Assessing watercourse quality using results-based indicators in an agri-environment scheme

Area of Science:

• Environmental Science
• Ecology
• Water Quality Management

Background:

• Small watercourses are vital for catchment water quality but face degradation across Europe.
• Ireland implemented a results-based agri-environment scheme with a drainage assessment to mitigate risks.
• This assessment links visual indicators of nutrient and sediment risk to farmer payments.

Purpose of the Study:

• To evaluate the effectiveness of a novel drainage risk assessment in reflecting actual instream water quality.
• To compare the assessment's findings with macroinvertebrate-based biotic indices.

Main Methods:

• Utilized three macroinvertebrate biotic indices: Q-value, Small Stream Impact Score, and Proportion of Sediment Sensitive Invertebrates.
• Conducted macroinvertebrate kick-sampling and physicochemical analysis in May and July 2021.
• Sampled 12 'At Risk' and 12 'Not at Risk' small watercourses identified by the scheme.

Main Results:

• The drainage risk assessment identified point source risks but did not directly correlate with instream quality assessed by biotic indices.
• Degradation was observed in 58% of upstream control sites, indicating uncaptured impacts.
• Significant species turnover occurred between sampling months, highlighting heterogeneity; Small Stream Impact Score showed less temporal influence than Q-value.

Conclusions:

• While the scheme can identify some risks, incorporating instream sedimentation measurements would enhance risk identification and management.
• Results-based payment schemes can aid watercourse quality improvement, but broader freshwater impact sources need further investigation.