AQA A-level Geography · 3.1.1

Systems and the global water cycle

50 exam-style questions with answers for 3.1.1 Systems and the global water cycle in AQA A-level Geography (spec 7037). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.

All 50 questions and answers

Question 1 · Spec 3.1.1.1 · Systems concepts
Define a system in physical geography. [2 marks]
Answer:
A set of components (stores) linked by flows or transfers (1); with inputs and outputs of energy and matter, which can be studied as a whole (1).
Question 2 · Spec 3.1.1.1 · Systems concepts
Distinguish between an open system and a closed system. [2 marks]
Answer:
An open system exchanges both energy and matter with its surroundings (1); a closed system exchanges energy but not matter across its boundary (1).
Question 3 · Spec 3.1.1.1 · Systems concepts
Explain why a drainage basin is an open system but the global water cycle is a closed system. [3 marks]
Answer:
In a drainage basin, precipitation enters and runoff and evapotranspiration leave across the boundary (1); so both energy and water cross the boundary (1); globally, almost no water enters or leaves the Earth, although solar energy does, so it is closed (1).
Question 4 · Spec 3.1.1.1 · Systems concepts
Define inputs and outputs in a system. [2 marks]
Answer:
Inputs are the energy or matter added to a system from outside (1); outputs are the energy or matter that leaves the system (1).
Question 5 · Spec 3.1.1.1 · Systems concepts
What is meant by a store (component) in a system? [1 mark]
Answer:
A place where energy or matter is held within a system, such as an ocean, the soil or an ice sheet.
Question 6 · Spec 3.1.1.1 · Systems concepts
What is meant by a flow (transfer) in a system? [1 mark]
Answer:
A movement of energy or matter from one store to another, such as infiltration or runoff.
Question 7 · Spec 3.1.1.1 · Systems concepts
Outline the role of energy in the water cycle. [2 marks]
Answer:
Solar energy drives evaporation and the atmospheric circulation that moves water vapour (1); gravitational energy moves water downslope as runoff and groundwater flow (1).
Question 8 · Spec 3.1.1.1 · Feedback
Define negative feedback. [2 marks]
Answer:
A process in which a change in a system triggers responses that counteract the change (1); so the system returns towards its original state (1).
Question 9 · Spec 3.1.1.1 · Feedback
Define positive feedback. [2 marks]
Answer:
A process in which a change in a system triggers responses that amplify the original change (1); moving the system further from its original state (1).
Question 10 · Spec 3.1.1.1 · Feedback
Explain how negative feedback may operate in the water cycle. [3 marks]
Answer:
Warmer temperatures increase evaporation and water vapour (1); more low-level cloud forms, reflecting more incoming solar radiation (1); the surface cools, reducing evaporation and counteracting the original warming (1).
Question 11 · Spec 3.1.1.1 · Feedback
Explain how positive feedback may amplify global warming through the water cycle. [3 marks]
Answer:
Warming increases evaporation, so the atmosphere holds more water vapour (1); water vapour is a greenhouse gas that traps more heat (1); causing further warming and still more evaporation (1).
Question 12 · Spec 3.1.1.1 · Dynamic equilibrium
Define dynamic equilibrium. [2 marks]
Answer:
A state in which inputs and outputs of a system are balanced on average (1); so the system fluctuates in the short term but stays stable over time (1).
Question 13 · Spec 3.1.1.1 · Dynamic equilibrium
Explain how a system in dynamic equilibrium responds to an external change. [3 marks]
Answer:
A change in inputs or outputs disturbs the balance (1); feedback mechanisms, often negative feedback, operate (1); the system adjusts to a new equilibrium over time (1).
Question 14 · Spec 3.1.1.1 · Systems concepts
Suggest why a systems approach is useful in physical geography. [2 marks]
Answer:
It simplifies complex environments into stores, flows, inputs and outputs (1); so links, feedbacks and the effects of change can be analysed and predicted (1).
Question 15 · Spec 3.1.1.2 · Global water stores
Name the four main global stores of water linked to the Earth's spheres. [4 marks]
Answer:
Lithosphere, water held in rock and soil such as groundwater (1); hydrosphere, the oceans, lakes and rivers (1); cryosphere, ice sheets, glaciers and permafrost (1); atmosphere, water vapour and cloud (1).
Question 16 · Spec 3.1.1.2 · Global water stores
