The Irish Agricultural Catchments Programme: catchment selection using spatial multi-criteria decision analysis

The Nitrates Directive is a European Union legislative framework for managing agricultural nutrient transfers from land to water and, in the Republic of Ireland, is the main Programme of Measures for agriculture in the Water Framework Directive regulations. As part of the requirement for evaluating the Nitrates Directive National Action Programme and an associated derogation for intensive grassland farming, Ireland is monitoring environmental and economic effectiveness at the catchment scale. The selection of representative catchments has been undertaken using national spatial datasets in a Geographical Information System and a multi-criteria decision analysis (MCDA) framework from over 1500 possible candidates. This ranked catchments (4-12 km2) in terms of maximizing agricultural landuse and intensity, and defining areas of predominantly grassland and arable enterprises. Catchments were also ranked according to potential phosphorus and/or nitrogen transfer risk using metrics of surface and sub-surface flow path susceptibility, respectively. A selection of four catchments has been augmented with a grassland catchment in a karst landscape that used individual MCDA data layers to define suitability. Some validation of the nutrient transfer risk from each catchment is presented from high resolution water quality data.