HYDROLOGY OF NEW YORK 



311 



These figures are cited to show that in years of low rainfall 

 the runoff of streams tributary to the Great Lakes is low, and as 

 a consequence the runoff of Niagara river will necessarily be 

 affected thereby. 



Aside from the measurements made by the Board of Engineers 

 on Deep Waterways in 1898, the most elaborate measurements 

 thus far made are those of the Lake Survey in 1867 and 1869 which 

 are, however, extremely unsatisfactory. According to these meas- 

 urements the mean discharge, rainfall and evaporation from the 

 Great Lakes for the year 1868, in cubic feet per second, were as 

 follows i 1 



r . Mean dis- Total rainfall Evaporation 



i - AKe charge on basin from surface 



Superior 86,000 171,430 27,690 



Huron and Michigan 225,000 251,450 59,890 



Erie 265,000 100,540 14,310 



Total ........ 523,420 101,890 



According to the Deep Waterways Commission's tabulation of 

 records of hights of the Great Lakes, it appears that the water 

 level fluctuated through a series of years to the extent of about 

 3.8 feet. In the present discussion we are chiefly concerned with 

 the fluctuations of Lake Erie, which control the discharge of 

 Niagara river. From table No, 44. which gives the mean monthly 

 elevations of Lake Erie at Buffalo for the years 1865-1898, in- 

 clusive, it appears that the highest mean monthly elevation during 

 these years was for June, 1876, when the mean lake surface was 

 574.31 feet. The lowest mean monthly elevation for the period was 

 for November, 1895. when the mean for the month was 570.49 feet. 

 The range in the mean monthly elevations for this period was 

 therefore 3.82 feet. 



In regard to table No. 44 it is stated in the Report of the Board 

 of Engineers on Deep Waiter-ways that the uncertainty concerning 

 the stability of the Buffalo gage previous to 1896, together with 

 the excessive fluctuations of the lake level at Buffalo, appear to 

 make the Cleveland gage record more reliable, and it has therefore 

 been used in determining the mean monthly elevations of the lake. 



1 These figures are derived from Mr Coo-ley's Lakes and Gulf Waterways, 

 as corrected and given in the Journal of the Assoc. of Eng. Soc, Vol. VIII 

 (March, 1889), p. 132. 