Approximately what percentage of the Earth's water is stored in the oceans? [1 mark]
Answer:
About 97%.
Question 17 · Spec 3.1.1.2 · Global water stores
Approximately what percentage of the Earth's water is fresh water? [1 mark]
Answer:
About 2.5% (the rest is salt water).
Question 18 · Spec 3.1.1.2 · Global water stores
Where is most of the world's fresh water stored, and in what form? [2 marks]
Answer:
In the cryosphere (1); as ice in ice sheets (mainly Antarctica and Greenland) and glaciers (1).
Question 19 · Spec 3.1.1.2 · Global water stores
Name the second largest store of fresh water. [1 mark]
Answer:
Groundwater in the lithosphere.
Question 20 · Spec 3.1.1.2 · Global water stores
Explain why the atmosphere is the smallest of the major water stores but is vital to the water cycle. [3 marks]
Answer:
It holds only a tiny fraction (about 0.001%) of the Earth's water (1); but water in the atmosphere has a short residence time, about 9 days, so it cycles rapidly (1); it transfers water from the oceans to the land and drives weather (1).
Question 21 · Spec 3.1.1.2 · Residence times
Define residence time. [1 mark]
Answer:
The average length of time a water molecule stays in a store before moving on.
Question 22 · Spec 3.1.1.2 · Residence times
Compare the residence time of water in the atmosphere with that in the oceans. [2 marks]
Answer:
Atmosphere: about 9 days, a very short time (1); oceans: thousands of years (about 3,000 or more) (1).
Question 23 · Spec 3.1.1.2 · Residence times
Explain why water in polar ice sheets has a long residence time. [2 marks]
Answer:
Very low temperatures mean little melting or ablation (1); ice accumulates in layers and moves very slowly, so water may stay frozen for thousands of years (1).
Question 24 · Spec 3.1.1.2 · Residence times
Explain why water has a longer residence time in groundwater than in rivers. [2 marks]
Answer:
Groundwater moves very slowly through permeable rock and soil pores (1); river water flows quickly along open channels to the sea, so is held for days or weeks (1).
Question 25 · Spec 3.1.1.2 · Global water stores
Explain how the cryosphere has changed the size of the hydrosphere over time. [3 marks]
Answer:
During glacial periods, water evaporated from the oceans was locked up as ice (1); ocean volume fell and sea level dropped by about 120 m at the last glacial maximum (1); melting in warmer interglacials returned water to the oceans, raising sea level (1).
Question 26 · Spec 3.1.1.2 · Global water stores
Explain how global warming is changing the size of the cryosphere and hydrosphere stores. [3 marks]
Answer:
Melting of ice sheets and glaciers is reducing the cryosphere (1); the meltwater adds to ocean volume (1); thermal expansion of warming sea water also raises sea level (1).
Question 27 · Spec 3.1.1.2 · Quantitative skills
The oceans hold 1,338 million km³ of the Earth's 1,386 million km³ of water. Calculate the percentage held in the oceans to one decimal place. [2 marks]
Answer:
(1,338 ÷ 1,386) × 100 (1); = 96.5% (1).
Question 28 · Spec 3.1.1.2 · Quantitative skills
Convert a volume of 1 km³ of water into cubic metres. [1 mark]
Answer:
1,000,000,000 m³ (10⁹ m³).
Question 29 · Spec 3.1.1.2 · Lithosphere store
Define an aquifer. [1 mark]
Answer:
A permeable rock that stores and transmits groundwater.
Question 30 · Spec 3.1.1.2 · Lithosphere store
What is meant by the lithosphere store of water? [1 mark]
Answer:
Water held in rock and soil, mainly as groundwater.
Question 31 · Spec 3.1.1.2 · Evaporation and transpiration
Define evaporation. [1 mark]
Answer:
The change of state from liquid water to water vapour, driven by solar energy.
Question 32 · Spec 3.1.1.2 · Evaporation and transpiration
Define transpiration. [1 mark]
Answer:
Loss of water vapour from plants, mainly through stomata on leaves.
Question 33 · Spec 3.1.1.2 · Evaporation and transpiration
Define evapotranspiration. [1 mark]
Answer:
The combined loss of water to the atmosphere by evaporation from surfaces and transpiration from plants.
Question 34 · Spec 3.1.1.2 · Evaporation and transpiration
Outline three factors that affect the rate of evaporation. [3 marks]
Answer:
Any three from: higher temperature increases evaporation (1); wind removes saturated air (1); lower humidity increases the rate (1); a larger exposed water surface (1); greater water availability (1).
Question 35 · Spec 3.1.1.2 · Condensation and clouds
Define condensation. [1 mark]
Answer:
The change of state from water vapour to liquid water when air cools to its dew point.
