Groundwater Resources Bedrock Aquifers 1:100,000 Ireland (ROI) ITM

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Different aquifers have differing abilities to store and transmit water. Based on the hydrogeological characteristics and on the value of the groundwater resource, GSI has classified Ireland’s land surface into aquifer categories.

GSI Aquifer classes are divided into three main groups based on their resource potential (Regionally or Locally important, or Poor), and further subdivided based on the type of openings through which groundwater flows (through fissures, karst conduits or intergranular). There are nine aquifer categories in total.

This is a polygon dataset containing nine Bedrock Aquifer classes. Scale: 1:100,000

1) Regionally Important Aquifers: Regionally important aquifers are capable of supplying regionally important abstractions (e.g. large public water supplies), or excellent yields (>400 m3/d). Bedrock aquifer units generally have a continuous area of >25 km2 and groundwater predominantly flows through fractures, fissures, joints or conduits. Regionally important sand/gravel aquifers are >10 km2, and groundwater flows between the sand and gravel grains. This group is subdivided into the following types: Rk Regionally Important Karstified Bedrock Aquifer Rf Regionally Important Fissured Bedrock Aquifer Rg Regionally Important Sand/Gravel Aquifer Regionally important karstified aquifers may be further subdivided based on the whether groundwater flows mainly through conduits (Rkc) or more diffusely through solutionally-enlarged fissures (Rkd).

2) Locally Important Aquifers: Locally important aquifers are capable of supplying locally important abstractions (e.g. smaller public water supplies, group schemes), or good yields (100-400 m3/d). In the bedrock aquifers, groundwater predominantly flows through fractures, fissures, joints or conduits. Locally important sand/gravel aquifers are typically >1 km2, and groundwater flows between the sand and gravel grains. This group is subdivided into the following types: Lm Locally Important Bedrock Aquifer, Generally Moderately Productive Ll Locally Important Bedrock Aquifer, Moderately Productive only in Local Zones Lk Locally Important Karstified Bedrock Aquifer Lg Locally Important Sand/Gravel Aquifer

3) Poor Aquifers:

These bedrock aquifers are capable of supplying small abstractions (e.g. domestic supplies, small group schemes), or moderate to low yields (<100 m3/d). Groundwater predominantly flows through a limited and poorly-connected network of fractures, fissures and joints. This group is subdivided into the following types: Pl Poor Bedrock Aquifer, Generally Unproductive except in Local Zones Pu Poor Bedrock Aquifer, Generally Unproductive

The Aquifer maps along with the Groundwater Vulnerability map and Source Protection Area maps are merged to produce Groundwater Protection Zones. Each zone enables an assessment of the risk to groundwater, independent of any particular hazard or contaminant type. The Groundwater Protection Zones form one of two components of Groundwater Protection Schemes. A Groundwater Protection Scheme provides guidelines for the planning and licensing authorities in carrying out their functions, and a framework to assist in decision-making on the location, nature and control of developments and activities in order to protect groundwater. Use of a scheme will help to ensure that within the planning and licensing processes due regard is taken of the need to maintain the beneficial use of groundwater. Groundwater Protection Schemes are county-based projects that are undertaken jointly between the GSI and the respective Local Authority. The groundwater protection scheme comprises two components: * A land surface zoning map (or maps) called the groundwater protection zone map, and * Groundwater protection responses for existing and new potentially polluting activities. The role of the GSI is in the production of the land surface zoning map, whereas decisions on groundwater protection responses are the responsibility of the statutory authorities.

Data Resources (5)

available as shp
available as data viewer
available as esri rest
available as WMS
available as wfs

