TABLE 2. ESTIMATED VOLUME OF FRESH GROUND WATER BENEATH PARTS OF LONG ISLAND 



Volume designation 



Volume of 

 deposits satu- 

 rated with 

 fresh ground 

 water (cubic 

 mi les) 



Total volume 



of fresh 

 ground water 



Range in estimated 

 storage capacity 



(trillions of gallons) 



Item (1) (2) 



(a) Above sea level in 



water-budget area 5 



(b) Beneath entire water- 



budget area 180 



(c) Beneath area adja- 



cent to water- 

 budget area' 100 



(d) Sums of Items b and c 



(rounded) 280 



(e) Beneath mainland 



Kings and Queens 



Counties 10 



(f) Sums of items d and e 



(rounded) 290 



(3) 



W 



1.6 

 59 



33 

 92 



3.3 



95 



0.28- 0.56 

 10 -20 



5.5 -11 



15 -31 



.55- 1.1 



16 -32 



1 Includes volume beneath the nearshore areas and the adjacent bays. 



Adapted from Franke and McClymonds (1972) 



Fresh ground water occurs from the bedrock surface to the water 

 table except in the Forks and islands of eastern Long Island. The estimated 

 quantities of fresh water stored beneath various parts of Long Island are 

 listed on Table 2. Only a part of the fresh water beneath Long Island is 

 available for use by man and the amount that can be recovered depends upon 

 the water management scheme. 



The water table and fresh-salt water interfaces are not station- 

 ary boundaries and their position depends on the balance between inflow 

 (recharge) to and outflow (discharge) from the ground-water reservoir. A 

 map prepared for this study (see Appendix C) shows the position of the upper 

 boundary, the water table, as of March 1971. The position of the fresh-salt 

 water interface generally lies seaward of the shore but has been accurately 

 determined only in southwestern Nassau and Southeastern Queens Counties. 



Recharge to the ground-water reservoir under natural conditions 

 is derived solely from precipitation. In the 760 square mile "water budget 

 area" it is estimated that the average annual recharge from precipitation 

 is approximately 820 million gallons per day (5). Most recharge takes place 

 during the period October to March when vegetation is generally dormant. 



The ground-water reservoir contains six major hydrogeologic units 

 whose properties affect the storage and movement of water. Maps showing the 

 known extent, thickness, depth to and hydraulic properties of these units 

 were prepared or modified for this study by the U.S. Geological Survey (see 

 Appendix C) . Such maps in conjunction with continuing programs will enable 



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