PUBLIC WORKS AND UTILITIES
151
The demand for water reached a new peak of 214.9 million gallons a day, an increase of 5.2 per cent over the 1970 peak. The average consumption throughout the year was 181.1 million gallons a day, an increase of 8.5 per cent over the 1970 average. A total of 66,100 million gallons of drinkable water were consumed compared with 60,917 million gallons in 1970. In addition, 13,938 million gallons of salt water for flushing were supplied, 18 per cent more than in 1970.
To meet future increases in demand, work continued on raising the Plover Cove dam by 12 feet, to increase the reservoir capacity by 13,000 million gallons to 50,000 million gallons. Additional pumping and filtration capacity is being provided simultaneously by exten- sions to the Tai Mei Tuk, Tai Po Tau and Sha Tin pumping stations and the Sha Tin treatment works. The output of the treatment works has already been increased from 80 to 110 million gallons a day, and will be increased to 175 million gallons a day by 1973.
Construction work began on the High Island water scheme--the last major conventional water supply project economically viable. This scheme will intercept water from the Sai Kung Peninsula and lead it through a system of stream intakes and tunnels to a 60,000 million gallon reservoir. The reservoir will be formed by the con- struction of two rockfill dams, each rising 200 feet above sea level, and linking High Island with the mainland at its eastern and western extremities. There will be about 24 miles of tunnels, from seven to 13 feet in diameter, 18 stream intakes to intercept water on the hill- sides at about 290 feet above sea level, eight flood pumping stations to collect water from low-lying land and pump it into the tunnel system, and there will be a major pumping station, treatment works, service reservoirs and pipelines to bring the water to the public. The cost will be over $1,000 million. The scheme is scheduled for com- pletion in 1978 but it is hoped to begin drawing water into the supply in 1976.
Since conventional water supplies cannot keep pace with the rate of increase in demand, and no more projects of colony wide signifi- cance are possible, large-scale desalting will eventually be necessary. This year a 50,000 gallon a day experimental desalting plant was commissioned to confirm the suitability of sites selected for large- scale desalting, to test materials for the construction of desalting plants, and to determine the treatment necessary to make such water suitable for injection into the distribution network. Work also began on the design of a 40 million gallon a day multi-stage flash desalter due for completion in 1974. This plant will cost about $200 million