Secas

Secas, in meteorology, refer to prolonged periods of deficient precipitation that cause water shortages, soil moisture decline, and ecological stress. They can be categorized as meteorological (low rainfall), agricultural (insufficient soil moisture for crops), hydrological (reduced river, reservoir, or groundwater levels), or socio-economic (water demand exceeding supply). Secas are influenced by natural climate variability, shifts in atmospheric patterns, sea-surface temperature anomalies such as El Niño or La Niña, and, in some regions, long-term climate change and land-use changes. They often begin with a sequence of dry months and can be tracked using climate forecasts and drought indices like the Standardized Precipitation Index (SPI) and the Palmer Drought Severity Index (PDSI).

Impacts of secas include crop failure and reduced food security, diminished household and industrial water supplies, stress on energy systems reliant on hydropower, loss of biodiversity, increased fire risk, economic losses, and, in severe cases, displacement of people. The severity and duration of a drought determine the response, ranging from monitoring and advisory notices to water restrictions, emergency aid, and long-term planning.

Monitoring and management involve national and regional meteorological and hydrological agencies, early warning systems, and drought risk assessments. Adaptation strategies emphasize water-use efficiency, crop diversification, soil moisture conservation, rainwater harvesting, sustainable groundwater management, optimized reservoir operations, and drought contingency planning. Addressing secas increasingly requires integrated water resources management that links climate information with local decision-making and infrastructure planning.

Notable drought events have affected various regions, such as the Sahel in the 1960s–1980s and episodes in Brazil’s Northeast in the 19th century and in the 2010s.