Date of Award
2024
Document Type
Open Access Dissertation
Degree Name
Doctor of Philosophy in Environmental Engineering (PhD)
Administrative Home Department
Department of Civil, Environmental, and Geospatial Engineering
Advisor 1
Alex Mayer
Advisor 2
David Watkins
Committee Member 1
John Gierke
Committee Member 2
Jason Gulley
Committee Member 3
Christian Langevin
Committee Member 4
Jonathan Martin
Abstract
Groundwater inundation due to sea level rise poses a threat to fresh groundwater availability in coastal areas, and small islands are particularly vulnerable. On an island, when sea level rises, the freshwater lens also rises due to the difference in density between the salt and fresh groundwater. As the water table rises above the land surface it forms a lake and the water is exposed to additional evaporative losses, reducing the amount of fresh water available. This work aims to improve our understanding of groundwater inundation due to sea level rise and the impact of different hydrogeologic settings and phenomena on lake salinity and the freshwater lens. We showcase using the Lake Transport package, a groundwater modeling tool for MODFLOW 6, to model groundwater inundation in a more physically accurate and computationally efficient way compared to past methods. We used these methods to investigate a common hydrogeologic setting where an upper low hydraulic conductivity layer is underlain by a high hydraulic conductivity layer in order to understand the impact of groundwater inundation of the layered system compared to a homogeneous one. Ultimately, the initial condition, regardless of other factors, was most significant in determining the impact of groundwater inundation on the freshwater lens. We also explored a particular phenomenon called density driven instability or fingering events (DF events), where a higher density fluid overlies and intrudes into a less density fluid below it. This can occur between a lake formed by groundwater inundation and the underlying aquifer. The onset of a DF event and the impacts of an event on the freshwater lens are a function of five factors: changes in land surface recharge, upconing, evapoconcentration, the upward movement of the freshwater lens from SLR, and connection/isolation between the lake and aquifer.
Recommended Citation
Mancewicz, Lauren K., "SEA LEVEL RISE DRIVEN GROUNDWATER INUNDATION: EFFECTS OF ISLAND HYDROGEOLOGY ON FRESHWATER LENS DYNAMICS", Open Access Dissertation, Michigan Technological University, 2024.