Forest drainage and water protection
Research within the WAMBAF project shows that big areas in the Baltic sea region countries is drained to improve forest growth.
During this first WAMBAF year we have collected information about forest drainage in the following Baltic Sea Region countries:
- Estonia
- Finland
- Latvia
- Lithuania
- Poland
- Sweden
We sent out a questionnaire to the national experts, who provided us with information about the following topics:
1) Existing knowledge on the impacts of forest drainage on the leaching of nutrients, suspended solids and mercury and the efficiency of the water protection methods in controlling the runoff water quality.
2)Tools and methods used for planning water protection in forest drainage.
3) Legislation, certification standards and guidelines.
Drainage to improve forest growth
We found that in the Baltic Sea Region (BSR) countries 10 Mha of peatlands is drained for improving forest growth. In Finland annual forest growth has increased on peatlands from 6.5 Mm3 to 22 Mm3 in 60 years. In Poland and the Baltic countries forest drainage is also used for retaining water in forest areas for dry periods.
Water protection methods
Drainage networks need maintenance, which in addition to the positive impacts on forest growth increases water pollution. Different water protection methods are developed to reduce the leaching of nutrients and suspended solids, including
- planning of water protection before drainage
- avoidance of unnecessary drainage
- use of water protection structures such as sedimentation ponds and pits
- overland-flow areas
- peak runoff control
- constructed wetlands.
More research is needed
Except the sedimentation ponds in Finland, the scientific knowledge on the efficiency of the water protection methods and structures to reduce element leaching is limited in the BSR countries. We think that more research is needed for their development. Only a very few tools are in use for planning water protection in forest drainage and they are available only in national languages.
We think that there is an obvious need to develop these planning tools. National legislation is regulating forest drainage in different ways in the different BSR countries either by aiming at reducing environmental impacts or guiding the technical aspects of the operations.
Certification standards need to be developed
A high proportion of forests in the BSR countries are certified either by the PEFC or the FSC system. Both systems allow forest drainage operations only on earlier drained areas. In all BSR countries the certification standards pay high attention on the maintenance of biodiversity and in most countries they also require water protection measures in forest drainage.
In most of the BSR countries there are no guidelines to help the operators in planning and carrying out forest drainage operations. We think that legislation, certification standards and guidelines can be further developed to support water protection in forest drainage in the BSR countries.
Leena Finér, Natural Resources Institute Finland -Luke