The restoration of Puurijärvi Lake

Puurijärvi Lake will be restored by raising the water level and excavating additional open water areas. The aim of this restoration is to prevent Puurijärvi Lake from becoming overgrown, and to preserve the diverse wetland environment as well as the valuable bird population. The state of the natural environment and the quality of the water will be monitored during and after the work in the area.

The first areas to be affected by the raising of the water level will be the lake's southern and central sections. A dam will be built in the southern section and an embankment constructed on the southeastern side, and these will provide 30 hectares of new open water. At the same time an important mosaic of water and vegetation will be created for the benefit of wetland life. The basic structure of the dam will be man-made rapids, which will also serve as a pathway for migrating fish. The dam floodgates can be used to control the amount of water and to reduce the potential for damage to bird nesting caused by floods. Terracing on the shores will be constructed in order to prevent the surrounding cultivated land from being damaged by waterlogging.

The combined surface area of the excavated areas will be 21-27 hectares. They will be concentrated mainly in the northern and central areas of the lake, and part of the excavation work will relate to the removal of bogbean growth. The location and shape of the excavation areas has been planned on avifaunal grounds. All excavated material will be taken away from the national park area.

The water level of Puurijärvi Lake will change as a result of the restoration work. At the southern end during the driest periods there is currently water only in the channel of the Ala-Kauvatsanjoki River, which flows inside the lake. After the restoration work the lowest water level in the southern part and the average water level will rise by approximately one metre. The lowest water levels at the northern end will rise by 20 centimetres, but the average water level will remain as before.

The restoration of Puurijärvi Lake is the largest wetland restoration carried out in Finland. The effects of the work and the experience gained will provide important background information for the implementation of future wetland restorations.

Published 2014-06-19 at 14:24, updated 2014-06-19 at 14:24