Methodology for the Characterisation of Unpolluted Groundwaters

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. One objective of the Directive is that all groundwater bodies should be of good status by 2015. Chemical status of a groundwater body is assessed by comparison to an ‘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.

ESI, with TMS Environment, were appointed by the Irish EPA to undertake a project to develop a methodology for the derivation of the natural background quality for Irish groundwater bodies. International methodologies for characterisation of groundwater quality were reviewed and a methodology appropriate for the data availability in Ireland developed.  This was tested on a selected number of groundwater bodies and groups of groundwater bodies in the South East of the country. Results from these 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 indicator 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. Statistical and graphical methods were presented that allow assessors to determine the natural background   concentration   from   a   given  set  of data; the method to be used depends on the data availability.

Please contact ESI (01743 276100 / email) for more information on 'Methodology for the Characterisation of Unpolluted Groundwaters '.