Hong Kong Water Supply – Kowloon Reservoir

October 11, 2024 Tymon Articles, Utilities

Tymon Mellor: The first water supply and distribution network for Kowloon commenced operations on the 24^th December 1895. The source of the water was from a series of wells, providing a daily capacity of 232,000 gallons and supporting a population of 13,200. By 1898, the demand for water was out-stripping supply; a new water source was required along with additional storage capacity. With the leasing of the New Territories in 1898, the hills to the north of Kowloon were now accessible for the collection and storage of water.

Water Sources

By 1898, with a population growth of over 33% between the 1891 and 1897 censuses, the existing well water supply system was insufficient to accommodate the growing needs. A number of short-term solutions were adopted including:- adopting intermittent supply and complementing the supply with water from Cheung Sha Wan streams. In the case of the latter, small dams were constructed with pipes conveying the water to the villages of Mongkoktsui and Yaumati, making them independent of the water distribution system.

In January 1900, the Director of Public Works, Lawrence Gibbs[i] published a report identifying possible new water sources for Kowloon and a new water distribution arrangement. The recommended approach would provide for growing residential and military demand, along with the provision of fire hydrants, a feature not included in the current system of the day.

The estimated water demand was calculated at around 413,000 gallons a day, based on:

Demand	Population	Gallons / Head	Gallons per day
European	1000	20	20,000
Chinese	30,000	10	300,000
Boat based	8,000	5	40,000
Military European	300	20	6,000
Military Asiatic	1,200	10	12,000
New Territories	3,500	10	35,000
*Total*	*44,000*		*413,0000*

This provided an average of 9 gallons a head, consistent with the provision for Hong Kong Island and assuming strict supervision of the supply with metered connections to private dwellings and no dedicated supply to Chinese houses. The report noted; “In proof of this it may be stated that during 1898 the domestic supply in Victoria, where water is laid into Chinese houses, amounted to 13.5 gallons per head, while in Kowloon, where it is not, the supply during the same period was at the rate of 6.1 gallons.” Clearly, the Chinese households were still more efficient than the Europeans!

With the lease of the New Territories in place, a detailed survey was undertaken of the Kowloon hills by Mr Xavier of the Public Works Department to identify water gathering grounds and possible sites for reservoirs. Five sources were identified:

Source 1 – a site just north of the current Kowloon Reservoir where a 65ft earth dam was proposed to provide a storage capacity of 120,000,000 gallons and with a catchwater providing a supply of up to 590,000 gallons a day;
Source 2 – west of the Source 1 and the future site of Kowloon Reception Reservoir, with a 50ft dam, 106,000,000 gallons could be impounded, yielding a supply of 390,000 gallons a day.
Source 3 – utilised the streams above Cheung Sha Wan, but with no possibility for a reservoir it could only supply 50,000 gallons in the winter and 200,000 to 300,000 in the summer;
Source 4 – the rivers to the north of what is now Diamond Hill, the rivers would need to be intercepted and directly feed into the supply network as there was no suitable location for a reservoir but this would supply up to 150,000 gallons a day.
Source 5 – a source below the Sai Kung Road, at present day Choi Hung with a possible supply of 200,000 gallons a day.

The report concluded that Source 1 was the best option, along with filter beds to be constructed on the ridge above Cheung Sha Wan and a service reservoir on the hill north of Kowloon Tong, feeding into the existing distribution network. The service reservoir would be 46m (150ft) in diameter, 6m (20 ft) deep with a capacity of 2,000,000 gallons. On the existing water distribution scheme, fire hydrants were omitted, partly due to the limited supply and partly as most of the developments were close to the harbour. With the new supply, hydrants would be installed at 91m (300 ft) intervals in the built-up districts.

The cost of the works was estimated at M$380,000 (Mexican Dollars, the local currency of the time) or £79,800.

Scheme Review

On receipt of the proposed works, the Colonial Government in London had the scheme reviewed by Mr Osbert Chadwick, the Government’s expert on all Hong Kong sanitary issues. He agreed with the principles of the report but made a number of key suggestions in August 1900. These included:

Establishing rain gauges in the area to confirm the local rain fall;
Acquiring the land for all the schemes to avoid delays in future if they were to be implemented;
Adopt a masonry dam rather than an earth dam, “With a masonry dam, a leakage merely amounts to a loss of water. With an earthen dam, it may result in destruction”;
If it was not possible to find good rock to construct the dam, provide a concrete cut-off rather than puddle clay below the base of the dam.

