Risk assessment of not meeting environmental objectives related to protection of human health and groundwater quality: The tiered approach in the context of the EU water framework directive

Abstract

This paper presents the tiered approach to risk assessment, aiming to recognize groundwater bodies for which it can be unequivocally defined, with an established confidence level, whether they are at risk of not meeting environmental objectives of the EU Water Framework Directive (WFD) related to the protection of drinking water protected areas and groundwater itself. As an upgrade of the risk screening tools derived in the context of the Common Implementation Strategy (CIS) of the WFD, the robust and comprehensive approach to risk assessment extensively addresses data uncertainty and confidence assessment. If a risk assessment is conducted with low confidence, further data collection on pressures, chemical status and hydrogeological characteristics is carried out, which lasts until data are of sufficient quality to make a reliable prediction in outcomes. The tiered approach is combined with the confidence assessment focusing the research to areas of high uncertainty and low degree of confidence. To test this approach, groundwater chemical data from the groundwater body (GWB), which is typical for the Pannonian region of Croatia, were used. The Tier 1 semi-quantitative risk screening resulted in development of the GIS-based risk map for the selected GWB. The Tier 2, monitoring-based risk assessment, was carried out by applying: a) relevant criteria to conduct trend analysis and to characterize the risk of deterioration of GWB chemical status and b) risk-based classification tests, in combination with the confidence assessment of tests results. Results of the assessment of risk of not meeting the “implement measures to reverse trends” and the “prevent GWB status deterioration” objectives for the selected GWB did not reveal an existence of environmentally significant trends and an exceedance of risk-based quality standards and threshold values with arithmetic and/or spatial means of targeted substances. The risk-based classification tests results confirmed no significant risk of not meeting good GWB chemical status related to the protection of human health and groundwater. All results demonstrate that proposed approach to risk assessment is straightforward and operational for use if a high-quality data derive from a high-resolution conceptual model of a GWB.