Policy development and delivery to tackle diffuse water pollution from agriculture relies on data from Environment Agency (EA) monitoring, local investigations and academic research. Taken together these have contributed to a growing evidence-base so that we now understand much about how pollutants are mobilised and the impacts they have in freshwater. Since the late 1990s, plot-scale experimental studies have helped us to understand the origins and dispersion of diffuse pollution, and to develop and test cost-effective mitigation measures. The science emerging from these studies has been used in developing numerical models for interpreting national datasets (e.g. from EA monitoring) and predicting the likely effectiveness of mitigation measures on water quality (e.g. the ADAS Farmscoper tool). However, these modelling approaches are highly generalised and uncertain, particularly when applied at the scale of smaller river catchments.
The major gap in our evidence base is in robust empirical evidence regarding the effectiveness of mitigation measures on water quality at a catchment scale. The episodic nature of agricultural diffuse pollution means that monthly EA monitoring is not sufficient on its own to detect improvements that result from the implementation of mitigation measures. Research that focuses on the smaller scale of river catchments is needed to:
- Predict the impacts of combinations of mitigation measures on water quality at catchment scales.
- Understand the spatial coverage and targeting of mitigation measures required to achieve WFD goals.
- Predict the length of time that water quality recovery will take following the implementation of mitigation measures. This varies significantly between catchments.
- Develop approaches to work with farmers and other stakeholders to target mitigation measures within a catchment (taking account of knock-on effects on agricultural production and wider environmental factors).
Addressing these challenges requires changes to the way in which research is conducted, including:
- Joining up the research community to deliver multi- and interdisciplinary evidence.
- Building closer working relationships between researchers, policy makers and practitioners so that research is more focused on the policy and operational questions and facilitating access to the evidence base (including relevant knowledge gleaned from across the national/international research community).
- Setting in place studies to understand and detect long-term environmental changes that may take years or decades to occur.
Defra research on diffuse water pollution from agriculture has historically largely consisted of individual research projects commissioned of a variety of separate contractors and undertaken in diverse and separate locations. The establishment of DTC entailed a reallocation of resources away from the multiple small, single-issue research projects that Defra has historically funded in this area, to a strategic initiative that aims to put water quality and catchment science into a real-world context. A major objective of DTC was to bring together a fragmented UK catchment science research community and establish a mechanism to bring researchers into closer dialogue with Defra, policy delivery bodies and stakeholders.