ENG-1997 — Page 290

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LAND, PUBLIC WORKS AND UTILITIES

dredging and disposal activities, and to investigate possible ways to avoid or minimise adverse effects on the marine environment.

Hydraulic Studies

Large reclamation projects may affect the flow of water, sediment transport and wave activity in the harbour. To minimise any adverse effects, the Civil Engineering Department employs sophisticated hydraulic models to analyse the likely effects of proposed schemes and check that they are within acceptable limits. The models are used for reclamation layout planning, design of marine structures, waterway studies and assessment of future maintenance dredging requirements. The models comprise computer-based mathematical models and a large physical model housed in the Harbour Hydraulics Laboratory at Tuen Mun.

To meet the requirements for comprehensive assessments of impact on the harbour arising from the large reclamation projects being planned, the Civil Engineering Department is enhancing the physical and mathematical models to improve their predictive capacity. Enhancement of the physical model has been completed. Upgrading of the mathematical models began at the end of 1996 and was completed at the end of 1997.

Water Supplies

Water from Guangdong

Guangdong rivers are Hong Kong's major source of water, and will meet all future increases in demand. This arrangement dates from 1960, when a scheme was formulated for receiving a piped supply of 22.7 million cubic metres a year. The supply from Guangdong stipulated under the agreements was increased to 750 million cubic metres a year in 1997. This will continue to increase in stages until the present designed maximum capacity of the supply system of 1.1 billion cubic metres per annum is reached.

Water Storage and Consumption

Full supply was maintained throughout the year. At the end of 1997, 485 million cubic metres of water were in storage, compared with 477 million cubic metres at the end of 1996. Hong Kong's two largest reservoirs, High Island and Plover Cove held 430 million cubic metres. A particularly high rainfall of 3 346 millimetres

51 per cent higher than the annual average of 2 214 millimetres — was recorded in 1997.

A peak daily consumption of 2.77 million cubic metres was recorded on May 14, compared with the 1996 peak of 2.82 million cubic metres. The average daily consumption throughout the year was 2.5 million cubic metres, a decrease of 1.3 per cent compared with the 1996 average of 2.54 million cubic metres. The consumption of potable water totalled 913 million cubic metres, compared with 928 million cubic metres in 1996. In addition, 198 million cubic metres of sea water were supplied for flushing, compared with 185 million cubic metres in 1996.

Water Works

Construction work for the two major treatment works at Tai Po and Ngau Tam Mei and for the additional service reservoirs, pumping stations and water supply networks in Tai Po, Tseung Kwan O and Tuen Mun was in progress. In addition, the major