HYDROLOGY OF NEW YORK 



399 



Table No. 64 gives the average daily flow of the Croton river at 

 the old Croton dam, including storage draft with catchment area 

 and reservoirs as existing in the given years. This table is com- 

 puted from the observed flow by deducting the quantity corres- 

 ponding to lowering of storage reservoirs or adding the quantity 

 taken to refill, without allowance for evaporation loss from stor- 

 age reservoirs. Tn his table, the average for each calendar month 

 is given in gallons for each day of twenty-four hours. 1 



In table No. 65 the mean monthly flow of the Croton river at 

 the old Croton dam is given from 1868 to 1899, inclusive, in cubic- 

 feet per second. 2 



In table No. 66 the runoff in inches on the catchment area is 

 given from 1868 to 1876, inclusive. The rainfall is not given 

 because Mr Freeman's investigations showed that previous to 

 1877 the Croton rainfall is so uncertain as to make it unsafe to 

 draw comparisons. 



In table No. 67 the rainfall, runoff and evaporation is given in 

 inches on the catchment area for the water years from 1877 to 

 1899, inclusive. 3 



In table No. 68 the mean monthly flow of the Croton river at the 

 old Croon dam is given from 1868 to 1899, inclusive, in cubic feet 

 per second per square mile. 4 



It will be seen that the tables on pages 204-5 and on pages 206-7 

 of Mr Freeman's report vary somewhat under the different sup- 

 positions on which they have been computed. There is another table 

 on pages 208-9, giving the average daily flow at the new Croton 

 dam exclusive of storage draft with rainfall as in the given year 

 and with reservoirs as in 1902. This table has been computed 

 from the natural flow at the old dam for the given year and month 

 by adding (>.4 per cent for increase in catchment area and de- 

 ducting an allowance for evaporation loss caused by substituting 

 water surface for land surface in the new reservoirs constructed 

 between the given years and 1902. The total catchment area is 

 taken at 360 square miles, with 16.1 square miles — equivalent to 



iFrom pp. 206-7 of Freeman's report. 



2 This table is based on the table on pp. 204-5 of Freeman's report. 

 3 The basis of tables Nos. 66 and 67 is the table on pp. 206-7 of Free- 

 man's report. 



4 This table is based on the table on pp. 204-5 of Freeman's report. 



