Analysing the impact of human economic activity on Irish water quality

In recent years there have been many EU directives that relate to the protection of water including the Groundwater Directive (1980), the Nitrates Directive (1991), the Drinking Water Directive (1998) and the Bathing Water Directive (2006) and the Marine Strategy Framework Directive. The Water Framework Directive (WFD) adopted by the European Commission in 2000 serves as an integrating directive in that it aims to bring together these existing directives in relation to water quality. In particular, it commits member states to ensure that all water bodies are of good status by 2015. Water can be divided into two types, groundwater and surface water. Surface water (as defined in the WFD) is “inland waters, except groundwater; transitional waters and coastal waters”. On the other hand, groundwater is defined as “all water which is below the surface of the ground of the saturation zone and in direct contact with the ground and subsoil”. In terms of drinking water, 75% of Irish drinking water comes from surface water.

The focus in the legislation on water quality and ecological outcomes results in part from difficulties in designing action plans to deliver on the objectives of the WFD. In order to achieve these objectives, the causes of negative water quality outcomes need to be comprehensively understood. Given the multiple potential sources of poor water quality and the complex environmental interactions at catchment level, it is very difficult to understand the drivers of negative outcomes. Direct causes of pollution are often difficult to trace to a particular source. Diffuse runoff from both urban and rural settings, as well as atmospheric deposition of pollutants are major non-point sources of water pollution. Control of these sources adds additional complexities for water pollution management. Non-point source pollution is the main concern for the policymakers as it is difficult to develop policies on the polluter-pays principle when it is often practically impossible to identify the sources of diffuse pollution.

In this project, we investigate the importance of a number of key drivers of water quality levels in Irish river systems by combining data from EPA water quality monitoring stations with spatially referenced information on the river catchments, information from the Irish census of agriculture, septic tank density data and population density data in a Geographical Information System (GIS) framework. The main factors associated with water quality in Irish rivers are assessed using an ordered probit model. The project uses an exploratory data analysis considering the spatial statistical relationship between agricultural and non-agricultural human activities and water quality in Ireland.

The analysis undertaken is a statistical analysis that aims to consider statistical associations between variables rather than a causal study. Future plans will attempt to assess in more detail the pathways by which sources of pollution drive water quality outcomes by factoring in hydrological characteristics. This is required to assess the level of mitigation required by sectors such as agriculture. Micro-level farm data will be incorporated in the analysis to assess the costs of mitigation strategies to meet the requirements of the water framework directive.

People involved:

Cathal O'Donoghue

Stephen Hynes