Groundwater Guideline

Mapping of Groundwater Vulnerability

Groundwater vulnerability is defined (VRBA & ZAPOROZEC 1994) as
'the tendency or likelihood for contaminants to reach (a specified position in) the groundwater system after introduction at some location above the uppermost aquifer'.

Over the past 20 years, groundwater vulnerability maps were developed in many countries as a base for the development of land-use strategies, which take aspects of groundwater protection from pollution into consideration. They have become a standard tool in the protection of groundwater resources and are especially valuable in the decision making process related to land use planning. Land use planners have mostly little experience and expertise at hand to decide which land uses and activities could be allowed in certain areas without causing a negative impact on the quality of groundwater resources.

Groundwater vulnerability maps maps show the distribution of areas with a different level of vulnerability to pollution. In highly vulnerable areas any polluting facilities and activities should be prohibited since contaminants can reach the groundwater within very short time periods. Areas with a better natural protection of the groundwater against pollution could be suitable as locations for industrial areas, wastewater treatment plants, waste disposal sites, storage facilities for oil products and toxic hazardous substances, etc.

However, such maps do not replace more detailed studies of the geological and hydrogeological conditions in order to ensure the suitability of a particular site for the envisaged use. It has to be borne in mind that all groundwater resources are vulnerable and that uncertainty is inherent in all vulnerability assessments.

The preparation of Maps of Hazards to Groundwater helps to identify the risk emanating from certain pollution sources. Based on the vulnerability of the groundwater resources in the area downstream of potential pollution sources and the associated level of risk, it could then be decided whether a monitoring program should be initiated or whether the pollution source has to be removed, relocated or whether technical modifications are required.

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