Hong Kong Water Supply – Shek Lei Pui and Kowloon Byewash Reservoir
Tymon Mellor: With the growing population in both Hong Kong Island and Kowloon there was a growing demand for drinking water, the existing supplies, primarily the Tai Tam reservoirs and Kowloon Reservoir were insufficient to meet such needs. With the failure of the spring rains, water famine became a common occurrence, and a quick fix was required.
Following the completion of the Tai Tam Tuk Reservoir in 1918 a constant supply of water was available to support the growing population until 1922. With a failure of the spring rains, increasingly severe water restrictions were introduced on Hong Kong Island commencing from the 1st April, 1922, with the implementation of the rider mains system, then followed by limiting the operational hours to only 2 hours of supply a day[i] from the 6th July which lasted until the 13th August 1923 when heavy rains allowed a constant supply to be reintroduced. Similar problems were experienced in Kowloon when from the 8th June, the supply was curtailed to three hours a day in “the Chinese Districts” and then all districts from the 17th June. These restrictions continued until the 8th September, with only a short break at the end of the June following two days of rain.
Mr R M Henderson the head of the Water Department of the Public Works Department[ii], recognised the need for new water sources and sites for new and larger storage reservoirs. Two solutions were identified, the development of the Aberdeen Valley on Hong Kong Island, and the hills around the Shing Mun Valley. Mr Henderson prepared detailed plans for the development of Shing Mun but he received little support from the Government due to the large sums of money required for the schemes. However, following the water famine in 1921, something had to be done. As reported to LegCo in October 1922[iii], “the construction of a small Reservoir at Shek Lai Pui a valley close to, but at a higher level than the existing Reservoir [Kowloon Reservoir]. By the erection of two comparatively small dams a Reservoir of about 120 million gallons capacity can be formed, the Catchment Area of which, however, will be comparatively small. It, however, appears to be the best possible solution for quickly augmenting the existing supply.”
Shek Lai Pui Reservoir
The proposed site for the reservoir was in a valley adjacent to and higher than the existing Kowloon Reservoir. The scheme would require the construction of two small dams to impound the water and feed into the existing larger reservoir. To enlarge the water catchment area, two short catchwaters were proposed to intercept nearby streams.
At the site of the proposed reservoir was the small village of Shek Lai Pui (Shek Li Pui), with 26 houses and 80 villagers along with their associated fields. They would have to be relocated. As reported in the New Territories Report of 1922[iv], “The villages of Shek Li Pui and those situated in the Shing Mun Valley will have to go, but the Government is taking special steps to secure the future welfare of the communities whose present homes must be removed for the general benefit of the whole Colony”.
A contract was tendered in June, 1923 for the construction of the reservoir works, consisting of the main dam to the south, a draw-off dam on the east and a small dam on the west side along with an east and a west catchwater. The works were awarded to the Hongkong Engineering and Construction Company for $248,697 in 1923[v] and works commenced in August, 1923.
There were clearly high expectations for rapid progress but the contractor struggled and by the end of 1923 excavation for the dam foundations was still ongoing. Progress on the main dam foundations was further delayed in 1924 when an area of soft rock was encountered at the south end of the dam[vi]. This necessitated the deepening of the foundations and managing the associated higher ground water ingress. However, by April 1924 placement of the concrete foundation commenced, followed by construction of the concrete dam and granite facing blocks. The completed main dam was 95m long with a maximum height of 22m from the lowest foundation.
Construction of the draw-off dam commenced in October, 1924 and proceeded without incident. The dam was 51m long and 12.8m from the lowest foundation level. The dam provided an overflow weir and three levels for water draw-off, controlled from a granite masonry valve tower.
A small dam was constructed on the west side, being 30m long and 10m high from the lowest foundation.
Construction of the 210m long east catchwater commenced in November 1924 and was completed by the end of the year. Work on the 177m long west catchwater was undertaken in early 1925.
In June 1925 impounding of water commenced and all works were substantially complete by the end of 1925, providing an additional 100.7 million gallons to the Kowloon storage capacity. The cost of the project was $239,456.
In 1926 the contents of the reservoir were discharged into Kowloon Reservoir on January 11th and March 21st to augment the Kowloon Supply during periods of restricted water supply, reducing the impact of the water shortage. It was clear further additional capacity was required to meet the growing demand. This would be addressed with the construction of the Shing Mun Scheme.
As for the villages of Shek Lei Pui, in 1924 a new village was constructed for them at the north end of the KCRC Beacon Hill tunnel for a cost of $57,200. The village Hin Tin (King Hau San Tsuen on old maps) was provided to accommodate those displaced by the new reservoir.
Kowloon Byewash Reservoir
In 1927 the water supply to Kowloon was supplemented with water from the first section of the Shing Mun Valley scheme, this provided additional water, but had only limited additional storage (see next article). Water consumption grew by 30% in 1927 and a further 15% in 1928 exceeding 4.5 million gallons a day. The growth in demand was identified[vii] as being due to:
- Influx of Chinese refugees from the Canton district;
- Larger number of metered services; and
- British troops billeted on the Peninsula.
