The assessment criteria for groundwater that are presented here are primarily intended as aids in evaluating groundwater potability. The characteristics of groundwater can be impacted by numerous factors.
The sharp rise in air pollution during the 20th century has impaired the ability of the soil, and hence of the groundwater, to resist acidification, resulting in elevated concentrations of metals in the water.
Growing use of nitrate fertilisers, leaks from septic tanks, and nitrogen deposition on already nitrogen-saturated soils have resulted in rising levels of nitrogen in groundwater.
Pesticides may also occasionally find their way into groundwater.
Aquifer flow patterns can be altered by the large-scale withdrawal of groundwater. This can result in the intrusion of salt water and changes in redox conditions, leading to elevated levels of iron and manganese.
Evaluating impacts
These threats to groundwater quality are reflected in the selection of assessment criteria presented here. The primary purpose of the criteria is to enable us to interpret the impact of the threats on groundwater potability, based on guidelines and threshold levels established by the National Food Administration. The criteria can also be useful for evaluating possible impacts of the metal content of groundwater on the flora and fauna of associated surface waters.
The assessment criteria relate to the water quality of discrete aquifers as indicated by samples collected from groundwater bores, springs and dug wells. It is important to keep in mind that the chemical and physical properties of groundwater vary widely in space and time. The results of individual analyses must therefore be interpreted with great caution.
Aquifer typology
To allow comparisons to be made between aquifers with similar characteristics, an aquifer typology has been set up which has been applied to the many thousands of well-water analyses collected by the Geological Survey of Sweden (SGU). By referring to this collection of data it is possible to determine whether or not an aquifer has been affected by human activity.
Individual assessment criteria have been established for:
- alkalinity and acidification
- nitrogen
- chloride (salt)
- redox conditions
- metals
- pesticides
- water table
Further reading
Swedish EPA Report 5051, Environmental Quality Criteria – Groundwater, explains how to collect samples and describes a method for determining whether your own groundwater analyses indicate impacts from local sources of contamination.
Environmental Quality Criteria – Groundwater (Swedish EPA Report no. 5051)