The supply of water from Dongjiang at Guangdong, a province in southern China, is now the major single source of raw water supply for Hong Kong. The annual Dongjiang water supply has been now almost 70 - 80 per cent of Hong Kong's total demand starting since the late nineties.
The Dongjiang water supply has a history dated back to 1960 when a scheme was first formulated for receiving a supply of 22.7 million cubic metres a year. The 1964 Agreement was reached with the Guangdong authorities whereby Hong Kong would purchase 68 million cubic metres of water each year. This was increased to 84 million cubic metres in 1972 and to 109 million cubic metres in 1976. In the 1978 Agreement, the Guangdong authorities agreed to progressively increase the yearly supply from 145 million cubic metres in 1979 to 182 million cubic metres in 1982.
Further discussion in December 1979 resulted in the signing of a supplementary agreement in May 1980 providing for further progressively increases in supply after 1982. This agreement was amended in October 1981 and again in 1982 when it was agreed that Guangdong would supply 220 million cubic metres in 1982 with provision for annual increments thereafter up to 1995. The 1987 Agreement was also reached to provide for further progressive increase in yearly quantity form 1989 up to 1995.
The long-term water supply agreement with Guangdong authorities was signed in 1989, which had secured sufficient water supplies to meet Hong Kong's needs well into the next century. It provided an annual increase from 690 million cubic metres in 1995 to 780 million cubic metres in 2000, through a system with a maximun designed capacity of 1,100 million cubic metres per year.
However, starting in the nineties the industry in Hong Kong moved northwards. The water consumption had dropped significantly. After extensive negotiations, the Guangdong authorities agreed in the 1998 Agreement that the annual increase in supply quantities from 1998 to 2004 could be reduced by 20 million cubic metres. As a result, the total supply quantities reduced in these seven years was 560 mcm cumulatively. The Guangdong side had also agreed the ultimate annual supply quantity of 1,100 million cubic metres per year would remain unchanged and the time of reaching this ultimate capacity could be suitably deferred and would be subject to further negotiation.
The current agreement, which adopted a package deal approach, was signed in April 2006 for the supply arrangement up to 2008. Under this package deal arrangements, an annual lump sum payment will be made to the Guangdong side in exchange for a reliable and flexible supply of Dongjiang water to meet the actual needs of Hong Kong, even under extreme drought conditions with a return period of one in 100 years. There will be greater flexibility in the daily supply rate to tie in with seasonal fluctuations in the local yield, which will enable Hong Kong to have better control of the storage level in reservoirs, thereby minimising wastage and saving pumping costs. The long-term supply of Dongjiang water to Hong Kong to cope with future development under the existing agreements has also been reassured by retaining the ultimate annual supply quantity of 1,100 million cubic metres, while the target date for achieving this projection will be subject to further review.
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The East River-Shenzhen Water Supply Schematic Diagram.
Dongjiang, or the East River, is the source of water from Guangdong. Initially, water extracted from the river at a point some 83 kilometres north of Hong Kong is pumped over a series of dams and open channels built across the Shima River, one of its tributaries. It eventually discharges into the Shenzhen Reservoir before being fed by pipelines to Shenzhen Special Economic Zone and across the border at Muk Wu to Hong Kong. Subsequent to the commissioning of the dedicated aqueduct system in June 2003, the new Dongjiang water supply route is now segregated from all pollution sources along the Shima River.
Water, after received at Muk Wu is then delivered along the following three major aqueduct systems for transfer to territory wide storage and treatment facilities:
- Western Route to Ngau Tam Mei and Au Tau Water Treatment Works and via Au Tau Pumping Station to Tai Lam Chung Reservoir;
- Central Route via Tau Pass Culvert to Tai Po Tau Pumping Stations, and thence to Tai Po and Sha Tin Water Treatment Works or Plover Cove Reservoir; and
- Eastern Route via Nam Chung Aqueduct to Plover Cove Reservoir, and thence to High Island Reservoir or Ma On Shan and Pak Kong Water Treatment Works via Harbour Island Pumping Station, Tolo Channel Aqueduct, Sai O Pumping Station and High Island Tunnels.
These three routes are inter-connected through the Tai Po Tau Pumping station complex to provide maximum flexibility in system operation throughout the year; this is particularly crucial during the annual Guangdong water shutdown period in December when reverse flow from Plover Cove Reservoir and High Island Reservoir is required to maintain the necessary throughput at the treatment works in Sha Tin and other parts of the territory.
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