{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/141633"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/141633","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Fluid and Pressure Dynamics in Natural and Engineered Coastal Aquifer Systems","abstract":"Coastal aquifers are increasingly impacted by groundwater depletion, seawater intrusion, and land subsidence driven by long-term pumping. This dissertation uses 3D numerical modeling to evaluate how variable-density flow and geological heterogeneity influence pressure response, intrusion geometry, and deformation in stressed coastal systems. Three aquifer domains are examined: homogeneous aquifers, confined aquifers with continuous clay layers, and heterogeneous aquifers containing discontinuous clay layers (DCLs). Results show that geology strongly governs intrusion patterns. Homogeneous systems produce broad inland intrusion, continuous clays enhance vertical upconing, and DCLs create irregular and asymmetric intrusion zones. Because seawater is denser and less viscous than freshwater, saltwater cases exhibit larger and more persistent drawdowns, increasing modeled subsidence by 0.2 to 0.5 m after 100 years of pumping. The dissertation also evaluates Managed Aquifer Recharge (MAR) through analysis of the Sustainable Water Initiative for Tomorrow (SWIFT) pilot program in the Virginia Coastal Plain. The Potomac aquifer overlies crystalline basement rock, raising concern about downward pressure propagation in the context of injection-induced seismicity. Ensemble simulations reproducing the 2018 to 2022 pilot injections show that injection rates near 2 million gallons per day may generate pressure increases of approximately 40 kPa in the upper 200 m of the basement, although this response remains localized to within 2 km of the injector. Finally, models incorporating newly identified heterogeneity demonstrate that 20 m thick clay interbeds and laterally extensive DCLs significantly reduce pressure transmission to the basement, improving the stability and safety of MAR operations.","abstract_html":"Coastal aquifers are increasingly impacted by groundwater depletion, seawater intrusion, and land subsidence driven by long-term pumping. This dissertation uses 3D numerical modeling to evaluate how variable-density flow and geological heterogeneity influence pressure response, intrusion geometry, and deformation in stressed coastal systems. Three aquifer domains are examined: homogeneous aquifers, confined aquifers with continuous clay layers, and heterogeneous aquifers containing discontinuous clay layers (DCLs). Results show that geology strongly governs intrusion patterns. Homogeneous systems produce broad inland intrusion, continuous clays enhance vertical upconing, and DCLs create irregular and asymmetric intrusion zones. Because seawater is denser and less viscous than freshwater, saltwater cases exhibit larger and more persistent drawdowns, increasing modeled subsidence by 0.2 to 0.5 m after 100 years of pumping. The dissertation also evaluates Managed Aquifer Recharge (MAR) through analysis of the Sustainable Water Initiative for Tomorrow (SWIFT) pilot program in the Virginia Coastal Plain. The Potomac aquifer overlies crystalline basement rock, raising concern about downward pressure propagation in the context of injection-induced seismicity. Ensemble simulations reproducing the 2018 to 2022 pilot injections show that injection rates near 2 million gallons per day may generate pressure increases of approximately 40 kPa in the upper 200 m of the basement, although this response remains localized to within 2 km of the injector. Finally, models incorporating newly identified heterogeneity demonstrate that 20 m thick clay interbeds and laterally extensive DCLs significantly reduce pressure transmission to the basement, improving the stability and safety of MAR operations.","abstract_has_math":false,"creators":["Ogunleye, John Babatunde"],"institution":"Virginia Tech","degree_name":"Doctor of Philosophy","degree_level":"doctoral","degree_discipline":"Geosciences","degree_department":"Geosciences","school":null,"contributors":[],"advisors":[],"committee_chairs":["Pollyea, Ryan"],"committee_members":["Schreiber, Madeline E.","Dura, Cristina","Chermak, John Alan"],"year":2026,"date_issued":"2026-03-02","date_published":"2026-03-02","updated_at":"2026-07-22T22:18:49Z","subjects":["Coastal aquifer","Managed Aquifer Recharge","Induced seismicity","Potomac aquifer","Fluid pressure"],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45682"],"render_values":[{"text":"vt_gsexam:45682","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/10919/141633","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Pollyea, Ryan"]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Schreiber, Madeline E.","Dura, Cristina","Chermak, John Alan"]},{"key":"dc:contributor.department","label":"Department","values":["Geosciences"]},{"key":"dc:creator","label":"Author","values":["Ogunleye, John Babatunde"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-03-03T09:00:10Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-03-03T09:00:10Z"]},{"key":"dc:date.issued","label":"Date","values":["2026-03-02"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Geosciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Coastal aquifer","Managed Aquifer Recharge","Induced seismicity","Potomac aquifer","Fluid pressure"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45682"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/10919/141633"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Coastal aquifers are increasingly impacted by groundwater depletion, seawater intrusion, and land subsidence driven by long-term pumping. This dissertation uses 3D numerical modeling to evaluate how variable-density flow and geological heterogeneity influence pressure response, intrusion geometry, and deformation in stressed coastal systems. Three aquifer domains are examined: homogeneous aquifers, confined aquifers with continuous clay layers, and heterogeneous aquifers containing discontinuous clay layers (DCLs). Results show that geology strongly governs intrusion patterns. Homogeneous systems produce broad inland intrusion, continuous clays enhance vertical upconing, and DCLs create irregular and asymmetric intrusion zones. Because seawater is denser and less viscous than freshwater, saltwater cases exhibit larger and more persistent drawdowns, increasing modeled subsidence by 0.2 to 0.5 m after 100 years of pumping. The dissertation also evaluates Managed Aquifer Recharge (MAR) through analysis of the Sustainable Water Initiative for Tomorrow (SWIFT) pilot program in the Virginia Coastal Plain. The Potomac aquifer overlies crystalline basement rock, raising concern about downward pressure propagation in the context of injection-induced seismicity. Ensemble simulations reproducing the 2018 to 2022 pilot injections show that injection rates near 2 million gallons per day may generate pressure increases of approximately 40 kPa in the upper 200 m of the basement, although this response remains localized to within 2 km of the injector. Finally, models incorporating newly identified heterogeneity demonstrate that 20 m thick clay interbeds and laterally extensive DCLs significantly reduce pressure transmission to the basement, improving the stability and safety of MAR operations."]