gradient at the times of measurement. 

 However, the system is a dynamic one, 

 with ground water moving slowly to- 

 ward the discharge points so that 

 changes in the system occur slowly. 

 Consequently, the most representative 

 value for flow is the average value. 



Based on the average value for 

 the gradient and the transmissivity 

 value stated previously, the average 

 groundwater flow is equal to 39.44 

 gallons per day per linear foot (0.49 

 meters per day per meter) of aquifer 

 width, or 208,000 gallons per day 

 per linear mile (489 meters per day 

 per kilometer) of aquifer. This 

 quantity moves into the area each 

 day on the average. Eventually it 

 discharges to saline bodies of sur- 

 face water and is evaporated from 

 the water table. 



Behavior of the flow system and 

 water quality relationships in the 

 principal water bearing zone can be 

 seen in the cross-section given in 

 Figure 2. The elevation of the water 

 table was highest at +4.54 ft 

 ( + 1.38m) NGVD on the upgradient end 

 of the section, at Well 2012, on 

 July 16, 1980; at Well 8 it was 

 +2.46 ft. (+0.75 m) NGVD, and +1.47 

 ft. (+0.45 m) NGVD at Well 2, showing 

 that ground water was moving to the 

 southwest from areas of higher head 

 or water level elevations to ones of 

 lower head (sea level). For a dis- 

 cussion of the fundamentals of ground 

 water flow, the reader is referred to 

 Freeze and Cherry (1979). 



The data presented in Figure 2 

 and from the other wells show that 

 the chloride concentration of the 

 water in the principal zone in- 

 creases as the marshes and bays 

 are approached. For example, at 

 Well 2012 the water had a chloride 

 concentration of 93 mg/1; at Well 8, 

 chlorides of 225 mg/1 are present, 

 whereas at Well 2 the chlorides were 

 found to be 23,000 mg/1. As noted 



previously, the presence of the 

 hypersaline water is anomalous and at- 

 tributed to a combination of evapor- 

 ation of the water table and the 

 downward infiltration of tidal sea 

 water whose density has been raised 

 by evaporation. This is a process 

 that has been going on for many 

 thousands of years. 



Figure 2 also shows relation- 

 ships between water levels and 

 quality in the lake and between 

 different depth zones at the site of 

 Well 7. At the time of measurement, 

 the water level in the lake was at 

 a lower elevation (+1.62 ft or + 

 0.49 m NGVD) than in both zones at 

 Well 7, showing that ground water was 

 discharging into the lake. In the 

 shallow zone, the water level stood 

 at +1.95 feet (+0.59 m) NGVD and the 

 chlorides were 616 mg/1, while the 

 water level in the deep zone stood 

 at +1.70 feet (+0.52 m) NGVD and the 

 chlorides were 17,200 mg/1. The 

 observed chloride values are a re- 

 flection of the presence of the 

 fresh water lens that has developed 

 in the artificial land area and a 

 local phenomenon which influences 

 the quality of the water in the shal- 

 low portion of the lake. The higher 

 level of chlorides present in the 

 deep zone probably represent the zone 

 of diffusion between fresh and salty 

 ground water. 



Water level data from deep and 

 shallow zones at Well 2 give an addi- 

 tional clue as to why the ground 

 water is hypersaline. Both zones 

 contain water with about 23,000 mg/1 

 of other chlorides. As shown in 

 Figure 2, the water level on July 

 16, 1980 was +1.91 feet (+0.58 m) 

 NGVD in the shallow zone and +1.47 

 feet (+0.45 m) NGVD in the deep zone. 

 The higher head or elevation in the 

 shallow zone indicates the downward 

 movement of ground water. This re- 

 lationship was observed following a 

 period of rainfall. Comparison of 



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