﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  127 
  

  

  between 
  the 
  runoff 
  and 
  the 
  rainfall, 
  runoff 
  increasing 
  as 
  rainfall 
  

   increases, 
  and 
  conversely. 
  

  

  As 
  regards 
  the 
  division 
  of 
  streams 
  into 
  classes 
  in 
  proportion 
  to 
  

   size 
  of 
  catchment 
  area, 
  it 
  appears, 
  therefore, 
  that 
  aside 
  from 
  

   floods 
  one 
  is 
  not, 
  on 
  present 
  information, 
  justified 
  in 
  such 
  classi- 
  

   fication, 
  and 
  even 
  in 
  cases 
  of 
  floods 
  it 
  is 
  quite 
  probable 
  that 
  there 
  

   are 
  other 
  considerations 
  of 
  such 
  importance 
  as 
  to 
  render 
  a 
  

   classification 
  of 
  this 
  character 
  inexpedient. 
  

  

  Since 
  there 
  is 
  no 
  vers' 
  definite 
  relation 
  between 
  size 
  of 
  catch- 
  

   ment 
  and 
  runoff 
  there 
  is 
  no 
  reason 
  why 
  comparison 
  may 
  not 
  be 
  

   made 
  of 
  streams 
  having 
  such 
  large 
  difference 
  in 
  size 
  of 
  catchment. 
  

   For 
  some 
  streams, 
  as 
  for 
  instance, 
  Pequannock 
  river, 
  where 
  the 
  

   slopes 
  are 
  very 
  steep, 
  the 
  runoff 
  is 
  somewhat 
  higher 
  than 
  it 
  would 
  

   be 
  with 
  other 
  conditions 
  the 
  same, 
  but 
  with 
  flatter 
  slopes. 
  But 
  

   generally 
  the 
  degree 
  of 
  forestation 
  and 
  other 
  elements 
  exercise 
  so 
  

   much 
  more 
  important 
  an 
  influence 
  that 
  a 
  comparison, 
  without 
  

   regard 
  to 
  size 
  of 
  catchment 
  area, 
  may 
  be 
  legitimately 
  made. 
  

   Nevertheless, 
  this 
  proposition 
  is 
  possibly 
  debatable, 
  and 
  for 
  the 
  

   present 
  the 
  conclusions 
  drawn 
  are 
  tentative 
  merely. 
  

  

  The 
  extreme 
  low-water 
  period. 
  In 
  the 
  discussion 
  of 
  the 
  streams 
  

   the 
  writer 
  has 
  given 
  the 
  low 
  water 
  of 
  the 
  minimum 
  year, 
  but 
  this 
  

   does 
  not 
  usually 
  include 
  the 
  extreme 
  low-water 
  period, 
  which 
  is 
  in 
  

   almost 
  every 
  case 
  much 
  more 
  than 
  one 
  year. 
  Space 
  will 
  not 
  be 
  

   taken 
  to 
  show 
  the 
  extreme 
  low-water 
  periods 
  of 
  all 
  the 
  streams. 
  

   It 
  is 
  considered 
  that 
  illustrations 
  from 
  Muskingum 
  and 
  Genesee 
  

   rivers 
  are 
  sufficient. 
  

  

  On 
  the 
  Muskingum 
  river 
  three 
  low-water 
  periods 
  have 
  occurred 
  

   during 
  the 
  time 
  covered 
  by 
  the 
  gagings. 
  The 
  first 
  was 
  from 
  

   December, 
  1887, 
  to 
  November, 
  1889, 
  inclusive, 
  a 
  period 
  of 
  twenty- 
  

   four 
  months, 
  during 
  which 
  the 
  total 
  runoff 
  was 
  18.55 
  inches, 
  or 
  

   if 
  we 
  assume 
  a 
  reservoir 
  on 
  said 
  stream 
  of 
  20 
  square 
  miles 
  water 
  

   surface, 
  the 
  total 
  net 
  runoff 
  becomes 
  18.15 
  inches. 
  The 
  computa- 
  

   tions 
  of 
  evaporation, 
  etc. 
  for 
  such 
  a 
  reservoir, 
  neglecting 
  variation 
  

   in 
  water 
  surface, 
  are 
  as 
  follows. 
  Assume 
  an 
  annual 
  evaporation 
  

   of 
  40 
  inches 
  and 
  with 
  distribution 
  for 
  the 
  several 
  months 
  as 
  per 
  

  

  