﻿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. 
  In 
  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 
  6.4 
  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 
  

  

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

  

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

   8 
  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. 
  

  

  