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Simulation of Water-Table and Freshwater/Saltwater Interface Response to Climate-Change-Driven Sea-Level Rise and Changes in Recharge at Fire Island National Seashore, New York

Scientific Investigations Report 2020-5117
Prepared in cooperation with the National Park Service
By:  and 
https://doi.org/10.3133/sir20205117

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Abstract

The fresh groundwater system at Fire Island National Seashore in New York is one of the natural resources that is most vulnerable to climate change; the various federally listed threatened or endangered species that live on Fire Island, including the piping plover, roseate tern shorebird, and seabeach amaranth may be affected by changes in the groundwater system. The U.S. Geological Survey, in cooperation with the National Park Service, developed a three-dimensional groundwater-flow model to simulate climate-change-related changes in depth to the water table and depth to freshwater/saltwater interfaces on Fire Island. An existing SEAWAT three-dimensional variable-density groundwater flow and transport model was converted to a MODFLOW–NWT three-dimensional finite-difference groundwater model with the Seawater Intrusion (SWI2) package and recalibrated using the UCODE_2005 automatic calibration software. The simulated groundwater divide was found to be skewed strongly toward the ocean shore in response to the modeled wave setup and tidal pumping overheight.

Effects of climate change include sea-level rise and changes in groundwater recharge rates. Sea-level rise scenarios included specified uniform steady states at 0.2-, 0.4-, and 0.6-meter increases above the 2015 level, applied to the existing topography. A high-recharge scenario was created by increasing 2015 recharge rates by 10 percent. Under all scenarios except the low-recharge scenario, the depth to the water table and the thickness of the unsaturated zone decreased. The thickness of the freshwater lens decreased under every scenario. Resulting maps were generated on a 25-meter grid and indicate changes in areas where natural resources may be vulnerable because of projected climate changes.

Suggested Citation

Misut, P.E., and Dressler, S., 2021, Simulation of water-table and freshwater/saltwater interface response to climate-change-driven sea-level rise and changes in recharge at Fire Island National Seashore, New York: U.S. Geological Survey Scientific Investigations Report 2020–5117, 47 p., https://doi.org/10.3133/sir20205117.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Hydrogeologic Framework
  • Results of Shallow Groundwater Flow System Simulations of Fire Island
  • Summary
  • References Cited
  • Appendix 1. Groundwater-Flow Model Design and Calibration
Publication type Report
Publication Subtype USGS Numbered Series
Title Simulation of water-table and freshwater/saltwater interface response to climate-change-driven sea-level rise and changes in recharge at Fire Island National Seashore, New York
Series title Scientific Investigations Report
Series number 2020-5117
DOI 10.3133/sir20205117
Year Published 2021
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) New York Water Science Center
Description Report: vii, 47 p.; Data Release
Country United States
State New York
Other Geospatial Fire Island National Seashore
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details