Aquifer parameters

Aquifer parameters

​Geological Survey Ireland has established regionalised aquifer properties described and captured in an aquifer parameters report and database.  

Download the Irish Aquifer Properties manual and guide. ​  

The report provides:

  • Guidance on parameter estimation, and outlines inter-relationships between aquifer properties;
  • Guidance on how to use the summary tables, and how to assess practitioners' own data;
  • Summary information for Rock Unit Group (RUGs) and aquifer type; and
  • Explanation of regional differences in hydraulic properties in RUGs.

Hydraulic data have been summarised for bedrock units and sand and gravel aquifers as a function of aquifer category and RUGs.  Realistic transmissivity values are provided for each of the aquifer categories and the RUGs.  The data collated, presented and assessed in this report are primarily the groundwater transport parameter 'transmissivity' (or its proxies).  This is for two reasons: transmissivity is a bulk transport parameter and is the one that is generally collected by Irish hydrogeologists during groundwater studies and therefore the most readily available.  The distribution and volume of the data enables estimates for transmissivity to be established across the entire country.  Secondly, Irish fractured bedrock aquifers are highly heterogeneous, and the whole-well aquifer tests that are typically undertaken integrate fracture flows along the length of the generally unscreened well, rather than measuring individual fracture inflows. 

The conceptual models outlined in this report describing the main types of groundwater flow and flow pathways should also be borne in mind when applying data, and also when acquiring and interpreting site-specific data.

In general, there is a decrease in the 'Best' estimate for transmissivity of the Regionally Important Aquifers through to the Poor Aquifers with the apparent exception of the karst sub-type (Rkc).  The 'Best' estimates are as follows for the general flow types:

  • Poorly Productive Aquifers (Pu, Pl and Ll categories) are less than 10 m2/d;
  • Productive Fissured Aquifers (Lm and Rf categories) range from 20 – 30 m2/d;
  • Karstic Aquifers (Lk, Rk and Rkd categories) range from 20 – 70 m2/d. The arithmetic mean bulk transmissivity for Rkc aquifers is greater than 500 m2/d; and
  • Sand and Gravel Aquifers (Rg and Lg categories) are approximately 350 m2/d. 

It is important to point out for the karstified aquifers that, when estimating a velocity in the context of a time of travel, it is important to consult with the GSI Karst tracing database to collate information on travel times from conducted tracer studies.

The report provides tables on summary statistics of transmissivity, hydraulic conductivity, including Best, Upper and Lower values for Aquifer categories, Rock Unit Groups and also provides estimates for permeability and storage properties.​