2025 Oct/Nov · Paper 21 · Q2 (b(i))1.2 marksIrrigation methods
2024
2024 Oct/Nov · Paper 21 · Q2 (a(i), a(ii), a(iii), b(i), b(ii), b(iii))7.2 marksDams and barrages · Irrigation methods
2024 May/June · Paper 21 · Q2 (b(i), b(ii), b(iii), b(iv), c, d)10.8 marksOfficial paper ↗Water supply, shortage and pollution
2024 May/June · Paper 21 · Q3 (c(i), c(ii))2.4 marksOfficial paper ↗Waterlogging and salinity
2023
2023 Oct/Nov · Paper 21 · Q3 (b(i), b(ii))3 marksDams and barrages
2023 May/June · Paper 21 · Q1 (d)3.6 marksWater supply, shortage and pollution
2022
2022 Oct/Nov · Paper 21 · Q2 (c(i), c(ii), c(iii), d)8.4 marksIrrigation methods · Waterlogging and salinity
2022 May/June · Paper 21 · Q4 (d)3.6 marksWater supply, shortage and pollution
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References only, not question text. Open Official paper ↗ where Cambridge publishes the paper,
or see the official Cambridge past-papers page; for other papers, ask your
school. “Paper 42” means Paper 4, variant 2.
Practice questions
Original questions written by HomiLabs in the style of the exam, with answers and mark schemes. They are not
Cambridge past paper questions and have not been reviewed by Cambridge. Try each one before opening the answer.
Q1Water supply, shortage and pollution · Core · Paper 2 style · 7 marks
In an illustrative example, a country has about 230 billion m³ of renewable water a year and a population of about 250 million. Countries with less than 1,000 m³ per person per year are said to face water scarcity.
(a)Calculate the water available per person per year.[2]
(b)State whether this country faces water scarcity, giving a reason.[1]
(c)Explain two reasons why water available per person is falling in Pakistan.[4]
Show answer
(a) 230 billion ÷ 250 million = 920 m³ per person.
M1 correct division with units; A1 920 m³.
(b) Yes: 920 m³ is below 1,000 m³ per person.
1 mark.
(c) The population is growing rapidly, so the same water is shared among more people. Reservoirs are losing storage to silt and little new storage has been built, while groundwater is being over-pumped faster than it is recharged.
1 + 1 development each: population growth; silting of reservoirs; limited new dams; over-pumping of groundwater; wastage; climate change and reduced glacier flows.
Q2Water supply, shortage and pollution · Core · Paper 2 style · 6 marks
(a)State two sources of drinking water for people in Pakistan's cities.[2]
(b)Explain two causes of water pollution in rivers near large cities.[4]
Show answer
(a) Any two: rivers/canals (e.g. Indus via Keenjhar Lake for Karachi); reservoirs/dams (Simly, Khanpur, Hub); groundwater from tube wells; bottled or tanker water.
1 each.
(b) Untreated sewage from homes is emptied straight into rivers and drains because there are few treatment plants. Factories such as tanneries and textile mills discharge chemicals and dyes without treatment, poisoning the water.
1 + 1 development each: raw sewage; industrial effluent; solid waste dumping; agricultural run-off (fertilisers, pesticides).
Q3Water supply, shortage and pollution · Core · Paper 2 style · 6 marks
(a)Define 'groundwater'.[1]
(b)Explain two reasons why the water table under Lahore has fallen.[4]
(c)State one problem caused by a falling water table.[1]
Show answer
(a) Water stored underground in the soil and in permeable rocks (aquifers).
1 mark.
(b) A growing city pumps large amounts of water from tube wells for homes and industry, faster than rain and rivers recharge it. The Ravi now carries little water and paved surfaces stop rain soaking into the ground, so recharge is reduced.
1 + 1 development each: over-pumping; population growth; reduced Ravi flow; less recharge from paved surfaces.
