Water quality in agricultural river catchments
Per-Erik Mellander, Catchment Scientist, Teagasc, explains how the Agricultural Catchments Programme (ACP) provides science to support the national targets of improving the quality of our waters agricultural landscapes and lists key findings of environmental studies in six ca 10km2 size catchments
While we need clean and healthy water, we also need to produce high quality food and this requires efficient ways to manage nutrients and avoid losses to water.
The ACP is funded by the Department of Agriculture, Food and the Marine, and staff have been working with more than 300 farmers across six catchments in Ireland for over ten years.
A better understanding of how farm practice, landscape and weather, influence the nutrient loss to water is needed to reshape the thinking on future nutrient management. The ACP has been carrying out extensive environmental studies in six ca 10km2 sized catchments since 2009.
The programme has contributed to a better understanding of when, where and in which pathways nutrients move from the source to receiving waters. Because of differences in the soils and bedrock, farming practices and weather - nutrients such as nitrogen and phosphorus are lost from some fields easier than others. We therefore need to consider variability in the landscape, the scale we are observing, changes in weather and how this all influences nutrient loss.
The concentration of nutrients was too high in some of the rivers, but for different reasons - it was not always linked to how large the source pressure was within the catchment. There are clearly no “one-size-fits-all” solutions for preventing nutrient losses to water. A better understanding of the underlying processes is needed to identify which areas and what times are the most critical for nutrient losses to water. This will help to identify methods to mitigate the losses and also to build realistic expectations on the methods.
Agricultural Catchments Programme (ACP) key findings
Some key findings of the Agricultural Catchments Programme (ACP) are:
- The importance of the landscape characteristics can be larger than the nutrient source pressures. There was no clear link between the nutrient concentrations in the rivers and nutrient loading at small catchments scale. Targeted and efficient mitigation measures are needed.
- The importance of changes in weather can be larger than changes in source pressures. Both long-term weather changes and short-term weather extremes need consideration and may require different ways to mitigate nutrient losses.
- There are time lags between agricultural pressures and water quality status. The response time mostly increases with catchment size. Time lags need consideration when linking agricultural pressure to water quality.
- Following heavy rainfall, phosphorus concentrations in the stream gradually decreased during the “closed period” for spreading organic manures. Phosphorus concentrations during storms did not increase in the four week period after the end of “closed period”. Advice on soil moisture conditions can facilitate better decisions on time and location for slurry spreading.
- Most of the sediment losses came from stream bank/bed erosion and road losses on the more common land uses. Soil permeability largely influenced the sediment loss.
- Sediment was the most common stressor on stream macroinvertebrate communities. Improving river ecological quality requires improved management of sediment inputs and influence of point sources in low river flow.
- There is room for improvement in reaching agronomical/environmental goals. The distribution of phosphorus sources can be improved. At the field-scale there was often a mismatch between phosphorus inputs and the crop/soil phosphorus requirements. There is a need for improved support to knowledge exchange that can deliver better farm and soil specific nutrient management planning.
In the video below ACP Catchment Scientist Per-Erik Mellander gives an overview of the programme's research from over ten years of intensive monitoring
The Agricultural Catchments Programme (ACP) is running a week of social media releases showcasing some of its activities from Monday 21 February to Friday 25 February. The week’s theme is “Working Together for Water Quality”. More details of what is on can be found at www.teagasc.ie/ACPweek22
The Agricultural Catchments Programme (ACP) was established in 2008 and is funded by the Department of Agriculture, Food and the Marine