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ScotlandEnvironmental ScienceSyllabus dot point

How can a limited supply of fresh water meet rising demand sustainably?

Water: the demand for water and the causes of water scarcity, the uneven supply of fresh water, and sustainable approaches to managing and supplying water.

An SQA Higher Environmental Science answer on water as a sustainability challenge, covering the demand for water, the causes of physical and economic water scarcity, the uneven supply of fresh water, and sustainable approaches to managing and supplying it.

Generated by Claude Opus 4.810 min answer

Reviewed by: AI editorial process; not yet individually human-reviewed

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  1. What this dot point is asking
  2. Demand for water and the supply problem
  3. Causes of water scarcity
  4. Sustainable water management
  5. Examples in context
  6. Try this

What this dot point is asking

The SQA wants you to explain the demand for water and the causes of water scarcity, the uneven supply of fresh water, and sustainable approaches to managing and supplying it. It builds on the hydrosphere from Earth's Resources and applies the sustainability framework to water.

Demand for water and the supply problem

Water is needed for drinking and sanitation, agriculture (irrigation), industry and energy generation. Demand rises with population growth, expanding farming and industrialisation. Yet, as the hydrosphere topic showed, only a tiny fraction of Earth's water is accessible fresh water, and it is spread unevenly in space and time, so some regions have plenty and others very little.

Causes of water scarcity

Scarcity is worsened by over-abstraction (taking water faster than it is replenished, depleting rivers and aquifers), pollution rendering water unusable, climate change altering rainfall and causing droughts, and inefficient use that wastes water. Distinguishing physical from economic scarcity matters because the solutions differ: physical scarcity needs new supply or reduced demand, while economic scarcity needs infrastructure and investment.

Sustainable water management

Sustainable water management balances supply and demand without depleting sources or harming ecosystems:

  • Conservation and efficiency: fixing leaks, water-efficient appliances, metering and efficient irrigation (drip systems) to cut demand;
  • Rainwater harvesting and water reuse: collecting rainwater and reusing treated grey water for irrigation or flushing;
  • Protecting catchments and groundwater: keeping abstraction within recharge rates and reducing pollution so sources stay usable;
  • Desalination: producing fresh water from seawater where other supplies are short.

Each option has trade-offs. Desalination provides reliable fresh water but is energy-intensive, expensive and produces salty brine waste. Conservation is cheap and low-impact but cannot eliminate demand. Sustainable management usually combines several methods suited to the region.

Examples in context

Example 1. Aquifer depletion in intensive farming regions. In several major agricultural regions, groundwater is pumped for irrigation far faster than rainfall recharges it, so water tables fall year on year. It is a clear case of over-abstraction creating future scarcity, showing why sustainable management must keep abstraction within recharge.

Example 2. Desalination in the Gulf states. Arid Gulf countries rely heavily on desalination to supply fresh water, gaining a reliable source but at high energy cost and with brine discharge that can harm coastal ecosystems. It illustrates both the value and the trade-offs of desalination as a response to physical water scarcity.

Try this

Q1. Define water scarcity and name its two main types. [2 marks]

  • Cue. A shortage of usable fresh water relative to demand; physical scarcity and economic scarcity.

Q2. State one drawback of using desalination to supply fresh water. [1 mark]

  • Cue. It is very energy-intensive and expensive (and produces salty brine waste).

Exam-style practice questions

Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

SQA Higher specimen3 marksExplain the difference between physical water scarcity and economic water scarcity, giving an example of each.
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A 3-mark answer needs both types defined and an example of each.

Physical water scarcity is where there is simply not enough fresh water available to meet demand, for example in arid desert regions with very low rainfall.

Economic water scarcity is where water is physically present but people cannot access it because of a lack of infrastructure, investment or money to treat and distribute it, for example in some lower-income regions with rivers but no treatment or piping.

The key contrast is that physical scarcity is a shortage of the resource itself, while economic scarcity is a shortage of the means to use available water.

Markers reward both definitions with the resource-versus-access contrast, and a valid example of each.

SQA Higher specimen4 marksDescribe two sustainable methods of increasing or managing water supply, and explain one drawback of each.
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A 4-mark answer needs two methods, each with a drawback.

Method 1: water conservation and efficiency, for example fixing leaks, water-efficient appliances and metering to cut demand. Drawback: it reduces but cannot eliminate demand, and depends on people changing behaviour.

Method 2: rainwater harvesting and reuse of treated grey water for irrigation or flushing. Drawback: supply is variable (depends on rainfall) and storage and treatment add cost.

Alternatively, desalination provides fresh water from seawater, but its drawback is that it is very energy-intensive and expensive and produces salty brine waste.

Markers reward two genuine management methods and a valid drawback for each.

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