﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  791 
  

  

  The 
  table 
  of 
  evaporation 
  from 
  a 
  water 
  surface, 
  as 
  observed 
  at 
  

   the 
  Mount 
  Hope 
  reservoir 
  of 
  the 
  Rochester 
  Waterworks, 
  shows 
  

   that 
  for 
  the 
  navigation 
  months, 
  April 
  to 
  November 
  inclusive, 
  

   evaporation 
  ranges 
  from 
  1.33 
  inches 
  in 
  November 
  1897, 
  to 
  6.85 
  

   inches 
  in 
  July 
  1898. 
  The 
  water 
  surface 
  of 
  the 
  proposed 
  summit 
  

   level 
  is 
  so 
  small 
  as 
  to 
  make 
  evaporation, 
  even 
  in 
  the 
  maximum 
  

   month, 
  hardly 
  worth 
  taking 
  into 
  account. 
  At 
  6.85 
  inches 
  for 
  the 
  

   month 
  the 
  evaporation 
  on 
  the 
  summit 
  level 
  becomes, 
  roundly, 
  5 
  

   cubic 
  feet 
  per 
  second. 
  In 
  order 
  to 
  give 
  evaporation 
  some 
  value 
  in 
  

   the 
  estimate 
  of 
  total 
  water 
  supply 
  we 
  will 
  take 
  it 
  at 
  from 
  5 
  to 
  10 
  

   cubic 
  feet 
  per 
  second. 
  

  

  There 
  is 
  no 
  rational 
  method 
  of 
  estimating 
  percolation 
  loss 
  for 
  a 
  

   canal 
  under 
  the 
  conditions 
  which 
  exist 
  in 
  the 
  Mohawk 
  valley. 
  The 
  

   drainage 
  is 
  all 
  towards 
  the 
  valley, 
  and 
  at 
  first 
  thought 
  it 
  might 
  

   appear 
  that 
  percolation 
  was 
  a 
  negligible 
  quantity. 
  However, 
  if 
  

   we 
  consider 
  that 
  the 
  total 
  water 
  supply, 
  as 
  estimated 
  for 
  the 
  

   summit 
  level, 
  takes 
  into 
  account 
  the 
  entire 
  yield 
  of 
  the 
  catchment 
  

   area 
  tributary 
  to 
  the 
  main 
  channel, 
  and 
  further 
  consider 
  that 
  the 
  

   channel, 
  as 
  located, 
  has 
  its 
  water 
  surface 
  for 
  a 
  considerable 
  dis- 
  

   tance 
  several 
  feet 
  above 
  the 
  ordinary 
  water 
  plane 
  of 
  the 
  Mohawk 
  

   river 
  and 
  Wood 
  creek 
  in 
  their 
  natural 
  condition, 
  we 
  may 
  conclude 
  

   that 
  percolation 
  ought 
  not 
  to 
  be 
  entirely 
  neglected, 
  more 
  specially 
  

   because 
  the 
  soils 
  in 
  the 
  Mohawk 
  bottom 
  are 
  open 
  and 
  porous, 
  and 
  

   without 
  some 
  method 
  of 
  consolidation 
  of 
  the 
  natural 
  soils, 
  which 
  

   does 
  not 
  now 
  occur 
  to 
  the 
  writer, 
  can 
  be 
  devised, 
  there 
  is 
  likely 
  

   to 
  be 
  considerable 
  loss 
  from 
  percolation. 
  By 
  way 
  of 
  showing 
  the 
  

   relation 
  of 
  water 
  surface 
  of 
  the 
  summit 
  level 
  to 
  ordinary 
  water 
  

   levels 
  in 
  the 
  Mohawk 
  river 
  and 
  Wood 
  creek 
  the 
  following 
  data 
  are 
  

   cited 
  : 
  

  

  At 
  a 
  distance 
  of 
  17,000 
  feet 
  east 
  of 
  Rome 
  the 
  ordinary 
  water 
  

   surface 
  of 
  the 
  Mohawk 
  river 
  is 
  at 
  an 
  elevation 
  of 
  415, 
  or 
  the 
  same 
  

   as 
  water 
  surface 
  of 
  the 
  summit 
  level 
  ; 
  24,000 
  feet 
  east 
  of 
  Rome 
  it 
  is 
  

   413; 
  32,000 
  feet 
  east 
  it 
  is 
  408; 
  41,000 
  feet 
  east, 
  404, 
  and 
  47,000 
  feet 
  

   east, 
  401. 
  

  

  At 
  17,500 
  feet 
  west 
  of 
  Rome 
  the 
  ordinary 
  water 
  surface 
  of 
  Wood 
  

   creek 
  is 
  at 
  414, 
  or 
  one 
  foot 
  lower 
  than 
  the 
  summit 
  level 
  ; 
  at 
  21,500 
  

   feet 
  west 
  of 
  Rome 
  it 
  is 
  408, 
  and 
  at 
  25,500 
  feet 
  west, 
  398. 
  

  

  The 
  writer 
  has 
  no 
  way 
  of 
  demonstrating 
  the 
  proposition, 
  

   although 
  it 
  seems 
  clear 
  enough 
  to 
  him 
  that 
  with 
  an 
  open, 
  porous 
  

   soil 
  the 
  percolation 
  from 
  the 
  canal 
  at 
  points 
  Avhere 
  the 
  summit 
  

   level 
  is 
  raised 
  somewhat 
  above 
  the 
  ordinary 
  water 
  level 
  of 
  the 
  

   Mohawk 
  river 
  and 
  W 
  r 
  ood 
  creek 
  will 
  be 
  considerable. 
  The 
  porous 
  

   soils 
  of 
  these 
  valleys 
  will 
  take 
  up 
  water 
  like 
  a 
  sponge, 
  making 
  

  

  