As described by the Governor to LegCo in September 1929[viii], “In the first place, Old Kowloon and New Kowloon are growing at an abnormal rate”, furthermore with the proposal to construct a cross harbour pipeline, unless there was additional storage there would not be any surplus water for Hong Kong Island. The long term solution would be the proposed Shing Mun Reservoir, but the project stalled due to funding, technical and political issues.
As with the Shek Lei Pui Reservoir, a quick solution was required to address the growing demand, thus Kowloon Byewash Reservoir was proposed. As described by the Governor, “Its site is in the valley immediately below the existing Kowloon reservoir. It has an estimated capacity of 175 million gallons, and it will impound the overflows both from Kowloon reservoir and from the raw water reception reservoir in the lower Shek Lai Pui valley. It requires no contingent works such as filters or pumping plant; and, although not a part of the Shing Mun scheme, it can be developed economically in connection with that scheme. Its cost is estimated at $600,000”. The scheme was approved 24th January 1929[ix].
The new reservoir would store the wet season overflow water from Kowloon Reservoir, making it available during the dry season. The surplus water Kowloon Reservoir water would be discharged over the spillway as by-wash water, or in Hong Kong it was known as Byewash and hence Kowloon Byewash Reservoir.
The contract for the construction of the new dam was awarded on the 11th June, 1929 to The Hong Kong Excavation Pile Driving and Construction Company for $499,344. The Contractor was also awarded the construction of Aberdeen Upper Reservoir some four months later. The two dams were of a similar design and the contractor introduced modern materials and mechanical handling methods, a first for Hong Kong.
A new access road from the Tai Po Road was completed by September 1929 and excavation for the foundations were ongoing by the end of 1929. At the west end of the dam, a site was levelled for the construction of a casting yard to produce concrete blocks for the construction of the dam. The contractor introduced constructing an overhead cableway and lifting arms to move the concrete blocks and concrete chutes with discharge equipment for the supply of concrete.
Excavation for the dam foundation proved to be problematic, despite having undertaken trial trenches to confirm the integrity of the foundations. A soft seam of material was located in the former stream-bed which had to be removed and replaced with concrete in stages. It was not until April, 1930 that the construction of the dam could commence.
By May 1931 the dam had reached the road level and was completed in August 1931. Impounding of water had already commenced at the start of the year and was connected to an existing water main, supplying the Kowloon Filter beds with water from the 14th January, 1931.
In June 1931 the reservoir was emptied and the original 450mm supply main from Kowloon Reservoir, located inside the reservoir was removed. The water from Kowloon Reservoir was now being discharged into the Byewash reservoir along with any overflow water.
The dam was a gravity structure with a mass concrete core and pre-cast concrete facing. The dam was 44m from the deepest foundation or 36m from the original river bed and 82m wide, with a storage capacity of 185.5 million gallons. Materials were delivered to the site using road trucks on the east side of the dam, then carried across the valley on a cableway to the works area and concrete batching plant on the west side. Sand and cement were deposited from the cableway directly into storage bins immediately above the one cubic yard capacity mixer. The mixed concrete was hoisted inside a steel tower and discharged into a chute suspended on cables across the valley.
The overflow section of the dam consists of sixteen 3.6m bays supporting a 3m wide road. A central valve house contained operating gear for the four 450mm draw-off pipes. A 12.8m long reinforced concrete skew arch bridge links the dam supply pipe to the adjacent Kowloon Filter bed. A total of 22,400 m3 of concrete was placed along with 14,100 precast concrete blocks. The final cost of the project $518,623 and was funded from the Government loan for the Shing Mun Scheme.
With the completion of the Kowloon Byewash Reservoir and the ever growing population in Kowloon and Hong Kong Island, it was time for the Government to take the next step and build the Shing Mun Dam, what was said to be “the highest in the British Empire”[x].
[i] Public Works Report 1922
[ii] Dr C A Middleton Smith The Hong Kong Centenary and Applied Science, The Engineer 7th March 1941
[iii] MR. T. L. Perkins (Director of Public Works), Hong Kong Legislative Council, 26th October 1922
[iv] Report on the New Territories for the Year 1922
[v] Public Works Report 1923
[vi] Public Works Report 1924
[vii] Public Works Report 1927
[viii] Sir Cecil Clementi, Hong Kong Legislative Council, 5th September 1929
[ix] Sir Cecil Clementi, Hong Kong Legislative Council, 5th September 1929
[x] Dr C A Middleton Smith, The Hong Kong Centenary and Applied Science, The Engineer 7th March, 1941
This article was first posted on 12th March 2020.
Related Indhhk articles:
- Hong Kong Water Supply – The Tai Tam Tuk Scheme First Section
- Hong Kong Water Supply – The Tai Tam Tuk Scheme – Second Section
- Hong Kong Water Supply – The Politics of Water Supply and Rider Main Districts (1890-1903)
- Hong Kong Water Supply – Kowloon Reservoir
- Hong Kong Water Supply – Tai Tam Upper Dam (formally Tytam Reservoir)
- Hong Kong Water Supply – Kowloon Peninsula
- Hong Kong Water Supply – Pok Fu Lam Reservoir
- Hong Kong Water Supply – Mint Dam and Other Early Structures
- Hong Kong Water Supply – The Aberdeen Reservoirs Scheme
- The Hongkong Engineering & Construction Company Ltd 1922-1993
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