The  type  of  fluctuation  peculiar  to  wells  on  the  outwash  slope  is
shown  on  Plate  VI  by  Wells  Nos.  31,  64,  25,  26,  and  59,  and  Citrus
No.  1.  Water  stands  10  ft.  or  more  below  the  surface  in  all  these
wells,  the  vegetation  of  the  surrounding  area  is  limited  to  desert  shrubs,
and  there  are  no  alkali  deposits  on  the  surface.  With  knowledge  of
the  sources  and  movements  of  ground-water  beneath  the  outwash  slopes,
the  assigned  cause  for  this  type  would  be  annual  variation  in  the  quan-
tity of  water  supplied  by  percolation  from  precipitation  on  the  inter-
mediate and  outwash  slopes  and  from  stream  channels.  This  is  con-
firmed by  the  observations.  For  example.  Well  No.  31,  which  is  7
miles  from  the  base  of  the  Sierra  and  500  ft.  south  of  the  old  channel
of  Pinyon  Creek,  exhibits  a  persistent  downward  tendency  which  was
partly  checked  during  the  summer  of  1909  and  1910.  The  maximum
effect  of  the  very  wet  years,  1906  and  1907,  evidently  reached  this  well
in  1908  and  early  in  1909.  During  the  following  years  the  water  had
a  tendency  to  return  to  its  normal  level.  This  was  twice  opposed  by
percolation  from  the  channel  of  Pinyon  Creek,  which  carried  flood-
water  during  a  few  weeks  in  June  and  July,  1909,  and  for  a  very  short
period  in  1910.  Citrus  Well  No.  1,  which  is  about  |  mile  south  of
Well  No.  31,  has  similar  fluctuations,  but  in  it  the  maximum  effect  of
seepage  from  Pinyon  Creek  is  registered  6  weeks  later  in  1909,  and  in
1910  is  much  smaller  in  quantity.  Well  No.  64,  situated  similarly
with  respect  to  the  mountains,  but  north  of  Little  Pine  Creek,  has  the
same  downward  tendency,  which  is  checked  temporarily  during  the  sum-
mer by  irrigation  in  a  near-by  alfalfa  field  and  a  small  garden  at  the
well.  Well  No.  59,  which  is  2  miles  from  the  base  of  the  Sierra  and
i  mile  south  of  Sawmill  Creek,  had  an  upward  tendency  during  1909,
due  to  the  percolation  from  precipitation  of  the  wet  winter,  1908-09.
