Hydrogeologic investigation of the Serpentine Bog, Belgrade Lakes Watershed, Maine
Document Type Dissertation/Thesis
Abstract
This study focused on how fluid flux changes seasonally in the Serpentine Bog, Belgrade Lakes Watershed, Maine. The bog is located in the Northern Belgrade Lakes Watershed between East Pond and North Pond. The presumed water-flow path of the system is out of East Pond into the Serpentine River, which flows north through the bog and eventually empties into North Pond. The study focused on a corridor in the southern section of the bog, which is bounded on the eastern and western sides by bedrock ridges. Cores show that peat in the bog is up to 5 m deep and is underlain by 0.5 m to 2.5 m of clay/peat transitional material. An unspecified amount of clay beneath provides a lowflow barrier to constrain flow into and out of the bog from below and from the western and eastern sides. Two parallel transects, with 4 piezometer nests in each, were installed in the bog to record changes in hydraulic head over time. Each nest had two piezometers consisting of a shallow (1 m) and a deep piezometer (2.5 m) in which a datalogger recorded changing water levels on an hourly basis. An additional datalogger recorded water levels in the Serpentine River that bisects the bog. Slug tests were performed in each of the deep piezometersto determine conductivity of the peat (3.49*10?? cm/s to ~2.36*10?? cm/s). A base numerical model of the bog was constructed, which used average hydraulic head values from the 8 deep piezometers as data for calibration. The model shows water flowing from the edges of the bog toward the river with steeper hydraulic gradients in areas of higher conductivity. Additional models were constructed to determine how changing conditions are likely to affect groundwater flow through the bog. Raising or lowering the water level of the river without changing recharge in the model affects the height of the water table but not the hydraulic gradients. Changes in the recharge of the model manifested themselves as changes in the hydraulic gradient; steeper gradients developed with increased recharge, and shallower gradients developed with decreased recharge.