The Coastal Salinity Index (CSI) is a long-term monitoring tool that characterizes relative changes in coastal salinity regimes for salinity gages with long periods of record. It is a standardized probability index. A value of zero indicates equality with historical mean salinity for the gage data, and negative and positive values represent above and below normal salinity conditions, respectively. The CSI is site-specific based on local historic conditions and can be computed for multiple time intervals from 1- to 24-months, to help users evaluate responses at monthly to interannual time scales.

The CSI was developed to characterize coastal drought, monitor changing salinity conditions, and improve understanding of the effects of changing salinities on fresh and saltwater ecosystems, fish habitat, and freshwater availability for municipal and industrial use. The CSI uses the same classification scheme as the U.S. Drought Monitor for high saline (or drought) conditions and the inverse for wet conditions.

Real-time Coastal Salinity Index Map
Time Interval of CSI Values:   
Coastal Salinity Classification Description CSI Values Color Cumulative Percentage
CD4 Exceptional salinity conditions -2 or less 2
CD3 Extreme salinity conditions -1.99 to -1.60 5
CD2 Severe salinity conditions -1.59 to -1.30 10
CD1 Moderate salinity conditions -1.29 to -0.80 20
CD0 Abnormal salinity conditions -0.79 to -0.50 30
Normal Normal salinity conditions -0.49 to 0.50 70
CW0 Abnormal freshwater conditions 0.51 to 0.80 80
CW1 Moderate freshwater conditions 0.81 to 1.30 90
CW2 Severe freshwater conditions 1.31 to 1.60 95
CW3 Extreme freshwater conditions 1.61 to 2.00 98
CW4 Exceptional freshwater conditions 2.01 or more 100
Not Available Missing Data
  CD = Coastal Drought
  CW = Coastal Wet
  Data last updated on .

Operating Agency
  • U.S. Geological Survey (USGS)
  • National Estuarine Research Reserves (NERRS)
  • National Park Service (NPS)

Coastal Salinity Index Gages

Click or hover mouse over rows to identify corresponding icons on the map. Click on column headers to sort columns; shift-click to sort by multiple columns. Use boxes below headers to search or filter through data.

Station ID Station Name Agency State CSI Value (1-mo) Station Data Page Input Salinity Data Output CSI Data CSI Monthly Graphs

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