TIME SERIES ANALYSIS OF HYDRAULIC HEAD DATA IN A CENTRAL MAINE OMBROTROPHIC PEATLAND

Peatlands are complex wetlands that are important in the global carbon budget. The hydrology of these systems exerts a significant control on overall carbon cycling as the position of the water table directly impacts carbon sequestration. At the same time, circulation within the peat basin will determine nutrient availability for biogeochemical processes to occur. Hydrogeophysical studies of northern peatlands in Maine over the last two decades have investigated the role of glacial deposits on peatland dynamics and have hypothesized that eskers and till deposits buried at the base of some peatlands act as a control on the hydrology of the system. In this study, multiple analysis methods were utilized on collected hydraulic head values to explore the role of subsurface geology on the hydrology of Caribou Bog, an ombrotrophic, domed peatland near Bangor, Maine. Water table values measured at 15-minute intervals from Aug. 2021 to Oct. 2024 were collected at nine well clusters distributed across Caribou Bog at a shallow depth (~2-3.5 m) and at the peat-mineral contact (~6-12 m). The wells were placed in differing vegetation communities, as well as over buried esker beads, till deposits, and proximal to pools. A geospatial analysis of water table position and peat properties found that wells located near esker and till deposits had higher hydraulic conductivity values than other sites with similar vegetation and a dampened seasonal flow-reversal that occurs at all other sites. A fast Fourier transform and continuous wavelet transformation of all 18 wells show strong 12- and 24-hour signals as well as a monthly signal that is attributed to the lunar cycle. The daily and twice daily signals closely correspond to earth and atmospheric tides; further linear regression analysis shows that the water table position strongly correlates with climatic conditions during peak summer and winter months but not during the spring or fall. This analysis further argues that glacial deposits exhibit a strong control on peatland hydrology which can have implications for the spatial distribution of carbon cycling. In addition, it highlights the correlation of climatic conditions and various tidal signals on the water table which suggests that the upper 1-2 m of the peat surface acts like a confining layer to deeper peat deposit hydrology.