The general usability classification of surface waters
The general usability classification of water bodies gives an idea about the average suitability of the water bodies for water supply, fishing and recreation in Finland. The quality class is determined based on the natural quality of the water and human impacts. The water bodies have been classified into five classes: excellent, good, satisfactory, passable and poor.
Water quality of lakes, rivers and sea areas in Finland in 2000–2003
The classification was based on data from the period 2000–2003 and covered 82% of the total area of lakes with size greater than one square kilometre, 16% of the total length of rivers with width more than two metres, and the sea area inside the Finnish territorial waters.
Water quality mostly good in lakes and the open sea
The quality of water was excellent or good in 80% of the classified lake area and in 73% of the sea area. In general, the water quality in rivers was worse than in lakes, because human activities, such as agriculture and development, are concentrated along rivers. Moreover, many rivers are sensitive to the effects of nutrient loading because of their low flow rates. Some 43% of rivers are classified as excellent or good quality. These rivers are mostly located in northern Finland.
More problems in rivers and in the Gulf of Finland
Eutrophication is a problem especially in the Gulf of Finland, in the Archipelago Sea and in the vicinity of some estuaries in the Gulf of Bothnia. Some 26% of sea areas were classified as satisfactory, passable or poor. In the Gulf of Finland, the area of the sea that was classified as passable had increased remarkably as compared with the earlier classification from the period 1994–1997.
In the Gulf of Finland, eutrophication is a consequence of excessive nutrient loads and the special physical conditions of the sea area. The nutrient load has actually decreased by nearly 40% since the late 1980s (nutrient load in 1987–2000, including point and diffuse source loading and natural background) for both nitrogen and phosphorus. However, eutrophication continues to be a problem, and is causing more abundant blue-green algae blooms in the summertime. The reason is that eutrophication is not only caused by nutrient loads from land areas, but also by the release of phosphorus from the sea bottom sediments. The release of phosphorus from the sediments has increased because of the lack of oxygen on the sea bottom.
Water quality affected by diffuse loading
In the vicinity of towns and industrial plants, water quality had improved considerably already at the beginning of the 1990s, because of long-term measures for water protection. These measures were further improved during the 1990s. However, a similar improvement in the state of water bodies has not been observed in areas with heavy diffuse loads.
Water quality is also affected by weather conditions and variations in runoff. During the years 2000–2003 there were periods where the water quality clearly deteriorated. In 2002 most of the country suffered from the worst drought in several decades, which caused water levels to drop in many water bodies. During the winter of 2002–2003, extremely poor oxygen conditions were observed in about 450 small and shallow lakes, especially in southern and western Finland, and mass die-offs of fish occurred in many of these lakes. The main reasons for the severe oxygen problems were an early ice cover and the low water levels. Low water levels also contributed to the degradation of rivers, especially in southwestern Finland.
Regular data collection
Water quality is monitored frequently in Finland in accordance with the national and regional programmes and under environmental permits. The national programme is based on monitoring networks of rivers, lakes and coastal waters. Several times annually, samples from about 550 sampling sites are analysed for some 20–40 water quality variables. In addition, there are thousands of sampling sites under regional and local monitoring programmes.
The results of the monitoring and control activities are stored in the national database maintained by the Finnish Environment Institute (SYKE). There are now more than 21 million records that have been entered into the database since the 1960s. In the classification done for 2000–2003, data from some 5370 lake sites, 3900 river sites and 1100 sea sites were used. In this period, some 2.6 million water quality records were entered into the database.
Antikainen, S., Joukola, M. & Vuoristo, H. 2000. Suomen pintavesien laatu 1990-luvun puolivälissä. Water quality in Finland in the mid-1990s. Vesitalous 2/2000. Vol. 41. (In Finnish with English abstract).
Vuoristo, H. 1998. Water quality classification of Finnish inland waters. European Water Management 1(6):35-41.
Mrs. Sari Mitikka, Finnish Environment Institute (SYKE),
Mrs. Heidi Vuoristo, Finnish Environment Institute (SYKE),