Coastal Salinity Index Along the Southeastern Atlantic Coast and the Gulf of Mexico, 1983 to 2018

Open-File Report 2019-1090
Prepared in cooperation with the National Integrated Drought Information System
By: , and 



Coastal droughts have a different dynamic than upland droughts, which are typically characterized by agricultural, hydrologic, meteorological, and (or) socioeconomic effects. Drought uniquely affects coastal ecosystems because of changes in the salinity conditions of estuarine creeks and rivers. The location of the freshwater-saltwater interface in surface-water bodies is an important factor in the ecological and socioeconomic dynamics of coastal communities. To address the data and information gap for characterizing coastal drought, the Coastal Salinity Index (CSI) was developed by using salinity data. The CSI uses a computational approach similar to the Standardized Precipitation Index. The CSI can be computed for unique time intervals (for example 1-, 6-, 12-, and 24-month intervals) to characterize short- and long-term drought (saline) conditions, as well as wet (high freshwater inflow) conditions.

To encourage the use of the CSI in current and future research endeavors, this investigation addressed three activities to enhance the use and application of the CSI. First, a software package was developed for the consistent computation of the CSI that includes preprocessing of salinity data, filling missing data, computing the CSI, post-processing, and generating the supporting metadata. This software package is available for download from the U.S. Geological Survey GitLab repository. Second, the CSI has been computed at sites along the southeastern Atlantic coast (Florida to North Carolina) and the Gulf of Mexico (Texas to Florida) to increase the opportunity for linking the CSI to ecological response data. Third, using telemetered salinity data, the real-time computation of the CSI has been prototyped and disseminated on the web.

Suggested Citation

Petkewich, M.D., Lackstrom, K., McCloskey, B.J., Rouen, L.F, and Conrads, P.A., 2019, Coastal Salinity Index along the southeastern Atlantic coast and the Gulf of Mexico, 1983 to 2018 (ver. 1.1, April 2023): U.S. Geological Survey Open-File Report 2019–1090, 26 p.,

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Development of the Coastal Salinity Index
  • Use and Interpretation of the Coastal Salinity Index
  • Summary
  • References Cited
  • Appendix 1. Coastal Salinity Index User Guide
Publication type Report
Publication Subtype USGS Numbered Series
Title Coastal Salinity Index along the southeastern Atlantic coast and the Gulf of Mexico, 1983 to 2018
Series title Open-File Report
Series number 2019-1090
DOI 10.3133/ofr20191090
Edition Version 1.0: October 1, 2019; Version 1.1: April 6, 2023
Year Published 2019
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) South Atlantic Water Science Center
Description Report: vi, 26 p.; Appendix; Data Release
Country United States
State Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, Puerto Rico, South Carolina, Texas
Other Geospatial Gulf of Mexico Coast, South Atlantic Coast
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details