The Idaho Republican. [volume] (Blackfoot, Idaho) 1904-1932, 1923-01-18
History Of Snake River Control
Plans for Future Storage and Flood Prevention,
Reclamation and Saving
Lawsuits
BY w. G.. SWENDSEN
CHAPTER v.


CHAPTER v.
l Evaporation Losses at Jackson Lake
1t is contended point No. 81 thai
evaporation losses on the era by
, which jackson Lake was increased
for purposes of storage should be
borne by storage interests alone
The present practice is to regard
the inflow from bank storage on q
descending stage of reservoir as
, natural flow and to consider this as
an offset to evaporation losses.
Studies are being made to deter
mine the amount of bank storage
which returns to the lake, but no
definite data are available at this
time as basis for equitable deter
mination.
The evaporation loss can be ap-
proximately computed. The sub
merged area at Jackson Lake res
ervoir has been increased from IT,
700 acres to 25,700 acres. In
other words, the reservoir when
full covers an area 5000 acres
greater than was covered by the
natural lake. The mean increased
area, considering the filling and
| OhPCyl h6 vi CnC lCoOIFOI, WOulu D6
about 1000 acres. The period dur
ing which losses by evaporation
would affect normal flow users
would extend from the time the
normal supply in the river is not
sufficient to- fill the decreed rights
to the time when the reservoir is
empty, or about seventy days in
ordinary years. The loss on Mud
Lake in August, 1921 was .02 feet
per day. Allowing for higher alti-
tude, cooler temperature and less
wind movement at Jackson Lake, it
may be assumed that the evapora-
| ton loss is about OILS feet per day
In seventy days this would amount
to LOS feet in depth. Applying the
depth loss over the mean increased
area exposed to evaporation, the
result would be loss of 1900 acre
feet. -~..
Bank storage begins to flow into
the reservoir soon after storage Is
released, as is evidenced by the up
per trend of the photographs at
Moran gaging station. Considering
the gravelly nature of the shores
and the indications upon the Moran
gage, the inflow must be consider
able. Whether or not 1t balances
the loss by evaporation In
time to be of value to the
upper valley users cannot be deter
mined accurately from data now
available, but the probabilities are
that the exchange is not unfavorable |
to- the natural flow users
Evaporation observations are now
hQjnp rpodo OF hn oh xrvtk L.,
year this element of loss should be |
definitely known.
From a consideration of data
ordering any change in the present !!
plan.
Conclusion
In considering the matters pre-
sented by the Snake River Union of
Water Users and referred to in the
foregoing, careful study has been
made of the methods heretofore,
and at present, employed in the po-
Icing Of streams and delivery of
water in District No. 36, together
with the data that has been col
lected; from all of which it is very
apparent that the present system,
providing as it does a permanent or
ganization to carry on the work
from year to year, is greatly super
or and is giving service much more
efficient and equitable than was
possible under any of the plans pre-
viously employed. In fact the very .
1ata which has been used by the ,
Union Of Water Users in compiling
heir budget for presentation would
lot and could not have been avail
lble under the old system. It Is my
that the data and infor- L
nation being collected is and will
,e of untold value to the water '
lsers and the state generally in p
ears to come.
1t is my hope, therefore, that the 6
'ol1cy of keeping permanent and
omplete records of distribution will V
re continued in the future, regard "
ess of whatever change may ulti-
nately be made in the details of dis y
ribution. !
After carefully considering all of :
he matters outlined in the forego- !.
1g, it is my conclusion that changes !.
I the present method of distribu-
ion are at this time unwarranted
nd not advisable. 1t appears that
ne present method is giving results CT
s nearly in harmony with fairness tt
nd equity as can be given with the fe
Sc of available data and funds.
A greater degree of refinement in a,
may, of course, be at h,
aimed provided the results will
lstify the expenditure and provided T
Inds are made available to cover m
lie increased cost. 1t would, in
eed, be a difficult and costly under fe
liking to determine with extreme
,curacy the exact amount of return NJ
DIV to Snake river in this district, p(
scause of the thousands of small
,ntributing streams which appar- sc
lily must reach the river as waste pc
ON the enormous irrigated area of til
lie district, but with sufficient funds
lis information could be obtained, m
tho it is my opinion that the re- w
Its would not justify the expense.
kewise, definite information could M
obtained thru an intricate system of
measuring stations upon the' la
ain stream and tributaries, to-