A once-thriving Greek lake has shrunk to a fraction of its former size as drought, heat and long-running pressure on water supplies deepen an environmental crisis in northern Greece. Lake Koroneia (Λίμνη Κορώνεια), east of Thessaloniki, covered about 2.7 square kilometers (1.0 square mile) in 2026, according to satellite analysis by the National Observatory of Athens.
The same analysis put its water surface at 42.8 square kilometers (16.5 square miles) in 1984, a decline of about 94%. The latest collapse follows several years of weak rainfall and rising evaporation.
Scientists noted that annual rainfall in the catchment had fallen to roughly 400 millimeters (15.7 inches) during recent years, about 150 millimeters (5.9 inches) below levels seen in earlier decades. Higher temperatures were also linked to an additional 100 to 150 millimeters (3.9 to 5.9 inches) of annual evaporation.
Greek lake shrinks further as drought compounds decades of damage
The crisis, however, began long before the current dry spell. In the 1970s, Koroneia covered about 46 square kilometers (17.8 square miles) and reached depths of around 8 meters (26 feet).
Decades of irrigation demand, groundwater pumping, industrial and agricultural pollution, sewage problems, and nutrient buildup steadily damaged the lake, according to Greek authorities, Ramsar records, and academic studies.
Koroneia suffered a major fish kill in 1995 and dried completely in the summer of 2002. Another severe collapse followed later in the decade. In 2004, thousands of waterbirds died during an outbreak linked to botulism under heavily degraded lake conditions.
Restoration projects later diverted water toward the lake, improved wastewater treatment, and supported a partial recovery.
Past die-offs and restoration efforts failed to secure recovery
The lake expanded again during wetter years, but the improvement did not last. Satellite data show the water surface at 34.4 square kilometers (13.3 square miles) in 2016 and 29.8 square kilometers (11.5 square miles) in 2024. It fell to 17.9 square kilometers (6.9 square miles) in 2025 before collapsing to the 2026 level.
The Greek lake shrinks as drought now combines with problems that have accumulated for decades. A 2019 fish die-off was linked not only to low water and heat but also to oxygen loss, harmful algae blooms and high ammonia levels.
European Union judges had already ruled in 2013 that Greece failed to meet environmental obligations involving protection of Koroneia and wastewater treatment in nearby Langadas.
Koroneia remains part of a protected Ramsar wetland and the Natura 2000 network. Greek authorities have used restoration plans, monitoring, and water-management measures over the years, but the latest satellite measurements show that the lake has again reached an extreme low.
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