Assessing localised rainfall and water table depth relationships in agricultural grassland peat soils

Actively managing the water table position, which dictates the carbon storage dynamics of grassland peat soils, is an important tool to reach European Union (EU) climate neutrality goals by 2050. Understanding water table and rainfall relationships at peat sites will aid in future water table management. Across six sites, four fen and two raised bogs (RB), a total of 30 fully screened monitored dipwells were installed, and hourly precipitation was measured for one year from September 2023 to August 2024. For each site, the correlation between water table rise and event rainfall and the soil's specific yield (S_Y) were calculated. Results showed that peat soil type has an impact on the drainage depth and that fen peat sites were more deeply drained (average water table depths ranging from 114.1 cm–41.3 cm) than RB sites (average water table depths of 15.7 cm and 12.2 cm), despite similar drainage system design. There were also larger water table fluctuations due to rainfall inputs at the fen sites than at the RB sites. An event-based analysis was used to correlate water table rise with rainfall at each site and for each peat classification type and it was found that the fen sites exhibited a stronger correlation between water table rise and event rainfall (R² = 0.79) than the RB sites (R² = 0.59). This type of analysis highlights the differences across peat soil types under grassland management and emphasises the need for individualised management on these areas to align with climate policy objectives.