Croatia, together with 13 other Danube basin countries, is marking International Danube Day on Monday under the slogan “United by the Danube”, with early results from a joint study indicating a long-term reduction in pollution along the river and its tributaries.

Key events in Croatia are traditionally held in Vukovar and Ilok, towns on the Danube riverbank. A central role in the commemoration is also played by Kopacki Rit Nature Park, the largest inland delta of the Danube and one of Europe’s best-preserved wetlands, home to more than 2,300 species, including the white-tailed eagle, the park’s symbol.

Early microbiological findings from the fifth Joint Danube Survey (JDS5), whose fieldwork began in summer 2025, show a sustained decline in pollution across the river basin, attributed to coordinated cross-border management and investment in wastewater treatment infrastructure. JDS5 is described as the world’s most comprehensive river basin monitoring programme, the Environment and Green Transition Ministry stated on Monday. The Joint Danube Survey 5 (JDS5)В was officially kicked-off on 1 July 2025 in Vienna. This large-scale scientific survey is bringing together experts from 14 countries to assess the health of the Danube River and its major tributaries.

The ministry also announced that the creative competition “Danube Art Master 2026” will be held in autumn under the same “United by the Danube” slogan, organised by the International Commission for the Protection of the Danube River (ICPDR) and the Global Water Partnership Central and Eastern Europe (GWP CEE).

The Danube is Europe’s second-longest river, stretching 2,850 kilometers from Germany’s Black Forest to the Black Sea. It flows through 10 countries including Croatia where the river section is 138 kilometres long.

The Danube River basin, covering around 817,000 square kilometres, spans 19 countries, feeds more than 300 tributaries and is home to over 80 million people.