(c) Wells and hand pumps dry up / deeper, more expensive pumping / poorer-quality (saline or arsenic-rich) water drawn up.
1 mark.
Q4Water supply, shortage and pollution · Core · Paper 2 style · 4 marks
(a)State two uses of water in Pakistan other than for irrigation.[2]
(b)Agriculture uses about nine-tenths of the water taken from rivers and groundwater in Pakistan. Suggest two reasons why.[2]
Show answer
(a) Any two: drinking/domestic use; industry (cooling, processing); hydroelectric power; fishing; transport; recreation/tourism.
1 each.
(b) Pakistan's climate is mainly arid or semi-arid, so most crops need irrigation; thirsty crops such as rice and sugarcane are widely grown; flood irrigation wastes much water (any two).
1 each.
Q5Water supply, shortage and pollution · Standard · Paper 2 style · 6 marks
A survey of 400 households in a village in southern Punjab found that 136 had piped water at home, 212 used a hand pump or tube well and the rest collected water from a canal or pond.
(a)Calculate the percentage of households with piped water.[1]
(b)Calculate how many households collected water from a canal or pond.[1]
(c)Explain two health risks for the households that use canal or pond water.[4]
Show answer
(a) 136 ÷ 400 × 100 = 34%.
B1 34%.
(b) 400 − 136 − 212 = 52.
B1 52.
(c) The water may carry bacteria and viruses from sewage and animals, causing diarrhoea, cholera and typhoid, especially in children. Standing water also breeds mosquitoes, spreading malaria and dengue.
1 + 1 development each: water-borne diseases; mosquito-borne disease; chemical contamination from farm run-off.
Q6Water supply, shortage and pollution · Standard · Paper 2 style · 6 marks
(a)Explain two reasons why many people in Karachi suffer from water shortages.[4]
(b)Suggest two ways to improve water supply to a large city like Karachi.[2]
Show answer
(a) The city's population has grown faster than its water supply, which depends mainly on the Indus (via Keenjhar Lake) and Hub Dam. Much water is lost through leaking pipes and illegal connections, and a 'tanker mafia' sells water at high prices.
1 + 1 development each: population growth; limited sources / dependence on Indus and Hub; leakage and theft; unequal distribution; low rainfall.
(b) Any two: repair leaking pipes; stop illegal connections; build new supply schemes (e.g. bulk water projects); desalination plants; recycle treated waste water for industry; rainwater harvesting.
1 each.
Q7Water supply, shortage and pollution · Standard · Paper 2 style · 6 marks
A school in Islamabad collects rainwater from a roof of area 120 m². The annual rainfall is taken as 500 mm, and about 80% of the water falling on the roof can be stored.
(a)Calculate the volume of water the school can collect in a year, in m³.[2]
(b)Explain two benefits of rainwater harvesting in Pakistan.[4]
Show answer
(a) 120 × 0.5 = 60 m³; × 0.8 = 48 m³.
M1 area × rainfall in metres; A1 48 m³.
(b) It reduces demand on piped supply and groundwater, so water tables fall more slowly. It stores monsoon water that would otherwise run off, which can be used for gardens, toilets or recharging aquifers, and it reduces urban flooding.
1 + 1 development each.
Q8Water supply, shortage and pollution · Standard · Paper 2 style · 6 marks
(a)Describe two effects of polluted water on farming and fishing in the Indus Delta and lower Sindh.[2]
(b)Explain two ways in which industrial water pollution could be reduced.[4]
Show answer
(a) Any two: crops irrigated with contaminated water give lower yields or unsafe food; fish stocks fall in lakes such as Manchar; fishermen lose income; mangroves damaged.
1 each.
(b) Factories could be made by law to install treatment plants before releasing waste, with fines for breaking the rules. Industrial estates could share combined effluent treatment plants, which are cheaper for small firms.
1 + 1 development each: laws/enforcement (EPA); treatment plants; combined plants in estates; recycling water; relocating polluting industry.
