CO129-459 - Individuals - 1919 — Page 263

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JAFFÉ ON HONG KONG WATERWORKS,

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In 1890-92 filter-beds were added to the Pokfulum supply, the distribution mains in the city were relaid with larger pipes, and the service was extended to the Peak, for which pumping was necessary, power being obtained from a hydraulic motor connected to the low-level supply, and a steam-driven set being provided as a stand-by,

In 1895, the capacity of Pokfulum reservoir was increased to 70 million gallons by the addition of overflow boards, and, in 1897, the capacity of Taitam reservoir was increased to 407 million gallons, by raising the height of the dam 12 feet 6 inches.

In 1899, a further addition of 33 million gallons was made to the storage by the construction of Wongneichong reservoir, which brought the storage up to 5103 million gallons, and in 1904 a small bywash reservoir containing 26 million gallons was added to Taitam reservoir, which brought the total storage of all the reser- voirs up to 537 million gallons.

The growth of Hong Kong at this period was very great (the census returns showed a water-consuming population of 156,396 for 1891, 182,576 for 1897, 205,626 for 1901, 203,408 for 1906 and 248,473 for 1911), the supply failed to keep up with it, and in 1901 a very low rainfall resulted in so severe a water-famine that water had to be transported in barges from the mainland and other expedients adopted to supplement the supply. An extension which would add very materially to the Colony's water-supply was therefore necessary, and, as the late Mr. Osbert Chadwick, C.M.G., M. Inst. C.E., was in the Colony at the time, reporting on sanitary matters, the question was referred to him. Mr. Chadwick recommended that the entire Taitam Valley down to sea-level should be developed for waterworks purposes, thus involving pumping arrangements of considerable magnitude.

Mr. Chadwick recommended :—

(1) The construction of a pumping-station on the shore of

Taitam Bay.

(2) The immediate installation of machinery capable of pump- ing 1 million gallons in 24 hours, to be ultimately triplicated.

(3) The construction of a low-level reservoir of at least 400

million gallons capacity.

(4) The provision of a 15-inch pumping main in the first

instance, to be supplemented later by a 21-inch main.

Papers.]

These recommendations were in part given effect to during 1904-7 when the first section of the Taitam Tuk works was under- taken.

LOW-LEVEL RESERVOIRS AND WORKS FOR PUMPING.

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These works comprised the construction of a concrete and masonry dam designated the Intermediate dam, 90 feet in height, about midway down the valley between Taitam dam and the sea, impound- ing 210 million gallons; the erection on the shore of Taitam Bay, where coal could be delivered at all states of the tide, of a pumping- station having two sets of triple-expansion vertical pumping-engines each capable of raising 14 million gallons in 24 hours; the laying of an 18-inch supply main from the Intermediate dam to the pumps, the provision of a road for and laying of a similar discharge main from the pumps to the gauge-basin at the inlet or east end of the tunnel which conveys water from Taitam reservoir to the City.

These works did not fully develop the resources of the Taitam Valley, nor did they suffice for a full supply to be maintained throughout the year; but, as other large works were in progress at the time, the Government decided that, for financial reasons, the The larger extensions contemplated must remain in abeyance. result was that, except in very favourable years, a restricted supply by rider-mains alone was available during some part of the dry

season,

The rainfall over the year is divided into two well-defined periods, a wet season which generally extends from May to September inclusive, and a dry season from October to April inclusive. The rains during the first months of the wet season are due to the change of the monsoon and are generally fairly light and pretty well distributed, but thunderstorms, which often occur at this period of the year, are generally accompanied by very heavy rain. The rains during August and September are chiefly caused by typhoons, and the influence of these storms may make itself felt in heavy rain even when they pass no closer to the Colony than 300 miles. In years when there are no typhoon disturbances the rainfall may cease early in August, but in most years at least one typhoon passes sufficiently close to the Colony to bring rain. The maximum annual rainfall recorded at the Observatory since 1884 is 119.72 inches in 1889, and the minimum 45 83 inches in 1895. The mean for As an the 30 years 1884 to 1913 inclusive is 83.16 inches. instance of the heavy falls, between 3 A.M. on the 29th of May and 5 P.M. on the 30th of May, 1889 (38 hours), 33 11 inches was recorded, the maximum hourly rainfall being 3.4 inches. The