514 



NEW YORK STATE MUSEUM 



Nothing is known as to the minimum yields of streams tribu- 

 tary to the Allegheny, Susquehanna and Delaware rivers, aside 

 from the measurements of Eaton and Madison brooks made in 

 1835. So far as can be learned, aside from those recently 

 inaugurated by' the United States Geological Survey, no measure- 

 ments of any other of these streams have been made. It is prob- 

 able that they will mostly be found substantially the same as 

 Genesee river and streams issuing from the Catskill region. 



Quantity of water which may be stored on the several plateaus. 

 The foregoing treats of the yield of streams in a general way, 

 but the practical summation of the preceding discussion is as 

 to the quantity of water that can be safely stored on different 

 catchment areas of Xew York in the year of minimum runoff. 

 The tables of precipitation on the several plateaus show that the 

 quantity which can be stored varies in different parts of the State 

 and in some degree in proportion to the rainfall. It is also shown 

 that when the rainfall is above a certain minimum amount, the 

 excess quantity of runoff is roughly in proportion to the rainfall. 

 In order to emphasize the preceding propositions, we have the 

 following as the mean rainfalls of the ten plateaus into which the 

 area of New York is divided for the twelve water years 1S91-1902, 

 inclusive, together with the low rainfalls of 1S95 and 1899. 





Mean of 

 12 years, 

 inches 



1S95, 

 inches 



1S99, 

 inches 



>A>stern plateau. . . . 



37.03 



29 . 76 



27.65 





40.30 



32.87 



35.26 





14.03 



36.67 



35 . 79 



Atlantic coast 



46.71 



40.77 



44.54 



Hudson vallev 



42.59 



35.74 



37.98 





42.13 



31.30 



35.31 





37. 0G 



32.95 



33.85 



St Lawrence vallev. 



36.18 



33.75 



28.51 





35.65 



29.13 



28.67 





34.46 



27.31 



27.83 



The difference in 



the average precipitation 



of the 



Atlantic 



coast and the Central Lakes regions is 12.25 inches. We may 

 expect, therefore, about 10 to 11 inches more average runoff in 



