Water Harvesting and Storage

25 Grade 8 Agriculture questions on Water Harvesting and Storage, with worked marking schemes. 25 questions are available on this topic in full.

1. Question 1

   4 marks

   A family in Machakos harvests rainwater from their iron-sheet roof into a 5000-litre plastic tank.

   (a) State two components of a roof water-harvesting system that they must install.

   (b) Explain one advantage of harvesting rainwater for such a household.

   (4 marks)

   Marking scheme

   (a) Any two (1 mark each): gutters; downpipe; storage tank; first-flush diverter; leaf/wire-mesh screen. (b) One advantage well explained (2 marks): e.g. provides water during dry seasons; reduces cost of buying water; reduces distance and time spent fetching water.

2. Question 2

   1 mark

   Which of the following is an example of harvesting water from surface run-off rather than from a roof?

   A. Placing a rain barrel under a gutter

   B. Constructing a water pan in a shallow depression

   C. Attaching a first-flush diverter to a gutter

   D. Fixing a downpipe to a corrugated iron roof

   (1 mark)

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3. Question 3

   4 marks

   A learner wants to check that water harvested from a roof is safe for drinking.

   (a) Give two methods the learner can use to treat the water at home.

   (b) State one reason why the roof catchment area should be kept clean.

   (4 marks)

   Marking scheme

   (a) Any two treatment methods (1 mark each): boiling; chlorination/adding water guard; filtration; solar disinfection (SODIS). (b) One reason (2 marks): a dirty roof washes debris, dust and bird droppings into the tank, contaminating the water and making it unsafe.

4. Question 4

   1 mark

   Which material is MOST suitable for lining a water pan to reduce loss of water through seepage into the soil?

   A. Dam liner (plastic sheeting)

   B. Dry grass

   C. Wood shavings

   D. Loose sand

   (1 mark)

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5. Question 5

   3 marks

   A school in a dry area plans to install a rainwater harvesting system to water its kitchen garden. Outline three factors the school should consider before choosing the size of the storage tank.

   (3 marks)

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6. Question 6

   1 mark

   A learner notices that the first rainwater flowing off a dusty roof is dirty. The device that discards this dirty first flow before clean water enters the tank is a

   A. Ball valve

   B. First-flush diverter

   C. Sediment pump

   D. Water meter

   (1 mark)

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7. Question 7

   6 marks

   During the long rains, a family in Kitui realises that all the rainwater falling on their iron-sheet roof simply runs to waste, yet they struggle with water shortage during the dry season.

   (a) State TWO components of a roof catchment system the family would need to harvest and store this rainwater. (2 marks)

   (b) Explain TWO reasons why it is important to discard or divert the first run-off (first flush) of rainwater from the roof before storing it. (4 marks)

   (6 marks)

   Marking scheme

   (a) Any TWO components (1 mark each): - Roof (catchment surface) of iron sheets. - Gutters fixed along the roof edge to collect the water. - Down-pipe to channel water from the gutters to the tank. - Storage tank/reservoir (e.g. plastic or ferro-cement tank). (b) Any TWO reasons explained (2 marks each): - The first run-off washes away dust, dry leaves, bird droppings and other dirt that have collected on the roof, so diverting it keeps the stored water clean and safe. - It removes contaminants that could cause water-borne diseases or give the water a bad smell/taste, protecting the health of the family. - It prevents debris and sediment from entering and clogging the tank, keeping the storage water of good quality for domestic use.

8. Question 8

   1 mark

   During the dry season a family in Kitui struggles to find water. They decide to collect rainwater from their iron-sheet roof. Which structure should they connect to the roof to channel water into a storage tank?

   A. A furrow

   B. A gutter

   C. A terrace

   D. A trench

   (1 mark)

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9. Question 9

   3 marks

   State three ways in which harvested water stored in an open pan can be lost before it is used.

   (3 marks)

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10. Question 10

    1 mark

    The main reason for covering a stored water tank with a tight lid on a small farm is to

    A. Speed up evaporation of the water

    B. Increase the pressure of the water

    C. Prevent breeding of mosquitoes and contamination

    D. Make the water taste sweeter

    (1 mark)

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11. Question 11

    1 mark

    In roof catchment, the volume of water harvested increases mainly with an increase in the

    A. Roof surface area

    B. Colour of the roof

    C. Height of the gutters

    D. Age of the building

    (1 mark)

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12. Question 12

    1 mark

    A zai pit is used in dryland farming mainly to

    A. Drain excess water from a field

    B. Store harvested grain

    C. Collect and concentrate rainwater and manure at the plant's roots

    D. House small livestock

    (1 mark)

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13. Question 13

    1 mark

    During the dry season, a family in Kitui struggles to find water for their kitchen garden. They decide to collect rainwater from their iron-sheet roof during the next rains. Which structure should they connect to the roof to direct and collect this rainwater?

