Reservoir Watch

In the three months to 11 October 2026, 36.1% of Portugal received much less rain than is normal for the season, and 3.5% extremely little, a shortfall seen about one year in forty. The EU drought indicator, which also weighs soil moisture and vegetation, had 9.7% of the country on watch or worse, 0.3% on alert. 17 of the 51 reservoir sites we track are in that rain-short area, 4 of them where the shortfall is extreme. The 51 reservoirs were 85.0% full on their latest readings.

“Much less rain than normal” means the last three months were drier than about five in six of the same seasons on record at that point; “extremely little” drier than about thirty-nine in forty. The measure is the Copernicus Global Drought Observatory's three-month Standardized Precipitation Index (SPI-3), on a 25 km grid; the first threshold is roughly where the U.S. Drought Monitor starts D1 (moderate drought), so this headline reads like the Monitor's, though the Monitor also weighs soil moisture, streamflow and local reports. Area shares count the grid cells inside the country outline, weighted by latitude. The EU drought indicator is the European Drought Observatory's Combined Drought Indicator: Watch means rain has been short, Warning that the soil has dried out, Alert that vegetation is visibly stressed. All of it describes conditions on the ground, not how much water is stored; a reservoir can be full after a dry season and low after a wet one. Source: drought.emergency.copernicus.eu. European Drought Observatory / Global Drought Observatory, https://drought.emergency.copernicus.eu © European Commission – JRC. Licensed CC BY 4.0.