A new study led by Teagasc has highlighted the critical relationship between the drainage status of peat soils and localised rainfall in water table management. These findings will be critical in identifying and targeting suitable sites for water table management, and ultimately maximising carbon storage potential in agricultural grassland peat soils.

Actively managing the water table of peat soils is an important tool to reach the EU target of climate neutrality by 2050. As the water table of peat soils drop, carbon dioxide emissions increase, due to the introduction of oxygen to the system and the breakdown of organic matter. As part of the ReWet project, researchers monitored six Irish peatland sites, four fens and two raised bogs, between September 2023 and August 2024. Using 30 monitored dip wells and hourly precipitation measurements, the relationship between water table rise, event rainfall and the water storage capacity of the soil was investigated.

Findings revealed that fen peat sites were significantly more deeply drained than raised bogs, despite similar drainage system designs. The sites also varied in water storage capacity. The water table in the raised bogs were less reactive to rainfall, drought, and artificial drainage. On the other hand, fen peat sites were more deeply drained, and the water table was more reactive to rainfall inputs and seasonal variability. This outcome reinforces previous Teagasc endeavours to highlight the variability of drainage status within peat soils under grassland, of which there are approximately 340,000 hectares, 141,000 hectares of which are considered to be effectively drained (with an average water table greater than 30 cm below the soil surface).

Patrick Tuohy, Teagasc Researcher, and lead researcher on the ReWet project comments: “Peat soils are being targeted for active water table management, but it is essential that we understand the initial water table behaviour at such sites so that their potential response to water table management can be predicted”. Lead author, PhD student, Hilary Pierce explains: “The methodology presented in the study can give insights to whether a site has potential for rewetting and enables the targeting of specific types of carbon farming efforts to specific sites. In particular, the fluctuations in the water table of fen peat sites will make future water table management in these areas more challenging.”

A proportion of grassland peat soils are being targeted for active water table management to reduce the average water table depth to within 30 cm of the soil surface. Karl Richards, Head of the Teagasc Climate Centre said “This research underscores the need for site-specific peatland water management strategies that reflect the water table behaviour of different peat types. Such tailored approaches are essential for maximising carbon storage potential and supporting climate action across European grassland landscapes.”

The research conducted in this publication was funded by the Department of Agriculture, Food and the Marine (DAFM) as part of the project ReWet – Facilitating water table management on carbon rich soils in Collaboration with the University of Galway. This work forms part of the Teagasc Climate Centre.

Reference: Pierce, H., Fenton, O., Daly, E., Shnel, A., O'Leary, D., Healy, M.G. and Tuohy, P., 2025. Assessing localised rainfall and water table depth relationships in agricultural grassland peat soils. Science of The Total Environment, 994, p.180074