Almost 6,350 aquifers have been mapped and classified in Finland. More than half of these reserves are exploitable for the water supply. It is estimated that Finland’s aquifers are replenished by an average of almost 5,4 million cubic metres of water a day. Since the 1970s the use of groundwater has steadily increased in municipal water supply.
Finland currently extracts around 0.7 million cubic metres of groundwater a day. Groundwater accounts for around 60 % of the water distributed by waterworks around the country. In sparsely populated areas most people depend on groundwater from wells or springs.
The capacity of natural groundwater formations can be increased by recharging surface water into the ground. The quality of water improves as it filters through the soil. This artificially recharged groundwater makes up 12% of the public water supply in Finland, and 25 waterworks currently use this method.
Finland’s plentiful groundwater resources
Although Finland has plenty of aquifers, these resources are not distributed evenly across the country. The most significant aquifers are in large moraine and esker features made of sands and gravels deposited at the end of the last Ice Age approximately 10 000 years ago. Water is typically clean, well oxygenated, and often also easily extractable. The Salpausselkä deposits in southern Finland particularly hold important aquifers.
The aquifers in Finland’s glacial deposits rank in quality among the best reserves of groundwater in the world. Groundwater in Finland is generally soft, with low concentrations of dissolved substances and low pH (6-7).
Most of Finland’s groundwater is of good quality, since it is better protected against contamination than surfacewater. In some coastal areas where groundwater is scarcer, however, water has had to be extracted from beneath clay deposits, and such reserves may have high iron and manganese content. In coastal areas, excessive groundwater extraction may also cause salt water intrusion to contaminate wells. Harmful concentrations of arsenic, fluorine and radon occur in certain areas due to local geological features.
Risks to groundwater quality
Contamination from industrial plants, petrol stations, landfills and use of salt for de-icing roads may reduce the quality of groundwater. It is vital that aquifers are carefully protected, as decontamination procedures are complex and costly. Groundwater resources are protected through special plans, usually drafted by the local authorities in co-operation with the local waterworks.
De-icing on the main roads can increase the salt content of groundwater in certain areas. Icreases in chloride concentrations have consequently been observed at some water-works since the 1980s . The use of de-icing salt has generally decreased since 1987, due to stricter controls over road maintenance. The Finnish Environment Institute (SYKE) have examined the degradation of alternative de-icers such as acetates and formates. Currently SYKE is examining transport and biodegration of potassiumformate.
SYKE has additionally assessed the environmental risk to groundwater from the fuel additive MTBE, following cases of contamination. A study of the occurrence of pesticides in groundwater has also been initiated.
Eskers contain high quality aggregates, as well as exploitable groundwater reserves, but sand and gravel extraction may detrimentally affect the landscape, and also increase the risk of groundwater contamination. Joint regional projects help by directing such activities to formations that are not vital for the local water supply.
Management of groundwater resources
The EU Water Framework Directive sets out the objectives for groundwater protection applied in Finland. One major objective is to ensure that all groundwater reserves have a good quantitative and chemical status. Finland’s Natural Resources Strategy covers the maintenance of the quantitative and chemical status of groundwater, as well as the appropriate and ethical management of groundwater areas of special importance, according to the principles of sustainable development. SYKE co-ordinates the national groundwater monitoring network and maintains GIS databases on groundwater, thus providing essential background information to promote the management of these vital resources. Groundwater modelling is increasingly used to estimate the extent of the available groundwater resources.