In response to Chadwick’s comments, the Public Works Office reviewed the site in detail and decided to move the dam location 182m (600ft) lower down the valley where the river passed “through a narrow cleft over solid rock”. With good rock available for foundations and construction, a 24m (80ft) high masonry dam would be adopted impounding 152,000,000 gallons but with the ability to raise the structure a further 6m (20ft), increasing the storage to 310,000,000 gallons. With the addition of catchwaters, the source could provide up to 961,620 gallons a day, sufficient to support Kowloon for the next ten years.

Kowloon Waterworks

Assent for the project was received from the Secretary of State in January 1902 and Messrs Denison, Ram and Gibbs, was appointed to proceed with the scheme. The Gibbs in the company name, was Mr Lawrence Gibbs, who had left the Public Works Department and would be responsible for the implementation of the Kowloon waterworks scheme. Mr Gibbs would be involved in many later developments, including the design and construction of his own house the Tai Po Lookout.

By the time construction commence on the dam, the cost of the project had increased to M$835,000[ii], primarily as a result of the increase in storage capacity to 310 million gallons. A number of contracts were awarded[iii][iv];

Mr Wong A Chi in April 1902 for the laying of 3.25 miles of 12” water main, connecting to intakes and caretakers bungalows;
Mr Tsang Keng in May 1902 for the construction of the main dam and caretakers bungalow;
Mr Tung Shing in February, 1903 for the Kowloon Tong service reservoir;
Mr Wing On in July 1903 for tunnels and site preparation of the filter beds;
Mr Li A Ping in March 1905 for catchwaters; and
Mr Wing On Firm in December 1905 for the construction of filter beds.

The final cost of the scheme was M$1,279,379 or £268,669.

Main Dam & Reservoir

Work commenced on construction of the dam in the summer of 1902 with the excavation for the dam foundation and abutments. The works immediately ran into trouble. After removing 18,000m³ (23,500 cubic yds) of soil they discovered the rock in the excavation was heavily jointed intersected with veins of decomposed granite. The soft material was dug out with picks and replaced with concrete, and then holes were drilled into the base to allow grout (a liquid cement) to be injected to strengthen the foundation and to provide a water cut-off. Based on the 1904 map[v] and a report by L Gibbs[vi], it would seem that the original dam was straight, similar to the Tai Tam (Upper) Dam, but was revised to a curved structure to accommodate the difficult foundation conditions.

An old pathway between Shing Mun and Tai Po crossed the site of the reservoir, thus the design of the dam provided for a 2.7m wide road across the top of the dam as compensation for the loss of the path.

By January 1904 the foundation was completed and work commenced on the main concrete dam. Good progress was made in the first year, completing 7,300m³ (9,600 cubic yd) of concrete, 260m³ (9,200 cubic ft) of dressed masonry and 76m³ (100 cubic yards) of rubble masonry[vii]. Work commenced on the bye-wash dam, the water overflow for the reservoir, with the removal of2,300m³ (3,000 cubic yds) of soil. The structure was 43m long and 7m high, carrying a path over the structure. The overflow comprised of 10 openings, each 3m wide, originally with iron sluices, allowing an additional 0.6m to be impounded.

During 1905, construction of the dam and bye-wash dam continued, with the main dam reaching a height 14.6m (48 feet) below the over-flow level, but progress had slowed as the contractor had financial problems[viii]. During 1906 there was only limited progress on the main dam, ending the year at still 9.1m (30 ft) below the overflow level. However, the scheme was sufficiently advanced that on the 24^th March, 1906 the catch waters were used to supplement the Kowloon supply by 75,000 gallons a day. By the end of the year the reservoir, filter beds and distribution systems were sufficiently complete to allow commissioning of the scheme on the 24^th December 1906, eleven years to the day of the commissioning of the original water supply scheme.

Construction of the main dam slowly progressed during 1907 and 1908, but since the scheme was commissioned, there was little focus on addressing the commercial issues. Some work resumed during 1909 but was finally suspended on the 16^th September 1909 with the dam still 2.4m (8 ft) below its final finished level. A new contractor, Mr Kang On was appointed in January 1910 and completed the remaining works by the 1^st December, 1910.

