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Pui O Beach downgraded to ‘fair’ in latest water quality rating

Posted in : News on by : Around DB , , Comments: 1

The Environmental Protection Department (EPD) released the latest grading of water quality last week, with the majority of beaches across Lantau receiving a rating of ‘good’, apart from Pui O Beach.

Pui O Beach was one of four beaches across Hong Kong that were downgraded from ‘good’ to ‘fair’ based on latest readings.

Silvermine Bay Beach was not included in the latest figures, as it is currently deemed ‘unclassified’ due to its temporary closure for the Signature Project Scheme (Islands District).

To view the latest results, visit http://www.beachwq.gov.hk/en/map.aspx.


Image: Wikimedia

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Comment(s) on - Pui O Beach downgraded to ‘fair’ in latest water quality rating

  • Merrin Pearse Reply

    Thanks for sharing the info about beach water quality.

    I would like to raise with people two things:
    1) the method used to determine the quality, and
    2) the warning about swimming for 3 days after heavy rains.

    I will start with the warning first. On all the pages showing individual beach data you will see these words:
    “During and after periods of heavy rain, many beaches are likely to be more polluted than the beach grades suggest. Bathers should avoid swimming at beaches for up to three days after a storm or heavy rain.”
    taken from http://www.beachwq.gov.hk/en/p_mawan.aspx?YX_MID=17

    Now to the method used. Water samples are not taken each day and even if they were there is normally about a 48hours delay in the data being released due to the time needed to test the water. So unlike air quality information the quality is not real time.

    Then the method that is used to come up with the quality number is a geometric mean of the last 5 results as stated at http://www.beachwq.gov.hk/en/grading_system.aspx (See also the actual number of E Coli for each grade here too)
    This geometric mean removes spikes in the data more than an average does so you won’t see how bad the water quality was unless you look at the raw data. However the raw data is only released many months later, like at the moment we can only see up until end of 2017 (have a go at getting the data via http://www.beachwq.gov.hk/en/request_info.aspx)

    For the Pui O Beach data from Jan 2010 to end Dec 2017 there were 17 measurements over 610 being classified as very poor with the worst measurement being over 5000.

    So in summary we really don’t know the sea water quality at a beach when we go swimming and after rains it will be worse. These beach gradings do though give you a good indication of what the long term average water quality is like so that is better than having nothing.

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