400 



NEW YORK STATE MUSEUM 



4.5 per cent — as water surface. The quantities iu this table are 

 averages for the calendar months in million gallons per day of 

 twenty-four hours. This table is not given here, because it is 

 in effect a computation as to the future yield of this basin. 



Geologically this catchment lies almost entirely in granites and 

 gneisses, although there is a small area of metamorphic Hudson 

 formation, consisting of slate, schist and quartzite, and also a 

 small area of metamorphic Trenton and ealciferous limestones. 



The present water supply of New York city is derived from the 

 following sources : 



1) Catchment of Croton river, thirty-three miles north of New 

 York. 



2) Catchment of Bronx and Byram rivers, fifteen miles north of 

 New York. 



3) Catchments of a series of streams on the southern shore of 

 Long Island. 



4) Ground water which is found underlying a stratum of clay 

 on Long Island and on Staten Island. These statements do not 

 take into account some unimportant well supplies on Manhattan 

 island. 



Discharge measurements of Schroon river. This gaging station 

 was established at the dam of the Schroon River Pulp Company, 

 two miles below Warrensburg, November 1, 1895, in connection 

 with the upper Hudson storage surveys. During ordinary water 

 an attempt is made to turn the entire flow of the stream through 

 the water wheels, which run twenty-four hours per day, Sundays 

 excepted. This is accomplished by the use of flashboards and by 

 draft from the storage impounded by the Starbuckville dam. The 

 natural ilow of the Schroon river is considerably modified by the 

 temporary storage of Schroon lake, which has a low-water airea of 

 9.1 square miles. There is a dam at Starbuckville, controlled by 

 the Schroon River Pulp Company and which stores from 4 to 5 

 feet in depth over Schroon lake area, which is let down as re- 

 quired for use during the summer months. r Tli is fad explains why 

 the Schroon river area apparently yields more water proportion- 

 ately in the storage period than the entire Hudson area and less 

 in the replenishing period. 



