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 May/June · Paper 21 · Q1 (d)3.6 marksWater supply, shortage and pollution
2022
2022 May/June · Paper 21 · Q4 (d)3.6 marksWater supply, shortage and pollution
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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 · 8 marks
(a)Name the river on which each of these dams is built: Tarbela; Mangla.[2]
(b)State two purposes of large dams in Pakistan, other than storing water for irrigation.[2]
(c)Explain two reasons why Pakistan needs more water storage. You should develop your answer.[4]
Show answer
(a) Tarbela: Indus; Mangla: Jhelum
1 mark each.
(b) Generating hydroelectricity; flood control.
1 mark each for any two: hydroelectricity; flood control; drinking water for cities; fishing; tourism/recreation.
(c) Most river flow comes in the summer months from snowmelt and the monsoon, so without storage much of it flows to the sea and there is a shortage in winter for rabi crops; existing reservoirs are losing capacity as they fill with silt, while the growing population needs more water for food, homes and industry.
1 mark for each of two reasons + 1 mark each for development (a consequence or 'which leads to'). Reasons: seasonal flow (summer peak, winter shortage); low storage compared with annual flow (only about a month of average flow); siltation of Tarbela and Mangla; rising population and demand; drought years; protection against floods.
Q2Water supply, shortage and pollution · Core · Paper 2 style · 8 marks
A water-testing survey of 250 drinking-water samples from hand pumps and wells in rural districts found that 155 samples were unsafe because of bacteria or harmful chemicals (illustrative figures).
(a)Calculate the percentage of samples that were unsafe.[1]
(b)Calculate the number of samples that were safe.[1]
(c)Name two diseases that are spread by polluted drinking water.[2]
(d)Explain two ways of providing safer drinking water in rural areas of Pakistan. You should develop your answer.[4]
Show answer
(a) 62%
155 ÷ 250 × 100 = 62%.
(b) 95
250 − 155 = 95.
(c) Cholera and typhoid
1 mark each for any two: cholera; typhoid; diarrhoea / dysentery; hepatitis A or E; gastroenteritis.
(d) Community water filtration plants can be set up in villages, which remove bacteria and harmful chemicals so that people collect clean water instead of using ponds or canals; hand pumps and tubewells can be sited away from latrines and drains and made deeper, so that sewage does not seep into the water people drink.
1 mark for each of two reasons + 1 mark each for development (a consequence or 'which leads to'). Ways: filtration plants; chlorination / boiling and awareness campaigns; deeper tubewells away from sewage; piped supply from protected sources; covered storage tanks; regular water testing; improved sanitation and drainage.
Q3Water supply, shortage and pollution · Core · Paper 2 style · 7 marks
(a)What is a karez?[2]
(b)State one reason why many karez in Balochistan have dried up.[1]
(c)Explain two reasons why Balochistan suffers more from water shortages than Punjab. You should develop your answer.[4]
Show answer
(a) An underground channel that carries groundwater by gravity from the foot of a hill to the surface, where it is used for drinking and irrigation.
1 mark for underground channel / tunnel; 1 mark for carrying groundwater by gravity from higher ground to fields or villages.
(b) Tubewells pumping groundwater have lowered the water table.
1 mark for any one: over-pumping by tubewells lowers the water table; long droughts; lack of maintenance / collapse of channels.
(c) Balochistan has a very dry climate with low and unreliable rainfall, so there is little surface water and long droughts are common; it has no large perennial rivers like the Punjab rivers and little of the canal network, so towns and farmers depend on groundwater, which is being used faster than it is replaced.
1 mark for each of two reasons + 1 mark each for development (a consequence or 'which leads to'). Reasons: low, unreliable rainfall / droughts; high evaporation; few perennial rivers; small share of the canal system; dependence on falling groundwater; scattered population makes piped supply costly.
Q4Water 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.
Q5Water 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).
Q6Water 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.
Q7Water 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.
Q8Water supply, shortage and pollution · Standard · Paper 2 style · 8 marks
A city has a population of 3.2 million. Its planners assume that each person needs 150 litres of water a day. The water board supplies 330 million litres a day (illustrative figures).
(a)Calculate the city's total daily water demand in million litres.[1]
(b)Calculate the daily shortfall.[1]
(c)Calculate the percentage of demand that is supplied. Give your answer to one decimal place.[1]
(d)Explain two ways in which demand for water in the city could be reduced. You should develop your answer.[4]
(e)Suggest one way in which the city's supply could be increased.[1]
Show answer
(a) 480 million litres per day
3.2 million × 150 L = 480 million litres per day.