Data Resource Preview - ESRI REST

Theme Science
Date released 2003-01-21
Date updated 2021-10-22
Dataset conforms to these standards The INSPIRE Directive or INSPIRE lays down a general framework for a Spatial Data Infrastructure (SDI) for the purposes of European Community environmental policies and policies or activities which may have an impact on the environment.
Rights notes ['Creative Commons Attribution 4.0 International (CC BY 4.0)', 'Data that is produced directly by the Geological Survey Ireland (GSI) is free for use under the conditions of Creative Commons Attribution 4.0 International license.\n\n\n\n\n\nUnder the CC-BY Licence, users must acknowledge the source of the Information in their product or application.\n\nPlease use this specific attribution statement: "Contains Irish Public Sector Data (Geological Survey Ireland) licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence".\n\nIn cases where it is not practical to use the statement users may include a URI or hyperlink to a resource that contains the required attribution statement.', 'license']
Update frequency Other
Language English
Landing page
Geographic coverage in GeoJSON format {"type":"Polygon","coordinates":[[[-10.47472, 51.44555],[-10.47472, 55.37999], [-6.01306, 55.37999], [-6.01306, 51.44555], [-10.47472, 51.44555]]]}
Spatial Reference Systems (SRS) Irish Transverse Mercator (ITM, EPSG:2157)
Vertical Extent {"verticalDomainName": "sea level", "minVerticalExtent": "0", "maxVerticalExtent": "0"}
Provenance information The process of assigning each aquifer to an appropriate category is termed ‘aquifer classification’. The detailed criteria and process can be found here: Bedrock aquifer classification is based firstly on the rock type (lithology), and the 1:100,000 simplified bedrock map is used as a basis. This map is known as the Rock Unit Group map, which was generalised to 27 hydrostratigraphic units. Yield is one of the main concerns in aquifer development projects, yields from existing wells are conceptually linked with the main aquifer categories: • Regionally important (R) aquifers should have (or be capable of having) a large number of ‘excellent’ yields: in excess of approximately 400 m3/d (4,000 gph). • Locally important (L) aquifers are capable of ‘good’ well yields 100-400 m3/d (1,000-4,000 gph). • Poor (P) aquifers would generally have ‘moderate’ or ‘low’ well yields - less than 100 m3/d. However, existing well yield information is often difficult to use because reliable, long term yield test data are quite rare (particularly for the less productive aquifers). In practice, then, the following criteria are used in aquifer classification: • Permeability and transmissivity data from formal pumping tests, where discharge and water levels readings have been taken over a period of many hours or days. • Productivity data from wells where either formal pumping tests have been undertaken or where at least one combined reading of discharge and drawdown data are available. The GSI has developed the concept of ‘productivity’ as a semi-quantitative method of utilising limited well test data (Wright, 2000). A ‘productivity index’ is assigned to a well from one of five classes: I (highest), II, III, IV, and V, using a graphical comparison of well discharge with specific capacity. • Occurrence of springs with ‘high’ flows (greater than 2160 m3/day total flow). • Occurrence of wells with ‘excellent’ yields (greater than 400 m3/day discharge). • Hydrological information such as drainage density where overlying strata are thin, and baseflows or flows in rivers (better aquifers will support higher baseflows and summer flows). • Lithological and/or structural characteristics of geological formations which indicate an ability to store and transmit water. Clean washed and sorted sands and gravels for example, are more permeable than poorly sorted glacial tills. Clean limestones are also more permeable than muddy limestones. Areas where folding and faulting has produced extensive joint systems tend to have higher permeabilities than areas where this has not occurred. • Aquifer assessments from Groundwater Protection Schemes in neighbouring counties and from existing reports. All seven factors are considered together; productivity and permeability data are only given ‘precedence’ over lithological and structural inferences where sufficient data are available. Data from neighbouring counties in similar geological environments are included. Some bedrock units have been grouped if they are of similar geological age and have similar lithological/structural characteristics. In considering the classifications provided, it is important to note that: • The bedrock aquifer classifications are based on the bedrock units mapped by the Bedrock Section of the Geological Survey of Ireland at 1:100,000 scale. Irish hydrogeology is unusually complex and variable. As a consequence, there will often be exceptionally low or high yields that do not conform with the aquifer category given. The top few metres of all bedrock types are likely to be relatively permeable, even in the poor aquifers. There may be localised areas where recharge is restricted. This could occur, for example, where the vulnerability is low, or where a small portion of the rock unit has been faulted away from the main body of the unit. In these situations, the development potential even of regionally important aquifers may be limited. In considering major groundwater development schemes at particular sites, it will be important to consider the long term balance between recharge and abstraction, as well as the aquifer potential. The groundwater resource value of bedrock units is determined by GSI Groundwater hydrogeologists using a range of criteria and inputs. These include: • GSI Bedrock Geology map 1:100,000 • GSI Hydrostratigraphic Rock Unit Groups map 1:100,000 • GSI wells and springs data • GSI Bedrock Geology Linework fault map 1:100,000 • GSI/EPA Aquifer parameter database • Specific dry weather flows (derived by GSI from EPA/OPW data)
Period of time covered (begin) 2005-01-07
Period of time covered (end) 2019-09-11