The Hawaiian gazette., 1896-07-03
Prof. Maxwell Gives Some Val
liable information.
POSSIBLE SUGAR PRODUCTION.
Can be Increased Three Fold-Scienti-
fic Study of Terrestrial Conditions.
Water Running to Waste-op-
portunity for Development, Etc.

Usually the term "water-power" is
used to express the mechanical equiva-
lent and value of a body or flow OF
water for industrial uses. There arr
situations, however, where natural con-
ditions, and among these specially the
character of the geological structure Of
the underground, prevent regular sur
face flow by streams, even where the
rainfall is ample, and in such cases-a
notable one obtaining on this island
value for the power-equivalent of the
rainfall may be sought in directions of
a non-mechanical character.
To approximate the available value
of the water-power of a given area it is
necessary first to estimate the volume
of the natural rainfall, and then to fol-
low its several modes of discharge and
waste.
After careful examination of rain
fall data, comparing the relative pre-
cipitations over the several areas of
different altitude, we are induced to
place the average rainfall of Oahu at
20 inches. The data available, how
ever, are very inadequate for anything
more than a distant approximation to
the actual, and we are, in certain locali-
ties, having gauges placed at all alti-
tudes, and of such form that the rain
fall will need to be measured only once
month, in order to secure actual data.
For the purpose of. the following con-
siderations we shall base our calcula-
tons upon an annual rainfall of 60
inches, which certainly keeps within
the actual precipitation.
The Surface area of Oahu is esti-
mated by measurement at 600 square
miles, which is equal to 2,4OS, SEQ, 76O, 900
square inches. Upon this area an an
nual rainfall of 60 inches would give
IA, 521, 625, 800, 900 cubic inches of rain.
If this latter sum be resolved into gal
Ions we obtain the total of 625, 634. 742.-
S57 gallons, which sum will be taken
as a basis of the following considera-
tions.
Having reached some approximation
to the volume of annual rainfall upon
Oahu, We may proceed to consider the
amounts of water which escape by the
several modes of discharge and waste
The three chief modes by which rain
fall is discharged from the surface
where it fallsoare; % Surface drainage
by bitches and streams. or Surface
: evaporation, direct and through vege-
tation. 30 Percolation through soil and
rock strata, and discharge by springs
at lower attitudes.
1t is at once apparent that the
amounts of water which shall be dis
charged in these several ways must be
extremely various, and are controlled
by such factors as the level or hilly
surface Of the land; the porous or close
texture of the surface and under soil:
the temperature of the air; and the vio-
lent or steady rate of precipitation of
the rain. There are localities where the
rainfall is so small that neither surface
nor underground drainage occur; the
whole OF the precipitation being re-
turned to the air by direct evaporation
or the Transportation of plants. Again.
there are localities where the surface
and under strata are so open that sur
face drainage is equally as impossible,
the whole of large rainfall passing
into the soil and, in part, being re-
turned to the air, and in greater part
being discharged by underestimate. For
example, on the Waiakea side of the
Hilo river, upon the Waiakea planta-
ton, the rainfall is about $50 inches
per annum; yet there is not one run
ming stream, the whole of that i'm
mense body of water being discharged
into the sea through underground
drainage, excepting what is returned
10 the air by the cane, trees, etc. On
the other hand, there are land surfaces
so impact and close that, where the
slope is great and the rain comes in
gluts, the greater portion of the water
goes directly to streams or the sea by
surface drainage.
In the light of these general con-
siderations we may now look at the
Island of Oahu. First, there are the
low lands which reach from the sea
gradually up to the forest-bearing al
titudes. Their baroness, relative to the
forest attitudes, is a result of a much
smaller rainfall. Only trees, like the al.
geroba, which subsist with very little
water, thrive on these lower levels
Continued rain measurements tell us
that the 4ctual rainfall is comparatively
small. The surface drainage from these
lands, even under heavy rains, is bu
small compared with the whole if we ex
cept the surfaces of the city and roads
On the other hand, the return of moist
ure to the air by direct evaporation
from these low lands is vast. 1t is tru'
there are few trees to aid the evapora
ton, but there are high Temperature
and almost constant and uninterrupted
solar light and heat acting upon thi
moisture of the soil. Moreover, expert
ments that have been conducted in thu
Hawaiian Experiment Station labora
tory, bearing upon the moisture alb
sorptive properties of different soils
furnish cause for belief that little of tn,
rainfall can pass through to the under
strata, most of it being absorbed b,
the surface soil and returned to the air
These experiments have shown that tn,
lands, baked by the sun, give up almos
all their moisture.
Again, the same experiments hav,
shown that the sun-dried soil viii alb
sorb so per cent Of its own weight O