﻿WATEK-POWEE 
  DEVELOPMENT 
  IN 
  THE 
  MISSISSIPPI. 
  15 
  

  

  bine 
  buckets 
  would 
  probably 
  interfere 
  less 
  with 
  its 
  couree 
  than 
  the 
  

   sohd 
  walls 
  that 
  confine 
  the 
  water. 
  

  

  There 
  are 
  not 
  infrequent 
  reports 
  of 
  the 
  finding 
  of 
  specimens 
  of 
  the 
  

   spoonbill-cat 
  or 
  paddle-fish 
  below 
  the 
  dam, 
  with 
  the 
  spoonbill 
  cut 
  

   or 
  broken 
  clean 
  off. 
  Such 
  injuries 
  are 
  attributed 
  to 
  the 
  blades 
  of 
  

   the 
  turbines, 
  but 
  the 
  reports 
  have 
  not 
  been 
  as 
  yet 
  of 
  such 
  frequency 
  

   as 
  to 
  indicate 
  any 
  serious 
  degree 
  of 
  damage.*^ 
  

  

  The 
  bottoms 
  of 
  the 
  lower 
  openings 
  of 
  the 
  draft 
  tubes 
  are 
  25 
  feet 
  

   below 
  the 
  natural 
  bottom 
  of 
  the 
  Mississippi. 
  (See 
  p. 
  14.) 
  The 
  tail- 
  

   race 
  is 
  excavated 
  to 
  a 
  corresponding 
  depth 
  from 
  the 
  upper 
  end 
  of 
  

   the 
  power 
  house 
  down 
  to 
  the 
  region 
  of 
  the 
  lock 
  below. 
  Tliis 
  is, 
  for 
  

   our 
  purpose, 
  one 
  of 
  the 
  most 
  significant 
  features 
  of 
  the 
  dam. 
  The 
  

   tail-race 
  constitutes 
  a 
  narrow 
  but 
  deep 
  channel, 
  through 
  which 
  the 
  

   water 
  used 
  in 
  the 
  power 
  house 
  is 
  conveyed 
  doAvnstream 
  to 
  join 
  the 
  

   natural 
  main 
  channel 
  of 
  the 
  river 
  on 
  the 
  Iowa 
  side 
  near 
  the 
  bridge. 
  

   The 
  remainder 
  of 
  the 
  river 
  bed 
  conveys, 
  besides 
  an 
  overflow 
  from 
  this 
  

   tail-race, 
  only 
  the 
  spilled 
  water 
  from 
  the 
  dam, 
  which 
  may 
  at 
  various 
  

   times 
  be 
  gretiter 
  or 
  less 
  than 
  the 
  flow 
  in 
  the 
  tail-race, 
  according 
  to 
  the 
  

   stage 
  of 
  the 
  river 
  above. 
  It 
  may 
  be 
  imagined 
  that 
  at 
  the 
  ultimate 
  

   development 
  of 
  the 
  plant 
  the 
  timoimt 
  of 
  water 
  used 
  regularly 
  in 
  the 
  

   power 
  house 
  will 
  be 
  approximately 
  equal 
  to 
  the 
  minimum 
  low-water 
  

   volume 
  of 
  the 
  river, 
  since 
  the 
  storage 
  capacity 
  of 
  the 
  lake 
  is 
  not 
  

   considerable 
  as 
  compared 
  with 
  the 
  size 
  of 
  the 
  plant. 
  

  

  Not 
  all 
  of 
  the 
  water 
  from 
  the 
  draft 
  tubes 
  will 
  foUow 
  the 
  direct 
  

   course, 
  for 
  the 
  chamiel 
  is 
  not 
  strictl}^ 
  confined, 
  and 
  a 
  considerable 
  

   surface 
  current 
  will 
  always 
  overflow 
  from 
  the 
  tail-race 
  toward 
  the 
  

   body 
  of 
  the 
  river. 
  At 
  the 
  time 
  of 
  this 
  writing 
  (October, 
  1913) 
  the 
  

   tail-race 
  is 
  to 
  a 
  considerable 
  extent 
  confined 
  by 
  the 
  old 
  cofferdam; 
  

   but 
  it 
  is 
  probable 
  that 
  this 
  wiU 
  be 
  blasted 
  out, 
  permitting 
  more 
  

   extended 
  lateral 
  overflow. 
  There 
  wiU 
  always 
  be 
  a 
  strong 
  flow 
  of 
  

   water 
  in 
  the 
  tail-race 
  corresponding 
  at 
  least 
  to 
  the 
  volume 
  of 
  water 
  

   required 
  to 
  supply 
  the 
  minimum 
  demands 
  of 
  power. 
  There 
  will 
  

   probably 
  be 
  httle 
  fluctuation 
  of 
  current 
  from 
  day 
  to 
  day 
  at 
  corre- 
  

   sponding 
  hours 
  except 
  with 
  seasonal 
  changes 
  of 
  fighting 
  demands, 
  

   but 
  there 
  wOl 
  be 
  a 
  regular 
  ebb 
  and 
  flow 
  (considering 
  the 
  tail-race 
  only) 
  

   in 
  the 
  course 
  of 
  each 
  24 
  houre, 
  since 
  the 
  use 
  of 
  electrical 
  power 
  is 
  

   usually 
  least 
  during 
  the 
  early 
  hours 
  of 
  the 
  morning. 
  This 
  variation 
  

   is 
  very 
  carefully 
  watched 
  by 
  the 
  company, 
  so 
  that 
  it 
  may 
  be 
  com- 
  

   pensated 
  by 
  opening 
  or 
  closing 
  gates 
  over 
  the 
  spiUways 
  of 
  the 
  dam 
  

   to 
  nfinimize 
  the 
  effect 
  on 
  navigation 
  in 
  the 
  river 
  below. 
  

  

  The 
  tail-race 
  is 
  the 
  one 
  perpetual 
  passageway 
  for 
  water 
  below 
  the 
  

   dam, 
  and 
  it 
  is 
  of 
  interest 
  to 
  inquire 
  in 
  a 
  later 
  paragraph 
  if 
  the 
  fish 
  

   which 
  may 
  be 
  attracted 
  against 
  this 
  current 
  may 
  not 
  be 
  deflected 
  

   by 
  some 
  simple 
  means 
  toward 
  the 
  only 
  avenue 
  of 
  escape 
  into 
  the 
  

  

  o 
  Several 
  cases 
  have 
  come 
  under 
  the 
  writer's 
  observation. 
  

  

  