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Chesapeake Bay [TMgure V.7.1] is aibout 165 nautical miles long, averages 

 less than 20 feet deep with a maximum depth of 175 feet, and contains about 

 18,520 billion gallons of water. The surface area is 4,300 square miles and the 

 shoreline is 4,500 miles long. The total drainage basin is 74,000 square miles. 

 This includes the Susqehanna River, the largest on the easit coast of the United 

 States, w*hich drains 42 percent of the basin and dominates the upper ibay. * * * 

 The Potomac drains 22 percent of the basin and the Rappahanock-Tork-James 

 complex drains about 24 percent. There are over 50 tributary rivers, with widely 

 varying geochemical and hydrological characteristics, so that the physical 

 circulation of the bay is complex. 



The bay is the drowned valley of the Susquehanna ; its natural deep channels 

 are the only remnants of the original flow-carved riverhead. It is characterized 

 by the presence of great deposits of fine sediments in the deeper iK>rtions. 



Large cities, especially Baltimore, Washington, and Norfolk, arose because of 

 the Ibay and increasingly impinge upon it. This is the southern end of the eastern 

 megalopolis, with an enormous growth of population in sight. 



'Salinity is near zero at the heiad of each tributary and at the north end of 

 the b'ay and about 30-31 parts per thousand at the Capes. Oirculation is con- 

 trolled primarily by river flow and the resulting density gradients. A strongly 

 two-layered stratified system develops in summer, with a somewhat weaker winter 

 system, and general vertical mixing occurs in spring and fall. This produces 

 a net downstream flow of surface water and net upstream flow of deeper waters. 

 This pattern of circulation affects many of the organisms of the bay. 



USES 



Trcmsportation 



Ships have used the hay since its discovery in the 16th century, and Baltimore 

 and Norfolk are among the Nation's great ports. In 1964, 107,253,730 tons of 

 material were handled by these ports, and Baltimore alone receives about 5,000 

 oceangoing ships per year. This commercially acti\'ity affects other uses of the 

 bay, principally throug'h pollution by bilgepumping and accidental spillage 

 and through insatiable demands for the deepening and maintenance of channels. 

 In the main channel of the bay, control depth is now 35 feet, but further cuts 

 to 45 feet are now proposed. 



Biotio Yield 



Extraction of organic material from the bay has increased from the inconse- 

 quential harvests by Indians and colonists to present efficient removal of fish 

 and shellfisih. Oyster produdtion has been decimated by excessive exploitation, and 

 other .si>ecies have been reduced by tributary dams and pollution ; but changes 

 in gear have vastly increased the catch of menhaden, soft shell clams, and 

 crabs. Landings for 1965 included 501,600,000 pounds of fish and shellfish for 

 commercial use, with a value of at least $65 million (twice the dockside value). 

 Menhaden dominated the fish catch, with 319 million pounds landed, but 

 108,200,000 pounds of shellfish provided 74 i)ercent of the value. . . . 



The yield to sport fishing is much more difficult to measure and evaluate. 

 [Researchers] . . . have made valuable surveys of parts of the burgeoning rec- 

 reational fishery, but no satisfactory estimates of baywide effort, catch or 

 value are available. 



In addition to these aquatic crops, the bay area supports large populations 

 of many species of birds and mammals. They cannot be fully reviewed here, 

 but are of high use to the human population and affected by the changes which 

 are occurring. 



Recreation and esthetios 



Recreational uses of the waters of the Chesapeake Bay are very poorly docu- 

 mented. Boating, swimming, skiing, beaching, fishing, and hunting are all 

 increasing rapidly, but reliable data are scarce. 



Boat registration provides one helpful index. Maryland salt water boat listings 

 increased 33 percent from 1960 to 1966. Sixty-one thousand craft are roistered, 

 about 20.000 are not required to register and about 20,000 visiting boats enter 

 the Maryland portion of the bay, for an annual total of 100,000. Over 300 marinas 

 serve these 'boats. Virginia has a fleet of about the same size. 



The 'Chesapeake is the focal point of the Atlantic flyway for migratory water- 

 fowl, and a)bout 30 species of ducks, geese, and swans concentrate there in winter. 

 These support heavy hunting during the winter months. 



