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NotesESSTopic 1.2Storages and flows
Back to ESS Topics
1.2.23 min read

Storages and flows

IB Environmental Systems and Societies • Unit 1

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Contents

  • The systems approach
  • Storages and flows
  • System boundaries
  • Exam-style question
See the whole, not one part: The systems approach is a holistic way of looking at a problem: all the parts, and how they interact.

One part at a time

  • A lake turns green. Test only the water.
  • It finds too many nutrients, but not why.

The systems approach

  • Look at the lake and everything linked to it.
  • It finds fertiliser washing in from farms.

It works for ecological systems, like a lake, and societal ones, like a town's waste collection.

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Every system has storages and flows. Flows bring inputs in and take outputs out.

TermMeaningIn a lake
StorageAn amount of matter or energy heldWater, fish, mud
FlowA movement of matter or energyWater running in from a river
InputA flow into the systemRain (matter), sunlight (energy)
OutputA flow out of the systemEvaporation (matter), heat (energy)

Storage change = inflow minus outflow. Move the sliders: when the inflow is bigger, the storage grows.

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Energy and matter: Say which one each flow carries. Sunlight is an input of energy; rain is an input of matter.

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A system boundary marks what you study. Where you draw it changes what you find.

Too narrow

  • A lake study that leaves out the farms around it.
  • It misses the fertiliser washing in.

Too wide

  • A lake study that takes in the whole country's economy.
  • Too many parts to measure or explain.
Boundaries in time: A boundary is also a time span. Measure a city's air for one week and you miss the change between winter and summer.
How this comes up: A short question on how the systems approach helps, or on what a figure's storages and flows show.
IB-style questionOutline[3 marks]

A town's river smells bad every summer. Outline how a systems approach could help the town council find the cause.

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Keep it about the river: Each point names something in this river system. A general definition of a system scores little.

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the term storage (stock) in a systems model. [1 mark]

Key Terms

Flow
The movement of matter or energy between storages in a system.
Input
Something that enters a system from the environment.
Output
Something that leaves a system and goes into the environment.
Storage
Where matter or energy is held within a system.
Transformation
A process where energy or matter changes form as it moves through a system.

Related ESS Topics

Continue learning with these related topics from the same unit:

1.1.1Perspectives
1.1.2What shapes a perspective
1.1.3Values
1.1.4Where values show
View all ESS topics

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1.2.1Systems
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