ཨབྷཱ དི ཙ ཨནྣཾ, ཨ ཨ སནིཉྩ བྷཱནྟཾ སུ
692
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55. I do not consider that it would be prudent to raise the Pokfulum dam, an opinion with which the Director of Public Works agrees, and which was also, I believe, held by Mr. Price, the former Surveyor General.
56. In view of a future increase in the population and augmentation in the legitimate consumption of water, the means of making a substantial increase to the total water supply should now be considered. It is very desirable that the supply derivable from the present gathering-ground should be developed to the utmost, rather than water should be collected from several gathering-grounds. To secure the purity of the water, it is necessary that the gathering-ground shall be uninhabited and uncultivated. Two gathering-grounds have already been taken
up for the purposes of the public water supply, and the waters of others have been granted to private individuals. It is therefore desirable that no more land be withdrawn from occupation than is absolutely necessary.
The same
57. The Tytam reservoir has a gathering-ground of 700 acres. stream, at a point lower down, where its bed is approximately 100 feet above the sea, has a total gathering-ground of 1,490 acres, of which 700 contribute to the existing Tytam reservoir. The flow from 790 acres, plus the overflow and leakage from Tytam reservoir, could be collected in a reservoir constructed at a level of 100 feet above the sea. If a reservoir of suitable size were con- structed at this point an additional supply at least equal to, and probably greater than, that which Tytam now affords could be obtained. The available quantity would depend mainly on the capacity of the reservoir, a point which can only be settled by survey.
58. The water of this reservoir would have to be pumped by steam power into the Tytam tunnel. This is not a very serious matter however. The Ordnance map of Hong Kong shews that no appreciable additional supply can be collected in the lower Tytam gathering-ground of 790 acres, at an elevation sufficient to flow by gravity into the Tytam tunnel. Nevertheless the evidence before me tends to show that the Tytam valley is the best source from which extensions to the water supply of Victoria can be obtained. The tunnel and conduit are ready to hand, and no alteration to the distributary system need be made. It will not, I believe, be difficult to arrange matters so that the works may be carried out progressively as demand arises. I therefore recommend that the project for the construction of a new reservoir in the Tytam valley be carefully studied, and the necessary surveys should be put in hand at once.
59. It is probable that a material increase to the water supply may be at once obtained from the Tytam valley, without the construction of a reservoir. Even in the dry season there is a considerable flow of water in the lower reaches of the Tytam stream: how much
cannot say. The Director of Public Works informs me that he left instructions to gauge the flow during last dry season. Even gaugings taken during October next would be valuable. If it appears that the flow of the Tytam river is about 1,000,000 gallons a day during October and November, then it will be worth
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while to put up pumping plant at once. If it were possible to pump some
30 or 40 millions of gallons into the reservoir after the beginning of October, the date at which overflow ceases, and the demand exceeds the supply, the reservoir might be kept full, say till January, and a valuable addition to the dry weather stock would be the result.
My
60. It is premature to go into close calculations as to the power of the engines and size of main that will be required until the sufficiency of the supply which the Tytam stream affords has been determined by gauging. The following figures may be useful to give a general idea of the magnitude of this work. To raise one million of gallons in twenty-four hours to the necessary height (310 feet nett) about 80 H.P. will be required, say three engines of 40 H.P., two to do the day work and one in reserve, in all—
120 H.P. effective at $600 per H.P. 2,000 yards main laid, at $8
Weir contingencies, &c.
Total
$ 72,000 16,000
12,000
$100,000
Such a plant would furnish an extra perennial supply of 1,000,000 gallons
a day, when the storage reservoir is constructed.
61. The Director of Public Works informs me that a large new reservoir could be constructed just below the Fokfulam dam. Though the water from this new reservoir would not go into the Pokfulum conduit, it would be high enough to supply the lower districts by gravity. In this case, however, a new set of filter beds would be required. It would be better, probably, to pump the water into the conduit, as the lift would not exceed 30 to 40 fect. This project should also be studied.
62. I understand that the recent epidemic of Plague has caused a great exodus, and that it is the intention of the Government to pull down and re-build the houses on the infected area. Consequently, a reduction in the population may be reasonably expected, which will continue for some years to come, and a proportional reduction in the consumption of water may be anticipated. Therefore 1 do not consider that it is necessary to adopt hastily any plan for augmenting the water supply.
CONCLUSION,
63. My recommendations may be summed up as follows:---
(a) The provisions of the Water Ordinance against waste should
be strictly and vigorously enforced.
(b) The Tytam dam should at once be raised to the utmost extent that appears to be safe.
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