4.2G Water stress (HL) Notes

1. Water stress indicates how much pressure a population or ecosystem is placing on available water resources.
2. It occurs when less than 1,700 m³ of clean, accessible water is available per person per year.
3. Below 1,000 m³ indicates water scarcity, and below 500 m³ marks extreme scarcity.
4. It considers not only physical availability but also pollution, infrastructure, and affordability.

Causes of Water Stress

1. Climate variability: prolonged droughts or erratic rainfall reduce surface and groundwater supplies.
2. Population growth: rising demand for food, energy, and sanitation increases water use.
3. Pollution: industrial and agricultural effluents contaminate rivers and aquifers.
4. Inefficient irrigation: traditional flood irrigation wastes water through evaporation and runoff.
5. Poor governance: corruption or weak regulation leads to inequitable distribution.

Key Components of Water Stress

1. Availability: The volume of water in a region, whether surface water or groundwater, relative to demand.
2. Water Quality: Pollution from industrial, agricultural, or domestic sources that compromises the safety and usability of water.
3. Environmental Flows: The water required to sustain ecosystems and maintain biodiversity.
4. Accessibility: The ease with which communities can access water due to infrastructure or socio-political constraints.

Environmental and Socio-Economic Impacts

1. Decline in agricultural productivity due to limited irrigation.
2. Conflict between sectors (agriculture vs industry vs households).
3. Ecosystem degradation as rivers and wetlands dry up.
4. Health risks from contaminated or insufficient water.
5. Reduced economic growth and increased poverty in affected regions.

Measuring Water Stress

Global Threshold

1. Water stress is measured by the annual availability of renewable freshwater per person.
2. Thresholds:
   1. Below 1,700 m³ per person/year = Water stress
   2. Below 1,000 m³ = Water scarcity
   3. Below 500 m³ = Extreme scarcity

Causes of Increasing Water Stress

1. Water stress has intensified globally due to industrialization, economic growth, and demographic pressure.
2. These factors affect both water quantity and quality.

1. Industrialization

1. Expanding industries require large volumes of water for manufacturing and cooling.
2. Pollution from untreated wastewater contaminates rivers and aquifers.
3. Industrial expansion in emerging economies (e.g., textile factories in Bangladesh, electronics manufacturing in China) has drastically increased freshwater demand.

2. Population Growth and Overabstraction

1. Rapid population growth increases domestic and agricultural demand.
2. Overuse of groundwater reduces water tables and causes saline intrusion

3. Urbanization and lifestyle

1. Growing middle classes demand more meat, processed foods, and consumer goods, all water-intensive.
2. Expanding cities require massive water infrastructure, which often lags behind population growth.

4. Climate Change

1. Increased frequency of droughts and heatwaves reduces surface water availability.
2. Melting glaciers and changing monsoon patterns alter seasonal flows.
3. Saltwater intrusion threatens coastal aquifers as sea levels rise.

5. Agricultural Expansion and Inefficient Irrigation

1. Agriculture consumes about 70 % of global freshwater withdrawals.
2. Inefficient irrigation leads to evaporation losses and soil salinization.
3. Water-intensive crops (e.g., rice, sugarcane) are often grown in arid regions.

6. Pollution and Poor Governance

1. Industrial, agricultural, and domestic pollutants render water unusable.
2. Weak regulations and corruption prevent equitable access.
3. Poor countries often lack investment in wastewater treatment facilities.

Transboundary Water Stress and Disputes

1. Transboundary water stress arises when shared rivers, lakes, or aquifers flow across political borders, and multiple nations depend on them for survival, agriculture, and energy.
2. Competing demands often lead to conflict or cooperation.

Understanding Transboundary Stress

1. Over 260 river basins worldwide cross national boundaries.
2. Upstream water use, through dams, irrigation, or diversion, reduces downstream flow and quality.
3. Political tension can escalate without agreements on fair sharing.

Promoting Cooperation

1. Bilateral treaties and joint river commissions help coordinate flow management.
2. Data sharing and seasonal release agreements prevent misunderstandings.
3. The UN Watercourses Convention (1997) promotes “equitable and reasonable use.”

Agricultural Strategies to Reduce Water Stress

1. Agriculture uses approximately 70% of all freshwater withdrawals.
2. Inefficient irrigation, soil degradation, and poor crop choices lead to major losses.
3. Sustainable solutions focus on precision irrigation, crop selection, and soil moisture management.

1. Efficient Irrigation Technologies

1. Drip irrigation delivers water directly to plant roots, minimizing evaporation and runoff.
2. Sprinkler systems simulate rainfall patterns, using less water than traditional flood irrigation.
3. Subsurface irrigation reduces surface evaporation in arid climates.