Q9Water supply, shortage and pollution · Challenge · Paper 2 style · 8 marks
(a)Explain how the Indus Waters Treaty (1960) affects water supply in Pakistan.[4]
(b)'Pakistan's water shortage is caused more by poor management than by a lack of water.' Do you agree? Give reasons to support your answer.[4]
Show answer
(a) The treaty gave the three eastern rivers (Ravi, Beas, Sutlej) to India and the three western rivers (Indus, Jhelum, Chenab) to Pakistan. To replace the eastern river water, Pakistan built link canals, Mangla and Tarbela dams and barrages under the Indus Basin Project; the Ravi and Sutlej now carry little water through Pakistan except in floods.
1 + 1 development each, max 4.
(b) Management: large losses from unlined canals; flood irrigation wastes water; little storage (only about a month of river flow); low water charges encourage waste; pollution makes water unusable. Natural/limited supply: arid climate, low rainfall in most of the country, dependence on one river system, variable monsoon and glacier melt, rising population. Judgement required.
Levels: L1 (1–2) simple points; L2 (3–4) both sides developed with judgement.
Q10Water supply, shortage and pollution · Challenge · Paper 2 style · 7 marks
(a)Explain why rural women and children are most affected by water shortages.[3]
(b)Explain two ways in which climate change may affect Pakistan's future water supply.[4]
Show answer
(a) In many villages it is their task to fetch water, so they walk long distances carrying heavy loads. This takes time from school and paid work, and lack of clean water at home increases illness among children.
1 per point, max 3.
(b) Higher temperatures are melting glaciers faster, giving more water at first but less in the long term as glaciers shrink. Rainfall is becoming more variable, with more droughts and more intense floods, making supply less reliable.
1 + 1 development each: glacier melt; changes to monsoon; higher evaporation; more floods/droughts.
Q11Water supply, shortage and pollution · Challenge · Paper 2 style · 5 marks
A town's water board pumps 1200 thousand litres a day into its pipes, but meters show only 780 thousand litres a day reach homes and businesses.
(a)Calculate the percentage of water lost.[2]
(b)Suggest two causes of this loss and one way to reduce it.[3]
Show answer
(a) 1200 − 780 = 420; 420 ÷ 1200 × 100 = 35%.
M1; A1 35%.
(b) Causes: leaking, old pipes; illegal connections / theft; unmetered use. Reduction: replace or repair pipes; detect and remove illegal connections; install meters.
1 each for two causes; 1 for a matching solution.
Q12Irrigation methods · Core · Paper 2 style · 7 marks
(a)Describe how a karez works.[3]
(b)Explain two advantages of the karez system in Balochistan.[4]
Show answer
(a) A karez is an underground channel dug into the foot of a hill or alluvial fan. It carries groundwater by gravity to the surface at a lower level. Vertical shafts at intervals are used for digging and cleaning; water is used in fields and villages, for example in Balochistan.
1 per point, max 3.
(b) Because the water flows underground, little is lost by evaporation in the hot, dry climate. It works by gravity, so no fuel or electricity is needed and it can supply water all year.
1 + 1 development each: low evaporation; no pumping cost; reliable supply; community-managed.
Q13Irrigation methods · Core · Paper 2 style · 6 marks
(a)What is the difference between a perennial canal and an inundation canal?[2]
(b)Explain two disadvantages of inundation canals.[4]
Show answer
(a) A perennial canal takes water from a barrage or dam and flows all year; an inundation canal flows only when the river is high in summer floods.
1 each.
(b) They have no water in winter when the river is low, so rabi crops cannot be irrigated. Their supply depends on the size of the flood: a poor flood brings too little water and a big flood can damage fields.
1 + 1 development each.
Q14Irrigation methods · Core · Paper 2 style · 5 marks
(a)Name two traditional methods of lifting water from wells in Pakistan.[2]
(b)Explain why tube wells have become a common method of irrigation.[3]
Show answer
(a) Any two: Persian wheel; shaduf; charsa (leather bag pulled by animals); hand pump.
