Seismic and Hydrostratigraphic Characterization of the Onshore-Offshore Freshwater Systems of Martha’s Vineyard and Nantucket, Massachusetts, USA

Coastal hydrological systems provide significant freshwater resources to coastal communities around the world. These resources are exploited by groundwater wells that produce from aquifers at depths of less than 100 m. Globally, these resources are declining due to overuse, increasing population, and climate change.

To improve water supplies and security, new approaches to understanding underused and poorly quantified freshwater resources are needed. One such resource is freshwater that extends from onshore to offshore, potentially extending up to 100km offshore in some regions, such as the northeastern margin of the United States. To better understand the dynamics of these onshore-offshore hydrologic systems, we need dedicated, coordinated onshore and offshore hydrogeological studies.

This research project on Martha’s Vineyard and Nantucket, MA, USA will increase our understanding of the coastal freshwater resources by characterizing the sedimentary layering in the coastal environment through geophysical surveys. This work is a critical piece to the integrative, multi-pronged (geophysics, drilling and sampling, modeling) research that is required to understand the dynamics of the onshore-offshore systems and to define their potential as a resource.

This study has the potential to establish the protocols for studying global onshore-offshore freshwater resources, to improve understanding of under-developed freshwater resources, and to inform future studies on the maintenance and sustainability of this resource.

Over the last 15-years, there has been growing research on onshore-offshore freshwater systems including geophysical surveys and numerical models that have been motivated by drilling data that were not collected to address freshwater resources. To date, however, no dedicated and integrated onshore-offshore study has been completed to study the dynamics, volumes, and producibility of these offshore freshwater resources.

Our proposed study of the hydrostratigraphy on Martha’s Vineyard and Nantucket Island, MA, USA through collection, processing, and interpretation of seismic data is a key portion to the first complete onshore-offshore characterization. The data obtained from this award will be used to support an International Continental Scientific Drilling Program (ICDP) proposal to drill wells to quantify the hydrologic properties and groundwater age for the onshore portion of this coastal aquifer system.

This complements an International Ocean Discovery Program (IODP) proposal to drill wells to quantify hydrologic properties and groundwater age for the offshore component of this onshore-offshore aquifer. Combined, this research would be the first dedicated, shoreline-crossing geological, geophysical, and hydrogeological study of onshore-offshore freshwater addressing many questions related to the dynamics, sustainability, and utility of these freshwater systems that exist globally. This award was co-funded by the Earth Sciences Hydrologic Sciences Program.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.