6. 1 Avai labi 1 i ty of Data 



Measurements of tides and tidal currents have been made in 

 various parts of Long Island Sound and adjacent estuaries for at least 136 

 years (33) . The National Ocean Survey (formerly the U.S. Coast and Geo- 

 detic Survey) publishes tide tables of daily tide predictions and tidal 

 current tables on an annual basis ( 22, 23) . This agency also periodically 

 publishes hydrographic charts and bathymetric contour maps of Long Island 

 Sound ( 21 , kO) . Information on water movement as well as other aspects of 

 physical oceanography in the Sound and estuaries is contained in numerous 

 publications of Oceanographic institutions and scientific journals, many of 

 which are cited in the list of references. 



6.2 Circulation and movement 



The circulation or movement of water within Long Island Sound 

 and the adjacent estuarine streams is controlled by tides, fresh-water in- 

 flow, winds and other weather conditions, bottom topography and salinity or 

 temperature gradients. The circulation pattern in turn affects the chemical 

 composition of water and sediment distribution within the Sound and estuaries, 



72° 00' 



Figure 16. Tidal currents at the eastern end of Long Island Sound two hours 

 after "slack water" at The Race. Speed of currents in knots at time of 

 spring tides. 



38 



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