HYDROLOGY OF NEW YORK 



105 



The foregoing data of precipitation in the State are cited for 

 the purpose of establishing the proposition that at times the run- 

 offs of New York streams are very low, though undoubtedly the 

 saving grace of the whole matter is that apparently the cycles 

 of low precipitation do not affect the whole State at the same 

 time. Indeed, it is only occasionally that catchment areas as large 

 as the Upper Hudson, Black, Mohawk, Oswego, Allegheny, Sus- 

 quehanna and Genesee rivers will be all subject to drought in 

 the same year. A balancing of conditions is thus to some extent 

 brought about. Nevertheless, while the preceding statement is 

 fairly deducible from the data, it is the writer's opinion that if 

 we had complete records it would be easily shown that the pre- 

 cipitation of nearly the entire State has in some year been on an 

 average less than 30 inches, and that consequently the streams 

 of the State, as a whole, did not average in such a year a runoff of 

 more than about 7 to 10 inches. For individual catchment areas, 

 like the Upper Genesee, where the total is 1070 square miles, or for 

 the Oneida lake area, with a total above Brewerton of 1265 square 

 miles, it is quite possible, and indeed probable, that the minimums 

 affecting the whole area may sink somewhat lower. Probably 25 

 inches precipitation is not an unreasonable figure. If such a 

 minimum should occur for the Oneida lake area, the runoff for 

 the water year would not exceed 5 inches. 1 



Runoff 



The laics of stream flow. A general statement of these laws 



from Mr Vermeule is as follows : 



The Avaters of the earth are taken up by the process which we 

 call evaporation and formed into clouds, to be again precipitated 

 to earth in the form >of rain or snow. Of the water which falls 

 upon the basin of a stream, a portion is evaporated directly by 

 the sun; another large portion is taken up by plant growth and 

 mostly transpired in vapor: still another portion, large in winter 

 but very small in summer, finds its way over the surface directly 



i The foregoing in regard to minimum precipitation records in New York 

 State has been abstracted from the writer's report' on Special Water Supply 

 Investigation, Appendix 16 of the Report of the Board of Engineers on Deep 

 Waterways Between the Great Lakes and Atlantic Tidewaters. Executive 

 Document No. 149 of the House of Representatives, 56th Congress. 2d 

 Session. 



