CISA: Carolinas Integrated Sciences and Assessments, A NOAA RISA Team

Coastal Salinity Index and Ecological Indicators of Coastal Drought

Spartina can be an indicator of saltwater intrusion
Freshwater impoundments, Bulls Island, Cape Romain National Wildlife Refuge, SC

As part of the Coastal Carolinas DEWS, NIDIS is currently providing funding to the US Geological Survey (USGS) South Atlantic Water Science Center and CISA to advance the development and use of the Coastal Salinity Index (CSI).

The Coastal Salinity Index

The Coastal Salinity Index (CSI) was developed as a way to characterize coastal drought. Commonly-used drought indices characterize hydrological, agricultural, and meteorological conditions; however they do not incorporate salinity, which is a key stressor associated with coastal drought. Paul Conrads, USGS, developed the CSI using an approach similar to the Standardized Precipitation Index (SPI), substituting total monthly precipitation with average monthly salinity data. The CSI provides a tool to monitor changing salinities in coastal surface-water bodies and associated effects on estuarine habitats, and freshwater availability for ecological, municipal, and industrial needs.

In 2018, USGS will create a CSI R-package for consistent computation of the CSI by different users, develop a prototype website with access to real-time CSIs, and compute the CSI at additional locations across the Southeast U.S. The CSI has been calculated for 32 sites in South Carolina, Georgia, and South Florida. More information is available through the USGS South Atlantic Water Science Center.

Read more about the CSI:

Indicators and Indices of Drought in Southeastern Coastal Ecosystems

With funding from the NOAA Climate Program Office (2013-2017), CISA conducted this project to improve understanding of coastal resources that are adapted to or dependent upon particular spatial and temporal patterns of salinity. Understanding the relationship between these resources and salinity will inform researchers and managers about the ways in which drought stresses coastal systems.

Phase 1. A needs assessment was completed through structured interviews with 30 resource managers along the Carolinas' coast. These interviews identified opportunities for drought early warning as well as additional data and research needed to effectively understand and monitor drought in coastal ecosystems.

Phase 2. The second component of this project involved collaboration with the US Geological Survey South Atlantic Water Science Center (USGS SAWSC) to inform the development of the Coastal Salinity Index (CSI). Activities include 1) synthesizing existing information about drought and salinity effects on coastal resources and 2) identifying and documenting salinity and ecological response datasets for calculating the CSI and assessing linkages between ecological variables and salinity levels as expressed by the CSI.

Salinity and ecological response records identified through the research review have been compiled into the following resources:

Explore the GIS resources available for download in the interactive map below.

Additional Resources

Next Steps: Testing and Applying the CSI

CISA’s 2018 activities will support research and engagement with users to assess how the CSI can be applied and provide value to drought monitoring and decision making. This will include ongoing work with Coastal Carolinas DEWS partners to assess linkages between coastal drought and salinity with affected environmental resources. Researchers have begun to investigate the linkages between ecological indicators (for example, blue crab landings, bald cypress growth, and fisheries monitoring data) and varying salinity conditions expressed by the CSI.

The CSI Working Group provides feedback on the development of the CSI and recommendations for its use by researchers and resource managers. Contact Kirsten Lackstrom ( to find out how you can participate.