Lake restoration

Lakes first began to be restored in Finland in the late 1960s. Over the subsequent decades favourable conditions have been restored in more and more lakes, using an increasingly wide range of methods (e.g. aeration, dredging, raising water levels, macrophyte control). By 2002, restoration work had been carried out or planned for a total of some 800 lakes or lake waters.

The waters requiring restoration have typically been shallow and limited in extent (usually less than 10 km²), and restoration measures have usually aimed to improve water quality or lake depths, in order to increase the lakes' recreational value.

The initiative for restoration projects has usually come from people with permanent or holiday homes by a lakeshore, when their opportunities to swim or enjoy other recreational activities begin to be limited by water quality or the characteristics of the lake bed.

Lake restoration schemes do not include the types of water protection measures taken on a broad scale in catchment areas of lakes, such as the various steps to reduce nutrient or pollutant discharges from point sources or diffuse sources. But for lake restoration projects to succeed, external loads must be suitably limited, so in practice the measures carried out to restore natural conditions in catchment areas are very closely linked with inland water restoration work in Finland.

Every lake requires monitoring and management after restoration  to maintain the desired conditions. Some lakes also require continuous or regularly repeated restoration measures even after restoration work is completed.