Mr Kang On disputed the final payments for the works, resulting in an arbitration action to recover funds. The arbitrator Mr Lindsey (formally of the Kowloon Canton Railway) found that Mr On was owed an additional M$35,600.

The key details on the final reservoir were:

capacity of 374 million gallons,
main dam set on a 73m (240 ft) curve, 183m (600ft) long at the top ;
maximum height of 34m (112 ft) with a maximum thickness of 22m (72 ft);
construction used 28,000m³ (36,740 cubic yard) of concrete,
inner face covered in 1,800m³ (64,529 cubic ft) of masonry;
outer face covered with 1,300m³ (1,750 cubic yards) rubble masonry;
two catchwaters extending 3.2 km to the north east and 152m to the south east.

In addition to the dam works, a 1.6km section of the Tai Po Road had to be reconstructed clear of the new reservoir and a caretakers bungalow constructed for the water works staff. The latter would seem to have been abandoned by WSD and is now in a poor state of repair.

The dam and associated operational buildings are declared grade 1 monuments[ix], unfortunately the bungalow and catchwaters have not been listed.

Catchwaters

The natural catchment area of the reservoir was 438 acres, insufficient to fill the reservoir in years of low rain fall. A 3.2km catchwater was constructed to intercept mountain streams and effectively extending the catchment area by a further 600 acres. This catchwater discharged into the eastern end of the reservoir, passing under Tai Po Road then contouring along the northern slopes of Beacon Hill, before terminating at a major stream, originating on the slopes of Lion Rock. In February 1923[x], a further contract was awarded to the Hong Kong Engineering and Construction Company to extend and enlarge this catchwater a further 3.3km to its current length, adding a further 151 acres of catchment[xi]. The extended catchwater was completed in 1925. This catchwater is now used for the Kowloon Hills Fitness Trial and forms part of the Wilson Trail, stage 5.

The catchwater discharged into the reservoir with an original configuration of 6.4m width and 2.3m deep, reducing down in size to 4.5m wide by 2.3m deep at the upper end, with a 1.8m maintenance path. A small V-shaped channel was provided on one side to carry the dry weather flow, and sand pits were provided at 60m intervals to intercept any grit or debris. The catchwater was laid at a grade of 1 in 2400 and when running full it could carry 20 million gallons an hour[xii], or 24mm of rain per hour.

Experience gained from the Tai Tam catchwater construction was that a small cross section with a good fall, resulted in strong currents that soon ripped out the catchwater base. Thus, a shallow gradient catchwater with a larger cross section was preferred, but this resulted in additional excavation[xiii].

A second and smaller catchwater, 152m long and with an area of 0.65m², (7 sq ft) was constructed to intercepted a stream near the caretakers bungalow providing an additional drainage area of 28 acres and discharging into the reservoir by the Byewash Dam.

Filter Beds & Tunnel

From the main dam, a 225mm (10 inch) pipe carried the water from the dam, 243m (800ft) down the river bank to an open gauging basin. From here, a 450mm (18 inch) transfer pipe, laid at a 1 in 1000 gradient transferred the water to a gauging basin by the filter beds. The transfer pipe crossed the existing river on a structure of “steel girders and stone piers”, before passing through a spur of the hill in a cut and cover tunnel 137m long. For this an excavation 33m deep was cut and the tunnel structure constructed before backfilling. During the summer of 1904 the nearly complete cutting collapsed in the August rains, and the loose material had to be dug out again. The tunnel was constructed from brick on a concrete base, 1.8m high and 2.2m wide, with space for an additional pipe line if required.

The water supply main also included a bifurcation to supply water to the new Lai Chi Kok filter beds, supplying water to water-boats.

The site for the filter beds was located in a thickly wooded valley to the west of the Tai Po Road. The site had to be levelled requiring around 34,400m³ (45,000 cubic yards) of material to be removed. This material was deposited adjacent to the site of the filter beds for future expansion to six beds. Construction of the filter beds commenced in December 1905 and the three beds, each of around 668m² (800 sq yard) were completed within 12 months. By the end of 1906 the pipework and fittings had still not arrived from the England so temporary timber components were fabricated until the fittings arrived. With the temporary components in place the dam and filter beds were commissioned on the 24^th December, 1906[xiv].

