Bottom salinity distribution cur\"es at high vratex slack for all fresh- 

 water discharges tested are shown in Figure 3-89. The curi^es were devel- 

 oped from detailed information to clearly show the effect of sustained 

 freshwater discharge on horizontal salinity distribution throughout the 

 estuary and the horizontal shift of a given isochlor with change in fresh- 

 water discharge. 



Results of these tests determined that sustained freshwater discharges 

 of about 12,000 and 10,600 cubic feet per second would hold the 50 and 100 

 isochlors, respectively, at the Delaware-Pennsylvania State line. Addi- 

 tional tests were conducted to determine the length of time required to 

 reestablish the 100 isochlor at the State line following periods of inean 

 [16,475 ciibic feet per second) and low (2,000 ci±)ic feet per second] dis- 

 charge [results are shoivTi in Fig. 3-90) . 



Tests to determine the effects of tidal range on salinity distribu- 

 tion throughout the estuaiy were conducted for conditions of mean fresh- 

 water discharge [16,475 cubic feet per second) and of low freshwater 

 discharge [5,000 ci±>ic feet per second). The tests for mean freshwater 

 discharge were made to determine the effects of tidal range on salinity 

 distribution for normal conditions; the tests for low freshwater dis- 

 charge were made to determine the effects of tidal range for critical 

 conditions of salinity intrusion [when the salinity front was well up- 

 stream from the Delaware-Pennsylvania State line). Tests were conducted 

 for neap, mean, and spring tides. The restilts are sumnarized in Figures 

 3-91 and 5-92 and indicate that the extent of salinity intrusion in the 

 estuaiy increases slightly as the tidal range decreases. The differences 

 in salinity at any given point: in the estuary for the various tidal ranges 

 were less for the tests of low freshwater discharge than for the tests of 

 mean freshwater discharge. 



Mean annual sea level at the sitrance to the Delaware River estuary 

 rose about 0.5 foot between about 1920 and 1950. To determine the effect 

 of changes in sea level of this order of magnitude on salinity intrusion 

 and distribution throughout the estuarv", tests were made for the 1948 

 mean sea level and with the sea level raised D.5 foot above and lowered 

 D.5 foot below the 1948 level. Each of these tests was made for mean 

 conditions of tide and freshwater discharge. 



Bottom salinity distribution curves at high water slack for the three 

 elevations of sea level indicate that the extent of salinity intrusion in 

 the estuarv' increases as sea level rJses [Fig. 3-93). Other characteris- 

 tics of the salinity distribution curves for the three conditions appear 

 to be identical. The upstream shift of equal isochlors as sea level 

 rises is believed to be attributable to corresponding increases in cross- 

 sectional area of the estuarv' with increase in sea level. 



7. Time and Cost Estimates. 



A generalization of the time and cost requirements for estuaiy models 



is difficult because of the wide variety of model sizes, problems to be 



89 



