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

Abstract

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 km 2 ) 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.

Supply of an ecosystem service—Farmers’ willingness to adopt riparian buffer zones in agricultural catchments

“…Catchments generally ranged from 4 km 2 to 12 km 2 and the criteria used for selection included maximisation of agricultural intensity (based on percentage arable or forage area and livestock grazing intensity), minimisation of non-agricultural land uses (residential housing density) and the selection of a range of high N or P transport risky landscapes. The MCDA process is described in detail by Fealy et al, (2010).…”

A review of phosphorus and sediment release from Irish tillage soils, the methods used to quantify losses and the current state of mitigation practice

“…The program is designed to assess the effectiveness of measures well before improvements are expected to translate into improved water quality in the f inal aquatic receptors, which in some cases may take up to twenty years (Schulte et al 2010b). In the first stage, four catchments (two arable and two grassland catchments) from 1500 possible candidates were selected to be included in the study using spatial multi-criteria decision analysis (Fealy et al 2010). Combined, the four catchments represent the range of intensive grassland and arable agriculture interests in Ireland across a soil and physiographic gradient that defines the potential risk of P and/or N transfers (Fealy et al 2010).…”

Implementation of the EU Nitrates Directive in the Republic of Ireland — A view from the farm

“…Research is starting to emerge in this area, for example, recent research by Jordan et al, (2011;2012) in a study of 4 intensively instrumented Irish agricultural catchments (2 grassland and 2 arable -Fealy et al, 2010;Wall et al, 2011) found that in the context of slurry spreading the closed periods represent approximately 25% of annual rainfall. However, the nutrient losses observed during the closed period in this dataset were all greater than 25% and up to 48% of the annual export of total P and 50% of nitrate.…”

“…The ND is a precursor of the Water Framework Directive (OJEC, 2000) and aims to minimise surplus P and N losses from agriculture to the aquatic environment. Nutrients in fertilisers promote plant growth but application in excess of plant requirement can cause negative environmental externalities such as eutrophication (EPA, 2008) As outlined by Fealy et al (2010) the GAP regulations address the need for managing both potential point and diffuse sources of nutrient transfers from agricultural land.…”

“…To represent a range of farming types and intensities, and physiographic differences in the country, as advised under EU guidelines, a GIS multi-criteria decision analysis (MCDA) was employed to select candidate catchments. The MCDA process is described in detail by Fealy et al (2010). In summary, the criteria used for 4 km 2 to 12 km 2 catchment selection were to maximise agricultural intensity (as livestock units per ha or percent arable landuse) minimise non-agricultural landuses (as peat soil percentage, forestry, building density, and major roadworks) and select for a range of high N or P transport risky landscapes (Anon., 2003;Anon., 2004).…”