Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1915-11-15
taylor SEES HOW
TO MAKE Saving
ON MAOLE ditch
CONTINUED from Page y

Map.
The accompanying contour map OF
scale OF 200 feet to one inch show.
the preliminary line of ditch with con
tours at fiye-foot intervals.
Location.
The final location Of the proposed
ditch will follow with easy curves
near the present angular line, except
the tunnel which will be on a 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:
HiIlebrand glen, rs acres.
Nuuanu valley, 175 acres.
Making total of 800 acres.
This watershed extends from an
elevation of 1880 to $500 feet and
about so per cent, or 80 acres, are
heavily wooded on steep slopes.
The general conditions and topogra-
phic features of this watershed are
favorable for runoff.
Rainfall.
| The average annual rainfall from
the rainfall records Of the Nuuanu
valley watershed from Luakaha mau.
ka is approximately 1877 inches, based
on the records of rainfall at Luakaha.
the Nuuanu dam and the Nuuanu pail
Runoff.
While runoff bears direct relation
10 rainfall, yet the amount of runoff
is affected by many varying climatic
and topographic conditions, such as
the depth OF soil, the vegetation, the
total rainfall, It's rate of fall, as well
as the temperature OF the air and
earth.
The runoff of given water shed
varies also, due to slopes, the per-
centage increasing with the rainfall
From the area and character of the
Glen and the water shed of that por-
tion Of the Nuuanu valley under con-
sideration, estimate the average rum
off to be as follows. One third at
40 per cent oneithird at SO per cent
and one-third at so per cent, making
a general average over the entire
water shed Of so per cent
From the records Of the u. s. Geo
logical Survey compiled from the data
obtained by L. A. Moore, observer,
find the following as very good ex-
ample Of the runoff from heavy rain
fall in the Nuuanu valley:
In the month Of September, 1914,
the runoff In the Nuuanu stream meas
ured at the Government weir below
reservoir No. wasteway, shows to-
tai of 5l2.70 million gallons, with a
maximum Of IS millions, minimum Of
AT millions and a monthly average
of Ill millions.
Slopes.
The slopes of the ground along the
line Of the preliminary survey were
carefully taken at each station.
The average of the slopes taken
from stations to SO, distance of
5000 feet, is % 1-3 degrees.
Rainfall.
From as careful study of the wa
ter shed, the rainfall and the runoff,
as the time and data at hand would
permit, estimate the water shed to
be 800 acres; the average annual rain.
fall at 132 inches and the rdnoff as
so per cent of the rainfall.
From an average rainfall of 1872
inches, or IL feet, over the water shed
In question of 800 acres, the runoff
calculated at an average of so per
cent, would yield approximately $50
million gallons per year, which is eQui-
yalent to continuous flow of Las
million gallons daily.
A six (6) inch rainfall in "a hours
on a water shed of 800 acres under
average conditions with so per cent
runoff. should yield approximately
24h million gallons, and rainfall of
eight inches under similar conditions
would yield approximately 3S million
gallons.
AS there are records of rainfall in
excess of eight inches, it would seem
wise to provide for maximum flow
of at least 35 to 40 millions.
Conduit.
The conduit should be so designed
and constructed as to have a maxi
mum carrying capacity for the largest
runoff from the heaviest rainfall
The bottom and sides of the ditch
should be cemented Ito sufficient
height to carry the normal flow, or
low stages of runoff and delivering the
same to the reservoir without loss, ex-
cept that due to evaporation in the
open ditch.
The various inlets from the natural
drainage should also be protected by
concrete work to prevent washing in
times of heavy rains or 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.
There is no doubt that the project
lis not only feasible and desirable but
viii prove to be profitable invest
ment. ~.
| Tunnel. ." n. i
The tunnel will be approximately
COO feet in length and the estimate of
cost including the lining of the bot
tom and portion of the sides. "
IL - Al.