HYDROLOGY OF NEW YORK 



633 



when developed up to a storage of 13.5 inches on the catchment 

 area — at $840,000. This was for a water storage reservoir 

 purely, and did not include clearing and stripping of margins 

 any further than that cutting and burning of standing timber 

 was provided for. Investigations made in 1896 indicated more 

 expense for foundation of dam at Tumblehead falls than 

 assumed in 1895. Moreover, for a storage reservoir for regula- 

 tion of stream flow purely, nothing was allowed for sanitary 

 protection of catchment or for removal of buildings along or 

 near new margins. 



The estimates herewith submitted take into account-all these 

 several items, as well as an allowance for present labor condi- 

 tions and price of materials in the State of Xew York. 



In the first report on upper Hudson surveys (1895) the writer 

 discussed extensively the question of proper hight of flow line 

 for upper Hudson reservoir system, reaching the conclusion that 

 for stream- regulation 13.5 inches in depth on the catchment area 

 was the approximate figure. This is about as large a storage 

 as can be ponded at the several upper Hudson sites. At Tumble- 

 head falls, however, there is apparently no reason why the 

 development may not be carried higher, and the present study 

 for a pure-water reservoir has accordingly been based upon a 

 development of storage up to 18 inches in depth on the tributary 

 catchment area of 518 square miles. Such development gives a 

 total storage of 21.662.000,000 cubic feet (162,248,380,000 gallons) 

 and will utilize, during a series of years, substantially the entire 

 flow of the stream. 



To accomplish this result the uniform outflow from the reser- 

 voir has been taken at 500.000,000 gallons in twenty-four hours; 

 or, for even figures, at 775 cubic feet per second. It is easy to 

 furnish this quantity from a single reservoir, although it is 

 necessary to fix the flow line higher than 13.5 inches. 



In order to show the effect of drawing 775 cubic feet per 

 second continuously from such a reservoir in Schroon valley, 

 table Xo. 87 has been prepared. The data are (1) the runoffs of 

 Hudson river for the twelve years 1888-1899, inclusive; and (2) 

 evaporation at Rochester. The computation has been made by 

 years, beginning with an assumed depth of 1 inches on the catch- 

 ment area in reservoir ai the end of November 1887, and is 



