EU to Establish Groundwater Standards

Groundwater standards in European Union (EU) member states are to be established by the end of 2008, according to the EU's new Groundwater Directive. Recent research has developed a new method to determine the chemical status of groundwater which is applicable across the EU. This procedure has been assessed by testing the quality of the groundwater of the Upper Rhine Valley in Germany, Switzerland and France.

The quality of groundwater is affected by natural and manmade influences. Some contaminants are directly attributable to humans (i.e., pesticides), whereas it is harder to assess the origin of some other chemicals which could be derived from either natural or manmade sources.

The researchers suggest that qualities of groundwater are measured against their natural chemical composition, or natural background levels (NBLs). Water samples, which are used to determine the NBLs, should be preselected according to two criteria: the exclusion of all water samples containing only manmade contaminants and the exclusion of all water samples containing only contaminants that are of ambiguous origin (i.e., nitrate) but at a high enough level to suggest that they are manmade.

Limits, or threshold values, for chemicals are set between the NBLs and a level that is unacceptably high: a not acceptable reference value (REF). The REF level could be a drinking water standard, environmental quality standard or toxicological water standard depending on the individual requirements of the test. This ensures that threshold values are above the NBLs but below the REF values.

In the case study of the Upper Rhine Valley water basin, researchers estimated the NBLs and threshold values from almost 1,700 samples of water from monitoring stations in France, Germany and Switzerland. Samples that did not meet the preselection criteria were excluded. Comparison of all water tested with these reference values showed that approximately 90 to 95 percent of the samples had values below the threshold values. The water was therefore of good chemical status, requiring no further action.

For the 5 to 10 percent of samples that were above the threshold value, the good status of groundwater could still be achieved if the higher levels of contaminants could be attributed to natural sources. Only in those instances, where the elevated levels were attributable to human influences, would the good status fail to be reached and remedial action required. A thorough understanding of local natural conditions (i.e., local rocks which can be sources of contaminants) helps determine whether contaminants are of human or natural original.

In addition to demonstrating that the method meets the requirements of the Groundwater Directive1 and the wider EU Water Framework Directive, researchers in the BRIDGE2 project have also developed a map of typical groundwater classifications for Europe, which can be used as a regional reference of natural background and threshold values.

Source: European Commission, Environment DG