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1) Subglacial groundwater movement along a flow line in Nordfjord, in the wester fjords region of Norway:

(see Moeller, Carolyn A ., Mickelson, D. M., Anderson, M. P., Winguth, C., 2007. Groundwater flow beneath late Weichselian glacier ice in Nordfjord, Norway. Journal of Glaciology , 53, 180, p. 84-90.)

Plan view of Nordfjord, with a dashed line showing the path of the studied flow line.

Modified after Rye, N. et al 1987. The Late Weichselian ice sheet in the Nordfjord-Sunnmøre area and deglaciation chronology for Nordfjord, western Norway. Norsk Geografisk Tidsskrift 41, 23-43.

Basal water pressure and flow patterns are significant factors in controlling the behavior of an ice sheet, because they influence ice sheet thickness, stability, and extent. Water produced by basal melting may infiltrate the subsurface and occur as sheet or channelized flow. We examine subglacial groundwater conditions along a flow line of the Scandinavian Ice Sheet through Nordfjord, in the western fjords region of southern Norway, using a steady state, two-dimensional MODFLOW-based profile model. Meltwater input to the groundwater model is calculated by a two-dimensional, time-dependent, thermomechanically coupled ice flow model oriented along the same flow line. Model results show that the subglacial sediments could not have transmitted all of the meltwater out of the fjord during times of ice advance and retreat, or when the ice sheet was at its maximum position at the edge of the continental shelf. In order for porewater pressures to remain at reasonable levels, sheet flow or a drainage network were necessary to remove excess water. Model results for retreat phases show that additional surface recharge could greatly impact the bed conditions. This addition of meltwater could explain non-climatically driven margin readvances during the overall retreat phase.

The potentiometric surface profiles from a three-layer model for each simulated ice position.

The results for the 3-layer simulations shown here are those in which the porewater pressures are lower than the ice overburden pressures.

The groundwater models for all of the ice margin positions (32 ka, 30.5 ka, 29.7 ka, 27.5 ka, 21 ka, 14.5 ka BP) show that the sediment layer underlying the ice would not have been capable of transmitting all of the meltwater out of the fjord. Model results indicate that the groundwater system could carry only 14 to 38% of the basal meltwater produced during all but the latest stage of ice retreat, when it could carry only 9%. The glacial retreat groundwater model for 14.5 ka BP shows that the sediments could have easily handled all of the basal meltwater, 17 but once an addition of surface melt is included in the simulation, groundwater flow through the sediment layer was no longer a sufficient means of meltwater evacuation. These results indicate that other paths of basal drainage were present during advance and retreat of ice in Nordfjord.
2) Groundwater recharge through a thick sequence of fine-grained sediment in the Fox River Valley, east-central Wisconsin:

The objective of this study is to determine flow across an aquitard that consists of extensive fine-grained sediment that covers a large part of the Fox River Valley. This fine-grained sediment consists mainly of glacial lake sediments that were deposited in front of the Green Bay Lobe of the Laurentide Ice Sheet as it retreated from east-central Wisconsin starting about 20,000 years ago. This proglacial lake is called glacial Lake Oshkosh and it occupied large parts of 9 counties. Thick layers of clay and silt deposited in this lake cover the bedrock surface with up to 150 m of sediment. Such thick, extensive, low-permeability sediment likely limits groundwater recharge to underlying aquifers in the Ordovician and Cambrian sandstones and carbonates. These aquifers are the primary water source for most residential and municipal water supplies throughout the entire Fox River Valley.


Although the thick fine-grained sediment in the Fox River Valley may limit recharge to bedrock aquifers, it is critical to note that it may also protect the aquifer from downward migration of contaminants from specific and non-point pollution sources (e.g., Nilsson et al., 2001, Lane et al., 1998; Herzog and Morse, 1984). Where the fine-grained sediment is exposed at the land surface, extensive surface water runoff often occurs impacting streams and lakes. Therefore, characterizing this aquitard is not only important in the long-term management of groundwater resources, but surface water as well. Enhanced design of infiltration systems could also benefit from this research.

Project Plan:
Two or three rotosonic boreholes will be drilled by the WGNHS in November 2006 as part of an independently funded project to characterize the fine-grained till and lake sediment sequences in the Fox River Valley, and this proposal leverages that work. In this proposed project we will describe the cores and collect sub-samples for extraction of pore water for various analyses including stable isotopes of oxygen and hydrogen. Other analyses will include consolidation testing to determine the hydraulic diffusivity. In one of the boreholes, a multilevel well system, equivalent to a group of nested wells, will be installed to measure hydraulic head across the thickness of the aquitard over a period of one year. This multilevel well will also be used to extract groundwater samples from select intervals for isotope analyses to confirm the results obtained from the pore water analyses.


The data collected as part of this project will help characterize the fine-grained sediment that forms the aquitard covering a large area of the Fox River Valley. Not only will these data help define important hydraulic properties of the aquitard, it may help determine whether important bedrock aquifers in the region contain a limited amount of water and indirectly identify the regional recharge area.
As part of my dissertation, I will also be doing groundwater modeling in order to explore both the current groundwater flow regime and the paleohydrology of this region. The results of this project will provide field data that can be used in future groundwater modeling studies.