HYDROLOGY OF NEW YORK 



189 



Family resemblance of streams. In tables ISos. 42, 43, 61 and 

 66 we have the mean rainfall, runoff and evaporation of the 

 storage, growing and replenishing periods for Muskingum, Gen- 

 esee, Croton and Hudson rivers. Those tables show what may 

 be termed the family resemblance between streams. For instance, 

 for the Muskingum and Genesee rivers the mean rainfall of the 

 storage period is about 19 inches, with a runoff of about 10 inches 

 and an evaporation of about 9 inches. For the growing period 

 the mean rainfall of each of these two streams is about 12 inches, 

 with runoff 1.7 inches and evaporation 10 inches. For the replen- 

 ishing period the mean rainfall of each is about 9 inches, with 

 runoff about 2 inches and evaporation 7.5 inches. The total rain- 

 fall of the whole year is 40 inches for each stream — runoff 13.5 

 inches and evaporation 26.5 inches. 



The Croton river has a much higher rainfall. Twenty-foiu* 

 inches in the storage period produces 17 inches of runoff, with an 

 evaporation of 7 inches. From 13.6 inches of rain in the summer 

 we have 2.6 inches of runoff, with 11 inches of evaporation. The 

 rainfall for the year is 49.4 inches, or, say, 9 inches more than for 

 Muskingum and Genesee rivers. The runoff is also about 9 inches 

 in excess of that of these two streams. The evaporation is, how- 

 ever, the same, pointing very strongly to a similar cause. 



The Hudson river shows apparently the effect of an impermeable 

 catchment, combined with a large forest area. It has a mean 

 annual rainfall of 44.2 inches, yielding 23.3 inches runoff, with 

 20.9 inches evaporation. For the storage period 20.6 inches rain- 

 fall yields 16.1 inches runoff, with 4.5 inches evaporation. For 

 the growing period 12.7 inches rainfall yields 3.5 inches runoff, 

 with 9.3 inches evaporation. For the replenishing period 10.9 

 inches rainfall yields 3.7 inches runoff and 7.1 inches evaporation. 



The classification here given is experimental merely, and is 

 subject to modification with the gathering of more complete 

 data. 1 



In the foregoing the classification is, with the exception of 

 Muskingum river, not only limited to the State of Xew York but 



iFor more extended discussion of classification of streams see paper on 

 Relation of Rainfall to Runoff. 



