Application of GIS-based hydrological modelling to assess ecohydrology of blanket bogs

Abstract A GIS-based hydrological model, developed to assess restoration potential of Irish raised bogs, was applied to four blanket bogs located across the island of Ireland. The model utilised high-resolution topographic data to predict surface/near-surface hydrological processes, based on climatic conditions, contributing catchment and local surface slope; these provided a prediction of relative surface wetness across each blanket bog catchment. Modifications to the raised bog modelling approach aimed to account for differences in hydrological processes. Application of a climatic correction factor, accounted for climatic variations between the four study sites, while monitoring of water table levels indicated a log-linear relationship between model outputs and summer water tables (median and D90 levels (i.e., water levels equalled or exceeded for 90% of the time)). Higher model outputs were associated with areas where the water table remains closer to the ground surface and a lower range of fluctuations during summer months. Deviations from model outputs were associated with hydrological pressures, such as artificial drainage or the occurrence of peat pipes, which lowered summer water tables. Model outputs also showed significant correlation with peat thickness. Despite being effective as a predictor of hydrological conditions, correlation with ecological variables such as Sphagnum spp. cover proved poor. This reflected the variation in vegetation within and between sites, pointing to the impact of past activities and damage caused by anthropogenic pressures. Findings demonstrate the model as an effective tool in simulating hydrological conditions within blanket bog-covered landscapes, thus proving useful to peatland practitioners in planning and prioritising restoration.