﻿340 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  The 
  catchment 
  area 
  of 
  Hemlock 
  lake 
  is, 
  as 
  stated, 
  27,554 
  acres 
  r 
  

   and 
  the 
  area 
  of 
  the 
  lake 
  itself 
  at 
  the 
  elevation 
  ± 
  0.0 
  is 
  1828 
  acres 
  ; 
  

   hence 
  the 
  lake 
  surface 
  is 
  6.6 
  per 
  cent 
  of 
  the 
  total 
  catchment 
  area, 
  

   or 
  the 
  catchment 
  area 
  is 
  15.1 
  times 
  the 
  area 
  of 
  the 
  lake 
  surface. 
  

   On 
  this 
  basis 
  1 
  inch 
  on 
  the 
  whole 
  area 
  is 
  15.1 
  inches 
  on 
  the 
  lake. 
  

   Taking 
  into 
  account 
  these 
  statements, 
  it 
  is 
  clear 
  that 
  the 
  data 
  

   of 
  the 
  table 
  give 
  approximately 
  the 
  natural 
  runoff, 
  although 
  for 
  

   exact 
  figures 
  corrections 
  for 
  actual 
  elevations 
  of 
  lake 
  surface 
  at 
  

   the 
  beginning, 
  as 
  well 
  as 
  at 
  the 
  end 
  of 
  each 
  year^should 
  be 
  applied. 
  

   On 
  this 
  point 
  see 
  the 
  discussion 
  on 
  the 
  minimum 
  flow 
  of 
  Hemlock 
  

   lake. 
  

  

  Comparison 
  of 
  the 
  runoff 
  of 
  Hemlock 
  lake 
  with 
  that 
  of 
  the 
  

   river 
  Thames 
  in 
  England. 
  Hemlock 
  lake 
  may 
  be 
  compared 
  with 
  

   the 
  river 
  Thames 
  in 
  England, 
  where 
  somewhat 
  similar 
  climatic 
  

   conditions 
  obtain. 
  The 
  catchment 
  area 
  of 
  the 
  Thames 
  above 
  the 
  

   point 
  of 
  gaging 
  is 
  3789 
  square 
  miles, 
  while 
  the 
  catchment 
  area 
  of 
  

   Hemlock 
  lake 
  is 
  given 
  at 
  43.1 
  square 
  miles. 
  It 
  is 
  shown 
  on 
  a 
  

   preceding 
  page 
  that 
  comparison 
  may 
  be 
  legitimately 
  made 
  be- 
  

   tween 
  streams 
  with 
  even 
  as 
  great 
  variation 
  in 
  catchment 
  areas 
  

   as 
  here 
  exists. 
  Accurate 
  gagings 
  are 
  at 
  hand 
  of 
  the 
  Thames 
  from 
  

   1883-1891, 
  inclusive, 
  from 
  which 
  it 
  appears 
  that 
  the 
  mean 
  or 
  

   average 
  rainfall 
  during 
  this 
  period 
  was 
  27.01 
  inches, 
  and 
  the 
  mean 
  

   or 
  average 
  runoff, 
  8.49 
  inches, 
  or 
  the 
  runoff 
  was 
  31 
  per 
  cent 
  of 
  

   the 
  rainfall. 
  In 
  order 
  to 
  compare 
  the 
  climate 
  of 
  the 
  catchment 
  

   of 
  the 
  Thames 
  with 
  that 
  of 
  Hemlock 
  lake 
  we 
  may 
  consider 
  the 
  

   following; 
  

  

  The 
  mean 
  annual 
  rainfall 
  at 
  Hemlock 
  lake 
  for 
  the 
  water 
  years 
  

   1877-1900, 
  inclusive, 
  was 
  27.70 
  inches; 
  the 
  mean 
  annual 
  tempera- 
  

   ture 
  for 
  the 
  same 
  years 
  was 
  50° 
  Fahr., 
  and 
  the 
  mean 
  annual 
  

   evaporation 
  for 
  the 
  years 
  1896 
  to 
  1903, 
  at 
  Mount 
  Hope 
  reser- 
  

   voir, 
  28 
  miles 
  north 
  of 
  Hemlock 
  lake, 
  was 
  34.55 
  inches. 
  The 
  rain- 
  

   fall 
  of 
  Hemlock 
  lake 
  exceeds 
  that 
  of 
  the 
  Thames 
  by 
  only 
  0.69 
  

   inch. 
  

  

  The 
  mean 
  evaporation 
  from 
  a 
  water 
  surface 
  at 
  Oxford, 
  Eng- 
  

   land, 
  for 
  five 
  years, 
  1852-1856, 
  inclusive, 
  was 
  31.01 
  inches; 
  the 
  

  

  