﻿92 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Increase 
  of 
  runoff 
  with 
  increase 
  of 
  rainfall. 
  In 
  making 
  allow- 
  

   ance 
  for 
  difference 
  in 
  rainfall, 
  it 
  should 
  be 
  remembered 
  (1) 
  that 
  

   in 
  many 
  catchment 
  areas 
  the 
  annual 
  runoff 
  is 
  in 
  nearly 
  constant 
  

   relation 
  to 
  the 
  precipitation; 
  and 
  (2) 
  that 
  such 
  relation 
  will 
  be 
  

   more 
  marked 
  when 
  the 
  excess 
  rainfall 
  above 
  a 
  certain 
  minimum 
  

   annual 
  depth 
  is 
  taken 
  into 
  account. 
  This 
  subject 
  will 
  not 
  be 
  

   pursued 
  at 
  length 
  any 
  farther 
  than 
  to 
  point 
  out 
  that 
  in 
  the 
  

   Genesee 
  catchment 
  an 
  average 
  of 
  10.5 
  inches 
  runs 
  off 
  in 
  the 
  stor- 
  

   age 
  period; 
  1.7 
  inches 
  in 
  the 
  growing 
  period, 
  and 
  2.0 
  inches 
  in 
  

   the 
  replenishing 
  period. 
  In 
  the 
  Hudson 
  catchment, 
  an 
  average 
  of 
  

   16.10 
  inches 
  runs 
  off 
  in 
  the 
  storage 
  period; 
  3.45 
  inches 
  in 
  the 
  

   growing 
  period, 
  and 
  3.72 
  inches 
  in 
  the 
  replenishing. 
  In 
  the 
  Cro- 
  

   ton 
  catchment, 
  an 
  average 
  of 
  16.83 
  inches 
  runs 
  off 
  in 
  the 
  storage 
  

   period 
  ; 
  2.57 
  inches 
  in 
  the 
  growing 
  period, 
  and 
  3.42 
  inches 
  in 
  the 
  

   replenishing. 
  These 
  figures, 
  it 
  may 
  be 
  again 
  stated, 
  are 
  the 
  

   means 
  — 
  the 
  maximum 
  and 
  minimum 
  runoffs 
  can 
  be 
  determined 
  

   by 
  examining 
  the 
  tables. 
  

  

  Broadly, 
  the 
  proposition 
  is 
  that 
  a 
  given 
  increase 
  in 
  rainfall 
  

   above 
  the 
  amounts 
  required 
  to 
  produce 
  the 
  foregoing 
  figures 
  will 
  

   be 
  followed 
  by 
  something 
  like 
  a 
  similar 
  increase 
  in 
  runoff. 
  Such 
  

   increase, 
  however, 
  is 
  not 
  very 
  definite, 
  although 
  the 
  broad 
  state- 
  

   ment 
  is 
  true 
  that 
  it 
  bears 
  a 
  relation 
  to 
  the 
  rainfall. 
  

  

  The 
  following 
  will 
  illustrate 
  the 
  essential 
  truth 
  of 
  this 
  proposi- 
  

   tion 
  : 
  

  

  , 
  Inches 
  * 
  

  

  Rainfall 
  Runoff 
  

  

  Genesee 
  river. 
  

  

  Yearly 
  average 
  40 
  . 
  3 
  14 
  . 
  20 
  

  

  1895 
  (minimum 
  year) 
  31.0 
  6.67 
  

  

  Difference 
  9.3 
  7.53 
  

  

  1894 
  (maximum 
  year) 
  47.79 
  19.38 
  

  

  Yearly 
  average 
  40.30 
  14.20 
  

  

  Difference 
  , 
  7.49 
  5.18 
  

  

  Comparing 
  the 
  maximum 
  year 
  with 
  the 
  minimum, 
  we 
  have: 
  

  

  1894 
  47.79 
  19.38 
  

  

  1895 
  31.00 
  6.67 
  

  

  Difference 
  16.79 
  12.71 
  

  

  