I layer is calculated by direct assignment of vadose zone material to I index values according to DRASTIC methodology, raning from 1 to 10. In areas covered by subsoil deposits, the vadose zone media classification (the ‘I’-rating) was based on soil and subsoil type. In areas of exposed bedrock and subcrop or areas with < 3 m of subsoil coverage, the characteristics of the vadose zone was taken from the aquifer characteristics.

Created using karst information for Rockingham Catchment Region in the West of Ireland. The catchment for each swallow hole was delineated and distance from each swallow hole was calculated within the catchment. These were assigned the appropriate value according to COP methodology. The slope and vegetation types within and outside that catchments were also assigned appropriate values.

The aquifer media layer is created by direct assignment of aquifers to A index values from 1-10. The metamorphic and igneous rocks were given the lowest ‘A’-value of 3 and the karstified limestone is given the highest value of 10. The majority of the catchment can be grouped into bedded sedimentary rocks and given a value of 6.

This layer considers the nature and thickness of soils, subsoils, unsaturated zone confinement. The lowest values correspond to areas of karst aquifer with no overlying subsoil and the water table is at or near the surface. The highest values are for non karst rocks overlain by thick impermeable subsoils with a deep water table. The biggest influencing factor here was the presence and thickness of clay subsoil

The soil media layer is created by direct assignment of soil layer to S index values from 1-10. Rock outcrops frequently and there is little or no subsoil over much of teh catchment. The majority of the catchment is given the higher ‘S’-ratings due to lack of soil and subsoil cover, with areas of little or no soil given a value of 10.

The aquifer media layer is created by calculation of the slope value from the national topographic data. S values were classified into DRASTIC S values from 1-10. Due the generally flat topography, the majority of the catchment is assigned the higher ‘T’-values.

R values are classified from 1 to 10. Groundwater recharge (GSI National Groundwater Recharge Map) varies between 55 mm/a and 681 mm/a across the Rockingham catchment. Areas underlain by clay have the lowest groundwater recharge and lowest R values. The highest groundwater recharge occurs in areas where rock is at near the surface or around karst features.

The D layer is the depth to the water table from the surface. The Boyne study area is based on 401 historical water level data points along with spring data and data from groundwater surface water interactions. Spatial interpolation using kriging was used and then the values were classified into the D index values. The highest D values correspond to where the water table is shallowest, generally found in the lower areas in the catchment, with the lowest D values meaning greater depth to the watertable, found in the upland areas

The D layer is the depth to the water table from the surface. The Rockingham study area is based on 120 historical water level data points along with spring data and data from groundwater surface water interactions. Spatial interpolation using kriging was used and then the values were classified into the D index values. The highest D values correspond to where the water table is shallowest, generally found in the lower areas in the catchment, with the lowest D values meaning greater depth to the watertable, found in the upland areas. The water table is generally very shallow, with much of the area having depths to water of less than 3 m bgl. The elevated karst plateau to the south has the deepest water with depths to water of up to 40 m.

The Hydraulic conductivity layer is taken as a direct assignment of the hydraulic conductivities from the aquifer parameter database to the C index values according to DRASTIC, ranging from 1 to 10.