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Perspectives on Marine Environment Change in Hong Kong and Southern China, 1977-2001 (ed . B. Morton). Proceedings o f a n Internationa l Worksho p Reunio n Conference, Hon g Kong 21-26 Octobe r 2001. Hong Kong: Hong Kong University Press , 2003. LONG-TERM WATE R QUALIT Y TREND S I N HON G KON G Malcolm Broom , Gar y Chi u an d Arthu r Le e Environmental Protectio n Departmen t The Government o f the Hong Kong Special Administrative Regio n 28/F, Southorn Centre, 13 0 Hennessy Road , Wan Chai, Hong Kon g ABSTRACT Based o n 1 5 years' continuou s dat a fro m th e Environmental Protectio n Department' s marine monitoring programme, Hong Kong's marine water quality is reviewed and trends identified. I t is demonstrated that improvements in water quality in terms of increasing dissolved oxyge n level s an d reducing nutrien t concentration s ar e becoming visibl e i n semi-enclosed areas where polluting loads have been reduced substantially. In those areas where ther e i s goo d tida l flushin g ther e i s littl e evidenc e o f continuin g deterioration , although it is clear that in areas such as Victoria Harbour, where wastewater treatmen t infrastructure ha s not kept pace with urbanisation and population growth, water quality remains poor. It is also shown that in inshore waters throughout Hong Kon g there ar e trends towards increasing temperature s an d decreasing pH values. These are emerging problems which have potentially significan t implications . INTRODUCTION Hong Kong's environment is subject to enormous pressures of population and economic growth, growth in traffic, growt h in wastes and so on. In the past 15 years the population has grown from around 5.5 million to about 6.8 million. Solid waste generation has more than doubled from about 1 0 million tonnes.annum-1 to around 23 million tonnes.annum-1 at present. Sewage flows have increased from abou t 1.87 m tonnes.day-1 to about 2.35m tonnes.day-1 . Dail y vehicle-kilometre s travelle d hav e increased fro m abou t 1 6 million to aroun d 3 0 million . Thes e statistic s reflec t th e increasin g pressur e o n th e loca l environment a s the population grow s and becomes more affluent . Hong Kong's Environmental Protection Department was established in April 198 6 and sinc e the n ha s develope d a comprehensiv e programm e aime d a t reducin g th e 520 M. BROOM, G. CHIU & A. LEE pollution pressure on local waters. At the same time a programme of regular monitoring has been put in place to track trends and provide feedback on how effective th e pollution control programmes hav e been. This paper describes som e of the water quality trend s observed ove r the 1 5 years in which th e programme has operated . THE PROGRAMM E There are three main water quality monitoring programmes run by the HKEPD covering river, beac h an d marin e waters . Th e mai n characteristic s o f thes e programme s ar e summarised i n Table 1 . Table 1 Summary characteristic s o f Hon g Kong's water quality monitorin g programme s Mo of station s Sampling frequenc y No of determinant s measured Beach 50 4-6 time s per mont h during bathin g season 6 River 81 Mainly monthl y 21 Marine 91 Monthly for ope n waters Bimonthly fo r typhoon shelter s 23 Details of the marine, river and beach sampling programmes are published separately (Hong Kong Special Administrative Region Government 2001a , b, 2000) and can als o be found a t the website www.epd.gov.h k This paper focuses o n monitoring of the marine environment. The locations of the marine samplin g station s ar e show n i n Figur e 1 . The determinant s measure d i n th e programme ar e shown in Table 2. RESULTS Data collecte d unde r th e marine monitoring programm e ar e subjecte d t o the Seasona l Kendall tes t a s modifie d b y Hirsc h an d Slac k (1984) . This i s a non-parametric tren d test which is robust to seasonality an d persistence. The test indicates...

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