Lakes

Large lakes faring well, but some smaller lakes have troubled waters

	Golden-brow algae, Dinobryon cylindr, Photo Reija Jokipii, SYKE

Finland has as many as 187,888 lakes, but sufficient monitoring data is only available to classify the ecological state of a fraction of them. About 72% of the classified lakes are in a high or good state, meaning that their water quality and planktonic algae productivity exhibit no significant changes due to nutrient loads. For large lakes this figure is even higher, at 86%.  

Aquatic vegetation conditions around the shores of some larger lakes reduce their status to good, even though water quality in their open stretches may be high. Examples of such lakes include Päijänne, Näsijärvi, Oulujärvi and Inarinjärvi.

Larger lakes classified as being in a moderate state include lakes that have long been affected by runoff from surrounding farmlands and wastewater from settlements and industry, such as Lappajärvi and Vanajavesi.

Almost a third of the evaluated small and medium-sized lakes are classified as being in a poorer state than good. These lakes are typically characterised by observable negative impacts of eutrophication induced by nutrient loads, such as algal blooms. They are mainly in areas dominated by agriculture.

Ecological status of lakes assessed by water bodies
Source: Regional Environment Centres and SYKE    © SYKE

Link to a more detailed picture:
Ecological status of lakes assessed by water bodies.pdf