IB Environmental systems and societies Topic 4.2G Water Stress Revision Notes (HL)

IB Environmental systems and societies Topic 4.2G Water Stress Revision Notes (HL) | RevisionDojo

Written by official IB examiners

Definition

Water stress

Water stress is defined as a situation in which the clean, accessible water supply falls below 1,700 cubic meters per year per capita.

Water stress measures pressure on water, not just how much water exists

Water stress indicates how much pressure a population or ecosystem places on available water resources.
A country is under water stress below 1,700 m3 per person per year, water scarcity below 1,000 m3, and extreme scarcity below 500 m3, using the UN benchmark.
Unlike scarcity, stress also counts water quality, infrastructure, affordability, and environmental flows.
A region may have enough water yet still be stressed because of pollution or poor infrastructure.

Four components determine water stress

Availability: the volume of surface or groundwater relative to demand.
Quality: pollution from industrial, agricultural, or domestic sources reduces usable water.
Environmental flows: the water needed to sustain ecosystems and biodiversity.
Accessibility: how easily communities can reach water given infrastructure and socio-political constraints.

Analogy

Think of water stress as credit-card debt.
When use outpaces repayment through recharge, the system slides toward crisis.

Even moderate-rainfall regions can be stressed

Example

In northern China, groundwater over-extraction for irrigation has dropped the water table by about one metre a year, raising stress even where rainfall is moderate.

Yemen case study

Case study

Yemen faces one of the world's most critical water crises.
It has less than 100 m3 of renewable water per person per year.
Agriculture uses 90% of water yet contributes only 6% of GDP.
Groundwater in parts of Sana'a has fallen from 30 m to over 1,000 m deep.
Heavy irrigation of the khat crop deepens depletion.
Rainfall has declined by 25% since the 1980s.

A few human and climate drivers push water stress higher

Industrialisation and pollution: factories draw large volumes and untreated wastewater contaminates rivers and aquifers.
Population growth and over-abstraction: rising demand lowers water tables and can drive saline intrusion.
Urbanisation and richer diets: growing cities and more water-intensive food raise demand faster than supply.

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Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

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Note

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Excepteur sint occaecat cupidatat non proident

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Tip

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Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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Definition

Water stress

Water stress is defined as a situation in which the clean, accessible water supply falls below 1,700 cubic meters per year per capita.

Water stress measures pressure on water, not just how much water exists

Water stress indicates how much pressure a population or ecosystem places on available water resources.
A country is under water stress below 1,700 m3 per person per year, water scarcity below 1,000 m3, and extreme scarcity below 500 m3, using the UN benchmark.
Unlike scarcity, stress also counts water quality, infrastructure, affordability, and environmental flows.
A region may have enough water yet still be stressed because of pollution or poor infrastructure.

Four components determine water stress

Availability: the volume of surface or groundwater relative to demand.
Quality: pollution from industrial, agricultural, or domestic sources reduces usable water.
Environmental flows: the water needed to sustain ecosystems and biodiversity.
Accessibility: how easily communities can reach water given infrastructure and socio-political constraints.

Analogy

Think of water stress as credit-card debt.
When use outpaces repayment through recharge, the system slides toward crisis.

Even moderate-rainfall regions can be stressed

Example

In northern China, groundwater over-extraction for irrigation has dropped the water table by about one metre a year, raising stress even where rainfall is moderate.

Yemen case study

Case study

Yemen faces one of the world's most critical water crises.
It has less than 100 m3 of renewable water per person per year.
Agriculture uses 90% of water yet contributes only 6% of GDP.
Groundwater in parts of Sana'a has fallen from 30 m to over 1,000 m deep.
Heavy irrigation of the khat crop deepens depletion.
Rainfall has declined by 25% since the 1980s.

A few human and climate drivers push water stress higher

Industrialisation and pollution: factories draw large volumes and untreated wastewater contaminates rivers and aquifers.
Population growth and over-abstraction: rising demand lowers water tables and can drive saline intrusion.
Urbanisation and richer diets: growing cities and more water-intensive food raise demand faster than supply.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

IB Environmental systems and societies 4.2G Water Stress Notes

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

Water stress measures pressure on water, not just how much water exists

Four components determine water stress

Even moderate-rainfall regions can be stressed

Yemen case study

A few human and climate drivers push water stress higher

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Water stress measures pressure on water, not just how much water exists

Four components determine water stress

Even moderate-rainfall regions can be stressed

Yemen case study

A few human and climate drivers push water stress higher

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account