The quality of groundwater is affected by the water interacting with sediments, rocks and fracture minerals through various chemical processes. Groundwater has therefore usually a different composition of soluble components compared with surface water.
During the time it takes precipitation to infiltrate the subsurface and reach the water table, the water undergoes an extensive cleaning and a change in chemical composition. Groundwater has therefore a good natural protection against contamination by disease-related bacteria, viruses and other micro-organisms from the surface environment. It is nevertheless important to avoid sources of contamination of both microbiological and chemical nature in the vicinity of groundwater wells.
The quality of groundwater is likely affected by the water interacting with sediments, rocks and fracture minerals through various chemical processes, such as mineral dissolution, chemical decomposition, adsorption and ion exchange. Groundwater has therefore usually a different composition of soluble components compared with surface water. Requirements for the quality of drinking water are established by law in Norway, and can be found in the Drinking water regulation (Drikkevannsforskriften).
Briefly summarized, groundwater in Norway, compared with surface water, contains relatively little organic matter, but elevated values for hardness, electrical conductivity and pH. In addition, groundwater has usually a stable temperature and quality throughout the year. However, the use of groundwater for water supply is not without problems. Elevated contents of radon, fluoride, iron and manganese are problematic in many bedrock wells, while low values for pH and alkalinity, and elevated contents of iron and manganese are common problems in wells in unconsolidated sediments. Elevated contents of nitrogen compounds are rarely encountered in Norwegian groundwaters. Various quality aspects for groundwater in Norway are further discussed in the GiN guidance document nr. 12 from NGU, and in the Water supply's ABC (Vannforsyningens ABC) from the National Institute for Public Health (FHI). All types of wells may experience problems with a reduction in the well's capacity to produce water due to chemical precipitates, sealing, and/or climatic variations.
More detailed information on the quality of groundwater may be found on the Groundwater in Norway website (www.grunnvann.no). Under the frequently-asked question (FAQ) menu, a number of questions deal with water chemistry and microbiology related to water supply based on groundwater.
Published: 24. January 2008