HYDROLOGY OP NEW YORK 



515 



the Atlantic coast region than in the region of the Central 

 Lakes. 



The preceding mean rainfalls are for a period of 12 years only, 

 which is not long enough for perfectly safe averages. Moreover, 

 while these 12 years have included the niinimums of 1895 and 

 1899, these minimums were not as well defined on some of the 

 plateaus as on others. 



Since the precipitation of the storage period largely determines 

 the runoff of that period, let us for a moment consider the relation 

 between precipitation in the storage period of the Atlantic coast 

 and Central Lakes regions. The minimum precipitation in the 

 storage period of the Atlantic coast region for the 12-year period 

 included in the tables was for the year 1896, and amounted to 

 19.70 inches. The minimum precipitation of the Central Lakes 

 region for the same period was in 1895 and amounted to 11.26 

 inches, a difference of 8.44 inches in the storage period alone. 



The yearly minimum precipitation of the Atlantic coast region 

 for the period considered was in 1895 and amounted to 40.77 

 inches. The yearly minimum precipitation of the Central Lakes 

 region was also in 1895 and amounted to 27.31 inches, a difference 

 of 13.46 inches. The proposition that there was over 10 inches 

 more runoff in the Atlantic coast region in 1895 than in the 

 Central Lakes region is therefore abundantly established. In the 

 same way a comparison of the balance of the regions will show 

 in a general way the runoff that may be expected in any given year. 



Taking into account in a broad way these several precipitation 

 areas, we may say that in the minimum year the following quan- 

 tities of water can be stored, the statement being made without 

 reference to the economic conditions involved in considering the 

 area of catchment, topography, cost, etc. The statement also 

 involves conclusions based on consideration of all the circum- 

 stances, which are much too extensive to again give in detail but 

 which are given in different parts of this report ■ 



1) On the western plateau, from 6 to 7 inches may be stored in 

 the minimum year. 



2) On the eastern plateau, 7 to 10 inches. 



3) On the northern plateau, 10 to 12 inches. 



4) In the Atlantic coast region, 13 to 15 inches. 