Service Reservoir & Distribution

From the filter beds a 244m long hard rock tunnel was excavated through the adjacent spur. Construction commenced from both ends, with only the initial soft excavations being lined. From the tunnel portal below the Tai Po Road, the 450mm pipe contoured around the hillside at a 1 in 1000 gradient to meet the road, close to the 4-mile marker point. From here, the main was located within the road until reaching the Kowloon Tong and the service reservoir[xv].

The service reservoir at Kowloon Tong was located on the top of a low hill, Woh Chai Shan, 70m above sea level. The structure was constructed within an excavation then backfilled. The base consisted of concrete, with granite pillars and brick arches to support a concrete vaulted roof. The circular structure had a top diameter of 47m (155ft) and a depth of 6m (20ft) with a capacity of 2,183,000 gallons.

From the service reservoir, a new main was installed along Tai Po Road, Shanghai Street to Yau Ma Tei where it connected into the existing water main at the pumping station. A total 4.8km of existing mains were upgraded and 11.2km of new mains laid along with 158 fire hydrants and 65 stand-pipes. With the commissioning of the new distribution system, the steam driven pumps at Yau Ma Tei were de-commissioned.

Lai Chi Kok Boat-Water

With a continuous supply of fresh water from the Kowloon Hills, Lai Chi Kok developed as a water supply point for marine transport. A number of companies operated water-boats, ferrying water out to the marine vessels, including Hongkong Steam Water-Boat Co and Union Water-Boat. With the out-break of Cholera in June of 1904[xvi], the Government decided that mitigation measures were needed to avoid contamination of this important water source. The immediate action was to close water intakes near Tai Po Road and to construct a 200,000 gallon a day water filter beds[xvii] along with a 100,000 gallon service reservoir.

On the 7th March 1905[xviii], the filter beds were commissioned providing a 150mm diameter pipe metered water supply. This new arrangement including staging and pipework allowed the water-boats to be filled while afloat. Complaints immediately arose as the water delivery was too slow. Thus, by the middle of 1905 a contract was awarded to double the size of the filter-bed from 170m² (200 sq yards) to 340m² (400 sq yards), provide an additional 100,000-gallon storage reservoir and an additional 200mm supply pipe. By the end of 1905, even with the new works complete, it was clear that the supply was still insufficient and a further filter bed of 370m² (440 square yards) constructed.

The Next Step

In 1900, the Director of Public Works, R D Ormsby noted[xix]; “The completion of this work will be a great boon to Kowloon in many ways, and will no doubt enhance the value of property greatly…It is not unreasonable to suppose that before many years British Kowloon will rival Victoria in population and trade”. He estimated that Kowloon Reservoir would support the development of Kowloon for the next ten years[xx].

The scheme supported development for over 20 years, at the start of the dam construction in 1902 there were 144 water meters in use, and on completion in 1910, there were 374. By 1922, there were 721 water meters and it was necessary to introduce water restrictions. The water supply was limited to just 3 hours a day in the Chinese Districts due to delay in the spring rains. The supply was now supporting an estimated population of 135,460[xxi] using 11.4 gallons per head per day. It was time to build more storage capacity.

Sources:

[i] Report on Water Supply, Kowloon by Lawrence Gibbs, 8^th January, 1900

[ii] Report of the Director of Public Works for the year 1901

[iii] Report of the Director of Public Works for the year 1902

[iv] Report of the Director of Public Works for the year 1903

[v] Mapping www.hkmaps.hk

[vi] Kowloon Water Works, Early History, L Gibbs February 1931, The Hong Kong Naturalist

[vii] Report of the Director of Public Works for the year 1904

[viii] Report of the Director of Public Works for the year 1905

[ix] http://www.aab.gov.hk/form/AAB-SM-chi.pdf

[x] Report of the Director of Public Works for the year 1923

[xi] Report of the Director of Public Works for the year 1925

[xii] Report of the Director of Public Works for the year 1910

[xiii] Kowloon Water Works, Early History, L Gibbs February 1931, The Hong Kong Naturalist

Hong Kong Water Supply – Kowloon Reservoir

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