Implications for forest management of the EU Water Framework Directive's stream water quality requirements -- A modeling approach

The EU Water Framework Directive (WFD) stipulates that measures should be taken to ensure that all lakes and streams in the EU have good ecological and chemical status, comparable to that of waters unaffected by human activities. This has profound potential implications for forestry, since operations such as harvesting and fertilization tend to reduce the quality of ground and stream water in affected catchments. The aim of this study is to assess the implications for forestry of limiting the concentrations of chemical substances reaching lakes and streams. A forest planning model with a horizon of 100Â years that includes requirements regarding water concentrations of nitrogen (N), phosphorus (P), methyl mercury (MeHg) and dissolved organic carbon (DOC) was applied to three intensively-studied sub-catchments at Balån in the boreal part of northern Sweden. Limiting maximum increases in concentrations of these substances to 10% above reference values resulted in an economic loss of ca. 20% or 35%, depending on whether the limits were applied to the whole area or to each sub-catchment individually. The results were also highly dependent on the assumptions, especially regarding the flux of MeHg. The results should be interpreted with caution as there are still major uncertainties concerning the cause and effect relationships. We also need to consider additional aspects to those addressed here, such as acidification, erosion and the biological effects of the operations.