Final Report (2002-W-DS/7-M1) - Buss et al
Summary: The principal aim of this project was to develop a methodology for the derivation of the natural background quality for Irish groundwater bodies (it was not the intention to determine the composition of pristine groundwater bodies). International groundwater characterisation methodologies were also reviewed.
The EU Water Framework Directive requires Member States to adopt measures to prevent and control groundwater pollution. Its implementation will be partly via a new Groundwater Directive, currently in draft form.
It is the intention that all groundwater bodies be of good status by 2015. Chemical status of a groundwater body is assessed by comparison to the unpolluted condition, and by the requirement that there be no deterioration in the status of receiving surface waters and dependent ecosystems. The natural background water quality of a groundwater can be used as a standard against which to measure anthropogenic impact.
It is defined as follows:
The range of concentrations of chemical species in solution that are, or would be, derived from the reactions of natural infiltration in a natural soil zone and aquifer system at a given point in the aquifer system.
For groundwater bodies these calculated values can be compared with the actual background water quality to assist in the determination of which groundwater bodies are of good status and which are not of good status, and which may be at risk of impacting upon the status of receiving surface waters and dependent ecosystems.
This will enable prioritisation of actions needed to preserve those of good status, improve those not of good status and encourage trend reversal. However, the defined natural background quality will not necessarily form part of any definition of ‘good status’.
The principal aim of this project was to develop a methodology for the derivation of the natural background quality for Irish groundwater bodies (note that it was not the intention to determine the composition of pristine groundwater bodies). International groundwater characterisation methodologies were reviewed as part of the development of a methodology appropriate for Ireland.
The methodology was developed and tested on a selected number of groundwater bodies and groups of groundwater bodies in the South Eastern River Basin District. Results from the trials were fed back to the methodology to ensure its applicability in the Irish context. In detail, the methodology is used to derive limiting concentrations or values that describe the upper and lower bounds of the ranges in concentration of indictor species in groundwater of natural background quality.
These indicator species are naturally present in groundwater but concentrations can be affected by pollution. Derivation of these concentration ranges is dependent on access to reliable analytical data. In particular, older data which would not have been influenced by the changes in agricultural practice since the mid-1970s, is preferred.
However, more recent data may be used with due allowance for anthropogenic impacts. Regardless of when or where the data were collected, it must be professionally assessed for its reliability before being used for characterisation of natural background quality of groundwater.