(b) 150 million litres per day
480 − 330 = 150 million litres per day.
(c) 68.8%
330 ÷ 480 × 100 = 68.75% ≈ 68.8%.
(d) Fitting water meters and charging by the amount used would encourage households and businesses to waste less, because higher use would cost them more; repairing leaking pipes and taps and running awareness campaigns would cut waste, and industries could be required to recycle their process water.
1 mark for each of two reasons + 1 mark each for development (a consequence or 'which leads to'). Ways: metering and charging by volume; awareness campaigns; repairing leaks in homes; water-saving taps and fittings; recycling water in industry; reusing treated waste water for parks; stopping illegal connections.
(e) Build rainwater harvesting systems on roofs.
1 mark for any one: new pipeline from a river or reservoir; rainwater harvesting; new tubewells (if aquifer allows); repairing leaks in mains; treating and reusing waste water; desalination (coastal city).
Q9Water supply, shortage and pollution · Standard · Paper 2 style · 8 marks
Biochemical oxygen demand (BOD) is a measure of organic pollution in water: the higher the BOD, the more polluted the water. Readings along a river passing a large city (illustrative figures):Upstream of the city: 4 mg/L; where the city's main drain enters: 68 mg/L; 20 km downstream: 41 mg/L; 60 km downstream: 22 mg/L.In this question, water with a BOD above 6 mg/L is taken as unsuitable for fish.
(a)Calculate the increase in BOD from upstream of the city to the point where the city's drain enters the river.[1]
(b)Calculate the percentage fall in BOD between the drain outlet and 60 km downstream. Give your answer to one decimal place.[2]
(c)Using the data, state at which sites the water is unsuitable for fish.[1]
(d)Explain two effects of this pollution on people living downstream of the city. You should develop your answer.[4]
Show answer
(a) 64 mg/L
68 − 4 = 64 mg/L.
(b) 67.6%
68 − 22 = 46 (M1); 46 ÷ 68 × 100 = 67.6% (A1).
(c) At the drain outlet, 20 km downstream and 60 km downstream
1 mark: all three sites below the city (BOD above 6 mg/L); only the upstream site is suitable.
(d) Fish die or become unsafe to eat, so fishermen lose their income and families lose a cheap source of protein; farmers who irrigate vegetables with the polluted water may spread disease to consumers, and people who drink or bathe in the water can catch diarrhoea, typhoid or skin infections.
1 mark for each of two reasons + 1 mark each for development (a consequence or 'which leads to'). Effects: loss of fish and fishermen's income; contaminated crops irrigated with waste water; water-borne diseases; polluted groundwater near the river; cost of treating drinking water; bad smells and loss of recreation.
Q10Water supply, shortage and pollution · Standard · Paper 2 style · 9 marks
Mean monthly flow of a large river in the north of Pakistan (illustrative figures, billion m³):Jan 2.1, Feb 2.0, Mar 2.8, Apr 4.5, May 8.6, Jun 13.9, Jul 17.8, Aug 16.2, Sep 8.1, Oct 3.9, Nov 2.6, Dec 2.2
(a)Calculate the total annual flow.[1]
(b)Calculate the percentage of the annual flow that occurs from June to September. Give your answer to one decimal place.[2]
(c)Calculate how many times greater the flow is in July than in February. Give your answer to one decimal place.[1]
(d)Explain two reasons why the flow of the river is highest in summer. You should develop your answer.[4]
(e)Suggest why this pattern of flow causes problems for water supply.[1]
(d) Rising temperatures in summer melt snow and glaciers in the Karakoram and Himalayas, which release large amounts of water into the river; the monsoon brings heavy rain in July and August, especially in the foothills, which adds to the river's flow.
1 mark for each of two reasons + 1 mark each for development (a consequence or 'which leads to'). Reasons: snowmelt; glacier melt; monsoon rainfall in July–August; relief rain on mountain slopes in the catchment.
(e) Much summer water flows to the sea because storage is limited, leaving too little in winter for rabi crops and towns.
1 mark for linking high summer flow / low winter flow with a shortage in winter or the need for storage (or floods in summer).
Q11Water 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.
Q12Water 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.