Question 36 · Spec 3.1.1.2 · Condensation and clouds
Explain how clouds form. [3 marks]
Answer:
Air rises and cools as pressure falls (1); at dew point the air is saturated and water vapour condenses (1); condensation occurs on tiny particles (condensation nuclei) such as dust or salt, forming droplets or ice crystals that make cloud (1).
Question 37 · Spec 3.1.1.2 · Precipitation
Name the three main causes of precipitation. [3 marks]
Answer:
Convectional (1); frontal (cyclonic) (1); orographic (relief) (1).
Question 38 · Spec 3.1.1.2 · Precipitation
Explain how convectional precipitation forms. [3 marks]
Answer:
Strong surface heating warms the air above, which rises (1); the rising air cools and condenses to form towering cumulonimbus cloud (1); large droplets form, giving heavy rain, often with thunderstorms (1).
Question 39 · Spec 3.1.1.2 · Precipitation
Explain how orographic precipitation forms. [3 marks]
Answer:
Moist air is forced to rise over high ground (1); it cools and condenses on the windward slopes, giving cloud and rain (1); air descending on the leeward side warms and dries, creating a rain shadow (1).
Question 40 · Spec 3.1.1.2 · Precipitation
Explain how frontal precipitation forms. [3 marks]
Answer:
Warm, moist air meets colder air at a front (1); the less dense warm air is forced to rise over the cold air (1); it cools and condenses, producing cloud and rain along the front (1).
Question 41 · Spec 3.1.1.2 · Precipitation
Explain how convergence near the equator causes high rainfall. [2 marks]
Answer:
Trade winds from both hemispheres converge at the ITCZ, where intense heating makes the air rise (1); the rising moist air cools and condenses, giving heavy convectional rainfall (1).
Question 42 · Spec 3.1.1.2 · Precipitation
Explain why rainfall is usually low at about 30° north and south of the equator. [3 marks]
Answer:
Air that rose at the equator descends at about 30° (part of the Hadley cell) (1); descending air warms and its relative humidity falls (1); this creates high pressure with little cloud, so deserts occur (1).
Question 43 · Spec 3.1.1.2 · Cryospheric processes
Distinguish between accumulation and ablation. [2 marks]
Answer:
Accumulation is the addition of snow and ice to a glacier or ice sheet (1); ablation is the loss of ice by melting, sublimation and calving (1).
Question 44 · Spec 3.1.1.2 · Cryospheric processes
What is sublimation? [1 mark]
Answer:
The direct change of ice to water vapour without becoming liquid first.
Question 45 · Spec 3.1.1.2 · Cryospheric processes
Describe three cryospheric processes by which water leaves a glacier. [3 marks]
Answer:
Melting produces meltwater that flows into rivers (1); sublimation turns ice directly into vapour (1); calving releases icebergs that melt in the ocean (1).
Question 46 · Spec 3.1.1.2 · Cryospheric processes
Explain why meltwater supplies in mountain drainage basins are seasonal. [2 marks]
Answer:
Snow and ice accumulate in winter, storing water (1); melting in the warmer spring and summer releases it, increasing river discharge (1).
Question 47 · Spec 3.1.1.2 · Global flows
Explain how the oceans and atmosphere transfer water around the globe. [3 marks]
Answer:
Evaporation from warm tropical oceans produces water vapour (1); winds carry the moist air over continents where it condenses and falls as precipitation (1); water returns to the oceans by rivers and groundwater flow (1).
Question 48 · Spec 3.1.1.2 · Global flows
Explain how solar energy and gravity drive the global water cycle. [2 marks]
Answer:
Solar energy powers evaporation and winds that lift and move water vapour (1); gravity returns water as precipitation and moves it downslope as runoff and groundwater flow (1).
Question 49 · Spec 3.1.1.2 · Scale and timescale
Explain how the time taken for water to cycle varies with scale. [3 marks]
Answer:
Hillslope: water can move from rainfall to a stream in minutes or hours (1); drainage basin: days to weeks, longer where water enters groundwater (1); global: months to many thousands of years because of oceans and ice (1).
Question 50 · Spec 3.1.1.2 · Spatial variation
Explain why the atmosphere holds more water vapour over the tropics than over the poles. [2 marks]
Answer:
Warm air can hold more water vapour than cold air (1); so the warm tropics have higher humidity than the cold polar regions (1).

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Systems and the global water cycle

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