GROUNDWATER MODELING OF SUBGLACIAL AQUIFERS BENEATH NEW JERSEY DURING THE LAST GLACIAL MAXIMUM

During the last glacial maximum the Laurentide Ice Sheet covered much of Northern New Jersey. As the ice sheet began to melt, pressurized basal water would have infiltrated the aquifers beneath the glacier, which likely affected hydraulic heads and gradients. Previous modeling studies along glacial boundaries in the Midwest suggest that groundwater head gradients and thus flow velocities are significantly impacted by the presence of sub-glacial water drainage systems. To understand the effects the Laurentide Ice Sheet on the aquifers of New Jersey, we compiled hydrostratigraphic data and used the groundwater modeling software MODFLOW to simulate the groundwater flow along a two-dimensional representation of the central flow line of a glacial lobe in North Eastern New Jersey. The groundwater model was manipulated to evaluate the effects of water film thickness, glacier basal melt rate, and glacier thickness on groundwater gradients. The model was also used to simulate non-glaciated conditions to compare with the glaciated models. The model results indicate that the presence of a sub-glacial water film reduced the hydraulic gradient in the aquifers, whereas the absence of a sub-glacial film resulted in significantly higher gradients in hydraulic head within the aquifers. These results suggest that the presence of a sub-glacial water film during glacial melt had a significant effect on the groundwater flow regime in the sub-glacial aquifers.