Drought

Drought is a prolonged period of deficient precipitation relative to the normal climate for a region, resulting in a shortage of water for ecosystems, agriculture, energy, industry, and domestic use. It is not a single event but a gradual phenomenon that can vary in duration, severity, and geographic extent.

Drought is commonly categorized by its primary impacts. Meteorological drought describes a deficit in rainfall; hydrological drought involves falling streamflow, reservoir, and groundwater levels; agricultural drought relates to soil moisture shortages affecting crops; socio-economic drought occurs when water demand outpaces supply, leading to economic or social consequences.

Causes and drivers include natural climate variability, such as El Niño and La Niña cycles and longer-term oscillations, as well as anthropogenic climate change that can alter precipitation patterns and increase evaporative demand. Droughts can occur in any climate region and may intensify or persist due to heat, land-use changes, and water management practices.

Measurement and monitoring rely on statistical indices and observations. The Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI), and SPEI are commonly used to quantify drought severity. Remote sensing, soil moisture data, and streamflow and groundwater trends support drought assessment and forecasting.

Impacts span agriculture, water supply, ecosystems, wildfire risk, energy production, and economies. Adaptation and management include drought forecasting and early warning, water conservation and allocation policies, drought contingency planning, infrastructural upgrades, and strategies for drought-resilient farming and urban water use.

Droughts occur worldwide and underscore the importance of integrated water resources management, risk reduction, and resilience to changing climate conditions.