Physical & Human Causes of Water Insecurity

• Over-abstraction: This occurs when water is extracted from rivers, lakes, or aquifers faster than it can be naturally replenished by precipitation. This leads to falling water tables and, in some cases, land subsidence.

• Water Contamination: Inadequate sanitation systems result in untreated sewage entering water sources. This introduces pathogens and chemicals that make the water unsafe for human consumption without expensive treatment.

• Agricultural and Industrial Pollution: Intensive farming uses nitrates and pesticides that leach into groundwater, causing eutrophication. Similarly, industrial processes often discharge heavy metals and toxic waste into river systems.

Physical vs. Economic Scarcity

• Water Stress vs. Scarcity: Stress is the initial warning phase ($< 1,700 m^3$), whereas scarcity ($< 1,000 m^3$) represents a critical failure to meet basic needs.

• Identify Multi-Causal Links: When discussing water insecurity, always link physical causes (like drought) to human factors (like population growth). Exams often reward students who show how these factors exacerbate one another.

• Use Specific Thresholds: Memorize the values for water stress ($1,700 m^3$) and water scarcity ($1,000 m^3$) to provide quantitative evidence in your answers.

• Distinguish Pollution Types: Be precise about the source of contamination. Differentiate between organic waste (sewage), chemical runoff (agriculture), and heavy metals (industry) as they require different management strategies.

• Check for Scale: Consider whether the cause is local (a single factory polluting a stream) or regional/global (climate change affecting an entire drainage basin).