Structure: Undisturbed habitats and aquifers
Successful water filtration resulting in high-quality groundwater deposits requires pristine habitats and soils. Human activities can affect groundwater filtration and the quality of groundwater to a great extent.
Taking of gravel and sand
Eskers and terminal moraines have been widely used for taking gravel and sand. There are at the moment about 2 000 sand and gravel pits in operation and 10 000 out of use. In gravel and sand pits removing of vegetation and soil increases the volume of groundwater and the contamination risk. It has been studied that in these areas concentrations of nitrate, chloride, sulphate, carbon dioxide, calcium, magnesium, sodium and some heavy metals had risen frequently in the groundwater.
The amount of extracted gravel and sand decreased in the beginning of the 1990s due to economic recession. In the mid-1990s the extraction started to increase slightly on average until the next recession begun in 2008–2009. Since then the taking of gravel and sand has decreased by 25–30%. In 2012 the amount of extracted gravel and sand was about 34 million tonnes.
Forestry and agriculture
Forestry and agriculture may affect both the groundwater quantity and quality. Clear fellings and soil preparation in forests have been studied to increase the amount of nitrates in the groundwater. Drainage may lower the groundwater level and bring the groundwater to contact with surface water that contains humus and other quality impairing compounds. Also the fertilizers and biocides both in forestry and in agriculture may cause decline in groundwater quality. In cultivated areas liquid fertilizers can filtrate all the way to the groundwater and contaminate it, and same holds true for urine and microbes originated from dung in livestock farms.
Traffic, sewage, shooting ranges, mining
Several other human activities also threaten the groundwater quality by contaminating it. Road salting is the most common risk factor of the traffic. Salt leaks rapidly to groundwater in areas with coarse-grained gravel and sand soils. Apart from salting, also accidents causing leakages of oil or other toxins may contaminate the groundwater.
Sewage water from scattered dwellings may cause increase of pathogens in groundwater and thus inflict a serious health risk. Other activities with elevated risks for groundwater quality are shooting ranges because of high lead content of the soil, and mining. Mining may cause leakages of sulphides, metals, sludge, chemicals and residues of explosives. Also domestic containers for heating oil, old waste tips, gas stations, sawmills and timber preserving facilities may weaken the groundwater quality.
There are 6 020 classified groundwater areas in Finland which cover altogether an area of 13 300 km2. Largest high-quality groundwater deposits are situated in areas of eskers, terminal moraines and glacial river and river bank depositions that are coarse-grained and porous in structure. The largest terminal moraine formation, Salpausselkä, passes from southwestern Finland through southern Finland and all the way to the North Karelia in eastern Finland. Another large terminal moraine, Sisä-Suomen reunamuodostuma, arises in southwestern and Central Finland. Eskers are fairly common topographic formations especially in northern and eastern Finland.
Maaperän pohjavesi. Geologian tutkimuskeskus. [In Finnish]
Rintala, J. 2014. Pohjaveden laadun muutokset soranottoalueilla 1985–2013. Suomen ympäristökeskuksen raportteja 20 / 2014. 156 p. [In Finnish]
Gustafsson, J., Kinnunen, T., Kivimäki, A.-L., Suomela, T. 2006. Pohjavesien suojelu. Taustaselvitys osa IV. Vesiensuojelun suuntaviivat vuoteen 2015. Suomen ympäristökeskuksen raportteja 25 / 2006. 56 s. [In Finnish]
Mannerkoski, H. 2007. Päätehakkuun ja maanmuokkauksen vaikutus pohjaveteen. Metsätieteen aikakauskirja 3 / 2007. [In Finnish]
Taking of gravel and sand. Notto register. Environmental Administration.
- Updated (26.01.2015)