GSI Groundwater Sand and Gravel Aquifers

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This dataset comprises sand and gravel aquifers. Sand and gravel aquifers may be locally important (Lg) or regionally important (Rg).

Rg - A sand/gravel aquifer is classed as regionally important if it can supply regionally important abstractions (e.g. large public water supplies with ‘excellent’ yields >400 m3/d). It is highly permeable, more than 10 m thick or has a saturated thickness of at least 5 m, and should extend over at least 5 km2, and usually over 10 km2.

Lg - Locally Important Sand/Gravel Aquifer: Similar to a Regionally Important Sand/Gravel Aquifer (Rg), but with a smaller continuous area (c.1-10 km2) and/or less consistent permeability. Although the aquifer may supply ‘excellent’ yields, the smaller size limits the amount of recharge available to meet abstractions.

Sand/gravel deposits have a dual role in groundwater development and supply. Firstly, in some cases they can supply significant quantities of water for supply and are therefore classed as aquifers, and secondly, they provide storage for underlying bedrock aquifers. A sand/gravel deposit is classed as an aquifer if the deposit is highly permeable, more than 10 m thick and greater than one square kilometre in aerial extent. The thickness of the deposit is often used rather than the more relevant saturated zone thickness as the information on the latter is rarely available. In many instances it may be assumed that a deposit with a thickness of 10 m will have a saturated zone of at least 5 m. This is not the case where deposits have a high relief (for example eskers or deposits in high topographic areas) as these gravels are often dry.

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Theme Science
Date dataset released 2013-01-15
Date dataset updated 2016-11-18
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 licence conditions apply', 'https://creativecommons.org/licenses/by/4.0/', 'license', 'https://creativecommons.org/licenses/by/4.0/', 'license']
Update frequency Irregular
Language English
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) TM75 / Irish Grid (EPSG:29903)
Vertical Extent {"maxVerticalExtent": "1041", "verticalDomainName": "sea level", "minVerticalExtent": "0"}
Provenance information Application of the data: Local details are generalised to fit the original mapping and interpretation scale of 1:50,000. Evaluation of specific sites and circumstances will normally require further and more detailed assessments, and will often require site investigations. Sources of Information: Teagasc/EPA 1:40,000 Subsoil Map + Teagasc/EPA soils 1:40,000 GSI 1:50,000 Subsoil Permeability Map from county GWPSs and NDP-funded national mapping programme GSI 1:50,000 groundwater vulnerability map. GSI 1:100,000 Bedrock Aquifer map GSI 1:50,000 Sand and Gravel Aquifer map Met Eireann 1971-2000 Rainfall + AE Groundwater Recharge map creation technique: Created using tools built though ArcGIS model builder. On a county by county basis. In order for the Recharge map to be created, the recharge coefficient has to be calculated. This calculation depends on a large combination of conditions that are worked out from overlaying the following layers through a combination of unioning, intersecting, adding fields and calculating fields: 1. Teagasc Soils: For indicating areas of Peat and whether soil is wet or dry. 2. Teagasc Subsoils: For indicating sand and gravel soils. 3. Permeability 4. Vulnerability 5. Sand & Gravel Aquifers 6. National Aquifer dataset 7. Effective Rainfall (Met Eireann) The Recharge Map Creation tool goes through several different geoprocessing tasks. For each county: 1. Selecting the county: Union the Teagasc soil, sub-soil, Permeability and Vulnerability layers. 2. Unioning and intersecting with Fixed layers: -Intersecting Sand and Gravel Aquifer: This data will be included for analysis along with the Sand and Gravel soils from the Teagasc subsoils layer. -Intersecting National Aquifer: This layer will be used to calculate what cap (if any) will be applied to the potential recharge mm amount. -Aquifers of type LL, PU and PL will entail a capping on this final recharge figure. (100 or 200 mm/yr) 3. A hydrological Category is applied according to combination of values for each record. A recharge Coefficient is then calculated. 4.The final recharge value is calculated as Effective Rain amount x the %Recharge Coefficient. For further Information got to http://www.opw.ie/hydrology/data/speeches/08%20-%20Hunter%20Williams%20-%20National%20Groundwater%20Recharge%20Map.pdf
Period of time covered (begin) 2005-04-15
Period of time covered (end) 2011-09-06