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Etusivu :: In English

Hiidenvesi restoration project

Hiidenvesi is the second largest lake in Uusimaa, southern Finland. The lake is a significant recreation area just near the metropolitan area of Helsinki. Hiidenvesi is strongly affected by eutrophication due to heavy nutrient load, originating from agriculture, forestry and other sources of diffuse loading.

The Hiidenvesi restoration project (2016-2021) aims to reduce the load of suspended solids and nutrients as well as promote conditions for recreation. Long-term objective for the restoration work is to improve the ecological state in Lake Hiidenvesi and diminish the signs of eutrophication.

The results of lake restoration are usually visible after many years of active work. Currently, the project activities are mainly concentrated on restoration measures in the drainage area. These include wetland constructions and environmental advisory for farmers. Studies are also done on lake ecology. For example, sub-project “Järvi Hoi” researched fish stocks and their utilization possibilities.

Facts about Lake Hiidenvesi

Hiidenvesi covers an area of 30 km² and its drainage area is as wide as 935 km². The average depth of the lake is 6.7 meters and the deepest point is in 33 meters. Hiidenvesi belongs to the Karjaanjoki water system and consists of several basins, which differ from each other in basic characteristics as well as water quality. Without heavy diffuse loading Lake Hiidenvesi would be relatively eutrophic in its natural state due to clay soil characterizing the area. Thus, restoration aims to reduce the nutrient load to the sustainable level for a middle eutrophic lake.

Project communication

Monthly press releases and Hiidenvesi newsletter are the main communication channels with our contact groups. Yearly publications provide detailed information on the state of the lake and on activities implemented in the project. Hiidenvesi project also participates in events for wider audience to raise awareness of restoration. Hiidenvesi brochure offers more information on lakes ecology, history and restoration. To keep up with the latest news, follow us on Facebook and Twitter!


The Hiidenvesi restoration project is funded by municipalities of Vihti, Lohja, Karkkila and Loppi, Helsinki Region Environmental Services Authority HSY, The Association for Water and Environment of Western Uusimaa LUVY and Hiidenvesi Fishery Area.

The State of Finland does not participate in the 2012-2015 project, but has funded the Vanjärvi wetland construction with finances of the previous project phase (280 000 €).

The project has also received additional funding from governmental organizations and grants from regional associations.

Project organization

Coordination of the project is led by The Association for Water and Environment of Western Uusimaa LUVY. See contact information here.

Steering group is the decision-making body of the Hiidenvesi project and selects e.g. the restoration and management measures. The steering group consists of representatives of the financiers.

Expert working group consists of e.g. regional authorities, the Finnish Environment Institute, University of Helsinki, Uusimaa ELY Centre and other related parties. The expert working group supports the project work and comments the planned activities.

Network of cooperation parties gathers related associations and organizations of the Hiidenvesi drainage area to discuss, comment and develop the Hiidenvesi restoration project.