THE TROHCAL AQRIOULTURlSt 
[February 2, 1891. 
560 
system cease to be perennial, and no wonder, 
when two, and we believe three, years of drought 
occur in succession. The tanks are then depen- 
dent entirely on rainfall; and considering the dry 
condition of the soil and the thirsty state 
of vegetation, we can understand why, for 
the re-filling of such a tank as Kalawewa, 
rain storms of 10 to 20 inches in a few days 
are desiderated rather than the same quantity of 
rain distributed over a month. In the latter case 
the arid soil and the drooping vegetation would 
gradually absorb every drop of moisture that fell, 
leaving none to even partially supply the tank. But 
not only must the loss from absorption be greater in 
the dry regions, say 35 per cent, at least of the 
rainfall at Kalawewa, against 22 to 25 at Labu- 
gama, but the further loss from evaporation, 
which is astonishingly great in the cases of 
the Colombo and Labugama Lakes, must be 
enormous in regard to the streams and irri- 
gation reservoirs in the hot, dry regions 
where the shade temperature goes up to 100°, 
and months succeed months, sometimes, when 
the heavens are as brass and the earth as 
iron. In Mr. Blanford’s book on the climates 
of India and Ceylon, we have been surprised 
to find how few and uncertain the data 
quoted by him for evaporation are. Extended 
and careful observations by the Survey Depart- 
ment in connection with the Colombo Lake and 
by the Engineer in charge in the case of the 
Labugama Lake, on a system — in this latter case, 
inaugurated by the late Mr, Burnett — are likely, as 
Mr. Burnett pointed out in his most interesting 
final report, to give results of unique value 
to hydraulic science. Readers will be scarcely 
prepared to learn that the average daily evapora- 
tion from the Colombo Lake, with a mean tempera- 
ture of a little over 80°, and an annual rainfall 
of 88 inches, is equal to 0'217 of sn inch 
(the total area being 410 acres) or 2,045,589 gallons ; 
the maximum evaporation on a dry day in February 
being 0‘480 inch, or 4,524,804 gallons. Such, 
however, are the results of observations taken by 
Mr, Wackrill of the Survey Department. The 
decimal given for a dry day in February, be it 
noted, is very close on half-an-inoh. We understood 
from Mr. Gibson, the experienced and intelligent 
Engineer in charge of the Labugama Lake, that 
he takes the most frequent and careful observations 
of the effects of evaporation on the mountain 
reservoir of which he is in charge, the extreme 
effect in one day being, we understood, §ths of 
an inch. This is consistent enough, the mean tom- 
Xrerature of Labugama being about the same as that 
of Colombo, but the atmosphere being so much the 
more charged with moisture in proportion to a 
rainfall of nearly twice the volume of that at Colombo. 
I cannot, in this connection, refrain from quoting 
the following paragraphs from the late Mr. Burnett’s 
exceedingly able, honest and interesting report: — 
The supply to the town at 3,000,000 gallons in 
twenty-four hours with strainer washing and scouring 
of wells, flushing, &c., absorbs about 33 to 34 in. of 
the rainfall. 
The proper maintenance and working of theReser- 
voir therefore, require the constant care and attention 
of a skilled and thoroughly reliable European officer 
at Labugama every day, and frequently at night, an 
the floods must bo met and dealt; with by the sluices 
•when and as they occur; and it has been, and will 
bo only by the best and constant care, both days and 
nights when required, of the officer in charge in 
carrying oul his instructions that the purity and safety 
of the waior .supply, which has now become a vital 
necessity to tho people of Colombo, can be mauri d. 
In the course of his work and inspection this 
paicer is required to lake, not only a daily record 
of the rainfall and level of the reservoir, but such 
constant observations both of rainfall and reservoir 
levels and opening and closing of sluices, as will 
enable a complete calculation to be made of 
the rainfall and the measure of its resulting flow 
of water, and the receipt info, and discharge from the 
reservoir of, this water. It is only on this knowledge 
that the volumes and duration of floods, and their 
proportions of yield of water to the rainfall, can 
be ascertained, and that the measures to meet them 
can be arranged. 
The observations thus made enable both the 
total yield of the year’s rainfall to be ascertained and 
the details of individual storms and floods, and give 
most important scientific information of, I believe 
almost unique value as to the yield of rainfall in 
water discharge and the loss by absorption in the 
ground and by vegetation and evaporation in tropical 
mountain valleys. It is extremely rare in such con- 
ditions that the entire results of rainfall and discharge 
can be measured into a reservoir, as at Labugama, from 
such an area as a drainage of nearly 2,400 acres, asd 
they should be of great value in the consideration of 
all works and matters connected with the discharge 
of the streams of the mountain and hill districts of 
this Island as well as elsewhere where similar con- 
ditions exist. These returns, both of the total annual 
results and particulars of exceptional floods, should 
form a part of the annual report of the Engineer. 
As the road to Labugama pierces the outlying 
hills of our mountain zone it crosses the beds 
of several streams, the multitude of large boulders 
in which show the evidences of exceptional floods. 
The Wakoya is not the largest of the streams. 
It is excelled by the Kalatawa, the waters of 
which, however, oould not be utilized for the forma- 
tion of the Lake, owing to the lower level of this river. 
The road to Labugama has helped to open up 
the country around to the tsa enterprise, and 
strikingly contrasted with the flat paddy fields near 
Wakoya were the tea fields on some hill slopes 
that for steepneFs oould compare with some 
of the cultivated precipices in Haputale, which 
the railway will skirt as it approaches, over 
the narrow ridge along which will lie its 
final course, “ the Pass ” by whioh Uva is entered. 
“ Mohideen’s tea estate ” (inscription on a board 
by the road side) looked so ship-shape and clean 
that we were curious to know about the exceptional 
“Moorman” who was so good a planter. The 
answer was “ Mohideen’s estate is looked after by 
Mr. Ross Wright.” “ All right,” was our natural 
response. Young coconut palms, planted amidst 
tea, or as a separate cultivation, looked flourishing, 
but scepticism was expressed as to the trees’ bearing 
well so far from the sea. The distance from the 
sea in a direct line being not more than twenty 
miles, the question arises as to the limit, in dis- 
tance from the saline influences of the ocean, of 
profitable coconut cultivation. The best zone for 
the palm is usually defined as two miles from the sea, 
but coconut cultivation in many parts goes much 
further inland, extending in the case of the valley of 
the Kelani in unbroken groves along the banka of the 
river, from its mouth to Hanwella and still further 
towards Ratnapura. Many of the fine and flourish- 
ing coconut plantations beyond Mirigama must be 
more than twenty miles from the sea. In southern 
India the destruction of coffee by borer was traced 
to the fact that the cultivation had taken place 
on “ bamboo-land ,” — Bamhusa arundimcea being, 
DO doubt, the species in that case. Along the 
road to Labugama and in the Kelani Valley 
generally, Ihe prevalence of the small bamboo of 
which tea baskets are pjade in such large numbers 
at Kalutara, and whioh is used so generally for fences 
in Colombo and elsewhere, seems to have no deter- 
ring influence on intending oultivators, — a consider- 
able proportion, indeed^ of the Kelani Valley teaestatep 
being opened on land, the main vegetaUpn pjE w Jliol} 