1 each.
(b) They can supply water whenever the farmer needs it, including when canals are closed. They supplement canal water in areas at the tail end of canals and also help lower high water tables. Cheap diesel and electric pumps and government schemes encouraged them.
1 per point, max 3.
Q15Irrigation methods · Core · Paper 2 style · 6 marks
(a)Name the two cropping seasons in Pakistan and give one crop grown in each.[4]
(b)Explain why rabi crops in the Indus Plain depend heavily on canal or tube-well irrigation.[2]
Show answer
(a) Kharif (summer) – e.g. rice, cotton, sugarcane, maize; Rabi (winter) – e.g. wheat, gram, mustard.
1 each for season names; 1 each for correct crop.
(b) Winter rainfall in the plains is low and unreliable, while river flow is low in winter, so water must be supplied from storage reservoirs through perennial canals or pumped from groundwater.
1 + 1 development.
Q16Irrigation methods · Standard · Paper 2 style · 4 marks
In a canal command area, 25% of the water entering the main canal is lost by seepage and evaporation before reaching the watercourses, and a further 20% of what remains is lost in the watercourses before reaching the fields.
(a)For every 100 units of water entering the canal, calculate how many units reach the fields.[2]
(b)Suggest two ways to reduce these losses.[2]
Show answer
(a) 100 × 0.75 = 75; 75 × 0.80 = 60 units.
M1 successive reductions; A1 60.
(b) Line canals and watercourses with bricks or concrete; cover/pipe watercourses; remove weeds and repair banks; level fields (any two).
1 each.
Q17Irrigation methods · Standard · Paper 2 style · 4 marks
A farmer near Multan irrigates orchards using flooding, which uses about 6000 m³ of water per hectare per season. Drip irrigation would use 40% less water.
(a)Calculate the water used per hectare with drip irrigation.[1]
(b)Calculate the total water saved on 15 hectares in one season.[1]
(c)Give two reasons why few farmers in Pakistan use drip irrigation.[2]
Show answer
(a) 6000 × 0.6 = 3600 m³.
B1 3,600 m³.
(b) 2400 × 15 = 36,000 m³.
B1 36,000 m³.
(c) High cost of pipes and equipment; small farms and poor farmers; lack of knowledge/training; canal water is cheap so there is little reason to save it; electricity/power needed for pumps (any two).
1 each.
Q18Irrigation methods · Standard · Paper 2 style · 6 marks
(a)Describe sprinkler irrigation.[2]
(b)Compare sprinkler irrigation with flood irrigation.[4]
Show answer
(a) Water is pumped through pipes and sprayed over crops through nozzles, like rain.
1 for pipes/pump; 1 for spraying like rain.
(b) Sprinklers use less water and spread it more evenly, giving less waterlogging and salinity; they suit uneven land. Flood irrigation is cheap and simple and needs no energy, but wastes water through run-off and seepage. Sprinklers cost more and need power and maintenance.
1 per valid comparison, max 4; must refer to both methods.
Q19Irrigation methods · Challenge · Paper 2 style · 6 marks
A tube well pumps water at 0.03 m³ per second and runs for 8 hours a day.
(a)Calculate the volume of water pumped in one day.[2]
(b)Explain two problems caused by the rapid growth in the number of private tube wells.[4]
Show answer
(a) 0.03 × 8 × 3600 = 864 m³.
M1 convert hours to seconds; A1 864 m³.
(b) Over-pumping lowers the water table, so wells must be deepened and pumping costs rise. In some areas the deeper water is saline, and using it damages soil; high fuel and electricity costs also burden farmers.
1 + 1 development each: falling water table; saline groundwater; energy cost/load-shedding; inequality between rich and poor farmers.
