Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1915-11-15
TAYLOR SEES HOW
TO MAKE SAVING
ON MAOLEDITCH
CONTINUED from Page u

WAIKIKI SIDE OF the fNuuanu vale.
into the Luanaha gulch.
Map. 4.~.
The accompanying contour map OF
scale Of 200 feet to one inch shows
the preliminary line of ditch with con
tours at five-foot intervals.
Location.
The final location of the proposed
ditch win follow with easy curves
near the present angular line, except
the tunnel which will be on direct
line from the upper end of the ditch
to the diversion at the Maole stream
in Hillebrand glen.
Watershed.
The entire watershed of the pro
posed ditch is within the boundaries
of the government forest reserve.
The approximate areas are as fol
lows:
Hillebrand glen, LIE acres.
Nuuanu valley, IT'S acres.
Making a total OF 300 acres
This watershed extends from an
elevation OF 1880 to $500 feet and
about so per cent, or $50 acres, are
heavily wooded on steep slopes.
The general conditions and topogra,
phic features of this watershed are
favorable for runoff.
The average annual rainfall from
valley watershed from Luakaha mau-
ka is approximately 1871 inches, based
on the records Of rainfall at Luakaha.
the Nuuanu dam and the Nuuanu palt
Runoff.
While runoff bears direct relation
to rainfall, yet the amount of runoff
Is affected by many varying climatic
and topographic conditions, l1such as
the depth of soil, the vegetation, the
total rainfall, its rate of fall, as well
as the temperature of the air and
earth.
The runoff Ola given water shed
varies also, due to slopes, the per
centage increasing with the rainfall.
From the area and character of the
water shed tributary at Hilfebrand
Glen and the water shed of that por-
ton of the Nuuanu valley under con-
sideration; j estimate the average run
off to be as follows: One third at
40 per cent, one-third ats50 per cent
and onesthird at so per cent, making
q general average over the entire
water shed of SO per cent,
From the records of the u. s. Geo
logical Survey complied from the data
obtained by LIZA Moore, observer, /
find the following as q very good ex-
ample Of the runoff from a-heavy rain
fan in the Nuuanu valley:
In the month of September, 1914.
therunoff in the Nuuanu.streamm meas
nred. at the Government weir below
reservoir No. 2 wasteway. shows a to-
tai Of 512.70 million gallons, with q
of Sc millions, a minimum Of
AT millions and a monthly average
Of Ill millions.
Slopes.
The slopes of the ground along the
line Of the preliminary strvey were
carefully taken at each ttion.
The average of the opes taken
from stations % to so, distance of
5000 feet. is % 1-3 degrea.
Rainfall. II.
/, From as Careful "a study of the wa,
ter shed, the rainfall and the runoff,
as the time and data at hand would
permit, j estimate the water shed to
be 300 acres; the average annual rain
fall at 1872 inches and the runoH as
SO per cent of the rainfall.
From an average rainfall of 132
inches, or IL feet, over the water shed
In question of 500 acres; the funoff
calculated at an average of so per
cent, would yield approximately 539
million gallons per year, which is equi-
valent to continuous flow of 1.4S
million gallons daily.
A six t6) inch rainfall in "a hours
on a water shed of 300 acres under
average conditions with a SO per cent
runoff, should yield approximately
24lk million gallons, and, a rainfall of
eight inches under similar conditions
would yield approximately. 3S million
gallons.
AS ethere are records Of rainfall in
excess of eight inches, it would seem
wise to provide for a maximum flow
of at least 35 to 40 millions.
Conduit.
The conduit should be so designed
and constructed as to have maxi
mum carrying capacity for the largest
runeff from the heaviest rainfall.
The bottom and sides of the. ditch
should be eemented ITO a sufficient
height to carry the normal fIow1, or
low stages of runoff and delivering the
same to the reservoir without loss, ex-
cept that due to evaporation in the
open ditch. tIT
( The various inlets from the natural
drainage should also be protected by
concrete work 10 prevent washing in
times of heavy rains OF freshets.
Final Location.
The final location of the proposed
conduit should be made with complete
plans, specifications and estimates OF
cost for the construction of the pro-
posed conduit on the general lines Civ,
en- in this preliminary report r
There is no doubt that the project
is not only feasible and desirable but
will prove to, be profitable invest
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