HYDROLOGY OF NEW YORK 



299 



These precipitation data are of special interest because the year 

 1895 was the culmination of a period of exceedingly low water. 

 They show that for a period of four years the precipitation of 

 this basin was low, and in consequence the runoff of the tributary 

 streams must have been exceedingly small. As illustrating this 

 proposition, we will refer to the runoff of the Upper Mississippi, 1 

 where there is a reservoir system controlling a catchment area 

 of 3265 square miles, first operated about 1885. The rainfall 

 of the area tributary to these reservoirs, as indicated by records 

 kept at Leech lake, Lake Winibigoshish, and Pokegania Falls 

 from 1885 until the present time is, on an average, from 24 to 

 26 inches per year. The highest recorded yearly precipitation 

 is 31.87 inches, at Pokegama Falls in 1894. The rainfall of the 

 area tributary to the Upper Mississippi reservoirs is found to 

 be quite similar to that of the region tributary to Lake Superior. 

 Hence the runoff of this reservoir system may be considered 

 as representing the runoff of the catchment area of Lake 

 Superior and the northern portion of Lakes Michigan and Huron. 

 The following gives the discharge from these reservoirs for the 

 years 1892 to 1895, inclusive, corresponding with the years of 

 precipitation shown in table No. 39. 







Mean rain- 



Runoff 



Proportion 







fall on 



of 



of runoff 







catchment 



catchment 



to 





Water year. 



area. 



ai-ea. 



rainfall. 







Inches 



Inches 



Per cent 



1892. 





21.33 



4.43 



20.8 



1893. 





25.42 



3.61 



14.2 



1894 





26.63 



3.62 



13.6 



1895 





25.11 



2.79 



11.1 





Total 



, , . , 98.49 



14.45 









24.62 



3.61 



14.7 



'Annual report of Chief of Engineers U. S. Army for 1896, part III, 

 p. 1843; also for 1897, part III, p. 2169. 



