SALINITY CHANGES IN CHARLESTON HARBOR 1922-1987

Charleston Harbor, South Carolina, has undergone pronounced changes in salinity regimes because of the diversion of the Santee River into the Cooper River in 1942 and rediversion of the Cooper into the Santee in 1985. The mean monthly harbor surface salinity changed from 30.1 ppt to 16.8 ppt as a result of the diversion, and has again increased to 22.0 ppt since rediversion. Postdiversion monthly mean Cooper River discharge was 418 m3 s-1, but since rediversion, the monthly mean discharge has decreased to 122 m3 s-1 and become less variable. Regression models for salinity variability in Charleston Harbor and Cooper River have been developed. Based on these models, discharge alone explains 78% of the salinity variance during the postdiversion period, but accounts for only 1% of the salinity variance after rediversion because of the near constant discharge. Thus, the estuary is presently much more susceptible to salinity changes due to far-field forcing from the coastal ocean. © ASCE.