HYDROLOGY OP NEW YORK 



89 



The Great Lakes region, with an average elevation of 494 feet, 

 has an average annual precipitation of 35.17 inches, while the 

 Central Lakes region, with an average elevation of 690 feet, has an 

 average annual precipitation of 43.41 inches. 



Mr Turner's table is based on a calendar year, from January to 

 December, inclusive. Further data may be obtained from this 

 excellent table. 



In table No. 24 of the Upper Hudson Storage Surveys Report for 

 1896 there is given the mean precipitation of the Upper Hudson 

 catchment area. The stations therein included are: Albany, 1825- 

 1895, 71 years; Glens Falls, 1879-1895, 17 years; Keene Valley, 

 1879-1895, 17 years; western Massachusetts, 1887-1895, 9 years; 

 northern plateau, 1889-1895, 6J years; Lowville Academy, 1827- 



1848, 22 years; Johnstown Academy, 1828-1845, 18 years; Cam- 

 bridge Academy, 1827-1839, 13 years; Fairfield Academy, 1828- 



1849, 22 years ; Granville Academy, 1835-1849, 15 years. Assum- 

 ing the northern plateau as a unit, the total number of years is 

 199 J, and the mean of all is 37.4 inches. A reference to the rain- 

 fall map in the report of the United States Board of Engineers on 

 Deep Waterways will show that this is necessarily an approxima- 

 tion, because of great lack of stations in the interior of this 

 region. 



As regards the catchment area of the Upper Genesee river, 

 there is a very decided increase in rainfall as one goes toward 

 the source. For the years 1889-1896, inclusive, the rainfall in 

 the upper af ea of this stream was 42.19 inches, while at Rochester 

 for the same years it was 35.64 inches. This statement is 

 specially interesting, because there seems to be a well-marked 

 line dividing the smaller rainfalls of the lower area from the 

 higher rainfalls of the upper. At Hemlock lake, Avon, and Mount 

 Morris the rainfalls are all low, the average at Hemlock lake 

 from 1876-1895, inclusive, being 27.56 inches. In 1880 it was 21.99 

 inches; in 1879, 22.16 inches, and in 1881 only 24.36 inches. We 

 have here three years of exceedingly low rainfall, in which the 

 runoff must have also been very low. In 1895 the rainfall at 

 Hemlock lake was only 18.58 inches. The average precipitation 

 at Avon and Mount Morris from 1891 to 1896, inclusive, was 30.12 



