Major works underway to protect Croatia’s largest natural lake from rising salinity

Vransko Lake (Photo: Anja Stojanov/CC BY-SA 4.0)

VRANA, 1 October 2026 – Major works are underway at Vransko Lake in northern Dalmatia to limit the intrusion of seawater and protect the biodiversity of Croatia’s largest natural lake.

The more than €2 million project is focused on the Prosika Canal, the waterway connecting the lake with the sea. A new and reinforced control structure will allow water flows between the lake and the sea to be regulated more effectively.

Vransko Lake is a protected nature area and an important habitat for wildlife, with around 260 recorded bird species as well as numerous protected plant and animal species.

The lake has a unique geological feature known as a cryptodepression, meaning that parts of its bottom lie below sea level. Seawater can enter the lake through the surrounding karst terrain as well as through the Prosika Canal, which was first excavated in the 18th century.

Climate change and increasingly frequent drought conditions have contributed to rising salinity levels in the lake, HRT reports.

One of the most serious examples occurred during the extreme drought of 2012, when high salinity contributed to a major fish die-off.

“We had a major fish die-off, particularly of larger specimens. As the fish die, they create an additional burden and organic matter which decomposes and further worsens the situation,” said Maja Ćuže Denona, an expert manager at Vransko Lake Nature Park.

She added that the event also resulted in severe oxygen depletion, or anoxia, affecting fish and other organisms in the lake.

The current works are intended to reduce the risk of similar events by giving authorities greater control over the exchange of water between the lake and the sea.

“The two main objectives are to prevent seawater from entering Vransko Lake and to ensure the safe evacuation of excess water from the lake itself and the wider Vransko Lake catchment, in order to prevent flooding,” said Šime Mršić, director of Vransko Lake Nature Park.

The project is being financed through funds allocated to Hrvatske vode from Croatia’s National Recovery and Resilience Plan.

Once completed, the control structure will allow the opening and closing of the barrier to regulate the interaction between the lake and the sea.

The measure is designed to help maintain water conditions in the lake while reducing the impact of seawater intrusion on its distinctive ecosystem.

Vransko Lake is also an important destination for visitors, with the Prosika fishing harbour serving as a starting point for local fishermen and a popular spot for people exploring the surrounding nature.

The protection project comes as climate-related pressures on freshwater ecosystems continue to increase, making the management of water levels and salinity increasingly important for the conservation of sensitive habitats.