Q20Irrigation methods · Challenge · Paper 2 style · 8 marks
(a)Explain why the Indus Basin irrigation system is important to Pakistan's economy.[4]
(b)'Modern irrigation methods should replace traditional methods everywhere in Pakistan.' Do you agree? Give reasons to support your answer.[4]
Show answer
(a) Most of Pakistan's crops, including wheat, rice, cotton and sugarcane, are grown on irrigated land because rainfall is too low. These crops feed the population and supply raw materials to industries such as textiles and sugar, which earn much of Pakistan's export income and provide many jobs.
1 + 1 development each: food security; raw materials for industry; exports; employment.
(b) For: drip and sprinkler save water and raise yields; lined canals reduce waterlogging. Against: modern methods are costly and need power; traditional methods such as karez are sustainable and suit local conditions, cost little and are community-run; small farmers cannot afford equipment. Judgement required.
Levels: L1 (1–2); L2 (3–4) both sides developed with judgement.
Q21Dams and barrages · Core · Paper 2 style · 5 marks
(a)Name the river on which Tarbela Dam is built.[1]
(b)State two differences between a dam and a barrage.[2]
(c)Name two barrages on the Indus.[2]
Show answer
(a) The Indus.
1 mark.
(b) A dam is a high wall that stores large amounts of water in a reservoir (for irrigation and HEP); a barrage is a lower structure with gates that raises the river level to divert water into canals and stores little water.
1 per difference, max 2.
(c) Any two: Jinnah, Chashma, Taunsa, Guddu, Sukkur, Kotri.
1 each.
Q22Dams and barrages · Core · Paper 2 style · 5 marks
(a)Name the river on which Warsak Dam is built.[1]
(b)Name the barrage at Sukkur by its other name.[1]
(c)Explain how a barrage helps irrigation.[3]
Show answer
(a) The Kabul River.
1 mark.
(b) Lloyd Barrage.
1 mark.
(c) Gates across the river hold back water and raise its level. This lets water flow by gravity into canals that start just above the barrage. Canal flow can be controlled by opening or closing the gates.
1 per point, max 3.
Q23Dams and barrages · Standard · Paper 2 style · 6 marks
A reservoir in northern Pakistan could originally store 9.0 km³ of water. Silt reduces its storage by about 0.09 km³ each year.
(a)Calculate the storage after 20 years.[1]
(b)Calculate the percentage of original storage lost in that time.[1]
(c)Explain two ways in which loss of storage affects Pakistan.[4]
Show answer
(a) 9.0 − 0.09 × 20 = 7.2 km³.
B1 7.2 km³.
(b) 1.8 ÷ 9.0 × 100 = 20%.
B1 20%.
(c) Less water can be stored from the summer floods for use in the dry winter, so canals receive less water for rabi crops. Lower water levels also mean less hydroelectric power, increasing the use of expensive imported fuel.
1 + 1 development each: less irrigation; less HEP; less flood control.
Q24Dams and barrages · Standard · Paper 2 style · 6 marks
(a)Explain two benefits of large multi-purpose dams such as Tarbela and Mangla.[4]
(b)Describe two problems of building large dams.[2]
Show answer
(a) They store monsoon and snow-melt water and release it through the year to canals, allowing two crops a year. Water flowing through turbines generates cheap hydroelectricity; they also help control floods and support fishing and tourism.
1 + 1 development each: irrigation; HEP; flood control; fishing/recreation.
(b) Any two: high cost and long construction time; people and villages displaced; farmland and forests drowned; silting; sites in earthquake zones; disputes between provinces.
1 each.
Q25Dams and barrages · Standard · Paper 2 style · 5 marks
(a)What is a link canal?[1]
(b)Explain why link canals were built in Pakistan after 1960.[4]
Show answer
(a) A canal that carries water from one river to another.
1 mark.
(b) Under the Indus Waters Treaty the water of the eastern rivers went to India, so canals in Punjab that had been fed by the Ravi and Sutlej would have run dry. Link canals carry water from the western rivers (Indus, Jhelum, Chenab) eastwards to keep these canals supplied.
