In the European Union, mitigation measures to abate diffuse pollution from agricultural land are implemented under the direction of the EU Nitrates and Water Framework Directives. As these measures are implemented in national policies, a review process will look at the efficacy of the measures with a view to recommending further measures as necessary and following scientific and stakeholder consultation. Riparian buffer zones, beyond those zones used as mandatory set back distances for fertiliser and organic manure spreading, have been used as filters in some countries to attenuate nutrient rich runoff and may be proposed as supplementary measures elsewhere. Notwithstanding the ongoing research on the physio-chemical efficiency of riparian buffer zones, this study examined the willingness of farmers to adopt such features on agricultural land. The sample size was 247 farmers in 12 catchments (approximately 4-12km 2 ) in the Republic of Ireland. The survey was based on a proposal to install a 10 metre deep riparian buffer zone on a five year scheme and the analysis was based on principal components analysis, contingent valuation methodology and a Generalized Tobit Interval model. Results from this analysis indicated that famers' willingness to supply a riparian buffer zone depended on a mix of economic, attitudinal and farm structural factors. A total of 53% of the sample indicated a negative preference for provision. Principle constraints to adoption include interference with production, nuisance effects and loss of production in small field systems. Of those willing to engage with supply, the mean willingness to accept based cost of provision for a 10 metre riparian buffer zone was estimated to be €1513 ha -1 per annum equivalent to €1.51 per linear metre of riparian area.

The degree to which waters in a given watershed will be affected by nutrient export can be defined as that watershed's nutrient vulnerability. This study applied concepts of specific phosphorus (P) vulnerability to develop intrinsic groundwater vulnerability risk assessments in a 32 km(2) karst watershed (spring zone of contribution) in a relatively intensive agricultural landscape. To explain why emergent spring water was below an ecological impairment threshold, concepts of P attenuation potential were investigated along the nutrient transfer continuum based on soil P buffering, depth to bedrock, and retention within the aquifer. Surface karst features, such as enclosed depressions, were reclassified based on P attenuation potential in soil at the base. New techniques of high temporal resolution monitoring of P loads in the emergent spring made it possible to estimate P transfer pathways and retention within the aquifer and indicated small-medium fissure flows to be the dominant pathway, delivering 52-90% of P loads during storm events. Annual total P delivery to the main emerging spring was 92.7 and 138.4 kg total P (and 52.4 and 91.3 kg as total reactive P) for two monitored years, respectively. A revised groundwater vulnerability assessment was used to produce a specific P vulnerability map that used the soil and hydrogeological P buffering potential of the watershed as key assumptions in moderating P export to the emergent spring. Using this map and soil P data, the definition of critical source areas in karst landscapes was demonstrated.

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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.

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Measures within the European Union Nitrates Directive National Action Programmes in many member states aim to reduce soil phosphorus (P) levels from excessive to agronomically optimum. This is to reduce the risk of diffuse P losses to water and ultimately help achieve the Water Framework Directive targets of good water quality status. In this study, a ‘Soil P Decline’ model was used to evaluate this expectation for soils in four intensive agricultural catchments. Realistic annual P‐balance scenario deficits (−30, −15, −7 kg P/ha) were used to estimate the average time required for soils to decline to optimum levels in two predominantly arable and two grassland catchments with excessive soil test P (STP). Depending on the STP concentration and total P reserves, for the smallest field P deficit scenario (−7 kg P/ha), the model predictions were for an average of between 5 and 20 yr for agronomically optimum levels to be reached. Under the largest P deficit scenario (−30 kg P/ha), it was forecast to take between 2 and 10 yr. These predictions highlight the likely time lag that exists between implementation of soil P mitigation regulations and the desired outcome of few or no fields with excessive soil P. Expectations for water quality improvement through diffuse P source mitigation must also factor in additional time for P decline model uncertainty, land management variability and time for P sources to transfer to and within river networks.