Drought as a hazard: causes, effects and management
OCR J383 Paper 2 tests drought as the third major natural hazard alongside tectonic hazards and tropical storms. You need a named HIC and a named LIC case study, and you must be able to explain why drought impacts differ.
What is drought?
A drought is a prolonged period of below-average rainfall that creates a shortage of water. Droughts are classified as:
- Meteorological drought: below-average precipitation.
- Agricultural drought: soil moisture too low to support crops.
- Hydrological drought: rivers, lakes and groundwater depleted.
- Socio-economic drought: water shortage disrupts economic activity and social well-being.
Droughts are a creeping hazard — they develop slowly, making them harder to communicate as emergencies than sudden-onset events like earthquakes.
Causes of drought
Physical causes
- El Niño: warm phase of the El Niño–Southern Oscillation (ENSO) — disrupts normal rainfall patterns, bringing drought to parts of southern Africa, Australia, Indonesia and Brazil.
- La Niña: cool phase — brings drought to parts of South America and elsewhere.
- Anticyclonic blocking: persistent high-pressure systems deflect rain-bearing depressions around them → prolonged dry spells (e.g. UK droughts 1976, 2018, 2022).
- Deforestation and land degradation: reduced interception and transpiration → drier soils and reduced local rainfall.
- Climate change: higher temperatures → increased evapotranspiration → more severe droughts; shifting precipitation patterns.
Human causes
- Overextraction of groundwater: irrigation, industry and domestic use exceed natural recharge rates.
- Population growth: greater demand from the same water sources.
- Inefficient irrigation: up to 60% of water used in agriculture is lost to evaporation in flood irrigation.
Case Study 1: California, USA (2012–2017) — HIC drought
Context
- Five-year drought — the most severe in at least 1,200 years (tree-ring evidence).
- California produces 25% of US food; Sacramento Valley = major agricultural hub.
Causes
- Anticyclonic blocking: a persistent high-pressure "Ridiculously Resilient Ridge" diverted Pacific storms northward.
- Climate change: warmer temperatures accelerated snowpack melt; reduced Sierra Nevada snowpack by 85–88% in 2015.
- Overextraction of groundwater: Central Valley groundwater used to compensate → land subsidence (sinking) of up to 60 cm per year.
Effects
- Agricultural losses: $5 billion+ annually; 17,000 farm jobs lost.
- Water rationing: mandatory water restrictions (25% cut statewide in 2015); $10,000 fines for wasting water.
- Wildfires: dry vegetation → 2016–17 wildfire season killed 250+ people.
- Environmental: salmon populations collapsed (rivers too low and warm); trees died in Sierra Nevada.
Responses
- Short-term: desalination plants; water trucking to communities; emergency groundwater regulations.
- Long-term: $7.5 billion water bond (2014); expanded reservoirs; statewide water efficiency programmes; "water markets" allowing farmers to sell water entitlements.
Case Study 2: Sub-Saharan Africa / Ethiopia (2015–16) — LIC drought
Context
- 2015–16 El Niño: one of the strongest on record; southern and eastern Africa worst affected.
- Ethiopia: 10.2 million people required emergency food aid; worst drought in 50 years.
Causes
- El Niño displaced the ITCZ — reduced rainfall in the main Ethiopian growing season (Meher).
- Climate change: rising temperatures increase evapotranspiration; more variable rainfall.
- Land degradation: overgrazing and deforestation reduced soil water retention.
Effects
- Food insecurity: failed harvest in 2015; 10.2 million people requiring emergency aid.
- Livestock losses: 40% of livestock in some areas died → loss of livelihoods and assets.
- Malnutrition: 435,000 children acutely malnourished.
- Water scarcity: women and children walked 10+ km daily for water (opportunity cost: girls missed school).
- Economic: GDP growth slowed; government diverted resources to drought response.
Responses
- Short-term: UN World Food Programme (WFP) food distributions; cash transfers; emergency water trucking.
- Long-term: Ethiopian government's Productive Safety Net Programme (PSNP) — food for work; reforestation; water harvesting schemes (check dams, catchment management).
Comparison: why LIC impacts are worse
| Factor | California, USA | Ethiopia |
|---|---|---|
| Food security | Agricultural losses (expensive but not life-threatening) | Famine-level food insecurity; malnutrition |
| Water access | Mandatory restrictions; desalination plants available | Women walking 10+ km for water |
| Economic response | $7.5 billion water bond; water markets | Dependent on international food aid |
| Structural vulnerability | Infrastructure stressed but functional | Poverty, land degradation, aid dependence |
Common OCR exam mistakes
- Treating drought as a "natural" hazard purely — human factors (overextraction, land degradation, climate change) intensify drought.
- Forgetting to name the El Niño/La Niña connection — many droughts are linked to ENSO cycles.
- Not explaining the opportunity cost of drought in LICs — girls missing school to collect water is a geographic-economic link.
- Confusing drought with aridity — aridity is a permanent climate state; drought is a temporary departure from normal conditions.
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