Riley ( 28, 29 ) and others have attempted to estimate the residual 

 volume transport through various parts of the Sound or for one cross section 

 for various periods of time. Because of incomplete data the calculations are 

 very uncertain and continuous monitoring of currents are required to give 

 reasonable estimates of transport. 



The vertical movement of the water surface in the Sound results 

 from the periodic tidal oscillations, from waves produced by wind and over 

 long periods by changes in sea level. Factors influencing the heights of 

 tides, abnormally high tides and storm generated waves are discussed in a 

 separate report prepared for this study by the Dept. of the Army, Corps of 

 Engineers ( 39) . 



Long-term changes in sea level over the last 10,000 to 15,000 

 years have produced extensive submergence of the coast (2). Tide gage records 

 and tidal benchmark data indicate that sea level may still be rising at a 

 rate of approximately 1 foot per century. 



6.3 Estuaries 



Estuaries are sometimes defined as the seaward ends of river 

 valleys that contain salty water.' Ocean tides affect the streamflow and 

 flow may be either upstream or downstream depending on location, tide and 

 fresh water inflow conditions. The major estuaries in the region are the 

 Connecticut, Thames, Housatonic and Quinnipiac. Studies {Sj ]Sj 32) indicate 

 that there is a two-layer transport system in the lower parts of these 

 estuaries. Fresh water flows seaward near the surface while the tides move 

 denser saline water upstream along the river bottom. Salinity generally 

 increases downstream and top to bottom at any point in the brackish part of 

 the estuary. The distribution of salinity changes with the tidal stage and 

 the amount of fresh water inflow. 



In the largest estuary, the Connecticut, saline water may reach 

 15 miles upstream from the mouth (J6} and tidal effects may extend upstream 

 approximately 60 miles. The upstream extent of salinity and tidal influence 

 is generally controlled by the amount of fresh-water inflow. During periods 

 of high fresh-water inflow (greater than 100,000 cfs), saline water is flushed 

 to the mouth of the river and the tide-affected reach extends upstream only 

 30 miles. Figure 19 shows the effect of different river discharge conditions 

 on chemical quality. 



In the second largest estuary, the Thames, tidal effects and 

 saline water extend upstream to Norwich. Information on the salinity dis- 

 tribution and its variability in this estuary is contained in a recent report 

 by Soderberg and Bruno (32) . The Housatonic and Quinnipiac estuaries extend 

 upstream 12 and 10 miles respectively. 



1 - Another commonly used definition is: a semi -enclosed coastal body of 



water which has a free connection with the open sea and within which sea 

 water is measurably diluted with fresh water derived from land drainage. 



k2 



