Isotopic and hydrochemical tracers of hydrological functioning in an Irish blanket-bog headwater catchment

Blanket bogs act as dynamic water reservoirs and regulate headwater runoff, yet their hydrological resilience under a warming and drying climate, coupled with anthropogenic activities, remains poorly constrained. Water stable isotopes (δ18O, δ2H, and d-excess) provide direct tracers of moisture sources and evapotranspiration, while hydrochemistry reveals solute pathways and mixing in peatland catchments. This study uses intensive monitoring in a blanket-bog headwater catchment in the Wicklow Mountains to investigate the environmental controls on temporal and spatial variability in stream water isotopes and water quality.
Since November 2024, monthly precipitation and stream samples have been collected at 21 runoff sites for isotopic analysis, providing a growing record of δ18O, δ2H, and d-excess. In parallel, water quality parameters (major anions and cations, and physicochemical variables) have been measured at 11 of these sites. A weather station in the Luggala Estate supplies continuous meteorological data, including precipitation amounts and variables relevant to evapotranspiration. Using these datasets, the study examines which environmental parameters control month-to-month variability in δ18O, δ2H, and d-excess in blanket bog streams, how isotopic signatures co-vary with hydrochemical indicators across the catchments and to what extent observed patterns reflect seasonal changes, evaporation and flow-path mixing between precipitation and bog waters.
Preliminary analysis will apply local meteoric and evaporation lines, time-series statistics and mixed effects models to separate catchment-wide seasonal signals from site-specific behavior. Principal component and correlation analysis will jointly evaluate isotopes and solutes, identifying groups of sites with similar hydrological functioning and reaches where evaporative enrichment is most pronounced. Together, these tracer-based analysis constrain conceptual models of storage, connectivity, and mixing in a blanket-bog headwater, provide a modern process-based reference for interpreting blanket-bog stream isotopes and offer initial guidance on how many and what kinds of sites are most informative for future isotope-enabled monitoring of peatland catchments.