38
1) The Pokfulam Reservoir,
2)
Two Reservoirs in the Aberdeen Valley,
3) Five Reservoirs comprising the Tytam Valley Scheme,
4) Four Reservoirs near Shek Lai Pui in Kowloon and
5)
The Shing Mun Reservoir.
The data of these various reservoirs is set out in Table No. 1 and some typical sections in Plate No. 1 and in the following notes it is only proposed to enlarge on their more interesting engineering features.
Pokfulam. The table shows quite clearly the fault of this reservoir, it should have been made quite a bit bigger to take full advantage of the catchment area behind it. With 6.44 acres per million gallons of storage, 10 ins. of rain with 66% run-off would fill the empty reservoir. Various schemes have been proposed to remedy this but the expenditure involved has ruled them out. The original dam, which was little more than a stream intake still exists below the earthern dam, a mystifying object to all viewing the reservoir for the first time.
recent of the Island supplies But the value of the stream dam had been built in 1890
In 1899
Aberdeen Valley. This is the most having been built since the 1929 shortage in this valley had early been realised as a to provide a water supply for some Paper Works in Aberdeen. This dam was 40 ft. high with a top water level of 243.85 A.P.D. it had been raised 18 ft. and strengthened by 10 ft. concrete counter- forts. In 1926 the Waterworks Engineer looking for further storage, investigated the possibility of further raising this dam, but reported in favour of another dam half a mile upstream with a T.W.L.* of 365.00 A.P.D. However, probably as a result of the 1929 shortage, the scheme as finally approved and commenced in 1929, consisted of two reservoirs formed by a new dam as proposed in 1924 but also raising the old dam slightly and strengthening it. The new dam is a straight- forward gravity section, the data for which is given in Table No. 1, and the lower dam was reconstructed to the same pattern. A portion of the old dam was first cut away to determine the exact nature and materials of its construction. It was found to consist of various grades of displacer concrete, generally of poor quality in the interior with better material near the face and faced with good rubble. It was decided therefore to strengthen the downstream face by cutting away a portion of the concrete buttresses and thickening up the remainder to a uniform cross section, with a spillway section which was con- tinuous except for the 9 ins. piers required to support a roadway across the dam.
T.W.L. Top Water Level.
41