    A. A windbreak

    B. Gutters leading to a storage tank

    C. A compost pit

    D. A drainage furrow

    (1 mark)

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14. Question 14

    6 marks

    A school in a semi-arid part of Kitui has a large iron-sheet roof on its classrooms but frequently runs short of water for the kitchen garden during the dry season.

    (a) Explain how the school can harvest rain water from the classroom roof for storage. (3 marks)

    (b) State THREE measures the school should take to keep the stored water clean and safe for use in the kitchen garden and for cleaning. (3 marks)

    (6 marks)

    Marking scheme

    (a) Rooftop water harvesting (3 marks): - Fix gutters along the edge of the iron-sheet roof to collect the rain water as it runs off the roof. - Connect the gutters to a down-pipe that channels the water into a storage tank/reservoir. - Fit a 'first-flush' diverter or screen so that the first dirty water and debris from the roof are not collected; the clean water then flows into a covered storage tank. (1 mark each for gutters, down-pipe to tank, and the screen/first-flush idea.) (b) Keeping stored water clean (any THREE, 1 mark each): - Cover the tank with a tight lid to keep out dust, leaves, animals and mosquitoes. - Fit a fine mesh/screen on the inlet and overflow to keep out debris and insects. - Clean the gutters and the tank regularly to remove silt and dirt. - Treat or filter the water before use; keep the tap/outlet clean. - Site the tank away from latrines and animal waste to avoid contamination.

15. Question 15

    1 mark

    Which practice BEST conserves harvested soil moisture directly around crops in a dry region?

    A. Compacting the topsoil

    B. Removing all ground cover

    C. Watering only at midday

    D. Mulching the soil surface

    (1 mark)

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16. Question 16

    1 mark

    A farmer wants to store harvested rainwater for use during the dry months but is worried about the water becoming contaminated and breeding mosquitoes. Which practice would BEST keep the stored water clean and safe?

    A. Leaving the tank open to the sun

    B. Adding fresh manure to the tank

    C. Covering the storage tank with a tight-fitting lid

    D. Storing the water in shallow open basins

    (1 mark)

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17. Question 17

    4 marks

    Explain two reasons why underground water storage tanks are preferred to raised open tanks in very hot, dry parts of Kenya.

    (4 marks)

    Marking scheme

    Any two, each explained (2 marks each): reduced evaporation because water is shaded from direct sun and heat; keeps water cooler; better protection from contamination and algae growth; saves surface space.

18. Question 18

    1 mark

    Which is a chemical method of treating stored water to make it safe for drinking?

    A. Adding chlorine (water guard)

    B. Filtering through sand

    C. Boiling on a jiko

    D. Exposing it to sunlight in a clear bottle

    (1 mark)

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19. Question 19

    4 marks

    During heavy rains a farmer's water pan overflows and washes away soil around it.

    (a) Suggest two measures to control the overflow and protect the pan.

    (b) State one benefit of harvesting the run-off water.

    (4 marks)

    Marking scheme

    (a) Any two (1 mark each): construct a spillway/overflow channel; build a silt trap upstream; plant grass/vegetation on the banks to hold soil; construct a diversion/cut-off drain. (b) One benefit (2 marks): stored water can be used for irrigation/livestock during dry periods; reduces reliance on rivers.

20. Question 20

    1 mark

    A gutter that slopes gently towards the downpipe is important because it

    A. Cleans the water automatically

    B. Prevents the roof from rusting

    C. Increases the roof size

    D. Allows water to flow steadily into the tank

    (1 mark)

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21. Question 21

    1 mark

    Before drinking harvested rainwater, a household boils it. This treatment is done to

    A. Cool the water

    B. Reduce the volume

    C. Kill disease-causing micro-organisms

    D. Remove the colour

    (1 mark)

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22. Question 22

    1 mark

    A farmer stores harvested rainwater in an open earth pan and notices the water level drops quickly even when it does not rain. Which method would BEST reduce this water loss through evaporation and seepage?

    A. Lining the pan and covering it with a shade

    B. Adding more soil into the pan

    C. Stirring the water daily

    D. Leaving the pan fully exposed to the sun

    (1 mark)

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23. Question 23

    1 mark

    A farmer places a wire-mesh screen at the mouth of the gutter leading to the tank. The purpose of the screen is to

    A. Trap leaves and debris

    B. Increase water flow speed

    C. Warm the water

    D. Add minerals to the water

    (1 mark)

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24. Question 24

    1 mark

    Which of the following is an underground water storage structure suited to areas with high evaporation rates?

    A. A metal drum on a stand

    B. An open earth pan

    C. A raised plastic tank

    D. A lined underground tank (cistern)

    (1 mark)

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25. Question 25

    1 mark

    A farmer in a semi-arid part of Kitui wants to collect rainwater falling on the roof of the farmhouse. Which structure directly channels this water into a storage tank?

    A. Retention ditches

    B. Contour ridges

    C. Cut-off drains

    D. Gutters

    (1 mark)

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