PUBLIC WORKS AND UTILITIES
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problems. During the year, the existing laboratories were again fully utilised and some 112,927 tests were carried out. Of these, about four per cent were for private firms.
Water Supplies
The continuous water supply enjoyed for the previous two years came to an end on June 1 when, as a result of below average rainfall, water restrictions had to be imposed. At the beginning of 1977, there were 238 million cubic metres in storage, compared with 274 million cubic metres at the start of the previous year. Rainfall during the year was below the average of 2,169 millimetres, with a total of 1,680 mm being recorded. Rainfall in the first nine months amounted to only 1,470 mm and Hong Kong entered the dry season in October with its reservoirs only 59.6 per cent full. Consequently, there were only 182 million cubic metres in storage on October 1 (ex- cluding 20 million cubic metres stored in High Island Reservoir), compared with 293 million cubic metres at the same time in 1976. A 16-hour daily supply from 6 a.m. to 10 p.m. was introduced on June 1. This was further reduced on July 5 to 10 hours' supply in two periods - from 6 a.m. to 10 a.m. and 4 p.m. to 10 p.m. Despite these restrictions, a continuous supply was maintained to hospitals, industrial areas and other consumers with essential needs.
On January 1, 197 million cubic metres of water were stored in Plover Cove. Despite the reduced inflow during the summer months, there was no significant increase in salinity of the impounded water and, at the end of the year, the salinity was 94 parts per million. The quality of the abstracted water remained satisfactory throughout the year.
By a supplementary agreement with the Bureau of Water Conservancy and Hydro- Electric Power, Kwantung Province, 16 million cubic metres of water were piped from China to Hong Kong, in addition to the agreed annual supply of 109 million cubic metres. This was achieved by extending the supply period from July 31 to August 31. Water consumption varied only slightly from the previous year, due mainly to the effect of water restrictions. Average consumption throughout the year was 1.06 million cubic metres a day, compared with 1.1 million cubic metres a day in 1976. A total of 387 million cubic metres of potable water was consumed, compared with 405 million cubic metres in 1976. In addition, 75 million cubic metres of salt water for flushing were supplied.
Work progressed satisfactorily at High Island Reservoir in the New Territories. Construction of the east dam core and the supporting rockfill reached a height of 54 metres above principal datum, and the west dam was built to its final elevation. All eight lowland pumping stations were commissioned. The main tunnel system also was commissioned and the yield from the associated intakes began contributing to total resources in June. The uprating of the filters at Sha Tin treatment works from 0.8 to 1.1 million cubic metres a day was completed and the plant commissioned. Work on constructing a 96,000-cubic metre service reservoir at Lion Rock was substantially completed.
The Lok On Pai desalting plant, which can produce 182,000 cubic metres of water a day, was completed. All six desalter units, and associated electrical and instrumenta- tion equipment were finally taken over during the year on completion of their main- tenance periods. The numerous operational problems, apart from a shortage of staff,