﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  123 
  

  

  At 
  this 
  point 
  Mr 
  Vermeule 
  was 
  confronted 
  by 
  the 
  difficulty 
  of 
  

   ground 
  storage. 
  In 
  regard 
  to 
  the 
  effect 
  of 
  this 
  it 
  may 
  be 
  men- 
  

   tioned 
  that, 
  with 
  rainfall 
  above 
  the 
  average 
  continuously 
  for 
  sev- 
  

   eral 
  years, 
  ground 
  water 
  may 
  be 
  expected 
  to 
  stand 
  above 
  its 
  

   average 
  night, 
  yielding 
  to 
  streams 
  the 
  maximum 
  flow 
  possible 
  to 
  

   ground 
  water. 
  On 
  the 
  other 
  hand, 
  when 
  the 
  rainfall 
  is 
  below 
  the 
  

   average 
  for 
  a 
  number 
  of 
  years 
  ground-water 
  flow 
  will 
  be 
  lower, 
  

   becoming 
  less 
  and 
  less 
  as 
  the 
  rainfall 
  approaches 
  the 
  minimum. 
  

   It 
  is 
  very 
  important 
  that 
  this 
  fact 
  be 
  taken 
  into 
  account, 
  because 
  

   without 
  it 
  one 
  is 
  certain 
  to 
  fall 
  into 
  error. 
  The 
  formulas 
  for 
  

   average 
  depletion 
  may 
  be 
  given 
  as 
  follows 
  : 
  

  

  d 
  z 
  = 
  d 
  1 
  +e+f—r; 
  (24) 
  

  

  rf= 
  T 
  + 
  *-7?- 
  (25) 
  

  

  In 
  which 
  d 
  x 
  and 
  $ 
  2 
  =depletion 
  at 
  end 
  of 
  previous 
  month 
  and 
  

   for 
  the 
  month 
  under 
  consideration; 
  d=±average 
  depletion; 
  e 
  and 
  

   r=monthly 
  evaporation 
  and 
  monthly 
  rainfall, 
  respectively, 
  and 
  

   /=computed 
  monthly 
  flow. 
  

  

  The 
  foregoing 
  does 
  not 
  fully 
  express 
  the 
  use 
  of 
  these 
  formulas, 
  

   but 
  as 
  all 
  that 
  is 
  wanted 
  at 
  this 
  time 
  is 
  an 
  illustration 
  of 
  methods, 
  

   this 
  brief 
  account 
  may 
  be 
  deemed 
  sufficient. 
  

  

  Mr 
  Vermeule 
  gives 
  a 
  diagram 
  showing 
  ground 
  flow 
  for 
  the 
  sev- 
  

   eral 
  different 
  streams 
  mentioned 
  for 
  a 
  given 
  depletion, 
  which 
  is 
  

   to 
  be 
  used 
  in 
  conjunction 
  with 
  the 
  foregoing 
  formulas. 
  In 
  his 
  

   opinion 
  the 
  diagrams 
  present 
  advantages 
  over 
  a 
  ground-flow 
  

   formula 
  with 
  varying 
  constants 
  and 
  coefficients 
  for 
  different 
  

   streams, 
  being 
  more 
  readily 
  compared 
  and 
  insuring 
  greater 
  accu- 
  

   racy. 
  Later, 
  in 
  his 
  Report 
  on 
  Forests, 
  1 
  Mr 
  Vermeule 
  modifies 
  his 
  

   formula, 
  as 
  follows: 
  

  

  E=(ll+0.29 
  R) 
  M. 
  (26) 
  

  

  In 
  which 
  E=evaporation, 
  R=rainfall, 
  and 
  M 
  is 
  a 
  factor 
  de- 
  

   pending 
  upon 
  the 
  mean 
  temperature 
  of 
  the 
  atmosphere. 
  The 
  

   writer 
  understands 
  Mr 
  Vermeule 
  to 
  say 
  that 
  this 
  is 
  also 
  an 
  

   expression 
  for 
  annual 
  evaporation. 
  

  

  l 
  Report 
  on 
  Forests, 
  by 
  C. 
  C. 
  Vermeule: 
  Ann. 
  Kept. 
  State 
  Geologist 
  New 
  

   Jersey 
  for 
  year 
  1899. 
  Trenton, 
  1900. 
  

  

  