Accounting for the role of uncertainty in declining water quality in an extensively farmed grassland catchment

Debate around the likelihood of achieving full compliance with Water Framework Directive objectives by 2027 has largely focused on the uncertainty in the lag-times between the implementation of mitigation measures and improvements in water quality. This paper examines uncertainties related to limited knowledge, predictability and ambiguity and their roles in declining water quality in Lough Melvin, a large lake in Ireland. Between 1991 and 2007 the total phosphorus (TP) concentration in the lake increased by 52%, raising concerns about eutrophication. Although agriculture in the catchment is extensive, operating at low stocking rates, it is estimated to contribute 62% of the TP load to the lake. Defining the reason(s) for this decline in water quality were hindered by sources of uncertainty in (1) understanding of farm practices; (2) understanding of the catchment hydrology; (3) monitoring and evaluation; and (4) farmer participation in agri-environmental schemes and policy implementation. Sources 1 and 2 contributed to the development of critical source areas of P in the catchment; source 3 reflects the accuracy both of water quality assessment and P source apportionment, and 4 played a part in the limited response to the observed changes in water quality. A number of approaches to overcoming these uncertainties are reviewed in the context of achieving the objectives of the WFD including: a catchment specific approach; stakeholder participation and critical appraisal of the decision – making processes for implementing the WFD.

► Agriculture in the Lough Melvin catchment is extensive but it is estimated to contribute 62% of the P load to the lake.
► Multiple EU and national water protection strategies failed to prevent this decline in water quality.
► Sources of uncertainty were farm practices, hydrology, monitoring and evaluation, knowledge transfer, and policy implementation.
► An appropriate catchment specific approach to the WFD is essential for overcoming theses sources of uncertainty.
► Minimising uncertainty in the WFD requires evaluation of the decision making processes within the ‘competent’ authorities.