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EPA Conference Series: Protecting water sources: reducing pesticide risks in the Erne-Larah catchment

Lorraine Gaston (Uisce Éireann) presented on The Erne-Larah Water Source Protection Project, a pilot initiative led by Uisce Éireann in County Cavan. The project aims to reduce the risk of pesticides entering source waters by exploring targeted land management practices. It serves as a model for scalable, catchment-based solutions to enhance water quality and protect source waters across Ireland.

EPA Water Conference 2025: Protecting water sources: reducing pesticide risks in the Erne-Larah catchment, Lorraine Gaston

Protecting Drinking Water at its Source: Lessons from the Erne-Larah Project

Tackling Pesticide Risks at Source

Uisce Éireann is committed to ensuring a clean, safe, and secure supply of drinking water for communities across Ireland. A critical part of this work involves protecting our drinking water sources—lakes, rivers, and groundwater—from contamination. One particular risk is from the use of pesticides, and in response to this, Uisce Éireann developed an Interim Pesticide Strategy (IPS) in 2021. This strategy provides a national framework for reducing pesticide risks at source through stakeholder collaboration, and understanding and managing risk.

The Erne-Larah Pilot Project

In 2023, Uisce Éireann launched its first pilot drinking water source protection project—the Erne-Larah Water Source Protection Project—to trial a suite of voluntary, farm-based measures aimed at reducing the risk of pesticide contamination in source waters. The project is located in the Larah catchment in Co. Cavan, a sub-catchment of the Upper Erne, where pesticide exceedances—particularly of the herbicide MCPA—have been a persistent issue.

A map view of the Larah Catchment, Co.Cavan — Larah Catchment Co.Cavan

MCPA is commonly used to control rushes and is one of the most frequently detected pesticides in Ireland’s drinking water sources. Although the levels detected are not a risk to human health, the World Health Organization’s guideline value is 7,000 times higher than the regulatory limit, exceedances are undesirable.

The Erne-Larah project was developed with input from National Pesticides and Drinking Water Action Group (NPDWAG) chaired by Department of Agriculture Ford and the Marine (DAFM). Uisce Éireann engaged with local farmers, 35 of whom voluntarily participated in the project. Each farm received a bespoke Water & Environment Management Plan, and one-on-one support from an agricultural advisor. Measures implemented included:

Free pesticide storage units, spill kits, and drip trays
Grassland management interventions such as mulching and weed wiping
Stock-proof fencing and alternative drinking water points (solar troughs and pasture pumps)
Hedgerow and native tree planting
Practical training events on sprayer use and buffer zone management

Early Results and Lessons Learned

To measure effectiveness, the project used a weight of evidence approach, combining quantitative monitoring of pesticide loads with qualitative changes in behaviour. A control catchment, the Bunnoe, was also monitored to account for background variability in weather and river flows.

Initial results are promising, with a modest reduction in MCPA loads was observed in the Larah catchment, while loads increased in the control catchment between 2022 and 2024. Although it’s too early to draw definitive conclusions, the early trend is encouraging.

A follow-up survey in 2024 also revealed behavioural shifts:

70% of participants changed how they use pesticides following completion of their Water & Environment Management Plans
59% said they were likely or very likely to reduce or stop pesticide use
The proportion of farmers leaving a 5m unsprayed buffer increased from 54% in 2022 to 88% in 2024
More farmers now rinse sprayers in the field rather than the farmyard

Reflecting on the project so far, it’s clear that time, trust, and targeted support are key to successful catchment management. Resource constraints, logistical delays, and the challenge of engaging the right stakeholders in a voluntary scheme have all been apparent. However, the direct relationship between agricultural advisors and farmers has proven to be one of the most powerful levers for change. Uisce Éireann will complete the project evaluation in 2025 and aims to share learnings that can inform national policy and future source protection projects.

Learn more

Uisce Éireann: Erne-Larah Water Source Protection Project

EPA Water Conference 2025 – Watch all presentations here

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EPA Catchments Unit

Administrator

The EPA Catchments Unit is based in Dublin, and the team is involved with catchment science, chemistry, ecology, hydromorphology, modelling, Geographic Information Systems and planning. We work with the wider EPA, all of our local authorities, the Local Authority Waters and Communities Office, the Department of Housing, Planning and Local Government, and other public bodies and Departments to ensure we have the best available data and information about our catchments.

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