Work to revitalise wetlands in Cassiobury Park Nature Reserve is set to start early next month.
It comes as part of council plans to boost biodiversity and accessibility in Watford parks.
The work includes removing silt build up which has affected the watercress beds, enhancing water quality, and adding a new pedestrian footbridge and fencing.
The watercress beds were previously the only ones in operation in Watford, but management was stopped in 1991, leading to excess silt and vegetation.
Watford Borough Council is leading the project, collaborating with Friends of Cassiobury Park, the Environment Agency, and Herts and Middlesex Wildlife Trust.
Watford mayor Peter Taylor said: "The restoration of this wetland area holds great significance as we work towards reviving the ecological diversity that has declined over the past four decades.
"By preserving the watercress bed structures, restoring ponds and channels, and addressing silt accumulation, we are taking vital steps towards enhancing the habitat for wildlife to thrive."
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The project is being supported by funding from Grundon Waste Management Ltd via the Landfill Communities Fund and a permit granted by the Environment Agency.
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