156 PROCEEDINGS OF THE BOSTON MEETING 



2. There are seasonal variations of the extent to which the well is drawn 

 upon. 



3. There is interference from later drilled wells. 



4. It is diflQcult to get periodical volume determinations. 



In spite of these difficulties, however, the accompanying curve is presented. 

 It was constructed by the segmental method, namely, determining the rate of 

 decline at different parts of the curve by the rate shown in wells of various 

 sizes, assuming the validity for practical purposes of Lewis and Beal's "Law 

 of Equal Expectations." 



The curve is based on wells in Cowanshanock Township, Armstrong County, 

 Pennsylvania. 



The curve is shown drawn on quadrille paper and also on logarithmic and 

 arithlog paper, to indicate the nature of the curve. It is to be seen that the 

 curve approaches more nearly the petroleum curve than might have been ex- 

 pected, from the pressure curves that have heretofore been published. 



Mr. W. I. Moyer and Mrs. Fisher Bossier have cooperated in the construc- 

 tion of these curves. 



Presented by title in the absence of the author. 



QUANTITATIVE METHODS OF ESTIMATING GROUND-WATER SUPPLIES 

 BY OSCAE E. MEINZER 



(Abstract) 



This paper relates only to ground water, or phreatic water — that is, water 

 in the zone of saturation. It is not concerned with the water that occurs 

 above the water-table. It relates not to the quantities of water stored in the 

 earth, but to the rate of replenishment of the ground-water supply, on which 

 conservative developments must be based. 



Four principal groups of methods are used to determine the annual recharge 

 or "safe yield" of ground water : The intake, discharge,- tvater-tahle, and under- 

 floio methods. The first of these consists in measuring the quantity of sur- 

 face water that seeps into the earth and percolates into the zone of saturation ; 

 the second in measuring the ground water that is discharged through springs 

 or by evaporation from soil and plants ; the third in observing the fluctuations 

 in the water-table, which represent filling or emptying of the ground-water 

 reservoir ; the fourth, like the gaging of surface streams, in measuring the flow 

 of ground water at selected cross-sections. In arid regions plants of certain 

 species habitually utilize water from the zone of saturation. For such plants 

 the name phreatophyte, meaning a "well plant," is proposed. The water-table 

 methods are best adapted to regions, such as California, which have well 

 defined rainy and dry seasons. The th%ee principal methods — intake, dis- 

 charge, and water-table — are entirely independent of each other and caw b^ 

 used as checks upon one another. 



Presented by title in the absence of the author. 