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["Coastal groundwater supplies are under growing stress due to long-term pumping, which can lower water levels, draw seawater inland, and even cause the land surface to sink. This research uses advanced computer simulations to better understand how these processes unfold underground and how local geology influences their severity. The study examines three types of coastal aquifers: uniform sandy systems, aquifers separated by thick clay layers, and more complex systems with patchy clay layers. The results show that underground geology plays a major role in shaping how seawater moves inland. In uniform aquifers, seawater spreads gradually inland. In systems with thick clay layers, pumping tends to pull saltwater upward from below. Where clay layers are irregular or broken, saltwater intrusion becomes uneven and unpredictable. Because seawater is heavier than freshwater, it also causes greater and longer-lasting pressure declines, which can increase land subsidence over time. The research also evaluates a groundwater recharge project in Virginia that injects treated water back underground to help restore water levels. Computer models of the pilot project suggest that injection can raise pressure in deeper rock layers, but the effects remain localized near the injection wells. Importantly, newly identified clay layers in the subsurface help limit how far pressure spreads downward, improving the overall stability and safety of the recharge program. Overall, this work highlights how differences in underground geology strongly influence coastal groundwater behavior and provides guidance for managing pumping and recharge projects more safely and sustainably."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Doctor of Philosophy"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Fluid and Pressure Dynamics in Natural and Engineered Coastal Aquifer Systems"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Pollyea, Ryan"],"dc:contributor.committeemember":["Schreiber, Madeline E.","Dura, Cristina","Chermak, John Alan"],"dc:contributor.department":["Geosciences"],"dc:creator":["Ogunleye, John Babatunde"],"dc:date.accessioned":["2026-03-03T09:00:10Z"],"dc:date.available":["2026-03-03T09:00:10Z"],"dc:date.issued":["2026-03-02"],"dc:description.abstract":["Coastal aquifers are increasingly impacted by groundwater depletion, seawater intrusion, and land subsidence driven by long-term pumping. This dissertation uses 3D numerical modeling to evaluate how variable-density flow and geological heterogeneity influence pressure response, intrusion geometry, and deformation in stressed coastal systems. Three aquifer domains are examined: homogeneous aquifers, confined aquifers with continuous clay layers, and heterogeneous aquifers containing discontinuous clay layers (DCLs). Results show that geology strongly governs intrusion patterns. Homogeneous systems produce broad inland intrusion, continuous clays enhance vertical upconing, and DCLs create irregular and asymmetric intrusion zones. Because seawater is denser and less viscous than freshwater, saltwater cases exhibit larger and more persistent drawdowns, increasing modeled subsidence by 0.2 to 0.5 m after 100 years of pumping. The dissertation also evaluates Managed Aquifer Recharge (MAR) through analysis of the Sustainable Water Initiative for Tomorrow (SWIFT) pilot program in the Virginia Coastal Plain. The Potomac aquifer overlies crystalline basement rock, raising concern about downward pressure propagation in the context of injection-induced seismicity. Ensemble simulations reproducing the 2018 to 2022 pilot injections show that injection rates near 2 million gallons per day may generate pressure increases of approximately 40 kPa in the upper 200 m of the basement, although this response remains localized to within 2 km of the injector. Finally, models incorporating newly identified heterogeneity demonstrate that 20 m thick clay interbeds and laterally extensive DCLs significantly reduce pressure transmission to the basement, improving the stability and safety of MAR operations."],"dc:description.abstractgeneral":["Coastal groundwater supplies are under growing stress due to long-term pumping, which can lower water levels, draw seawater inland, and even cause the land surface to sink. This research uses advanced computer simulations to better understand how these processes unfold underground and how local geology influences their severity. The study examines three types of coastal aquifers: uniform sandy systems, aquifers separated by thick clay layers, and more complex systems with patchy clay layers. The results show that underground geology plays a major role in shaping how seawater moves inland. In uniform aquifers, seawater spreads gradually inland. In systems with thick clay layers, pumping tends to pull saltwater upward from below. Where clay layers are irregular or broken, saltwater intrusion becomes uneven and unpredictable. Because seawater is heavier than freshwater, it also causes greater and longer-lasting pressure declines, which can increase land subsidence over time. The research also evaluates a groundwater recharge project in Virginia that injects treated water back underground to help restore water levels. Computer models of the pilot project suggest that injection can raise pressure in deeper rock layers, but the effects remain localized near the injection wells. Importantly, newly identified clay layers in the subsurface help limit how far pressure spreads downward, improving the overall stability and safety of the recharge program. Overall, this work highlights how differences in underground geology strongly influence coastal groundwater behavior and provides guidance for managing pumping and recharge projects more safely and sustainably."],"dc:description.degree":["Doctor of Philosophy"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:45682"],"dc:identifier.uri":["https://hdl.handle.net/10919/141633"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Coastal aquifer","Managed Aquifer Recharge","Induced seismicity","Potomac aquifer","Fluid pressure"],"dc:title":["Fluid and Pressure Dynamics in Natural and Engineered Coastal Aquifer Systems"],"dc:type":["Dissertation"],"thesis:degree_discipline":["Geosciences"],"thesis:degree_level":["doctoral"],"thesis:degree_name":["Doctor of Philosophy"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:18:49Z"}