1 + 1 development each: treaty context; transfer water from west to east; keep existing canals and farmland in use.
Q26Dams and barrages · Challenge · Paper 2 style · 8 marks
(a)Explain why the building of new large dams in Pakistan is often controversial.[4]
(b)'Pakistan should build more small dams instead of large dams.' Do you agree? Give reasons to support your answer.[4]
Show answer
(a) Downstream provinces, especially Sindh, fear that new dams upstream will reduce the water reaching their canals and the Indus Delta. Large dams displace thousands of people and drown land, and their huge cost and debts make governments hesitate.
1 + 1 development each.
(b) Small dams: cheaper, quicker, fewer people displaced, serve local farms in barani areas, less controversy. Large dams: store far more water, generate much more HEP, give greater flood control and serve the whole Indus system. Judgement required.
Levels: L1 (1–2); L2 (3–4) both sides developed with judgement.
Q27Waterlogging and salinity · Core · Paper 2 style · 5 marks
(a)Define 'waterlogging'.[1]
(b)Explain how salinity develops in irrigated areas.[4]
Show answer
(a) When the water table rises to (or near) the surface so the soil is saturated and roots cannot breathe.
1 mark.
(b) When the water table is high, water rises to the surface through the soil by capillary action. In the hot climate it evaporates quickly, leaving the dissolved salts behind as a white crust (kallar) on the surface, which harms crops.
1 per point, max 4: high water table; capillary action; evaporation; salts left / crust; reduced fertility.
Q28Waterlogging and salinity · Standard · Paper 2 style · 6 marks
On a farm in Sindh, wheat yields fell from 3.2 tonnes per hectare to 2.4 tonnes per hectare as salinity increased.
(a)Calculate the percentage fall in yield.[2]
(b)Explain two causes of waterlogging in the Indus Plain.[4]
Show answer
(a) 3.2 − 2.4 = 0.8; 0.8 ÷ 3.2 × 100 = 25%.
M1; A1 25%.
(b) Water seeps from unlined canals and watercourses into the ground, raising the water table. Farmers over-irrigate with flood methods and the flat land has poor natural drainage, so excess water cannot drain away.
1 + 1 development each: canal seepage; over-irrigation; poor drainage; flat land; heavy monsoon/floods.
Q29Waterlogging and salinity · Standard · Paper 2 style · 5 marks
(a)What do the letters SCARP stand for?[1]
(b)Explain two ways in which waterlogging and salinity can be reduced.[4]
Show answer
(a) Salinity Control and Reclamation Project(s).
1 mark.
(b) Tube wells (as in SCARP) pump out groundwater to lower the water table, and the water can be reused for irrigation. Lining canals stops seepage; drains such as the Left Bank Outfall Drain carry saline water away to the sea.
1 + 1 development each: tube wells; canal lining; drainage; leaching with extra water; salt-tolerant crops; gypsum; tree planting.
Q30Waterlogging and salinity · Challenge · Paper 2 style · 8 marks
(a)Explain two effects of waterlogging and salinity on farmers.[4]
(b)'Waterlogging and salinity are caused more by people than by nature.' Do you agree? Give reasons to support your answer.[4]
Show answer
(a) Crop yields fall and some land becomes too salty to farm, so farmers' incomes drop and some must leave the land. Treating the land (gypsum, drainage, extra water) is costly, and houses and roads can be damaged by the high water table.
1 + 1 development each.
(b) People: unlined canals, over-irrigation, poor drainage design, cutting trees, poor maintenance. Nature: flat land with little natural drainage, hot climate with high evaporation, saline rocks and groundwater, heavy rain/floods. Judgement required.
Levels: L1 (1–2); L2 (3–4) both sides developed with judgement.
Similar questions
Questions that test the same subtopic in different years, grouped so you can work on one skill at a time.
References only: find each question in its paper (official link where available, otherwise through your school).
Water supply, shortage and pollution3 questions · 3/9 sessions
