface.
India has about 18 per cent of the world's people but only about 4 per cent of its fresh water, and its rain is seasonal and uneven.
Himalayan rivers are perennial because they are fed by snow and rain; peninsular rivers are rain-fed and seasonal.
Ground water is richest in the alluvial northern plains and scarce in the hard-rock Deccan Plateau; over-pumping is lowering the water table in many states.
Water must be conserved because of uneven rainfall, rising demand, over-use of ground water, pollution, wastage and falling water per person.
Rainwater harvesting collects rain where it falls, by rooftop systems, recharge pits, check dams and traditional methods such as tankas, johads, kuls and eris; it recharges ground water and supplies water in the dry season.
Irrigation is needed because the monsoon is seasonal, uncertain and uneven, and because rice, sugarcane, multiple cropping and high-yielding varieties need assured water.
Wells and tube wells, the largest source of irrigation, suit soft alluvium and a high water table; tube wells dominate in Punjab, Haryana and Uttar Pradesh.
Tanks suit the undulating, hard-rock plateau of Tamil Nadu, Karnataka, Andhra Pradesh and Telangana, but dry up in summer and silt up.
Canals, inundation or perennial, irrigate large areas of the northern plains, the eastern deltas and Rajasthan, but can cause waterlogging and salinity.
Drip irrigation delivers water drop by drop to the roots and saves the most water; sprinkler irrigation sprays water like rain and suits uneven and sandy land.

Questions answered

Define surface water and ground water.

Surface water is the water found on the land in rivers, streams, lakes, ponds, tanks and reservoirs. Ground water is the water that has seeped down through the soil and is stored in the pores and cracks of rocks below the surface.

What is meant by the water table?

The water table is the upper level of the saturated zone below the ground, below which all the pores and cracks in the rocks are filled with water.

Why do the Himalayan rivers flow throughout the year while many peninsular rivers do not?

The Himalayan rivers are fed by both monsoon rain and the melting of snow and glaciers in summer, so they are perennial. The peninsular rivers depend only on rain, so their flow falls sharply or stops in the dry season.

Why are the northern plains rich in ground water while the Deccan Plateau is not?

The northern plains are made of thick, soft, porous alluvium that soaks up rain and river water easily. The Deccan Plateau is made of hard, non-porous rocks that hold water only in their cracks.

Give three reasons why water must be conserved in India.

Rainfall is seasonal and uneven; demand from a growing population, irrigation, industry and cities is rising; and ground water is being over-used, so the water table is falling. (Also: pollution of rivers and ground water, wastage, falling water per person.)

What is rainwater harvesting? State three advantages of it.

Rainwater harvesting is the collection and storage of rain water where it falls, for direct use or to recharge ground water. It raises the water table, provides water in the dry season, and reduces urban flooding and soil erosion. (Also: reduces demand on municipal supply, dilutes salts and fluoride, cheap.)

Name two traditional methods of rainwater harvesting and the regions where they are practised.

Tankas, underground tanks in Rajasthan; kuls, channels in the Western Himalaya. (Also: johads and khadins in Rajasthan and Haryana, bamboo drip irrigation in Meghalaya, eris in Tamil Nadu, zabo in Nagaland.)

Define irrigation and give three reasons why it is needed in India.

Irrigation is the artificial supply of water to agricultural land to make up for rain that is too little, uncertain or badly timed. It is needed because rainfall is seasonal, the monsoon is uncertain, and some regions receive too little rain. (Also: water-loving crops, multiple cropping, high-yielding varieties, sandy soils.)

Past board exam questions

ICSE 2027 sample paper · 2 marks

Drip irrigation is a powerful solution to prevent crop failure, especially during critical dry periods. Give two suitable reasons in support of this statement.

Show answer

1. It delivers water directly to the root zone of the crops, so water is conserved and reaches where it is needed. 2. Water is released drop by drop at a slow rate, preventing wastage through evaporation and run-off, so limited water lasts through dry periods.

ICSE 2027 sample paper · 2 marks

Why is canal irrigation a more suitable method of irrigation in the northern plains of India? Mention any two reasons.

Show answer

Any two: the plains are flat and level, so canals are easy to build; many perennial (snow-fed) rivers supply water throughout the year; the soft alluvial soil makes digging canals easy; the region is agriculturally important and needs a large, steady water supply.

ICSE 2026 board paper · 1 mark

Assertion (A): Irrigation is practised in large parts of India. Reason (R): India has a variety of soil types.

(A) is true and (R) is false.
(A) is false and (R) is true.
Both (A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true but (R) is not the correct explanation of (A).

Show answer

Both (A) and (R) are true but (R) is not the correct explanation of (A).

ICSE 2026 sample paper · 2 marks

The need for irrigation in India is to a large extent, influenced by the rainfall pattern of the country. Explain.

Show answer

Any two: Rainfall in India is seasonal, confined to about four months of the monsoon, so irrigation is needed in the dry months; it is uncertain and erratic (late onset, early withdrawal, breaks); it is unevenly distributed, so low-rainfall areas need irrigation; and water-loving crops such as rice and sugarcane need more water than rain provides.

ICSE 2026 sample paper · 2 marks

Why is canal irrigation a more suitable method of irrigation in the northern plains of India?

Show answer

The northern plains have level land and soft alluvial soil, so canals are easy to dig; and they are drained by perennial snow-fed rivers (Ganga, Yamuna, Sutlej) that supply water to the canals throughout the year.

ICSE 2026 sample paper · 3 marks

Study the picture given below and answer the questions that follow: [Picture: rain falls from clouds (labelled 'Rainfall') onto the sloping roof of a house (labelled 'Catchment Area'). A pipe from the roof (labelled 'Drain Line'), carrying 'Runoff', leads down into a large 'Storage Tank' beside the house; a tap on the tank is labelled 'Reuse'.] (a) Name the water conservation method shown in the picture. (b) Mention any two similar water harvesting practices followed in India.

Show answer

(a) Rainwater harvesting (rooftop rainwater harvesting). (b) Any two: percolation pits/recharge pits; johads; tankas; percolation tanks; zings; dug wells or bore wells for recharge.

ICSE 2026 board paper · 2 marks

Raghu wants to irrigate his large field in a manner that will ensure uniform water distribution across the field along with water conservation. (a) Name the irrigation method that will be suitable as per his need. (b) How will the method of irrigation mentioned by you in (a) above help to conserve water?

Show answer

(a) Sprinkler irrigation. (b) Water is sprayed evenly over the crops like rain through pipes and rotating nozzles, so only the required amount is given; there is no loss of water through seepage in open channels, waterlogging or run-off, so much less water is used than in flood irrigation.

ICSE 2026 board paper · 2 marks

What is the difference between Inundation canals and Perennial canals?

Show answer

Inundation canals are taken out of rivers without any dam or barrage; they carry water only in the rainy season when the river is in flood, so they are seasonal. Perennial canals are taken out of perennial rivers by building a dam, barrage or weir across the river; they supply water throughout the year.