Q13Water 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.
Q14Water 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.
Q15Water supply, shortage and pollution · Challenge · Paper 2 style · 9 marks
(a)Name the river on which the Diamer-Bhasha dam is being built.[1]
(b)State two problems caused by building large dams.[2]
(c)Read the two views.View A: Building more large dams is the best way to solve Pakistan's water shortage.View B: Using existing water more efficiently is a better way to solve Pakistan's water shortage.Which view do you agree with more? Give reasons for your answer, referring to both views.[6]
Show answer
(a) Indus
1 mark: Indus.
(b) People living in the valley lose their homes and land; they are very expensive and take many years to build.
1 mark each for any two: displacement of people; loss of farmland and heritage sites; very high cost / loans; long construction time; reservoirs silt up; earthquake risk; reduced flow downstream harms the delta.
(c) View A: dams such as Diamer-Bhasha would store summer flood water for the dry winter season, replace storage lost through silting at Tarbela and Mangla and produce cheap hydel power; but they are very costly, take decades and displace people. View B: large amounts of water are lost through seepage from unlined canals and watercourses and through flood irrigation, and leaks in city pipes waste much drinking water, so lining canals, drip and sprinkler irrigation, laser land levelling and metering could save water more quickly and cheaply. Judgement supported by the argument, e.g. both are needed but efficiency gives faster results.
Level marking. L1 (1–2): simple points, one side only. L2 (3–4): developed points, mainly on one side, or simple points on both. L3 (5–6): developed points on both sides, at least one named example from Pakistan, and a judgement. Points to credit: View A: storage of summer flow, lost storage through silting, hydel power, flood control; cost, time, displacement, sediment. View B: canal seepage losses, flood irrigation, water-hungry crops, city leaks, groundwater over-pumping; lining, drip/sprinkler, laser levelling, pricing and metering; efficiency alone cannot store seasonal flow.
Q16Water supply, shortage and pollution · Challenge · Paper 2 style · 11 marks
(a)What is meant by 'desalination'?[1]
(b)Explain two reasons why desalination is not widely used to supply water in Pakistan. You should develop your answer.[4]
(c)'Desalination is the best solution to the water shortages of coastal cities such as Karachi and Gwadar.' Evaluate this view.[6]
Show answer
(a) Removing salt from sea water (or brackish groundwater) to make fresh water.
1 mark.
(b) Desalination plants use large amounts of energy, and electricity in Pakistan is expensive and in short supply, so the water produced costs much more than river or groundwater; the plants are expensive to build and maintain, and they produce very salty waste (brine) that must be disposed of without harming the sea and mangroves.
1 mark for each of two reasons + 1 mark each for development (a consequence or 'which leads to'). Reasons: high energy use and cost; high construction and maintenance cost; brine disposal and marine pollution; only practical near the coast, while most people live inland; pumping water inland is costly; shortage of technical skills.
(c) For: both cities are beside the sea, which is an unlimited source; Gwadar has very low rainfall and its reservoirs dry up in droughts, and Karachi's supply from the Indus and Hub dam is not enough for its growing population. Against: desalination is very costly in energy and money; Karachi loses a large share of its supply through leaks, theft and illegal hydrants, so reducing losses, building bulk supply schemes from the Indus, rainwater harvesting and recycling waste water may be cheaper. Judgement, e.g. useful for Gwadar but for Karachi better management comes first.
Level marking. L1 (1–2): simple points, one side only. L2 (3–4): developed points, mainly on one side, or simple points on both. L3 (5–6): developed points on both sides, at least one named example from Pakistan, and a judgement. Points to credit: For: unlimited sea water, independent of rainfall and river flow, useful in droughts, Gwadar's lack of alternatives. Against: cost, energy, brine; Karachi's losses (leaks, theft, tanker mafia); other options such as new bulk supply schemes, rainwater harvesting, recycling, small dams.
Q17Water 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.
Q18Water 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.
Q19Water 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.
Q20Irrigation 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.
Q21Irrigation 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.
Q22Irrigation 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.
Q23Irrigation 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.
Q24Irrigation 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.
Q25Irrigation 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.
Q26Irrigation 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.
Q27Irrigation 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.
Q28Irrigation 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.
Q29Waterlogging 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.
Q30Waterlogging 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.
Q31Waterlogging 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.
Q32Waterlogging 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]
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(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 · 3/5 sessions
