This aerial drone photo taken on Aug. 4, 2026 shows the exposed riverbed of the Danube River near Vukovar, Croatia after a prolonged heatwave. (Davor Javorovic/PIXSELL via Xinhua)

This aerial drone photo taken on Aug. 4, 2026 shows the exposed riverbed of the Danube River near Vukovar, Croatia after a prolonged heatwave. (Davor Javorovic/PIXSELL via Xinhua)

This aerial drone photo taken on Aug. 4, 2026 shows the exposed riverbed of the Danube River near Vukovar, Croatia after a prolonged heatwave. (Davor Javorovic/PIXSELL via Xinhua)

This aerial drone photo taken on Aug. 4, 2026 shows the exposed riverbed of the Danube River near Vukovar, Croatia after a prolonged heatwave. (Davor Javorovic/PIXSELL via Xinhua)

This aerial drone photo taken on Aug. 4, 2026 shows the exposed riverbed of the Danube River near Vukovar, Croatia after a prolonged heatwave. (Davor Javorovic/PIXSELL via Xinhua)